Research Article
Abstract
β Cell apoptosis and dedifferentiation are 2 hotly debated mechanisms underlying β cell loss in type 2 diabetes; however, the molecular drivers underlying such events remain largely unclear. Here, we performed a side-by-side comparison of mice carrying β cell–specific deletion of ER-associated degradation (ERAD) and autophagy. We reported that, while autophagy was necessary for β cell survival, the highly conserved Sel1L-Hrd1 ERAD protein complex was required for the maintenance of β cell maturation and identity. Using single-cell RNA-Seq, we demonstrated that Sel1L deficiency was not associated with β cell loss, but rather loss of β cell identity. Sel1L-Hrd1 ERAD controlled β cell identity via TGF-β signaling, in part by mediating the degradation of TGF-β receptor 1. Inhibition of TGF-β signaling in Sel1L-deficient β cells augmented the expression of β cell maturation markers and increased the total insulin content. Our data revealed distinct pathogenic effects of 2 major proteolytic pathways in β cells, providing a framework for therapies targeting distinct mechanisms of protein quality control.
Authors
Neha Shrestha, Tongyu Liu, Yewei Ji, Rachel B. Reinert, Mauricio Torres, Xin Li, Maria Zhang, Chih-Hang Anthony Tang, Chih-Chi Andrew Hu, Chengyang Liu, Ali Naji, Ming Liu, Jiandie D. Lin, Sander Kersten, Peter Arvan, Ling Qi
Abstract
AMPK is a key regulator at the molecular level for maintaining energy metabolism homeostasis. Mammalian AMPK is a heterotrimeric complex, and its catalytic α subunit exists in 2 isoforms: AMPKα1 and AMPKα2. Recent studies suggest a role of AMPKα overactivation in Alzheimer’s disease–associated (AD-associated) synaptic failure. However, whether AD-associated dementia can be improved by targeting AMPK remains unclear, and roles of AMPKα isoforms in AD pathophysiology are not understood. Here, we showed distinct disruption of hippocampal AMPKα isoform expression patterns in postmortem human AD patients and AD model mice. We further investigated the effects of brain- and isoform-specific AMPKα repression on AD pathophysiology. We found that repression of AMPKα1 alleviated cognitive deficits and synaptic failure displayed in 2 separate lines of AD model mice. In contrast, AMPKα2 suppression did not alter AD pathophysiology. Using unbiased mass spectrometry–based proteomics analysis, we identified distinct patterns of protein expression associated with specific AMPKα isoform suppression in AD model mice. Further, AD-associated hyperphosphorylation of eukaryotic elongation factor 2 (eEF2) was blunted with selective AMPKα1 inhibition. Our findings reveal isoform-specific roles of AMPKα in AD pathophysiology, thus providing insights into potential therapeutic strategies for AD and related dementia syndromes.
Authors
Helena R. Zimmermann, Wenzhong Yang, Nicole P. Kasica, Xueyan Zhou, Xin Wang, Brenna C. Beckelman, Jingyun Lee, Cristina M. Furdui, C. Dirk Keene, Tao Ma
Abstract
Multiple sclerosis (MS) is an inflammatory demyelinating disorder of the CNS. Bile acids are cholesterol metabolites that can signal through receptors on cells throughout the body, including in the CNS and the immune system. Whether bile acid metabolism is abnormal in MS is unknown. Using global and targeted metabolomic profiling, we identified lower levels of circulating bile acid metabolites in multiple cohorts of adult and pediatric patients with MS compared with controls. In white matter lesions from MS brain tissue, we noted the presence of bile acid receptors on immune and glial cells. To mechanistically examine the implications of lower levels of bile acids in MS, we studied the in vitro effects of an endogenous bile acid, tauroursodeoxycholic acid (TUDCA), on astrocyte and microglial polarization. TUDCA prevented neurotoxic (A1) polarization of astrocytes and proinflammatory polarization of microglia in a dose-dependent manner. TUDCA supplementation in experimental autoimmune encephalomyelitis reduced the severity of disease through its effects on G protein–coupled bile acid receptor 1 (GPBAR1). We demonstrate that bile acid metabolism was altered in MS and that bile acid supplementation prevented polarization of astrocytes and microglia to neurotoxic phenotypes and ameliorated neuropathology in an animal model of MS. These findings identify dysregulated bile acid metabolism as a potential therapeutic target in MS.
