Lrp4 in hippocampal astrocytes serves as a negative feedback factor in seizures.
Yu Zheng,Zhang Meiying,Luo Bin,Jing Hongyang,Yu Yue,Wang Shunqi,Luo Shiwen
Cell & bioscience
BACKGROUND:Epilepsy is characterized by the typical symptom of seizure, and anti-seizure medications are the main therapeutic method in clinical, but the effects of these therapy have not been satisfactory. To find a better treatment, it makes sense to further explore the regulatory mechanisms of seizures at genetic level. Lrp4 regionally expresses in mice hippocampus where is key to limbic epileptogenesis. It is well known that neurons release a high level of glutamate during seizures, and it has been reported that Lrp4 in astrocytes down-regulates glutamate released from neurons. However, it is still unclear whether there is a relationship between Lrp4 expression level and seizures, and whether Lrp4 plays a role in seizures. RESULTS:We found that seizures induced by pilocarpine decreased Lrp4 expression level and increased miR-351-5p expression level in mice hippocampus. Glutamate reduced Lrp4 expression and enhanced miR-351-5p expression in cultured hippocampal astrocytes, and these effects can be partially attenuated by AP5. Furthermore, miR-351-5p inhibitor lessened the reduction of Lrp4 expression in glutamate treated hippocampal astrocytes. Local reduction of Lrp4 in hippocampus by sh Lrp4 lentivirus injection in hippocampus increased the threshold of seizures in pilocarpine or pentylenetetrazol (PTZ) injected mice. CONCLUSIONS:These results indicated that high released glutamate induced by seizures down-regulated astrocytic Lrp4 through increasing miR-351-5p in hippocampal astrocytes via activating astrocytic NMDA receptor, and locally reduction of Lrp4 in hippocampus increased the threshold of seizures. Lrp4 in hippocampal astrocytes appears to serve as a negative feedback factor in seizures. This provides a new potential therapeutic target for seizures regulation.
10.1186/s13578-020-00498-w
Intrafusal-fiber LRP4 for muscle spindle formation and maintenance in adult and aged animals.
Nature communications
Proprioception is sensed by muscle spindles for precise locomotion and body posture. Unlike the neuromuscular junction (NMJ) for muscle contraction which has been well studied, mechanisms of spindle formation are not well understood. Here we show that sensory nerve terminals are disrupted by the mutation of Lrp4, a gene required for NMJ formation; inducible knockout of Lrp4 in adult mice impairs sensory synapses and movement coordination, suggesting that LRP4 is required for spindle formation and maintenance. LRP4 is critical to the expression of Egr3 during development; in adult mice, it interacts in trans with APP and APLP2 on sensory terminals. Finally, spindle sensory endings and function are impaired in aged mice, deficits that could be diminished by LRP4 expression. These observations uncovered LRP4 as an unexpected regulator of muscle spindle formation and maintenance in adult and aged animals and shed light on potential pathological mechanisms of abnormal muscle proprioception.
10.1038/s41467-023-36454-8
LRP4 is required for the olfactory association task in the piriform cortex.
Cell & bioscience
BACKGROUND:Low-density lipoprotein receptor-related protein 4 (LRP4) plays a critical role in the central nervous system (CNS), including hippocampal synaptic plasticity, maintenance of excitatory synaptic transmission, fear regulation, as well as long-term potentiation (LTP). RESULTS:In this study, we found that Lrp4 was highly expressed in layer II of the piriform cortex. Both body weight and brain weight decreased in Lrp4 mice without TMD (Transmembrane domain) and ICD (intracellular domain) of LRP4. However, in the piriform cortical neurons of Lrp4 mice, the spine density increased, and the frequency of both mEPSC (miniature excitatory postsynaptic current) and sEPSC (spontaneous excitatory postsynaptic current) was enhanced. Intriguingly, finding food in the buried food-seeking test was prolonged in both Lrp4 mice and Lrp4 cKO (conditional knockout of Lrp4 in the piriform cortex) mice. CONCLUSIONS:This study indicated that the full length of LRP4 in the piriform cortex was necessary for maintaining synaptic plasticity and the integrity of olfactory function.
10.1186/s13578-022-00792-9
Upregulated YB-1 protein promotes glioblastoma growth through a YB-1/CCT4/mLST8/mTOR pathway.
The Journal of clinical investigation
Y-box-binding protein 1 (YB-1) is a multifunctional RNA binding protein involved in virtually every step of RNA metabolism. However, the functions and mechanisms of YB-1 in one of the most aggressive cancers, glioblastoma, are not well understood. In this study, we found that YB-1 protein was markedly overexpressed in glioblastoma and acted as a critical activator of both mTORC1 and mTORC2 signaling. Mechanistically, YB-1 bound the 5'UTR of CCT4 mRNA to promote the translation of CCT4, a component of the CCT chaperone complex, that in turn activated the mTOR signaling pathway by promoting mLST8 folding. In addition, YB-1 autoregulated its own translation by binding to its 5'UTR, leading to sustained activation of mTOR signaling. In patients with glioblastoma, high protein expression of YB-1 correlated with increased expression of CCT4 and mLST8 and activated mTOR signaling. Importantly, the administration of RNA decoys specifically targeting YB-1 in a mouse xenograft model resulted in slower tumor growth and better survival. Taken together, these findings uncover a disrupted proteostasis pathway involving a YB-1/CCT4/mLST8/mTOR axis in promoting glioblastoma growth, suggesting that YB-1 is a potential therapeutic target for the treatment of glioblastoma.
