Role of Autophagy in Von Willebrand Factor Secretion by Endothelial Cells and in the In Vivo Thrombin-Antithrombin Complex Formation Promoted by the HIV-1 Matrix Protein p17
Abstract:Although the advent of combined antiretroviral therapy has substantially improved the survival of HIV-1-infected individuals, non-AIDS-related diseases are becoming increasingly prevalent in HIV-1-infected patients. Persistent abnormalities in coagulation appear to contribute to excess risk for a broad spectrum of non-AIDS defining complications. Alterations in coagulation biology in the context of HIV infection seem to be largely a consequence of a chronically inflammatory microenvironment leading to endothel… Show more
“…Intriguingly, GO term analysis revealed a strong enrichment of extracellular-region- and cell-adhesion-related proteins among the proteins that are secreted in a GRASP55-dependent manner (e.g., MMP2, COL6A1-3, CDH13, BCAM, CADM1) ( Figures 5 B–5E; Table S5 ), suggesting that GRASP55 influences ECM composition and cell adhesion by controlling unconventional cargo secretion. Of note, nearly half of the GRASP55-dependent secretome proteins harbor a signal peptide ( Figure 5 F), in line with previous reports showing that cargoes that either contain or lack a signal peptide can be secreted via UPS routes ( Bugatti et al., 2020 ; Gee et al., 2011 ; Nüchel et al., 2018 ; Schotman et al., 2008 ). Figure 5 The GRASP55-dependent secretome (A) Experimental outline of the SILAC-based GRASP55-dependent secretome assay in WI-26 cells (details in text).…”
Section: Resultssupporting
confidence: 90%
“…Our secretome and surfactome studies highlight another important mechanistic aspect of UPS: although the presence of a signal peptide is indeed necessary for bulk protein secretion, proteins that either harbor or lack a signal peptide can be secreted via UPS. Our findings are in line with recent examples from the literature showing that proteins such as transforming growth factor (TGF)-b1 (N€ uchel et al, 2018), TGF-a (Kuo et al, 2000), vWF (von Willebrand factor) (Bugatti et al, 2020), the DF508-CFTR mutant (Gee et al, 2011), or Drosophila integrins (Schotman et al, 2008)-all of which contain signal peptidesrequire GRASP55 and/or UPS routes for their delivery to the cell surface, at least under certain conditions (e.g., cellular stress). Future work will be necessary to qualitatively and quantitatively characterize the differences between secretory and degradative autophagosomes and to mechanistically explain how cargo selection happens.…”
Section: Cell Biological Aspects Of Grasp55 Regulation and Cargo Selection In Upssupporting
Summary
Cells communicate with their environment via surface proteins and secreted factors. Unconventional protein secretion (UPS) is an evolutionarily conserved process, via which distinct cargo proteins are secreted upon stress. Most UPS types depend upon the Golgi-associated GRASP55 protein. However, its regulation and biological role remain poorly understood. Here, we show that the mechanistic target of rapamycin complex 1 (mTORC1) directly phosphorylates GRASP55 to maintain its Golgi localization, thus revealing a physiological role for mTORC1 at this organelle. Stimuli that inhibit mTORC1 cause GRASP55 dephosphorylation and relocalization to UPS compartments. Through multiple, unbiased, proteomic analyses, we identify numerous cargoes that follow this unconventional secretory route to reshape the cellular secretome and surfactome. Using MMP2 secretion as a proxy for UPS, we provide important insights on its regulation and physiological role. Collectively, our findings reveal the mTORC1-GRASP55 signaling hub as the integration point in stress signaling upstream of UPS and as a key coordinator of the cellular adaptation to stress.