Authors
Pavan Bhargava, Matthew D. Smith, Leah Mische, Emily Harrington, Kathryn C. Fitzgerald, Kyle Martin, Sol Kim, Arthur Anthony Reyes, Jaime Gonzalez-Cardona, Christina Volsko, Ajai Tripathi, Sonal Singh, Kesava Varanasi, Hannah-Noelle Lord, Keya Meyers, Michelle Taylor, Marjan Gharagozloo, Elias S. Sotirchos, Bardia Nourbakhsh, Ranjan Dutta, Ellen M. Mowry, Emmanuelle Waubant, Peter A. Calabresi
Abstract
The sensory nerve was recently identified as being involved in regulation of bone mass accrual. We previously discovered that prostaglandin E2 (PGE2) secreted by osteoblasts could activate sensory nerve EP4 receptor to promote bone formation by inhibiting sympathetic activity. However, the fundamental units of bone formation are active osteoblasts, which originate from mesenchymal stromal/stem cells (MSCs). Here, we found that after sensory denervation, knockout of the EP4 receptor in sensory nerves, or knockout of COX-2 in osteoblasts, could significantly promote adipogenesis and inhibit osteogenesis in adult mice. Furthermore, injection of SW033291 (a small molecule that locally increases the PGE2 level) or propranolol (a beta blocker) significantly promoted osteogenesis and inhibited adipogenesis. This effect of SW033291, but not propranolol, was abolished in conditional EP4-KO mice under normal conditions or in the bone repair process. We conclude that the PGE2/EP4 sensory nerve axis could regulate MSC differentiation in bone marrow of adult mice.
Authors
Bo Hu, Xiao Lv, Hao Chen, Peng Xue, Bo Gao, Xiao Wang, Gehua Zhen, Janet L. Crane, Dayu Pan, Shen Liu, Shuangfei Ni, Panfeng Wu, Weiping Su, Xiaonan Liu, Zemin Ling, Mi Yang, Ruoxian Deng, Yusheng Li, Lei Wang, Ying Zhang, Mei Wan, Zengwu Shao, Huajiang Chen, Wen Yuan, Xu Cao
Abstract
Alloantibodies in presensitized transplant candidates deposit complement membrane attack complexes (MACs) on graft endothelial cells (ECs), increasing risk of CD8+ T cell–mediated acute rejection. We recently showed that human ECs endocytose MACs into Rab5+ endosomes, creating a signaling platform that stabilizes NF-κB–inducing kinase (NIK) protein. Endosomal NIK activates both noncanonical NF-κB signaling to synthesize pro–IL-1β and an NLRP3 inflammasome to process and secrete active IL-1β. IL-1β activates ECs, increasing recruitment and activation of alloreactive effector memory CD4+ T (Tem) cells. Here, we report that IFN-γ priming induced nuclear expression of IL-15/IL-15Rα complexes in cultured human ECs and that MAC-induced IL-1β stimulated translocation of IL-15/IL-15Rα complexes to the EC surface in a canonical NF-κB–dependent process in which IL-15/IL-15Rα transpresentation increased activation and maturation of alloreactive CD8+ Tem cells. Blocking NLRP3 inflammasome assembly, IL-1 receptor, or IL-15 on ECs inhibited the augmented CD8+ Tem cell responses, indicating that this pathway is not redundant. Adoptively transferred alloantibody and mouse complement deposition induced IL-15/IL-15Rα expression by human ECs lining human coronary artery grafts in immunodeficient mice, and enhanced intimal CD8+ T cell infiltration, which was markedly reduced by inflammasome inhibition, linking alloantibody to acute rejection. Inhibiting MAC signaling may similarly limit other complement-mediated pathologies.