10.1172/JCI146536
EGFR ligand shifts the role of EGFR from oncogene to tumour suppressor in EGFR-amplified glioblastoma by suppressing invasion through BIN3 upregulation.
Nature cell biology
The epidermal growth factor receptor (EGFR) is a prime oncogene that is frequently amplified in glioblastomas. Here we demonstrate a new tumour-suppressive function of EGFR in EGFR-amplified glioblastomas regulated by EGFR ligands. Constitutive EGFR signalling promotes invasion via activation of a TAB1-TAK1-NF-κB-EMP1 pathway, resulting in large tumours and decreased survival in orthotopic models. Ligand-activated EGFR promotes proliferation and surprisingly suppresses invasion by upregulating BIN3, which inhibits a DOCK7-regulated Rho GTPase pathway, resulting in small hyperproliferating non-invasive tumours and improved survival. Data from The Cancer Genome Atlas reveal that in EGFR-amplified glioblastomas, a low level of EGFR ligands confers a worse prognosis, whereas a high level of EGFR ligands confers an improved prognosis. Thus, increased EGFR ligand levels shift the role of EGFR from oncogene to tumour suppressor in EGFR-amplified glioblastomas by suppressing invasion. The tumour-suppressive function of EGFR can be activated therapeutically using tofacitinib, which suppresses invasion by increasing EGFR ligand levels and upregulating BIN3.
10.1038/s41556-022-00962-4
Nodal regulates energy metabolism in glioma cells by inducing expression of hypoxia-inducible factor 1α.
Lai Jing-Huei,Jan Hsun-Jin,Liu Li-Wen,Lee Chin-Cheng,Wang Shyang-Guang,Hueng Dueng-Yuan,Cheng Yung-Yen,Lee Horng-Mo,Ma Hsin-I
Neuro-oncology
BACKGROUND:A shift in glucose metabolism from oxidative phosphorylation to anaerobic glycolysis is the biochemical hallmark of malignant cancer cells. METHODS:In the present study, we demonstrated that Nodal stimulated the expression of glycolytic enzymes and decreased reliance on mitochondrial oxidative phosphorylation in human glioma cancer cells. The shift in glucose metabolism was mediated by induction of the hypoxia-inducible factor (HIF). RESULTS:Nodal protein expression was shown to be correlated with expression levels of glucose transporter (Glut)-1, hexokinase (HK)-II, pyruvate dehydrogenase kinase (PDK)-1, the phosphorylation level of pyruvate dehydrogenase (PDH), glucose uptake, and lactate accumulation in human glioma cells. These effects were inversely correlated with mitochondrial oxygen consumption and ATP production. Knockdown of Nodal expression with specific small hairpin RNA reduced Glut-1, HK-II, and PDK-1 expressions and PDH phosphorylation. Nodal knockdown also reduced glucose uptake and lactate generation, which in turn increased mitochondrial membrane potential (Ψ), O2 utilization, and ATP synthesis. The ectopic expression of Nodal in low-expressing Nodal glioma cells resulted in the opposite results compared with those of Nodal knockdown glioma cells. Treatment of cells with recombinant Nodal increased HIF-1 expression, and this effect was regulated at the transcriptional level. Blockage of the Nodal receptor by a pharmacological inhibitor or Nodal knockdown in U87MG cells decreased HIF-1α expression. Furthermore, HIF-1α knockdown in U87MG cells decreased Glut-1, HK-II, and PDK-1 expressions and PDH phosphorylation, which were similar to results in Nodal knockdown cells. CONCLUSION:Taken together, these results suggest that Nodal affects energy metabolism through HIF-1α.
10.1093/neuonc/not086
Gboxin is an oxidative phosphorylation inhibitor that targets glioblastoma.
Shi Yufeng,Lim S Kyun,Liang Qiren,Iyer Swathi V,Wang Hua-Yu,Wang Zilai,Xie Xuanhua,Sun Daochun,Chen Yu-Jung,Tabar Viviane,Gutin Philip,Williams Noelle,De Brabander Jef K,Parada Luis F
Nature
Cancer-specific inhibitors that reflect the unique metabolic needs of cancer cells are rare. Here we describe Gboxin, a small molecule that specifically inhibits the growth of primary mouse and human glioblastoma cells but not that of mouse embryonic fibroblasts or neonatal astrocytes. Gboxin rapidly and irreversibly compromises oxygen consumption in glioblastoma cells. Gboxin relies on its positive charge to associate with mitochondrial oxidative phosphorylation complexes in a manner that is dependent on the proton gradient of the inner mitochondrial membrane, and it inhibits the activity of FF ATP synthase. Gboxin-resistant cells require a functional mitochondrial permeability transition pore that regulates pH and thus impedes the accumulation of Gboxin in the mitochondrial matrix. Administration of a metabolically stable Gboxin analogue inhibits glioblastoma allografts and patient-derived xenografts. Gboxin toxicity extends to established human cancer cell lines of diverse organ origin, and shows that the increased proton gradient and pH in cancer cell mitochondria is a mode of action that can be targeted in the development of antitumour reagents.
10.1038/s41586-019-0993-x
Electrical and synaptic integration of glioma into neural circuits.
