Cell biologies
Abstract
Programmed death-ligand 1 (PD-L1), a critical immune checkpoint ligand, is a transmembrane protein synthesized in the endoplasmic reticulum of tumor cells and transported to the plasma membrane to interact with programmed death 1 (PD-1) expressed on T cell surface. This interaction delivers coinhibitory signals to T cells, thereby suppressing their function and allowing evasion of antitumor immunity. Most companion or complementary diagnostic devices for assessing PD-L1 expression levels in tumor cells used in the clinic or in clinical trials require membranous staining. However, the mechanism driving PD-L1 translocation to the plasma membrane after de novo synthesis is poorly understood. Herein, we showed that mind bomb homolog 2 (MIB2) is required for PD-L1 transportation from the trans-Golgi network (TGN) to the plasma membrane of cancer cells. MIB2 deficiency led to fewer PD-L1 proteins on the tumor cell surface and promoted antitumor immunity in mice. Mechanistically, MIB2 catalyzed nonproteolytic K63-linked ubiquitination of PD-L1, facilitating PD-L1 trafficking through Ras-associated binding 8–mediated (RAB8-mediated) exocytosis from the TGN to the plasma membrane, where it bound PD-1 extrinsically to prevent tumor cell killing by T cells. Our findings demonstrate that nonproteolytic ubiquitination of PD-L1 by MIB2 is required for its transportation to the plasma membrane and tumor cell immune evasion.
Authors
Xinfang Yu, Wei Li, Haidan Liu, Xu Wang, Cristian Coarfa, Chao Cheng, Xinlian Yu, Zhaoyang Zeng, Ya Cao, Ken H. Young, Yong Li
Abstract
SIPRα on macrophages binds with CD47 to resist pro-engulfment signals, but how the downstream signal of SIPRα controls tumor-infiltrating macrophages (TIMs) is still poorly clarified. Here we reported that the CD47/SIRPα axis requires the deneddylation of tyrosine phosphatase SHP2. Mechanistically, SHP2 is constitutively neddylated on K358 and K364 sites, thus its auto-inhibited conformation is maintained. In response to CD47-liganded SIRPα, SHP2 is deneddylated by SENP8, which leads to the dephosphorylation of relevant substrates at the phagocytic cup and subsequent inhibition of macrophage phagocytosis. Furthermore, neddylation inactivated myeloid-SHP2 and greatly boosted the efficacy of colorectal cancer (CRC) immunotherapy. Importantly, we observed that the supplementation with SHP2 allosteric inhibitors sensitized the immune treatment-resistant CRC to immunotherapy. Our results emphasized that the CRC subtype which is unresponsive to immunotherapy relies on SIRPαhiSHP2hiNEDD8lo TIMs, and highlighted the need to further combine the strategy of SHP2 targeting in colorectal cancer therapy.
Authors
Yiqing Li, Hui Zhou, Pan Liu, Dandan Lv, Yichun Shi, Bufu Tang, Jiaqi Xu, Tingting Zhong, Wangting Xu, Jie Zhang, Jianying Zhou, Kejing Ying, Yongchao Zhao, YI Sun, Zhinong Jiang, Hongqiang Cheng, Xue Zhang, Yue-Hai Ke
Abstract
Ubiquitin-conjugating enzyme E2C (UBE2C) mediates the ubiquitylation chain formation via the K11 linkage. While previous in vitro studies showed that UBE2C plays a growth-promoting role in cancer cell lines, the underlying mechanism remains elusive. Still unknown is whether and how UBE2C plays a promoting role in vivo. Here we reported that UBE2C is indeed essential for growth and survival of lung cancer cells harboring Kras mutations, and UBE2C is required for KrasG12D-induced lung tumorigenesis, since Ube2c deletion significantly inhibits tumor formation and extends the life-span of mice. Mechanistically, KrasG12D induces expression of UBE2C, which couples with APC/CCDH1 E3 ligase to promote ubiquitylation and degradation of DEPTOR, leading to activation of the mTORC signals. Importantly, DEPTOR levels are fluctuated during cell cycle progression in a manner dependent of UBE2C and CDH1, indicating their physiological connection. Finally, Deptor deletion fully rescues the tumor inhibitory effect of Ube2c deletion in the KrasG12D lung tumor model, indicating a causal role of Deptor. Taken together, our study shows that the UBE2C/CDH1/DEPTOR axis forms an oncogene-tumor suppressor cascade that regulates cell cycle progression and autophagy and validates that UBE2C is an attractive target for lung cancer associated with Kras mutations.