Authors
Catherine B. Xie, Bo Jiang, Lingfeng Qin, George Tellides, Nancy C. Kirkiles-Smith, Dan Jane-wit, Jordan S. Pober
Abstract
Plasmacytoid DCs (pDCs), the major producers of type I interferon, are principally recognized as key mediators of antiviral immunity. However, their role in tumor immunity is less clear. Depending on the context, pDCs can promote or suppress antitumor immune responses. In this study, we identified a naturally occurring pDC subset expressing high levels of OX40 (OX40+ pDC) enriched in the tumor microenvironment (TME) of head and neck squamous cell carcinoma. OX40+ pDCs were distinguished by a distinct immunostimulatory phenotype, cytolytic function, and ability to synergize with conventional DCs (cDCs) in generating potent tumor antigen–specific CD8+ T cell responses. Transcriptomically, we found that they selectively utilized EIF2 signaling and oxidative phosphorylation pathways. Moreover, depletion of pDCs in the murine OX40+ pDC–rich tumor model accelerated tumor growth. Collectively, we present evidence of a pDC subset in the TME that favors antitumor immunity.
Authors
Kate Poropatich, Donye Dominguez, Wen-Ching Chan, Jorge Andrade, Yuanyuan Zha, Brian Wray, Jason Miska, Lei Qin, Lisa Cole, Sydney Coates, Urjeet Patel, Sandeep Samant, Bin Zhang
Abstract
The absence of alloantibodies is a feature of transplantation tolerance. Although the lack of T cell help has been evoked to explain this absence, herein we provide evidence for B cell–intrinsic tolerance mechanisms. Using a murine model of heart tolerance, we showed that alloreactive B cells were not deleted but rapidly lost their ability to differentiate into germinal center B cells and secrete donor-specific antibodies. We inferred that tolerant alloreactive B cells retained their ability to sense alloantigen because they continued to drive T cell maturation into CXCR5+PD-1+ T follicular helper cells. Unexpectedly, dysfunctional alloreactive B cells acquired the ability to inhibit antibody production by new naive B cells in an antigen-specific manner. Thus, tolerant alloreactive B cells contribute to transplantation tolerance by foregoing germinal center responses while retaining their ability to function as antigen-presenting cells and by actively suppressing de novo alloreactive B cell responses.
Authors
Stella H.W. Khiew, Dharmendra Jain, Jianjun Chen, Jinghui Yang, Dengping Yin, James S. Young, Alexander Dent, Roger Sciammas, Maria-Luisa Alegre, Anita S. Chong
Abstract
Vaccination is a mainstay in preventive medicine, reducing morbidity and mortality from infection, largely by generating pathogen-specific neutralizing antibodies. However, standard immunization strategies are insufficient with increasing age due to immunological impediments, including defects in T follicular helper (Tfh) cells. Here, we found that Tfh generation is inversely linked to the expression of the ecto-NTPDase CD39 that modifies purinergic signaling. The lineage-determining transcription factor BCL6 inhibited CD39 expression, while increased Tfh frequencies were found in individuals with a germline polymorphism preventing transcription of ENTPD1, encoding CD39. In in vitro human and in vivo mouse studies, Tfh generation and germinal center responses were enhanced by reducing CD39 expression through the inhibition of the cAMP/PKA/p-CREB pathway, or by blocking adenosine signaling downstream of CD39 using the selective adenosine A2a receptor antagonist istradefylline. Thus, purinergic signaling in differentiating T cells can be targeted to improve vaccine responses, in particular in older individuals who have increased CD39 expression.
