In this issue, Ali et al. report that CXCR3-dependent localization of NK cells in T cell zones is vital for immunoregulatory suppression of T cell responses. The cover image shows T cells (purple), B cells (red), and NK cells (green) in the lymphoid follicles of a mouse spleen
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Tumor-infiltrating myeloid cells contribute to the development of the immunosuppressive tumor microenvironment. Myeloid cell expression of arginase 1 (Arg-1) promotes a protumor phenotype by inhibiting T cell function and depleting extracellular L-arginine, but the mechanism underlying this expression, especially in breast cancer, is poorly understood. In breast cancer clinical samples and in our mouse models, we identified tumor derived GM-CSF as the primary regulator of myeloid cell Arg-1 expression and local immune suppression through a gene knockout screen of breast tumor cell-produced factors. The induction of myeloid cell Arg-1 required GM-CSF and a low pH environment. GM-CSF signaling through STAT3, p38 MAPK, and acid signaling through cAMP were required to activate myeloid cell Arg-1 expression in a STAT6 independent manner. Importantly, breast tumor cell-derived GM-CSF promoted tumor progression by inhibiting host anti-tumor immunity, driving a significant accumulation of Arg-1 expressing myeloid cells compared to lung and melanoma tumors with minimal GM-CSF expression. Blockade of tumoral GM-CSF enhanced the efficacy of tumor-specific adoptive T-cell therapy and immune checkpoint blockade. Taken together, breast tumor cell-derived GM-CSF contributes to the development of the immunosuppressive breast cancer microenvironment by regulating myeloid cell Arg-1 expression and can be targeted to enhance breast cancer immunotherapy.
Xinming Su, Yalin Xu, Gregory C. Fox, Jingyu Xiang, Kristin A. Kwakwa, Jennifer L. Davis, Jad I. Belle, Wen-Chih Lee, Wing H. Wong, Francesca Fontana, Leonel Hernandez-Aya, Takayuki Kobayashi, Helen M. Tomasson, Junyi Su, Suzanne J. Bakewell, Sheila A. Stewart, Christopher Egbulefu, Partha Karmakar, Melissa A Meyer, Deborah J. Veis, David G. DeNardo, Gregory M. Lanza, Samuel Achilefu, Katherine N. Weilbaecher
Insulin resistance is present in one-quarter of the general population, predisposing to a wide-range of diseases. Our aim was to identify cell-intrinsic determinants of insulin resistance in this population using IPS cell-derived myoblasts (iMyos). We found that these cells exhibited a large network of altered protein phosphorylation in vitro. Integrating these data with data from type-2-diabetic iMyos revealed critical sites of conserved altered phosphorylation in IRS-1, AKT, mTOR and TBC1D1, in addition to changes in protein phosphorylation involved in Rho/Rac signaling, chromatin organization and RNA processing. There were also striking differences in the phosphoproteome in cells from males versus females. These sex-specific and insulin resistance defects were linked to functional differences in downstream actions. Thus, there are cell-autonomous signaling alterations associated with insulin resistance within the general population and important differences in males and females, many of which are shared with diabetes, and contribute to differences in physiology and disease.
Nida Haider, Jasmin Lebastchi, Ashok Kumar Jayavelu, Thiago M. Batista, Hui Pan, Jonathan M. Dreyfuss, Ivan Carcamo-Orive, Joshua W. Knowles, Matthias Mann, C. Ronald Kahn
Formation of nitric oxide (NO) by the endothelial NO-synthase (eNOS) is a central process in the homeostatic regulation of vascular functions including blood pressure regulation and fluid shear stress exerted by the flowing blood is a main stimulus of eNOS activity. Previous work has identified several mechanosensing and -transducing processes in endothelial cells, which mediate this process and result in the stimulation of eNOS activity through phosphorylation of the enzyme via various kinases including AKT. How the initial mechanosensing and signaling processes are linked to eNOS phosphorylation is unclear. In human endothelial cells, we demonstrated that protein kinase N2 (PKN2), which is activated by flow through the mechanosensitive cation channel Piezo1 and Gq/G11-mediated signaling, as well as Ca2+ and PDK1, plays a pivotal role in this process. Active PKN2 promoted phosphorylation of human eNOS at serine 1177 and at a newly identified site, serine 1179. These phosphorylation events additively led to increased eNOS activity. PKN2-mediated eNOS phosphorylation at serine 1177 involved phosphorylation of AKT synergistically with mTORC2-mediated AKT phosphorylation while active PKN2 directly phosphorylated human eNOS at serine 1179. Mice with induced endothelium-specific deficiency of PKN2 showed strongly reduced flow-induced vasodilation and developed arterial hypertension accompanied by reduced eNOS activation. These results uncover a central mechanism that couples upstream mechanosignaling processes in endothelial cells to the regulation of eNOS-mediated NO formation, vascular tone and blood pressure.