Authors
Shizhen Zhang, Xiahong You, Yawen Zheng, Yanwen Shen, Xiufang Xiong, Yi Sun
Abstract
Leptin exerts its biological actions by activating LepRb. LepRb signaling impairment and leptin resistance are believed to cause obesity. Transcription factor Slug (also known as Snai2) recruits epigenetic modifiers and regulates gene expression by an epigenetic mechanism; however, its epigenetic action has not been explored in leptin resistance. Here, we uncover a pro-obesity function of neuronal Slug. Hypothalamic Slug was upregulated in obese mice. LepRb cell-specific Slug knockout (SlugΔLepRb) mice were resistant to diet-induced obesity, type 2 diabetes, and liver steatosis, accompanied by decreased food intake and increased fat thermogenesis. Leptin stimulated hypothalamic Stat3 phosphorylation and weight loss to a significantly higher level in SlugΔLepRb than in Slugf/f mice even before their body weight divergence. Conversely, hypothalamic LepRb neuron-specific overexpression of Slug, mediated by AAV-DIO-Slug transduction, induced leptin resistance, obesity, and metabolic disorders in mice on a chow diet. At the genomic level, Slug bound to and repressed the LepRb promoter, thereby inhibiting LepRb transcription. Consistently, Slug deficiency decreased LepRb promoter histone 3 lysine-27 methylations, repressive epigenetic marks, and increased LepRb mRNA levels in the hypothalamus. Collectively, these results unravel a previously-unrecognized hypothalamic neuronal Slug/epigenetic reprogramming/leptin resistance axis that promotes energy imbalance, obesity, and metabolic disease.
Authors
Min-Hyun Kim, Yuan Li, Qiantao Zheng, Lin Jiang, Martin G. Myers, Wen-Shu Wu, Liangyou Rui
Abstract
Modification of cysteine residues by oxidative and nitrosative stress affects structure and function of proteins, thereby contributing to the pathogenesis of cardiovascular disease. Although the major function of thioredoxin 1 (Trx1) is to reduce disulfide bonds, it can also act as either a denitrosylase or transnitrosylase in a context-dependent manner. Here we show that Trx1 transnitrosylates Atg7, an E1-like enzyme, thereby stimulating autophagy. Trx1 was S-nitrosylated at Cys73 when Cys32-35, the oxidoreductase catalytic center, was oxidized and forms a disulfide bond during ischemia. Unexpectedly, Atg7 Cys545-548 reduced the disulfide bond in Trx1 at Cys32-35 through thiol-disulfide exchange and this then allowed NO to be released from Cys73 in Trx1 and transferred to Atg7 at Cys402. Experiments conducted with Atg7 C402S knock-in mice showed that S-nitrosylation of Atg7 at Cys402 promotes autophagy by stimulating E1-like activity, thereby protecting the heart against ischemia. These results suggest that the thiol-disulfide exchange and the NO transfer are functionally coupled, allowing oxidized Trx1 to mediate a salutary effect during myocardial ischemia through transnitrosylation of Atg7 and stimulation of autophagy.