Nature
High-grade gliomas are lethal brain cancers whose progression is robustly regulated by neuronal activity. Activity-regulated release of growth factors promotes glioma growth, but this alone is insufficient to explain the effect that neuronal activity exerts on glioma progression. Here we show that neuron and glioma interactions include electrochemical communication through bona fide AMPA receptor-dependent neuron-glioma synapses. Neuronal activity also evokes non-synaptic activity-dependent potassium currents that are amplified by gap junction-mediated tumour interconnections, forming an electrically coupled network. Depolarization of glioma membranes assessed by in vivo optogenetics promotes proliferation, whereas pharmacologically or genetically blocking electrochemical signalling inhibits the growth of glioma xenografts and extends mouse survival. Emphasizing the positive feedback mechanisms by which gliomas increase neuronal excitability and thus activity-regulated glioma growth, human intraoperative electrocorticography demonstrates increased cortical excitability in the glioma-infiltrated brain. Together, these findings indicate that synaptic and electrical integration into neural circuits promotes glioma progression.
10.1038/s41586-019-1563-y
Automethylation of PRC2 promotes H3K27 methylation and is impaired in H3K27M pediatric glioma.
Lee Chul-Hwan,Yu Jia-Ray,Granat Jeffrey,Saldaña-Meyer Ricardo,Andrade Joshua,LeRoy Gary,Jin Ying,Lund Peder,Stafford James M,Garcia Benjamin A,Ueberheide Beatrix,Reinberg Danny
Genes & development
The histone methyltransferase activity of PRC2 is central to the formation of H3K27me3-decorated facultative heterochromatin and gene silencing. In addition, PRC2 has been shown to automethylate its core subunits, EZH1/EZH2 and SUZ12. Here, we identify the lysine residues at which EZH1/EZH2 are automethylated with EZH2-K510 and EZH2-K514 being the major such sites in vivo. Automethylated EZH2/PRC2 exhibits a higher level of histone methyltransferase activity and is required for attaining proper cellular levels of H3K27me3. While occurring independently of PRC2 recruitment to chromatin, automethylation promotes PRC2 accessibility to the histone H3 tail. Intriguingly, EZH2 automethylation is significantly reduced in diffuse intrinsic pontine glioma (DIPG) cells that carry a lysine-to-methionine substitution in histone H3 (H3K27M), but not in cells that carry either EZH2 or EED mutants that abrogate PRC2 allosteric activation, indicating that H3K27M impairs the intrinsic activity of PRC2. Our study demonstrates a PRC2 self-regulatory mechanism through its EZH1/2-mediated automethylation activity.
10.1101/gad.328773.119
Olig2-Dependent Reciprocal Shift in PDGF and EGF Receptor Signaling Regulates Tumor Phenotype and Mitotic Growth in Malignant Glioma.
Lu Fanghui,Chen Ying,Zhao Chuntao,Wang Haibo,He Danyang,Xu Lingli,Wang Jincheng,He Xuelian,Deng Yaqi,Lu Ellen E,Liu Xue,Verma Ravinder,Bu Hong,Drissi Rachid,Fouladi Maryam,Stemmer-Rachamimov Anat O,Burns Dennis,Xin Mei,Rubin Joshua B,Bahassi El Mustapha,Canoll Peter,Holland Eric C,Lu Q Richard
Cancer cell
Malignant gliomas exhibit extensive heterogeneity and poor prognosis. Here we identify mitotic Olig2-expressing cells as tumor-propagating cells in proneural gliomas, elimination of which blocks tumor initiation and progression. Intriguingly, deletion of Olig2 resulted in tumors that grow, albeit at a decelerated rate. Genome occupancy and expression profiling analyses reveal that Olig2 directly activates cell-proliferation machinery to promote tumorigenesis. Olig2 deletion causes a tumor phenotypic shift from an oligodendrocyte precursor-correlated proneural toward an astroglia-associated gene expression pattern, manifest in downregulation of platelet-derived growth factor receptor-α and reciprocal upregulation of epidermal growth factor receptor (EGFR). Olig2 deletion further sensitizes glioma cells to EGFR inhibitors and extends the lifespan of animals. Thus, Olig2-orchestrated receptor signaling drives mitotic growth and regulates glioma phenotypic plasticity. Targeting Olig2 may circumvent resistance to EGFR-targeted drugs.
10.1016/j.ccell.2016.03.027
Glioma-induced inhibition of caspase-3 in microglia promotes a tumor-supportive phenotype.
Nature immunology
Glioma cells recruit and exploit microglia (the resident immune cells of the brain) for their proliferation and invasion ability. The underlying molecular mechanism used by glioma cells to transform microglia into a tumor-supporting phenotype has remained elusive. We found that glioma-induced microglia conversion was coupled to a reduction in the basal activity of microglial caspase-3 and increased S-nitrosylation of mitochondria-associated caspase-3 through inhibition of thioredoxin-2 activity, and that inhibition of caspase-3 regulated microglial tumor-supporting function. Furthermore, we identified the activity of nitric oxide synthase 2 (NOS2, also known as iNOS) originating from the glioma cells as a driving stimulus in the control of microglial caspase-3 activity. Repression of glioma NOS2 expression in vivo led to a reduction in both microglia recruitment and tumor expansion, whereas depletion of microglial caspase-3 gene promoted tumor growth. Our results provide evidence that inhibition of the denitrosylation of S-nitrosylated procaspase-3 mediated by the redox protein Trx2 is a part of the microglial pro-tumoral activation pathway initiated by glioma cancer cells.
