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    The AKT kinase signaling network is rewired by PTEN to control proximal BCR signaling in germinal center B cells. Luo Wei,Hawse William,Conter Laura,Trivedi Nikita,Weisel Florian,Wikenheiser Daniel,Cattley Richard T,Shlomchik Mark J Nature immunology B cell antigen receptor (BCR) and CD40 signaling are rewired in germinal center (GC) B cells (GCBCs) to optimize selection for high-affinity B cells. In GCBC, BCR signals are constrained, but the mechanisms are not well understood. Here we describe a GC-specific, AKT-kinase-driven negative feedback loop that attenuates BCR signaling. Mass spectrometry revealed that AKT target activity was altered in GCBCs compared with naive B cells. Retargeting was linked to differential AKT T308 and S473 phosphorylation, in turn controlled by GC-specific upregulation of phosphoinositide-dependent protein kinase PDK1 and the phosphatase PTEN. In GCBCs, AKT preferentially targeted CSK, SHP-1 and HPK1, which are negative regulators of BCR signaling. We found that phosphorylation enhances enzymatic activity of these proteins, creating a negative feedback loop that dampens upstream BCR signaling. AKT inhibition relieved this negative feedback and enhanced activation of BCR-proximal kinase LYN, as well as downstream BCR signaling molecules in GCBCs. 10.1038/s41590-019-0376-3
    T and B-cell signaling in activated PI3K delta syndrome: From immunodeficiency to autoimmunity. Preite Silvia,Gomez-Rodriguez Julio,Cannons Jennifer L,Schwartzberg Pamela L Immunological reviews Phosphatidylinositol 3 kinases (PI3K) are a family of lipid kinases that are activated by a variety of cell-surface receptors, and regulate a wide range of downstream readouts affecting cellular metabolism, growth, survival, differentiation, adhesion, and migration. The importance of these lipid kinases in lymphocyte signaling has recently been highlighted by genetic analyses, including the recognition that both activating and inactivating mutations of the catalytic subunit of PI3Kδ, p110δ, lead to human primary immunodeficiencies. In this article, we discuss how studies on the human genetic disorder "Activated PI3K-delta syndrome" and mouse models of this disease (Pik3cd mice) have provided fundamental insight into pathways regulated by PI3Kδ in T and B cells and their contribution to lymphocyte function and disease, including responses to commensal bacteria and the development of autoimmunity and tumors. We highlight critical roles of PI3Kδ in T follicular helper cells and the orchestration of the germinal center reaction, as well as in CD8 T-cell function. We further  present data demonstrating the ability of the AKT-resistant FOXO1 mutant to rescue IgG1 class switching defects in Pik3cd B cells, as well as data supporting a role for PI3Kδ in promoting multiple T-helper effector cell lineages. 10.1111/imr.12790
    PI3Kδ hyper-activation promotes development of B cells that exacerbate Streptococcus pneumoniae infection in an antibody-independent manner. Stark Anne-Katrien,Chandra Anita,Chakraborty Krishnendu,Alam Rafeah,Carbonaro Valentina,Clark Jonathan,Sriskantharajah Srividya,Bradley Glyn,Richter Alex G,Banham-Hall Edward,Clatworthy Menna R,Nejentsev Sergey,Hamblin J Nicole,Hessel Edith M,Condliffe Alison M,Okkenhaug Klaus Nature communications Streptococcus pneumoniae is a major cause of pneumonia and a leading cause of death world-wide. Antibody-mediated immune responses can confer protection against repeated exposure to S. pneumoniae, yet vaccines offer only partial protection. Patients with Activated PI3Kδ Syndrome (APDS) are highly susceptible to S. pneumoniae. We generated a conditional knock-in mouse model of this disease and identify a CD19B220 B cell subset that is induced by PI3Kδ signaling, resides in the lungs, and is correlated with increased susceptibility to S. pneumoniae during early phases of infection via an antibody-independent mechanism. We show that an inhaled PI3Kδ inhibitor improves survival rates following S. pneumoniae infection in wild-type mice and in mice with activated PI3Kδ. These results suggest that a subset of B cells in the lung can promote the severity of S. pneumoniae infection, representing a potential therapeutic target. 10.1038/s41467-018-05674-8