Authors
Narayani Nagarajan, Shin-ichi Oka, Jihoon Nah, Changgong Wu, Peiyong Zhai, Risa Mukai, Xiaoyong Xu, Sanchita Kashyap, Chun-Yang Huang, Eun-Ah Sung, Wataru Mizushima, Allen Sam Titus, Koichiro Takayama, Youssef Mourad, Jamie Francisco, Tong Liu, Tong Chen, Hong Li, Junichi Sadoshima
Abstract
Three principal ER quality-control mechanisms, namely, unfolded protein response (UPR), ER-associated degradation (ERAD) and ER-phagy are each important for the maintenance of ER homeostasis, yet how they are integrated to regulate ER homeostasis and organellar architecture in vivo is largely unclear. Here we report intricate crosstalk among the three pathways, centered around the SEL1L-HRD1 protein complex of ERAD, in the regulation of organellar organization in β-cells. SEL1L-HRD1 ERAD deficiency in β-cells triggers activation of autophagy via IRE1α [an endogenous ERAD substrate]. In the absence of functional SEL1L-HRD1 ERAD, proinsulin is retained in the ER as high molecular weight conformers, which are subsequently cleared via ER-phagy. A combined loss of both SEL1L and autophagy in β-cells leads to diabetes in mice shortly after weaning, with premature death by ~11 weeks of age, associated with marked ER retention of proinsulin and β-cell loss. Using focus-ion beam scanning electron microscopy (FIB-SEM) powered by deep-learning automated image segmentation and 3D reconstruction, our data demonstrate a profound organellar restructuring with a massive expansion of ER volume and network in β-cells lacking both SEL1L and autophagy. These data reveal at an unprecedented detail the intimate crosstalk among the three ER quality-control mechanisms in the dynamic regulation of organellar architecture and β-cell function.
Authors
Neha Shrestha, Mauricio Torres, Jason Zhang, You Lu, Leena Haataja, Rachel B. Reinert, Jeffrey Knupp, Yu-Jie Chen, Gunes Parlakgul, Ana Paula Arruda, Billy Tsai, Peter Arvan, Ling Qi
Abstract
Invasive bacterial infections remain a major cause of human morbidity. Group B Streptococcus (GBS) are Gram-positive bacteria that cause invasive infections in humans. Here, we show that Factor XIIIA (FXIIIA) -deficient female mice exhibited significantly increased susceptibility to GBS infections. Additionally, female wild-type mice had increased levels of FXIIIA and were more resistant to GBS infection compared to isogenic male mice. We observed that administration of exogenous FXIIIA to male mice increased host resistance to GBS infection. Conversely, administration of a FXIIIA transglutaminase inhibitor to female mice decreased host resistance to GBS infection. Interestingly, male gonadectomized mice exhibited decreased sensitivity to GBS infection, suggesting a role for gonadal androgens in host susceptibility. FXIIIA promoted GBS entrapment within fibrin clots by crosslinking fibronectin with ScpB, a fibronectin binding GBS surface protein. Thus, ScpB-deficient GBS exhibited decreased entrapment within fibrin clots in vitro and increased dissemination during systemic infections. Finally, using mice where FXIIIA expression was depleted in mast cells, we observed that mast cell derived FXIIIA contributes to host defense against GBS infection. Our studies provide insights into the effect of sexual dimorphism and mast cells on FXIIIA expression and its interactions with GBS adhesins that mediate bacterial dissemination and pathogenesis.
Authors
Adrian M. Piliponsky, Kavita Sharma, Phoenicia Quach, Alyssa Brokaw, Shayla Nguyen, Austyn Orvis, Siddhartha S. Saha, Nyssa Becker Samanas, Ravin Seepersaud, Yu Ping Tang, Emily Mackey, Gauri Bhise, Claire Gendrin, Anna Furuta, Albert J. Seo, Eric Guga, Irina Miralda, Michelle M. Coleman, Erin L. Sweeney, Charlotte A. Bäuml, Diana Imhof, Jessica M. Snyder, Adam J. Moeser, Lakshmi Rajagopal
Abstract
Bone is a common site of metastasis in lung cancer but the regulatory mechanism remains incompletely understood. Osteoclasts are known to play crucial roles in osteolytic bone metastasis by digesting bone matrix and indirectly enhancing tumor colonization. In this study, we found that IL20RB mediated a direct tumoral response to osteoclasts. Tumoral expression of IL20RB was associated with bone metastasis of lung cancer, and functionally IL20RB promoted metastatic growth of lung cancer cells in bone. Mechanistically, tumor cells induced osteoclasts to secrete the IL20RB ligand IL19, and IL19 stimulated IL20RB-expressing tumor cells to activate the downstream JAK1-STAT3 signaling and enhanced proliferation of tumor cells in bone. Importantly, blocking IL20RB with a neutralizing antibody significantly suppressed bone metastasis of lung cancer. Overall, our data revealed a direct pro-tumor role of osteoclastic niche in bone metastasis and supported IL20RB-targeting approaches for metastasis treatment.