Young-June Jin, Ramesh Chennupati, Rui Li, Guozheng Liang, ShengPeng Wang, András Iring, Johannes Graumann, Nina Wettschureck, Stefan Offermanns
Apolipoprotein L1 (APOL1) risk-alleles in donor kidneys associate with graft loss but whether recipient risk-allele expression impacts transplant outcomes is unclear. To test whether recipient APOL1 risk-alleles independently correlate with transplant outcomes, we analyzed genome-wide SNP genotyping data of donors and recipients from two kidney transplant cohorts, Genomics of Chronic Allograft Rejection (GOCAR) and Clinical Trials in Organ Transplantation (CTOT1/17). We estimated genetic ancestry (quantified as proportion of African ancestry or pAFR) by ADMIXTURE and correlated APOL1 genotypes and pAFR with outcomes. In the GOCAR discovery set, we observed that the number of recipient APOL1 G1/G2 alleles (R-nAPOL1) associated with increased risk of death-censored allograft loss (DCAL), independent of ancestry (HR = 2.14; P = 0.006), and within the subgroup of African American and Hispanic (AA/H) recipients (HR = 2.36; P = 0.003). R-nAPOL1 also associated with increased risk of any T cell-mediated rejection (TCMR) event. These associations were validated in CTOT1/17. Ex vivo studies of peripheral blood mononuclear cells revealed unanticipated high APOL1 expression in activated CD4+/CD8+ T cells and natural killer cells. We detected enriched immune response gene pathways in risk-allele carriers vs. non-carriers on the kidney transplant waitlist and among healthy controls. Our findings demonstrate an immunomodulatory role for recipient APOL1 risk-alleles associating with TCMR and DCAL. This finding has broader implications for immune mediated injury to native kidneys.
Zhongyang Zhang, Zeguo Sun, Jia Fu, Qisheng Lin, Khadija Banu, Kinsuk Chauhan, Marina Planoutene, Chengguo Wei, Fadi Salem, Zhengzi Yi, Ruijie Liu, Paolo Cravedi, Haoxiang Cheng, Ke Hao, Philip J. O’Connell, Shuta Ishibe, Weijia Zhang, Steven G. Coca, Ian W. Gibson, Robert B. Colvin, John C. He, Peter S. Heeger, Barbara T. Murphy, Madhav C. Menon
The endocannabinoid system regulates appetite and energy expenditure and inhibitors of the cannabinoid receptor-1 (CB-1) induce weight loss with improvement in components of the metabolic syndrome. While CB-1 blockage in brain is responsible for weight loss, many of the metabolic benefits associated with CB-1 blockade have been attributed to inhibition of CB-1 signaling in the periphery. As a result, there has been interest in developing a peripherally restricted CB-1 inhibitor for the treatment of nonalcoholic fatty liver disease (NAFLD) that would lack the unwanted centrally mediated side effects. Here, we produced mice that lacked CB-1 receptors in hepatocytes or stellate cells to determine if CB-1 signaling contributes to the development of NAFLD or liver fibrosis. Deletion of CB-1 receptors in hepatocytes did not alter the development of NAFLD in mice fed a high sucrose high fat diet or high fat diet (HFD). Similarly, deletion of CB-1 deletion specifically in stellate cells also did not prevent the development of NAFLD in mice fed the HFD nor did it protect mice for carbon tetrachloride (CCl4)-induced fibrosis. Combined, these studies do not support a direct role for hepatocyte or stellate cell CB-1 signaling in the development of NAFLD or liver fibrosis.
Simeng Wang, Qingzhang Zhu, Guosheng Liang, Tania Franks, Magalie Boucher, Kendra K. Bence, Mingjian Lu, Carlos M. Castorena, Shangang Zhao, Joel K. Elmquist, Philipp E. Scherer, Jay D. Horton
JCI This Month is a digest of the research, reviews, and other features published each month.
This collection of reviews focuses on the gut-brain axis, highlighting crosstalk between the gastrointestinal tract and the enteric and central nervous systems. While the enteric nervous system can exert independent control over the gut, multi-directional communication with the central nervous system, as well as intestinal epithelial, stromal, immune, and enteroendocrine cells can result in wide-ranging influences on health and disease. The gut microbiome and its metabolites add further complexity to this intricate interactive network. Reviews in this series take a critical approach to describing the role of gut-brain connections in conditions affecting both gut and brain, with the common goal of illuminating the importance of the central and enteric nervous system interface in disease pathogenesis and identifying nodes that offer therapeutic potential.