    Phosphatase and tensin homolog (PTEN) mutation can cause activated phosphatidylinositol 3-kinase δ syndrome-like immunodeficiency. Tsujita Yuki,Mitsui-Sekinaka Kanako,Imai Kohsuke,Yeh Tzu-Wen,Mitsuiki Noriko,Asano Takaki,Ohnishi Hidenori,Kato Zenichiro,Sekinaka Yujin,Zaha Kiyotaka,Kato Tamaki,Okano Tsubasa,Takashima Takehiro,Kobayashi Kaoru,Kimura Mitsuaki,Kunitsu Tomoaki,Maruo Yoshihiro,Kanegane Hirokazu,Takagi Masatoshi,Yoshida Kenichi,Okuno Yusuke,Muramatsu Hideki,Shiraishi Yuichi,Chiba Kenichi,Tanaka Hiroko,Miyano Satoru,Kojima Seiji,Ogawa Seishi,Ohara Osamu,Okada Satoshi,Kobayashi Masao,Morio Tomohiro,Nonoyama Shigeaki The Journal of allergy and clinical immunology BACKGROUND:Activated phosphatidylinositol 3-kinase δ syndrome (APDS) is a recently discovered primary immunodeficiency disease (PID). Excess phosphatidylinositol 3-kinase (PI3K) activity linked to mutations in 2 PI3K genes, PIK3CD and PIK3R1, causes APDS through hyperphosphorylation of AKT, mammalian target of rapamycin (mTOR), and S6. OBJECTIVE:This study aimed to identify novel genes responsible for APDS. METHODS:Whole-exome sequencing was performed in Japanese patients with PIDs. Immunophenotype was assessed through flow cytometry. Hyperphosphorylation of AKT, mTOR, and S6 in lymphocytes was examined through immunoblotting, flow cytometry, and multiplex assays. RESULTS:We identified heterozygous mutations of phosphatase and tensin homolog (PTEN) in patients with PIDs. Immunoblotting and quantitative PCR analyses indicated that PTEN expression was decreased in these patients. Patients with PTEN mutations and those with PIK3CD mutations, including a novel E525A mutation, were further analyzed. The clinical symptoms and immunologic defects of patients with PTEN mutations, including lymphocytic AKT, mTOR, and S6 hyperphosphorylation, resemble those of patients with APDS. Because PTEN is known to suppress the PI3K pathway, it is likely that defective PTEN results in activation of the PI3K pathway. CONCLUSION:PTEN loss-of-function mutations can cause APDS-like immunodeficiency because of aberrant PI3K pathway activation in lymphocytes. 10.1016/j.jaci.2016.03.055
    Activated PIK3CD drives innate B cell expansion yet limits B cell-intrinsic immune responses. Wray-Dutra Michelle N,Al Qureshah Fahd,Metzler Genita,Oukka Mohamed,James Richard G,Rawlings David J The Journal of experimental medicine Activated PI3K-delta syndrome (APDS) is an immunodeficiency caused by gain-of-function mutations in PIK3CD. This disease exhibits complex immune phenotypes including increased IgM, recurrent infection, and impaired vaccine responses. To better understand the impact of B cells in this disease, we generated an inducible model of the common APDS mutation (h-E1021K; referred to as aPIK3CD) and intercrossed these mice with B cell-specific Cre models. Mb1-aPIK3CD mice exhibited bone marrow B lymphopenia and, conversely, expansion of the peripheral innate B1a and MZ B cell compartments. aPIK3CD B cells manifest increased pS6 and increased survival at several stages, without alterations in cycling, and baseline increases in plasma cells, natural IgM, and IgG3. Finally, Mb1-aPIK3CD mice exhibited blunted T cell-independent immune responses, and both AID- and CD21-aPIK3CD mice displayed reduced class-switched antibodies following T cell-dependent immunization. Thus, aPIK3CD alters B cell development and function and is counter-productive during immune responses, providing insight into B cell-intrinsic contributions to the APDS phenotype. 10.1084/jem.20180617
    Enhanced AKT Phosphorylation of Circulating B Cells in Patients With Activated PI3Kδ Syndrome. Asano Takaki,Okada Satoshi,Tsumura Miyuki,Yeh Tzu-Wen,Mitsui-Sekinaka Kanako,Tsujita Yuki,Ichinose Youjiro,Shimada Akira,Hashimoto Kunio,Wada Taizo,Imai Kohsuke,Ohara Osamu,Morio Tomohiro,Nonoyama Shigeaki,Kobayashi Masao Frontiers in immunology Activated PI3Kδ syndrome (APDS) is a primary immunodeficiency characterized by recurrent respiratory tract infections, lymphoproliferation, and defective IgG production. Heterozygous mutations in , or , which are related to the hyperactive phosphoinositide 3-kinase (PI3K) signaling, were recently presented to cause APDS1 or APDS2 (APDSs), or APDS-like (APDS-L) disorder. In this study, we examined the AKT phosphorylation of peripheral blood lymphocytes and monocytes in patients with APDSs and APDS-L by using flow cytometry. CD19 B cells of peripheral blood in APDS2 patients showed the enhanced phosphorylation of AKT at Ser473 (pAKT) without any specific stimulation. The enhanced pAKT in CD19 B cells was normalized by the addition of a p110δ inhibitor. In contrast, CD3 T cells and CD14 monocytes did not show the enhanced pAKT in the absence of stimulation. These findings were similarly observed in patients with APDS1 and APDS-L. Among CD19 B cells, enhanced pAKT was prominently detected in CD10 immature B cells compared with CD10 mature B cells. Enhanced pAKT was not observed in B cells of healthy controls, patients with common variable immunodeficiency, and hyper IgM syndrome due to CD40L deficiency. These results suggest that the enhanced pAKT in circulating B cells may be useful for the discrimination of APDS1, APDS2, and APDS-L from other antibody deficiencies. 10.3389/fimmu.2018.00568