“…Intriguingly, GO term analysis revealed a strong enrichment of extracellular-region- and cell-adhesion-related proteins among the proteins that are secreted in a GRASP55-dependent manner (e.g., MMP2, COL6A1-3, CDH13, BCAM, CADM1) ( Figures 5 B–5E; Table S5 ), suggesting that GRASP55 influences ECM composition and cell adhesion by controlling unconventional cargo secretion. Of note, nearly half of the GRASP55-dependent secretome proteins harbor a signal peptide ( Figure 5 F), in line with previous reports showing that cargoes that either contain or lack a signal peptide can be secreted via UPS routes ( Bugatti et al., 2020 ; Gee et al., 2011 ; Nüchel et al., 2018 ; Schotman et al., 2008 ). Figure 5 The GRASP55-dependent secretome (A) Experimental outline of the SILAC-based GRASP55-dependent secretome assay in WI-26 cells (details in text).…”
Section: Resultssupporting
confidence: 90%
“…Our secretome and surfactome studies highlight another important mechanistic aspect of UPS: although the presence of a signal peptide is indeed necessary for bulk protein secretion, proteins that either harbor or lack a signal peptide can be secreted via UPS. Our findings are in line with recent examples from the literature showing that proteins such as transforming growth factor (TGF)-b1 (N€ uchel et al, 2018), TGF-a (Kuo et al, 2000), vWF (von Willebrand factor) (Bugatti et al, 2020), the DF508-CFTR mutant (Gee et al, 2011), or Drosophila integrins (Schotman et al, 2008)-all of which contain signal peptidesrequire GRASP55 and/or UPS routes for their delivery to the cell surface, at least under certain conditions (e.g., cellular stress). Future work will be necessary to qualitatively and quantitatively characterize the differences between secretory and degradative autophagosomes and to mechanistically explain how cargo selection happens.…”
Section: Cell Biological Aspects Of Grasp55 Regulation and Cargo Selection In Upssupporting
Summary
Cells communicate with their environment via surface proteins and secreted factors. Unconventional protein secretion (UPS) is an evolutionarily conserved process, via which distinct cargo proteins are secreted upon stress. Most UPS types depend upon the Golgi-associated GRASP55 protein. However, its regulation and biological role remain poorly understood. Here, we show that the mechanistic target of rapamycin complex 1 (mTORC1) directly phosphorylates GRASP55 to maintain its Golgi localization, thus revealing a physiological role for mTORC1 at this organelle. Stimuli that inhibit mTORC1 cause GRASP55 dephosphorylation and relocalization to UPS compartments. Through multiple, unbiased, proteomic analyses, we identify numerous cargoes that follow this unconventional secretory route to reshape the cellular secretome and surfactome. Using MMP2 secretion as a proxy for UPS, we provide important insights on its regulation and physiological role. Collectively, our findings reveal the mTORC1-GRASP55 signaling hub as the integration point in stress signaling upstream of UPS and as a key coordinator of the cellular adaptation to stress.
“…Created with BioRender.com. by chloroquine treatment results in a downregulation of VWF secretion [43]. Further support to the importance of secretory autophagy in ECs comes from the analysis of autophagic vacuoles secreted by ECs under starvation, showing that these autophagic vacuoles contain high levels of VWF [44].…”
Section: Autophagy Controls Endothelial Cells Homeostasis and Functionsmentioning
Autophagy is an essential intracellular process for cellular quality control. It enables cell homeostasis through the selective degradation of harmful protein aggregates and damaged organelles. Autophagy is essential for recycling nutrients, generating energy to maintain cell viability in most tissues and during adverse conditions such as hypoxia/ischaemia. The progressive understanding of the mechanisms modulating autophagy in the vasculature has recently led numerous studies to link intact autophagic responses with endothelial cell (EC) homeostasis and function. Preserved autophagic flux within the ECs has an essential role in maintaining their physiological characteristics, whereas defective autophagy can promote endothelial pro‐inflammatory and atherogenic phenotype. However, we still lack a good knowledge of the complete molecular repertoire controlling various aspects of endothelial autophagy and how this is associated with vascular diseases. Here, we provide an overview of the current state of the art of autophagy in ECs. We review the discoveries that have so far defined autophagy as an essential mechanism in vascular biology and analyse how autophagy influences ECs behaviour in vascular disease. Finally, we emphasise opportunities for compounds to regulate autophagy in ECs and discuss the challenges of exploiting them to resolve vascular disease.
“…TAT can be detected in thrombus-related diseases since it indicates the activation of thrombin which contributes to thrombus generation [30]. Hence, it is meaningful to nd biomarkers with diagnostic value.…”
Background and objectiveThrombin-antithrombin complex (TAT) is a prethrombotic marker, and its application in ischemic stroke is still uncertain. The purpose of this systematic review and meta-analysis is to evaluate the relationship between plasma TAT and ischemic stroke base on the current evidence.MethodsA systematic literature search was conducted for searching the relative studies that investigated the association of TAT and ischemic stroke in PubMed, EMBASE, and Cochrane library databases. Mean difference and 95% confidence interval as the effect sizes were synthesized by random effects model in Review Manager (RevMan) Version 5.4. Then, the heterogeneity was investigated using the Chi-square test and the possible sources of heterogeneity were explored by sensitivity analysis. The publication bias was estimated through Begg’s and Egger’s tests.ResultsA total of 12 eligible studies were included involving 1431 stroke cases and 532 healthy controls, of which six studies were eventually included in the meta-analysis. Plasma TAT in patients with ischemic stroke was significantly higher than that in healthy controls (MD 5.31, 95% CI =4.12-6.51, P<0.0001, I2=97.8 %). There is a difference of TAT level in the same period among cardioembolic, lacunar and atherothrombotic stroke (all P<0.0001), in which the cardioembolic stroke with the highest level. Meanwhile, it is significant of TAT levels among various phases of cardioembolic stroke and the acute phase are markedly elevated (MD 7.75, 95CI%, 6.07-9.43, P<0.001). However, no difference was found in the atherothrombotic (P=0.13) and lacunar stroke (P=0.34). Besides, the higher TAT level is closely related to the poor prognosis of patients with ischemic stroke, including higher recurrence, mortality, unfavorable recovery (modified Rankin scale >2), and poor revascularization.ConclusionsThis study suggested that plasma TAT levels are different in ischemic stroke subtypes, which are closely associated with the progression and might have an effect on the prognosis. PROSPERO CRD: 42021248787
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