The importance of the proper localization of most receptors at the cell surface is often underestimated, although this feature is essential for optimal receptor response. Endospanin 1 (Endo1) (also known as OBRGRP or LEPROT) is a protein generated from the same gene as the human leptin receptor and regulates the trafficking of proteins to the surface, including the leptin receptor. The systemic role of Endo1 on whole-body metabolism has not been studied so far. Here, we report that general Endo1-KO mice fed a high-fat diet develop metabolically healthy obesity with lipid repartitioning in organs and preferential accumulation of fat in adipose tissue, limited systematic inflammation, and better controlled glucose homeostasis. Mechanistically, Endo1 interacts with the lipid translocase CD36, thus regulating its surface abundance and lipid uptake in adipocytes. In humans, the level of Endo1 transcripts is increased in the adipose tissue of patients with obesity, but low levels rather correlate with a profile of metabolically healthy obesity. We suggest here that Endo1, most likely by controlling CD36 cell surface abundance and lipid uptake in adipocytes, dissociates obesity from diabetes and that its absence participates in metabolically healthy obesity.
Arturo Roca-Rivada, Marcio Do Cruzeiro, Raphaël G.P. Denis, Qiang Zhang, Christine Rouault, Yves Rouillé, Jean-Marie Launay, Céline Cruciani-Guglielmacci, Virginie Mattot, Karine Clément, Ralf Jockers, Julie Dam
Portal hypertension (PHTN) is a severe complication of liver cirrhosis and is associated with intrahepatic sinusoidal remodeling induced by sinusoidal resistance and angiogenesis. Collagen type IV (COL4), a major component of basement membrane, forms in liver sinusoids upon chronic liver injury. However, the role, the cellular source and expression regulation of COL4 in liver diseases is unknown. Here, we examined how COL4 is produced and how it regulates sinusoidal remodeling in fibrosis and PHTN. Human cirrhotic liver sample RNA-sequencing showed increased COL4 expression, which was further confirmed via immunofluorescence staining. scRNA-sequencing identified liver sinusoidal endothelial cells (LSECs) as the predominant source of COL4 upregulation in mouse fibrotic liver. In addition, COL4 was upregulated in a tumor necrosis factor α–nuclear factor–κB dependent manner through an epigenetic mechanism in liver sinusoidal endothelial cells in vitro. Indeed, by utilizing a CRISPRi-dCas9-KRAB-mediated epigenome editing approach, epigenetic repression of the enhancer-promoter interaction showed silencing of COL4 gene expression. LSEC-specific COL4 gene mutation or repression in vivo abrogated sinusoidal resistance and angiogenesis, which thereby alleviated sinusoidal remodeling and PHTN. Our findings reveal that LSECs promote sinusoidal remodeling and PHTN during liver fibrosis through COL4 deposition.
Can Gan, Usman Yaqoob, Jianwen Lu, Man Xie, Abid A. Anwar, Nidhi Jalan-Sakrikar, Sofia Jerez, Tejasav Sehrawat, Amaia Navarro-Corcuera, Enis Kostallari, Nawras W. Habash, Sheng Cao, Vijay H. Shah
The roles of fibronectin leucine-rich transmembrane protein 2 (FLRT2) in physiological and pathological processes are not well known. Here, we identify a potentially novel function of FLRT2 in preventing endothelial cell senescence and vascular aging. We found that FLRT2 expression was lower in cultured senescent endothelial cells as well as in aged rat and human vascular tissues. FLRT2 mediated endothelial cell senescence via the mTOR complex 2, AKT, and p53 signaling pathway in human endothelial cells. We uncovered that FLRT2 directly associated with integrin subunit beta 4 (ITGB4) and thereby promoted ITGB4 phosphorylation, while inhibition of ITGB4 substantially mitigated the induction of senescence triggered by FLRT2 depletion. Importantly, FLRT2 silencing in mice promoted vascular aging, and overexpression of FLRT2 rescued a premature vascular aging phenotype. Therefore, we propose that FLRT2 could be targeted therapeutically to prevent senescence-associated vascular aging.
Hyun Jung Hwang, Donghee Kang, Jae-Ryong Kim, Joon Hyuk Choi, Ji-Kan Ryu, Allison B. Herman, Young-Gyu Ko, Heon Joo Park, Myriam Gorospe, Jae-Seon Lee
Thrombosis and inflammation are intimately linked and synergistically contribute to the pathogenesis of numerous thromboinflammatory diseases, including sickle cell disease (SCD). While platelets are central to thrombogenesis and inflammation, the molecular mechanisms of crosstalk between the 2 remain elusive. High-mobility group box 1 (HMGB1) regulates inflammation and stimulates platelet activation through Toll-like receptor 4. However, it remains unclear whether HMGB1 modulates other thrombotic agonists to regulate platelet activation. Herein, using human platelets, we demonstrate that HMGB1 significantly enhanced ADP-mediated platelet activation. Furthermore, inhibition of the purinergic receptor P2Y12 attenuated HMGB1-dependent platelet activation. Mechanistically, we show that HMGB1 stimulated ADP secretion, while concomitantly increasing P2Y12 levels at the platelet membrane. We show that in SCD patients, increased plasma HMGB1 levels were associated with heightened platelet activation and surface P2Y12 expression. Treatment of healthy platelets with plasma from SCD patients enhanced platelet activation and surface P2Y12, and increased sensitivity to ADP-mediated activation, and these effects were linked to plasma HMGB1. We conclude that HMGB1-mediated platelet activation involves ADP-dependent P2Y12 signaling, and HMGB1 primes platelets for ADP signaling. This complementary agonism between ADP and HMGB1 furthers the understanding of thromboinflammatory signaling in conditions such as SCD, and provides insight for therapeutic P2Y12 inhibition.