    Hyperactive PI3Kδ predisposes naive T cells to activation via aerobic glycolysis programs. Jia Yanjun,Yang Qiuyun,Wang Yanping,Li Wenyan,Chen Xuemei,Xu Tao,Tian Zhirui,Feng Minxuan,Zhang Liang,Tang Wenjing,Tian Na,Zhou Lina,Song Wenxia,Zhao Xiaodong Cellular & molecular immunology Activated phosphoinositide 3-kinase δ syndrome (APDS) is an autosomal-dominant combined immunodeficiency disorder resulting from pathogenic gain-of-function (GOF) mutations in the PIK3CD gene. Patients with APDS display abnormal T cell homeostasis. However, the mechanisms by which PIK3CD GOF contributes to this feature remain unknown. Here, with a cohort of children with PIK3CD GOF mutations from multiple regions of China and a corresponding CRISPR/Cas9 gene-edited mouse model, we reported that hyperactive PI3Kδ disrupted T cell homeostasis in the periphery by intrinsically promoting the growth, proliferation, and activation of T cells. Our results showed that PIK3CD GOF resulted in loss of the quiescence-associated gene expression profile in naive T cells and promoted naive T cells to overgrow, hyperproliferate and acquire an activated functional status. Naive PIK3CD GOF T cells exhibited an enhanced glycolytic capacity and reduced mitochondrial respiration in the resting or activated state. Blocking glycolysis abrogated the abnormal splenic T cell pool and reversed the overactivated phenotype induced by PIK3CD GOF in vivo and in vitro. These results suggest that enhanced aerobic glycolysis is required for PIK3CD GOF-induced overactivation of naive T cells and provide a potential therapeutic approach for targeting glycolysis to treat patients with APDS as well as other immune disorders. 10.1038/s41423-020-0379-x
    Clinical, Immunological, and Genetic Features in Patients with Activated PI3Kδ Syndrome (APDS): a Systematic Review. Jamee Mahnaz,Moniri Shakiba,Zaki-Dizaji Majid,Olbrich Peter,Yazdani Reza,Jadidi-Niaragh Farhad,Aghamahdi Fatemeh,Abolhassani Hassan,Condliffe Alison M,Aghamohammadi Asghar,Azizi Gholamreza Clinical reviews in allergy & immunology Activated phosphoinositide 3-kinase delta syndrome (APDS) is a novel primary immunodeficiency (PID) caused by heterozygous gain of function mutations in PI3Kδ catalytic p110δ (PIK3CD) or regulatory p85α (PIK3R1) subunits leading to APDS1 and APDS2, respectively. Patients with APDS present a spectrum of clinical manifestations, particularly recurrent respiratory infections and lymphoproliferation. We searched PubMed, Web of Science, and Scopus databases for APDS patients and screened for eligibility criteria. A total of 243 APDS patients were identified from 55 articles. For all patients, demographic, clinical, immunologic, and molecular data were collected. Overall, 179 APDS1 and 64 APDS2 patients were identified. The most common clinical manifestations were respiratory tract infections (pneumonia (43.6%), otitis media (28.8%), and sinusitis (25.9%)), lymphoproliferation (70.4%), autoimmunity (28%), enteropathy (26.7%), failure to thrive (20.6%), and malignancy (12.8%). The predominant immunologic phenotype was hyper-IgM syndrome (48.1%). Immunologic profiling showed decreased B cells in 74.8% and CD4 T cells in 64.8% of APDS patients. The c.3061 G>A (p. E1021K) mutation in APDS1 with 85% frequency and c.1425+1 G> (A, C, T) (p.434-475del) mutation in APDS2 with 79% frequency were hotspot mutations. The majority of APDS patients were placed on long-term immunoglobulin replacement therapy. Immunosuppressive agents such as rituximab, tacrolimus, rapamycin, and leniolisib were also administered for autoimmunity and inflammatory complications. In addition, hematopoietic stem cell transplantation (HSCT) was used in 12.8% of patients. APDS has heterogynous clinical manifestations. It should be suspected in patients with history of recurrent respiratory infections, lymphoproliferation, and raised IgM levels. Moreover, HSCT should be considered in patients with severe and complicated clinical manifestations with no or insufficient response to the conventional therapies. 10.1007/s12016-019-08738-9