10.1038/ni.3545
A Glial Signature and Wnt7 Signaling Regulate Glioma-Vascular Interactions and Tumor Microenvironment.
Griveau Amelie,Seano Giorgio,Shelton Samuel J,Kupp Robert,Jahangiri Arman,Obernier Kirsten,Krishnan Shanmugarajan,Lindberg Olle R,Yuen Tracy J,Tien An-Chi,Sabo Jennifer K,Wang Nancy,Chen Ivy,Kloepper Jonas,Larrouquere Louis,Ghosh Mitrajit,Tirosh Itay,Huillard Emmanuelle,Alvarez-Buylla Arturo,Oldham Michael C,Persson Anders I,Weiss William A,Batchelor Tracy T,Stemmer-Rachamimov Anat,Suvà Mario L,Phillips Joanna J,Aghi Manish K,Mehta Shwetal,Jain Rakesh K,Rowitch David H
Cancer cell
Gliomas comprise heterogeneous malignant glial and stromal cells. While blood vessel co-option is a potential mechanism to escape anti-angiogenic therapy, the relevance of glial phenotype in this process is unclear. We show that Olig2 oligodendrocyte precursor-like glioma cells invade by single-cell vessel co-option and preserve the blood-brain barrier (BBB). Conversely, Olig2-negative glioma cells form dense perivascular collections and promote angiogenesis and BBB breakdown, leading to innate immune cell activation. Experimentally, Olig2 promotes Wnt7b expression, a finding that correlates in human glioma profiling. Targeted Wnt7a/7b deletion or pharmacologic Wnt inhibition blocks Olig2 glioma single-cell vessel co-option and enhances responses to temozolomide. Finally, Olig2 and Wnt7 become upregulated after anti-VEGF treatment in preclinical models and patients. Thus, glial-encoded pathways regulate distinct glioma-vascular microenvironmental interactions.
10.1016/j.ccell.2018.03.020
APP interacts with LRP4 and agrin to coordinate the development of the neuromuscular junction in mice.
Choi Hong Y,Liu Yun,Tennert Christian,Sugiura Yoshie,Karakatsani Andromachi,Kröger Stephan,Johnson Eric B,Hammer Robert E,Lin Weichun,Herz Joachim
eLife
ApoE, ApoE receptors and APP cooperate in the pathogenesis of Alzheimer's disease. Intriguingly, the ApoE receptor LRP4 and APP are also required for normal formation and function of the neuromuscular junction (NMJ). In this study, we show that APP interacts with LRP4, an obligate co-receptor for muscle-specific tyrosine kinase (MuSK). Agrin, a ligand for LRP4, also binds to APP and co-operatively enhances the interaction of APP with LRP4. In cultured myotubes, APP synergistically increases agrin-induced acetylcholine receptor (AChR) clustering. Deletion of the transmembrane domain of LRP4 (LRP4 ECD) results in growth retardation of the NMJ, and these defects are markedly enhanced in APP(-/-);LRP4(ECD/ECD) mice. Double mutant NMJs are significantly reduced in size and number, resulting in perinatal lethality. Our findings reveal novel roles for APP in regulating neuromuscular synapse formation through hetero-oligomeric interaction with LRP4 and agrin and thereby provide new insights into the molecular mechanisms that govern NMJ formation and maintenance. DOI:http://dx.doi.org/10.7554/eLife.00220.001.
10.7554/eLife.00220
Lrp4 in osteoblasts suppresses bone formation and promotes osteoclastogenesis and bone resorption.
Xiong Lei,Jung Ji-Ung,Wu Haitao,Xia Wen-Fang,Pan Jin-Xiu,Shen Chengyong,Mei Lin,Xiong Wen-Cheng
Proceedings of the National Academy of Sciences of the United States of America
Bone mass is maintained by balanced activity of osteoblasts and osteoclasts. Lrp4 (low-density lipoprotein receptor related protein 4) is a member of the LDL receptor family, whose mutations have been identified in patients with high-bone-mass disorders, such as sclerosteosis and van Buchem diseases. However, it remains unknown whether and how Lrp4 regulates bone-mass homeostasis in vivo. Here we provide evidence that Lrp4-null mutation or specific mutation in osteoblast-lineage cells increased cortical and trabecular bone mass, which was associated with elevated bone formation and impaired bone resorption. This phenotype was not observed in osteoclast-selective Lrp4 knockout mice. Mechanistic studies indicate that loss of Lrp4 function in osteoblast-lineage cells increased serum levels of sclerostin, a key factor for bone-mass homeostasis that interacts with Lrp4, but abolished the inhibition of Wnt/β-catenin signaling and osteoblastic differentiation by sclerostin. Concomitantly, sclerostin induction of RANKL (receptor activator of nuclear kappa B ligand) was impaired, leading to a lower ratio of RANKL over OPG (osteoprotegerin) (a key factor for osteoclastogenesis). Taken together, these results support the view for Lrp4 as a receptor of sclerostin to inhibit Wnt/β-catenin signaling and bone formation and identify Lrp4 as a critical player in bone-mass homeostasis.
10.1073/pnas.1419714112
The synaptic receptor Lrp4 promotes peripheral nerve regeneration.
