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作者 Chang, Eugene
書名 The Role of MK2 in Endothelial Biology
國際標準書號 9781124655765
book jacket
說明 147 p
附註 Source: Dissertation Abstracts International, Volume: 72-08, Section: B, page:
Adviser: Jun-ichi Abe
Thesis (Ph.D.)--University of Rochester, 2011
One of the hallmarks of atherogenesis is focalized endothelial dysfunction, which includes altered vasoregulation, activation of inflammatory processes, and compromised barrier function due to endothelial cell (EC) apoptosis. A combination of risk factors such as hypertension, obesity, diabetes, smoking, hyperlipidemia, and genetic predisposition creates a proinflammatory environment that leads to EC dysfunction. However, the exact mechanism of endothelial dysfunction in atherosclerosis remains largely unknown
In the past decade, changes in protein functions by post-translational modifications such as phosphorylation, ubiquitination, SUMOylation, and acetylation have come into focus as important regulators of signal transduction in different pathologies. Of particular interest is SUMOylation, a unique post-translational modification akin to ubiquitination that conjugates small ubiquitin-like proteins called SUMO (Small Ubiquitin-like MOdifier) to target proteins. It is a reversible modification that affects targeted proteins subcellular localization, degradation, protein partnering, DNA binding, and transcription factor regulation However, the role of SUMOylation in kinase regulation remains relatively unknown. In this thesis I examine the effects of SUMOylation on the MAPK-activated protein kinase-2 (MK2) and examine its role in actin filament remodeling and inflammation
In the Chapter 1, I introduce the signal transduction pathways of MK2 function and review the existing literature on its known roles in actin filament remodeling and inflammation. In addition I will discuss about the role of SUMOylation in modulating protein function and its recognized roles in regulating endothelial function
In Chapter 2, I describe the role of MK2 SUMOylation in actin filament remodeling in endothelial cells. Actin filament remodeling regulates a number of endothelial cell processes such as contraction, migration, adhesion, and shape determination. MK2-mediated phosphorylation of heat shock protein-27 kDa (HSP27) promotes actin filament remodeling, but little is known about the regulation of this event in ECs. We found that TNF SUMOylated MK2 at lysine (K)-339 affected EC actin filament organization and migration. Loss of the MK2 SUMOylation site (MK2-K339R) increased MK2 kinase activity and prolonged HSP27 phosphorylation, enhancing its effects on actin filament-dependent events. Both tumor necrosis factor-alpha (TNF)-mediated EC elongation and steady laminar shear stress-mediated EC alignment were increased by MK2-K339R. Moreover, kinase dead dominant-negative (DN-) MK2 inhibited these effects. Cell migration is a dynamic process regulated by actin filament remodeling. Both wild-type (WT-) and DN-MK2 significantly enhanced TNF-mediated inhibition of EC migration and MK2-K339R further augmented this effect. Interestingly, the p160-Rho-associated coiled-coil kinase (ROCK) inhibitor Y-27632 reversed this effect by MK2-K339R, which strongly suggests that both excessive and insufficient levels of actin filament remodeling can block EC migration. Our study shows that MK2 SUMOylation is a new mechanism for regulating actin filament dynamics in ECs
In Chapter 3, I present my findings on the role of MK2 in endothelial inflammation and its effects on the PIAS1-NFkappaB inflammatory signal transduction pathway in a unique negative feedback loop mechanism. Persistent activation of NF-kappaB during endothelial inflammation is a hallmark of atherosclerosis. Although the mechanisms of NF-kappaB activation are well documented, the negative feedback mechanisms that restrict NF-kappaB largely remain poorly understood. Protein inhibitor of activated STAT-1 (PIAS1) is a known transrepressor of NF-kappaB. MAPK-activated protein kinase-2 (MK2) is a proinflammatory kinase involved in the upregulation of numerous cytokines and cell adhesion molecules that are NF-kappaB target genes including TNF-alpha (TNF), VCAM-1, and MCP-1. In fact, we show the critical role of MK2 activation and PIAS1-mediated transrepression on TNF-mediated NF-kappaB activation in endothelial cells. We found that MK2 is able to phosphorylate PIAS1 at the serine-510, -517, and -522 sites. Interestingly, the phosphorylation defective PIAS1 serine-522 alanine mutant (PIAS1-S522A) could not inhibit TNF-mediated NF-kappaB activation, suggesting the critical role of MK2-mediated PIAS1 S522 phosphorylation. The S510A and S517A mutants behaved similarly to wild-type PIAS1 in transrepressing NF-kappaB. Our results have identified a novel negative feedback regulatory pathway through which the proinflammatory kinase MK2 can limit endothelial inflammation through phosphorylation of PIAS1
Lastly in Chapter 4, I summarize and discuss the significance of this thesis in the field and its potential clinical implications in our understanding of cardiovascular disease treatments. The results of these studies presented in this thesis will expand on our knowledge of human pathophysiology in cardiovascular biology and further push the current clinical limitations of cardiovascular disease therapeutics to new boundaries
School code: 0188
Host Item Dissertation Abstracts International 72-08B
主題 Health Sciences, Pathology
0571
Alt Author University of Rochester
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