Authors
Yunfei He, Wenqian Luo, Yingjie Liu, Yuan Wang, Chengxin Ma, Qiuyao Wu, Pu Tian, Dasa He, Zhenchang Jia, Xianzhe Lv, Yu-Shui Ma, Haitang Yang, Ke Xu, Xue Zhang, Yansen Xiao, Peiyuan Zhang, Yajun Liang, Da Fu, Feng Yao, Guohong Hu
Abstract
The switch from anchorage-dependent to anchorage-independent growth is essential for epithelial metastasis. The underlying mechanism, however, is not fully understood. Here in this study, we identified growth factor independent-1 (GFI1), a transcription factor that drives transition from adherent endothelial cells to suspended hematopoietic cells during hematopoiesis, as a critical regulator of anchorage-independence in lung cancer cells. GFI1 elevated the numbers of circulating and lung infiltrating tumor cells in xenograft models and predicted poor prognosis of lung cancer patients. Mechanistically, GFI1 inhibited the expression of multiple adhesion molecules and facilitated substrate detachment. Concomitantly, GFI1 reconfigured chromatin structure of the RASGRP2 gene and increased its expression, causing Rap1 activation and subsequent sustained ERK activation upon detachment, and this leaded to ERK signaling dependency in tumor cells. Our studies unveiled a mechanism by which carcinoma cells hijacked a hematopoietic factor to gain anchorage independence and suggested that the intervention of ERK signaling may suppress metastasis and improve the therapeutic outcome of GFI1-positive lung cancer patients.
Authors
Hao Wang, Zhenzhen Lin, Zhe Nian, Wei Zhang, Wenxu Liu, Fei Yan, Zengtuan Xiao, Xia Wang, Zhenfa Zhang, Zhenyi Ma, Zhe Liu
Abstract
Lymph node (LN) fibroblastic reticular cells (FRCs) define LN niches and regulate lymphocyte homeostasis through producing diverse extracellular matrix (ECM) components. We examined the role of ECM laminin α4 (Lama4) using FRC-Lama4 conditional KO Pdgfrb-Cre–/– × Lama4fl/fl mice. Single-cell RNA-sequencing (scRNA-Seq) data showed the promoter gene Pdgfrb was exclusively expressed in FRCs. Depleting FRC-Lama4 reduced Tregs and dendritic cells, decreased high endothelial venules, impaired the conduit system, and downregulated T cell survival factors in LNs. FRC-Lama4 depletion impaired the homing of lymphocytes to LNs in homeostasis and after allografting. Alloantigen-specific T cells proliferated, were activated to greater degrees in LNs lacking FRC-Lama4, and were more prone to differentiate into effector phenotypes relative to the Treg phenotype. In murine cardiac transplantation, tolerogenic immunosuppression was not effective in FRC-Lama4 recipients, which produced more alloantibodies than WT. After lung transplantation, FRC-Lama4–KO mice had more severe graft rejection with fewer Tregs in their LNs. Overall, FRC-Lama4 critically contributes to a tolerogenic LN niche by supporting T cell migration, constraining T cell activation and proliferation, and promoting Treg differentiation. Hence, it serves as a therapeutic target for immunoengineering.
Authors
Lushen Li, Marina W. Shirkey, Tianshu Zhang, Wenji Piao, Xiaofei Li, Jing Zhao, Zhongcheng Mei, Yizhan Guo, Vikas Saxena, Allison Kensiski, Samuel J. Gavzy, Yang Song, Bing Ma, Jing Wu, Yanbao Xiong, Long Wu, Xiaoxuan Fan, Holly Roussey, Meng Li, Alexæander S. Krupnick, Reza Abdi, Jonathan S. Bromberg
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Copyright © 2023 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)