Nature communications
Early during PNS regeneration, regenerating axons emerge from the proximal nerve stump, yet whether they extend simultaneously or whether pioneering axons establish a path for follower axons remains unknown. Moreover, the molecular mechanisms underlying robust regeneration are incompletely understood. Using live imaging, we demonstrate that in zebrafish pioneering axons establish a regenerative path for follower axons. We find this process requires the synaptic receptor lrp4, and in lrp4 mutants pioneers are unaffected while follower axons frequently stall at the injury gap, providing evidence for molecular diversity between pioneering and follower axons in regeneration. We demonstrate that Lrp4 promotes regeneration through an axon extrinsic mechanism and independent of membrane anchoring and MuSK co-receptor signaling essential for synaptic development. Finally, we show that Lrp4 coordinates the realignment of denervated Schwann cells with regenerating axons, consistent with a model by which Lrp4 is repurposed to promote sustained peripheral nerve regeneration via axon-glia interactions.
10.1038/s41467-018-04806-4
Diverging roles for Lrp4 and Wnt signaling in neuromuscular synapse development during evolution.
Remédio Leonor,Gribble Katherine D,Lee Jennifer K,Kim Natalie,Hallock Peter T,Delestrée Nicolas,Mentis George Z,Froemke Robert C,Granato Michael,Burden Steven J
Genes & development
Motor axons approach muscles that are prepatterned in the prospective synaptic region. In mice, prepatterning of acetylcholine receptors requires Lrp4, a LDLR family member, and MuSK, a receptor tyrosine kinase. Lrp4 can bind and stimulate MuSK, strongly suggesting that association between Lrp4 and MuSK, independent of additional ligands, initiates prepatterning in mice. In zebrafish, Wnts, which bind the Frizzled (Fz)-like domain in MuSK, are required for prepatterning, suggesting that Wnts may contribute to prepatterning and neuromuscular development in mammals. We show that prepatterning in mice requires Lrp4 but not the MuSK Fz-like domain. In contrast, prepatterning in zebrafish requires the MuSK Fz-like domain but not Lrp4. Despite these differences, neuromuscular synapse formation in zebrafish and mice share similar mechanisms, requiring Lrp4, MuSK, and neuronal Agrin but not the MuSK Fz-like domain or Wnt production from muscle. Our findings demonstrate that evolutionary divergent mechanisms establish muscle prepatterning in zebrafish and mice.
10.1101/gad.279745.116
Presynaptic LRP4 promotes synapse number and function of excitatory CNS neurons.
Mosca Timothy J,Luginbuhl David J,Wang Irving E,Luo Liqun
eLife
Precise coordination of synaptic connections ensures proper information flow within circuits. The activity of presynaptic organizing molecules signaling to downstream pathways is essential for such coordination, though such entities remain incompletely known. We show that LRP4, a conserved transmembrane protein known for its postsynaptic roles, functions presynaptically as an organizing molecule. In the brain, LRP4 localizes to the nerve terminals at or near active zones. Loss of presynaptic LRP4 reduces excitatory (not inhibitory) synapse number, impairs active zone architecture, and abolishes olfactory attraction - the latter of which can be suppressed by reducing presynaptic GABA receptors. LRP4 overexpression increases synapse number in excitatory and inhibitory neurons, suggesting an instructive role and a common downstream synapse addition pathway. Mechanistically, LRP4 functions via the conserved kinase SRPK79D to ensure normal synapse number and behavior. This highlights a presynaptic function for LRP4, enabling deeper understanding of how synapse organization is coordinated.
10.7554/eLife.27347
The VWF/LRP4/αVβ3-axis represents a novel pathway regulating proliferation of human vascular smooth muscle cells.
Cardiovascular research
AIMS:Von Willebrand factor (VWF) is a plasma glycoprotein involved in primary haemostasis, while also having additional roles beyond haemostasis namely in cancer, inflammation, angiogenesis, and potentially in vascular smooth muscle cell (VSMC) proliferation. Here, we addressed how VWF modulates VSMC proliferation and investigated the underlying molecular pathways and the in vivo pathophysiological relevance. METHODS AND RESULTS:VWF induced proliferation of human aortic VSMCs and also promoted VSMC migration. Treatment of cells with a siRNA against αv integrin or the RGT-peptide blocking αvβ3 signalling abolished proliferation. However, VWF did not bind to αvβ3 on VSMCs through its RGD-motif. Rather, we identified the VWF A2 domain as the region mediating binding to the cells. We hypothesized the involvement of a member of the LDL-related receptor protein (LRP) family due to their known ability to act as co-receptors. Using the universal LRP-inhibitor receptor-associated protein, we confirmed LRP-mediated VSMC proliferation. siRNA experiments and confocal fluorescence microscopy identified LRP4 as the VWF-counterreceptor on VSMCs. Also co-localization between αvβ3 and LRP4 was observed via proximity ligation analysis and immuno-precipitation experiments. The pathophysiological relevance of our data was supported by VWF-deficient mice having significantly reduced hyperplasia in carotid artery ligation and artery femoral denudation models. In wild-type mice, infiltration of VWF in intimal regions enriched in proliferating VSMCs was found. Interestingly, also analysis of human atherosclerotic lesions showed abundant VWF accumulation in VSMC-proliferating rich intimal areas. CONCLUSION:VWF mediates VSMC proliferation through a mechanism involving A2 domain binding to the LRP4 receptor and integrin αvβ3 signalling. Our findings provide new insights into the mechanisms that drive physiological repair and pathological hyperplasia of the arterial vessel wall. In addition, the VWF/LRP4-axis may represent a novel therapeutic target to modulate VSMC proliferation.