Deirdre Nolfi-Donegan, Gowtham K. Annarapu, Claudette St. Croix, Michael Calderon, Cheryl A. Hillery, Sruti Shiva
Myocardial ischemia/reperfusion (MI/R) injury is a major cause of adverse outcomes of revascularization following myocardial infarction. Anaerobic glycolysis during myocardial ischemia is well-studied, but the role of aerobic glycolysis during the early phase of reperfusion is incompletely understood. Lactylation of Histone H3 (H3) is an epigenetic indicator of the glycolytic switch. Heat shock protein A12A (HSPA12A) is an atypic member of the HSP70 family. In the present study, we report that during reperfusion following myocardial ischemia, HSPA12A was downregulated and aerobic glycolytic flux was decreased in cardiomyocytes. Notably, HSPA12A knockout in mice exacerbated MI/R-induced aerobic glycolysis decrease, cardiomyocyte death, and cardiac dysfunction. Gain- and loss-of-function studies demonstrated that HSPA12A was required to support cardiomyocyte survival upon hypoxia/reoxygenation (H/R) challenge, and that its protective effects were mediated by maintaining aerobic glycolytic homeostasis for H3 lactylation. Further analyses revealed that HSPA12A increased Smurf1-mediated Hif1α protein stability, thus increasing glycolytic gene expression to maintain appropriate aerobic glycolytic activity to sustain H3 lactylation during reperfusion, and ultimately improving cardiomyocyte survival to attenuate MI/R injury.
Wansu Yu, Qiuyue Kong, Surong Jiang, Yunfan Li, Zhaohe Wang, Qian Mao, Xiaojin Zhang, Qianhui Liu, Pengjun Zhang, Yuehua Li, Chuanfu Li, Zhengnian Ding, Li Liu
In humans, Type 2 Diabetes Mellitus (T2DM) shows a higher prevalence in men compared to women, phenotype that has been attributed to a lower peripheral insulin sensitivity in men. Whether sex-specific differences in pancreatic β-cell function also contribute is largely unknown. Here we characterized the electrophysiological properties of β-cells in intact mouse male and female islets. Elevation of glucose concentration above 5 mM triggers an electrical activity with a similar glucose dependence in β-cells of both sexes. However, female β-cells have a more depolarized membrane potential and increased firing frequency compared to males. The higher membrane depolarization in female β-cells is caused by ~50% smaller Kv2.1 K+ currents compared to males but otherwise unchanged KATP, Ca2+-activated BK and SK, and background TASK1/TALK1 K+ current densities. In female β-cells the higher depolarization causes a membrane potential-dependent inactivation of the voltage-gated Ca2+ channels (CaV) resulting in reduced Ca2+ entry. Nevertheless, this reduced Ca2+ influx is offset by the higher action potential firing frequency. Since exocytosis of insulin granules does not show a sex-specific difference we conclude that the higher electrical activity promotes insulin release in females improving glucose tolerance.
Noelia Jacobo-Piqueras, Tamara Theiner, Stefanie M. Geisler, Petronel Tuluc
Linear ubiquitin chains, which are generated specifically by the linear ubiquitin assembly complex (LUBAC) ubiquitin ligase, play crucial roles in immune signaling, including NF-κB activation. LUBAC comprises catalytic large isoform of heme-oxidized iron regulatory protein 2 ubiquitin ligase 1 (HOIL-1L) interacting protein (HOIP), accessory HOIL-1L, and SHANK-associated RH domain-interacting protein (SHARPIN). Deletion of the ubiquitin ligase activity of HOIL-1L, an accessory ligase of LUBAC, augments LUBAC functions by enhancing LUBAC-mediated linear ubiquitination, which is catalyzed by HOIP. Here, we show that HOIL-1L ΔRING1 mice, which exhibit augmented LUBAC functions upon loss of the HOIL-1L ligase, developed systemic lupus erythematosus (SLE) and Sjögren’s syndrome in a female-dominant fashion. Augmented LUBAC activity led to hyperactivation of both lymphoid and myeloid cells. In line with the findings in mice, we sought to identify missense single nucleotide polymorphisms/variations of the RBCK1/HOIL-1L gene in humans that attenuate HOIL-1L ligase activity. We found that the R464H variant, which is encoded by rs774507518 within the RBCK1/HOIL-1L gene, attenuated HOIL-1L ligase activity and augmented LUBAC-mediated immune signaling, including that mediated by Toll-like receptors. We also found that rs774507518 was enriched significantly in patients with SLE, strongly suggesting that RBCK1/HOIL-1L is an SLE susceptibility gene and that augmented linear ubiquitin signaling generated specifically by LUBAC underlies the pathogenesis of this prototype systemic autoimmune disease.