Authors
Wenqiang Cao, Fengqin Fang, Timothy Gould, Xuanying Li, Chulwoo Kim, Claire Gustafson, Simon Lambert, Cornelia M. Weyand, Jörg J. Goronzy
Abstract
The atypical cadherin FAT4 has established roles in the regulation of planar cell polarity and Hippo pathway signaling that are cell context dependent. The recent identification of FAT4 mutations in Hennekam syndrome, features of which include lymphedema, lymphangiectasia, and mental retardation, uncovered an important role for FAT4 in the lymphatic vasculature. Hennekam syndrome is also caused by mutations in collagen and calcium binding EGF domains 1 (CCBE1) and ADAM metallopeptidase with thrombospondin type 1 motif 3 (ADAMTS3), encoding a matrix protein and protease, respectively, that regulate activity of the key prolymphangiogenic VEGF-C/VEGFR3 signaling axis by facilitating the proteolytic cleavage and activation of VEGF-C. The fact that FAT4, CCBE1, and ADAMTS3 mutations underlie Hennekam syndrome suggested that all 3 genes might function in a common pathway. We identified FAT4 as a target gene of GATA-binding protein 2 (GATA2), a key transcriptional regulator of lymphatic vascular development and, in particular, lymphatic vessel valve development. Here, we demonstrate that FAT4 functions in a lymphatic endothelial cell–autonomous manner to control cell polarity in response to flow and is required for lymphatic vessel morphogenesis throughout development. Our data reveal a crucial role for FAT4 in lymphangiogenesis and shed light on the mechanistic basis by which FAT4 mutations underlie a human lymphedema syndrome.
Authors
Kelly L. Betterman, Drew L. Sutton, Genevieve A. Secker, Jan Kazenwadel, Anna Oszmiana, Lillian Lim, Naoyuki Miura, Lydia Sorokin, Benjamin M. Hogan, Mark L. Kahn, Helen McNeill, Natasha L. Harvey
Abstract
Neutrophilic inflammation is central to disease pathogenesis, for example, in chronic obstructive pulmonary disease, yet the mechanisms that retain neutrophils within tissues remain poorly understood. With emerging evidence that axon guidance factors can regulate myeloid recruitment and that neutrophils can regulate expression of a class 3 semaphorin, SEMA3F, we investigated the role of SEMA3F in inflammatory cell retention within inflamed tissues. We observed that neutrophils upregulate SEMA3F in response to proinflammatory mediators and following neutrophil recruitment to the inflamed lung. In both zebrafish tail injury and murine acute lung injury models of neutrophilic inflammation, overexpression of SEMA3F delayed inflammation resolution with slower neutrophil migratory speeds and retention of neutrophils within the tissues. Conversely, constitutive loss of sema3f accelerated egress of neutrophils from the tail injury site in fish, whereas neutrophil-specific deletion of Sema3f in mice resulted in more rapid neutrophil transit through the airways, and significantly reduced time to resolution of the neutrophilic response. Study of filamentous-actin (F-actin) subsequently showed that SEMA3F-mediated retention is associated with F-actin disassembly. In conclusion, SEMA3F signaling actively regulates neutrophil retention within the injured tissues with consequences for neutrophil clearance and inflammation resolution.
Authors
Tracie Plant, Suttida Eamsamarng, Manuel A. Sanchez-Garcia, Leila Reyes, Stephen A. Renshaw, Patricia Coelho, Ananda S. Mirchandani, Jessie-May Morgan, Felix E. Ellett, Tyler Morrison, Duncan Humphries, Emily R. Watts, Fiona Murphy, Ximena L. Raffo-Iraolagoitia, Ailiang Zhang, Jenna L. Cash, Catherine Loynes, Philip M. Elks, Freek Van Eeden, Leo M. Carlin, Andrew J.W. Furley, Moira K.B. Whyte, Sarah R. Walmsley
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Copyright © 2020 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)