10.1093/cvr/cvab042
Astrocytic Lrp4 (Low-Density Lipoprotein Receptor-Related Protein 4) Contributes to Ischemia-Induced Brain Injury by Regulating ATP Release and Adenosine-AR (Adenosine A2A Receptor) Signaling.
Stroke
BACKGROUND AND PURPOSE:Lrp4 (low-density lipoprotein receptor-related protein 4) is predominantly expressed in astrocytes, where it regulates glutamatergic neurotransmission by suppressing ATP release. Here, we investigated Lrp4's function in ischemia/stroke-induced brain injury response, which includes glutamate-induced neuronal death and reactive astrogliosis. METHODS:The brain-specific Lrp4 conditional knockout mice (Lrp4), astrocytic-specific Lrp4 conditional knockout mice (Lrp4), and their control mice (Lrp4) were subjected to photothrombotic ischemia and the transient middle cerebral artery occlusion. After ischemia/stroke, mice or their brain samples were subjected to behavior tests, brain histology, immunofluorescence staining, Western blot, and quantitative real-time polymerase chain reaction. In addition, primary astrocytes and neurons were cocultured with or without oxygen and glucose deprivation and in the presence or absence of the antagonist for adenosine-AR (adenosine A2A receptor) or ATP-P2X7R (P2X purinoceptor 7) signaling. Gliotransmitters, such as glutamate, d-serine, ATP, and adenosine, in the condition medium of cultured astrocytes were also measured. RESULTS:Lrp4, largely expressed in astrocytes, was increased in response to ischemia/stroke. Both Lrp4 and Lrp4 mice showed less brain injury, including reduced neuronal death, and impaired reactive astrogliosis. Mechanistically, Lrp4 conditional knockout in astrocytes increased ATP release and the production of ATP derivative, adenosine, which were further elevated by oxygen and glucose deprivation. Pharmacological inhibition of ATP-PXR or adenosine-AR signaling diminished Lrp4's protective effect. CONCLUSIONS:The astrocytic Lrp4 plays an important role in ischemic brain injury response. Lrp4 deficiency in astrocytes seems to be protective in response to ischemic brain injury, likely because of the increased ATP release and adenosine-AR signaling.
10.1161/STROKEAHA.117.018115
Multiple modes of Lrp4 function in modulation of Wnt/β-catenin signaling during tooth development.
Ahn Youngwook,Sims Carrie,Murray Megan J,Kuhlmann Paige K,Fuentes-Antrás Jesús,Weatherbee Scott D,Krumlauf Robb
Development (Cambridge, England)
During development and homeostasis, precise control of Wnt/β-catenin signaling is in part achieved by secreted and membrane proteins that negatively control activity of the Wnt co-receptors Lrp5 and Lrp6. Lrp4 is related to Lrp5/6 and is implicated in modulation of Wnt/β-catenin signaling, presumably through its ability to bind to the Wise (Sostdc1)/sclerostin (Sost) family of Wnt antagonists. To gain insights into the molecular mechanisms of Lrp4 function in modulating Wnt signaling, we performed an array of genetic analyses in murine tooth development, where Lrp4 and Wise play important roles. We provide genetic evidence that Lrp4 mediates the Wnt inhibitory function of Wise and also modulates Wnt/β-catenin signaling independently of Wise. Chimeric receptor analyses raise the possibility that the Lrp4 extracellular domain interacts with Wnt ligands, as well as the Wnt antagonists. Diverse modes of Lrp4 function are supported by severe tooth phenotypes of mice carrying a human mutation known to abolish Lrp4 binding to Sost. Our data suggest a model whereby Lrp4 modulates Wnt/β-catenin signaling via interaction with Wnt ligands and antagonists in a context-dependent manner.
10.1242/dev.150680
Ablation of Lrp4 in Schwann Cells Promotes Peripheral Nerve Regeneration in Mice.
Hui Tian-Kun,Lai Xin-Sheng,Dong Xia,Jing Hongyang,Liu Ziyang,Fei Erkang,Chen Wen-Bing,Wang Shunqi,Ren Dongyan,Zou Suqi,Wu Hai-Tao,Pan Bing-Xing
Biology
Low-density lipoprotein receptor-related protein 4 (Lrp4) is a critical protein involved in the Agrin-Lrp4-MuSK signaling pathway that drives the clustering of acetylcholine receptors (AChRs) at the neuromuscular junction (NMJ). Many studies have shown that Lrp4 also functions in kidney development, bone formation, nervous system development, etc. However, whether Lrp4 participates in nerve regeneration in mammals remains unknown. Herein, we show that Lrp4 is expressed in SCs and that conditional knockout (cKO) of Lrp4 in SCs promotes peripheral nerve regeneration. In Lrp4 cKO mice, the demyelination of SCs was accelerated, and the proliferation of SCs was increased in the injured nerve. Furthermore, we identified that two myelination-related genes, Krox-20 and Mpz, were downregulated more dramatically in the cKO group than in the control group. Our results elucidate a novel role of Lrp4 in peripheral nerve regeneration and thereby provide a potential therapeutic target for peripheral nerve recovery.