Yasuhiro Fuseya, Keiichiro Kadoba, Xiaoxi Liu, Hiroyuki Suetsugu, Takeshi Iwasaki, Koichiro Ohmura, Takayuki Sumida, Yuta Kochi, Akio Morinobu, Chikashi Terao, Kazuhiro Iwai
The glucocerebrosidase (GCase) encoded by the GBA1 gene hydrolyzes glucosylceramide (GluCer) to ceramide and glucose in lysosomes. Homozygous or compound heterozygous GBA1 mutations cause the lysosomal storage disease Gaucher disease (GD) due to severe loss of GCase activity. Loss-of-function variants in the GBA1 gene are also the most common genetic risk factor for Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). Restoring lysosomal GCase activity represents an important therapeutic approach for GBA1-associated diseases. We hypothesized that increasing the stability of lysosomal GCase protein could correct deficient GCase activity in these conditions. However, it remains unknown how GCase stability is regulated in the lysosome. We found that cathepsin L, a lysosomal cysteine protease, cleaves GCase and regulates its stability. In support of these data, GCase protein was elevated in the brain of cathepsin L–KO mice. Chemical inhibition of cathepsin L increased both GCase levels and activity in fibroblasts from patients with GD. Importantly, inhibition of cathepsin L in dopaminergic neurons from a patient GBA1-PD led to increased GCase levels and activity as well as reduced phosphorylated α-synuclein. These results suggest that targeting cathepsin L–mediated GCase degradation represents a potential therapeutic strategy for GCase deficiency in PD and related disorders that exhibit decreased GCase activity.
Myung Jong Kim, Soojin Kim, Thomas Reinheckel, Dimitri Krainc
High grade serous carcinoma (HGSC) is the most lethal gynecological malignancy in the United States. Late diagnosis and the emergence of chemoresistance have prompted studies into how the tumor microenvironment, and more recently tumor innervation, may be leveraged for HGSC prevention and interception. In addition to biobehavioral sources, concentrations of the sympathetic neurotransmitter norepinephrine (NE) in the ovary increase during ovulation and after menopause. Importantly, NE exacerbates advanced HGSC progression. However, little is known about the role of NE in early disease pathogenesis. Here, we investigated the role of NE in instigating anchorage independence and micrometastasis of preneoplastic lesions from the fallopian tube epithelium (FTE) to the ovary, an essential step in HGSC onset. We found that in the presence of NE, FTE cell lines are able to survive in ultra-low attachment (ULA) culture in a beta-adrenergic receptor (β-AR)-dependent manner. Importantly, spheroid formation and cell viability conferred by treatment with physiological sources of NE can be abrogated using the beta-adrenergic receptor blocker propranolol. We have also identified that NE-mediated anoikis resistance may be attributable to downregulation of colony stimulating factor 2 (CSF2). These findings provide mechanistic insight and identify targets that may be regulated by ovarian-derived NE in early HGSC.
Hunter D. Reavis, Stefan M. Gysler, Grace B. McKenney, Matthew Knarr, Hannah J. Lusk, Priyanka Rawat, Hannah S. Rendulich, Marilyn A. Mitchell, Dara S. Berger, Jamie S. Moon, Suyeon Ryu, Monica Mainigi, Marcin P. Iwanicki, Dave S.B. Hoon, Laura M. Sanchez, Ronny Drapkin
Vascular calcification is a severe complication of cardiovascular diseases. Previous studies demonstrated that endothelial lineage cells transitioned into osteoblast-like cells and contributed to vascular calcification. Here, we found that inhibition of cyclin-dependent kinase (CDK) prevented endothelial lineage cells from transitioning to osteoblast-like cells and reduced vascular calcification. We identified a robust induction of CDK1 in endothelial cells (ECs) in calcified arteries and showed that endothelial-specific gene deletion of CDK1 decreased the calcification. We found that limiting CDK1 induced E-twenty-six specific sequence variant 2 (ETV2), which was responsible for blocking endothelial lineage cells from undergoing osteoblast differentiation. We also found that inhibition of CDK1 reduced vascular calcification in a diabetic mouse model. Together, the results highlight the importance of CDK1 suppression and suggest CDK1 inhibition as a potential option for treating vascular calcification.
Yan Zhao, Yang Yang, Xiuju Wu, Li Zhang, Xinjiang Cai, Jaden Ji, Sydney Chen, Abigail Vera, Kristina I. Boström, Yucheng Yao
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