10.3390/biology10060452
Competitive blocking of LRP4-sclerostin binding interface strongly promotes bone anabolic functions.
Katchkovsky Svetlana,Chatterjee Biplab,Abramovitch-Dahan Chen-Viki,Papo Niv,Levaot Noam
Cellular and molecular life sciences : CMLS
Induction of bone formation by Wnt ligands is inhibited when sclerostin (Scl), an osteocyte-produced antagonist, binds to its receptors, the low-density lipoprotein receptor-related proteins 5 or 6 (LRP5/6). Recently, it was shown that enhanced inhibition is achieved by Scl binding to the co-receptor LRP4. However, it is not clear if the binding of Scl to LRP4 facilitates Scl binding to LRP5/6 or inhibits the Wnt pathway in an LRP5/6-independent manner. Here, using the yeast display system, we demonstrate that Scl exhibits a stronger binding affinity for LRP4 than for LRP6. Moreover, we found stronger Scl binding to LRP6 in the presence of LRP4. We further show that a Scl mutant (Scl), which tightly binds LRP4 but not LRP6, does not inhibit the Wnt pathway on its own. We demonstrate that Scl competes with Scl for a common binding site on LRP4 and antagonizes Scl inhibition of the Wnt signaling pathway in osteoblasts in vitro. Finally, we demonstrate that 2 weeks of bi-weekly subcutaneous injections of Scl fused to the fragment crystallizable (Fc) domain of immunoglobulin (SclFc), which retains the antagonistic activity of the mutant, significantly increases bone formation rate and enhances trabecular volumetric bone fraction, trabecular number, and bone length in developing mice. Our data show that LRP4 serves as an anchor that facilitates Scl-LRP6 binding and that inhibition of the Wnt pathway by Scl depends on its prior binding to LRP4. We further provide evidence that compounds that inhibit Scl-LRP4 interactions offer a potential strategy to promote anabolic bone functions.
10.1007/s00018-022-04127-2
[Wnt Signaling and Skeletal Dysplasias.]
Michigami Toshimi
Clinical calcium
Identification of responsible genes for skeletal dysplasias evidences their critical roles in the skeletal development and maintenance. Mutations in the genes encoding the components of Wnt canonical pathway, which include , , , and , cause the disorders characterized by abnormal in bone mass. On the other hand, mutations in the genes for the components of Wnt non-canonical pathway such as , , and are associated with dysmorphic skeletal disorders which manifest short limbs and facial anomalies. Thus, both canonical and non-canonical pathways of Wnt signaling play substantial roles in the human skeletons, and it is suggested that the former mainly controls bone mass while the latter regulates skeletal morphogenesis.
10.20837/4201903323
Agrin-Lrp4-Ror2 signaling regulates adult hippocampal neurogenesis in mice.
eLife
Adult neurogenesis in the hippocampus may represent a form of plasticity in brain functions including mood, learning and memory. However, mechanisms underlying neural stem/progenitor cells (NSPCs) proliferation are not well understood. We found that Agrin, a factor critical for neuromuscular junction formation, is elevated in the hippocampus of mice that are stimulated by enriched environment (EE). Genetic deletion of the gene in excitatory neurons decreases NSPCs proliferation and increases depressive-like behavior. Low-density lipoprotein receptor-related protein 4 (Lrp4), a receptor for Agrin, is expressed in hippocampal NSPCs and its mutation blocked basal as well as EE-induced NSPCs proliferation and maturation of newborn neurons. Finally, we show that Lrp4 interacts with and activates receptor tyrosine kinase-like orphan receptor 2 (Ror2); and 2 mutation impairs NSPCs proliferation. Together, these observations identify a role of Agrin-Lrp4-Ror2 signaling for adult neurogenesis, uncovering previously unexpected functions of Agrin and Lrp4 in the brain.
10.7554/eLife.45303
Nerve, Muscle, and Synaptogenesis.
Swenarchuk Lauren Eric
Cells
The vertebrate skeletal neuromuscular junction (NMJ) has long served as a model system for studying synapse structure, function, and development. Over the last several decades, a neuron-specific isoform of agrin, a heparan sulfate proteoglycan, has been identified as playing a central role in synapse formation at all vertebrate skeletal neuromuscular synapses. While agrin was initially postulated to be the inductive molecule that initiates synaptogenesis, this model has been modified in response to work showing that postsynaptic differentiation can develop in the absence of innervation, and that synapses can form in transgenic mice in which the agrin gene is ablated. In place of a unitary mechanism for neuromuscular synapse formation, studies in both mice and zebrafish have led to the proposal that two mechanisms mediate synaptogenesis, with some synapses being induced by nerve contact while others involve the incorporation of prepatterned postsynaptic structures. Moreover, the current model also proposes that agrin can serve two functions, to induce synaptogenesis and to stabilize new synapses, once these are formed. This review examines the evidence for these propositions, and concludes that it remains possible that a single molecular mechanism mediates synaptogenesis at all NMJs, and that agrin acts as a stabilizer, while its role as inducer is open to question. Moreover, if agrin does not act to initiate synaptogenesis, it follows that as yet uncharacterized molecular interactions are required to play this essential inductive role. Several alternatives to agrin for this function are suggested, including focal pericellular proteolysis and integrin signaling, but all require experimental validation.
10.3390/cells8111448
A Role of Low-Density Lipoprotein Receptor-Related Protein 4 (LRP4) in Astrocytic Aβ Clearance.
Zhang Hongsheng,Chen Wenbing,Tan Zhibing,Zhang Lei,Dong Zhaoqi,Cui Wanpeng,Zhao Kai,Wang Hongsheng,Jing Hongyang,Cao Rangjuan,Kim Chae,Safar Jiri G,Xiong Wen-Cheng,Mei Lin
The Journal of neuroscience : the official journal of the Society for Neuroscience
Amyloid-β (Aβ) deposition occurs years before cognitive symptoms appear and is considered a cause of Alzheimer's disease (AD). The imbalance of Aβ production and clearance leads to Aβ accumulation and Aβ deposition. Increasing evidence indicates an important role of astrocytes, the most abundant cell type among glial cells in the brain, in Aβ clearance. We explored the role of low-density lipoprotein receptor-related protein 4 (LRP4), a member of the LDLR family, in AD pathology. We show that 4 is specifically expressed in astrocytes and its levels in astrocytes were higher than those of and 1, both of which have been implicated in Aβ uptake. LRP4 was reduced in postmortem brain tissues of AD patients. Genetic deletion of the 4 gene augmented Aβ plaques in 5xFAD male mice, an AD mouse model, and exacerbated the deficits in neurotransmission, synchrony between the hippocampus and PFC, and cognition. Mechanistically, LRP4 promotes Aβ uptake by astrocytes likely by interacting with ApoE. Together, our study demonstrates that astrocytic LRP4 plays an important role in Aβ pathology and cognitive function. This study investigates how astrocytes, a type of non-nerve cells in the brain, may contribute to Alzheimer's disease (AD) development. We demonstrate that the low-density lipoprotein receptor-related protein 4 (LRP4) is reduced in the brain of AD patients. Mimicking the reduced levels in an AD mouse model exacerbates cognitive impairment and increases amyloid aggregates that are known to damage the brain. We show that LRP4 could promote the clearance of amyloid protein by astrocytes. Our results reveal a previously unappreciated role of LRP4 in AD development.
10.1523/JNEUROSCI.0250-20.2020
LRP4 promotes migration and invasion of gastric cancer under the regulation of microRNA-140-5p.
Mao Zhijun,Wang Zhen,Zhang Shiping,Pu Yansong,Wang Jianhua,Zhang Tao,Long Yanbin,Liu Yi,Ma Yu,Zhu Jing
Cancer biomarkers : section A of Disease markers
BACKGROUND:Low-density lipoprotein receptor-related protein 4 (LRP4) has been reported to be implicated in multiple types of cancers. However, the significance of LRP4 in gastric cancer (GC) remains poorly elucidated. Therefore, it's urgent to investigate the importance and underlying mechanisms of LRP4 in GC. OBJECTIVE:To investigate the clinical roles of LRP4 in GC. METHODS:The LRP4 mRNA and miR-140-5p was measured by qRT-PCR. The protein expression was determined Western blot. Kaplan-Meier survival curves and Cox proportional hazard regression models were performed to evaluate prognosis. RESULTS:We demonstrated that LRP4 mRNA and protein was up-regulated in GC tissues for the first time. Its high expression was significantly correlated with malignant clinical features including TNM stage and lymph-node metastasis and poor prognosis for GC patients. LRP4 promotes migration, invasion and epithelial-mesenchymal transition (EMT) progress of GC cells. Mechanically, LRP4 regulated PI3K/AKT in GC cells. AKT inhibitors reversed the effects of LRP4. Finally, LRP4 was regulated by miR-140-5p in GC. CONCLUSIONS:Our findings showed that LRP4 has an important function in GC progression and promotes GC migration, invasion and EMT by regulating PI3K/AKT under regulation of miR-140-5p, providing a potential therapeutic target for GC.
10.3233/CBM-190571
LRP4 LDLα repeats of astrocyte enhance dendrite arborization of the neuron.
Yan Min,Guo Amin,Chen Peng,Jing Hongyang,Ren Dongyan,Zhong Yanzi,Wu Yongqiang,Fei Erkang,Lai Xinsheng,Zou Suqi,Wang Shunqi
Molecular brain
The low-density lipoprotein receptor-related protein 4 (LRP4) is essential for inducing the neuromuscular junction (NMJ) formation in muscle fibers, and LRP4 plays a critical role in dendritic development and synaptogenesis in the central nervous system (CNS). As a single transmembrane protein, LRP4 contains an enormously sizeable extracellular domain (ECD), containing multiple LDLα repeats in the N-terminal of ECD. LRP4 only with extracellular domain acts as a similar mechanism of full-length LRP4 in muscles to stimulate acetylcholine receptor clustering. In this study, we elucidated that LDLα repeats of LRP4 maintained the body weight and survival rate. Dendritic branches of the pyramidal neurons in Lrp4-null mice with LRP4 LDLα repeats residue were more than in Lrp4-null mice without residual LRP4 domain. Supplement with conditioned medium from LRP4 LDLα overexpression cells, the primary culture pyramidal neurons achieved strong dendritic arborization ability. Besides, astrocytes with LRP4 LDLα repeats residue could promote pyramidal neuronal dendrite arborization in the primary co-cultured system. These observations signify that LRP4 LDLα repeats play a prominent underlying role in dendrite arborization.
10.1186/s13041-020-00708-z