Kalirin promotes neointimal hyperplasia by activating Rac in smooth muscle cells.
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2013-04
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Abstract
Objective
Kalirin is a multifunctional protein that contains 2 guanine nucleotide exchange factor domains for the GTPases Rac1 and RhoA. Variants of KALRN have been associated with atherosclerosis in humans, but Kalirin's activity has been characterized almost exclusively in the central nervous system. We therefore tested the hypothesis that Kalirin functions as a Rho-guanine nucleotide exchange factor in arterial smooth muscle cells (SMCs).Approach and results
Kalirin-9 protein is expressed abundantly in aorta and bone marrow, as well as in cultured SMCs, endothelial cells, and macrophages. Moreover, arterial Kalirin was upregulated during early atherogenesis in apolipoprotein E-deficient mice. In cultured SMCs, signaling was affected similarly in 3 models of Kalirin loss-of-function: heterozygous Kalrn deletion, Kalirin RNAi, and treatment with the Kalirin Rho-guanine nucleotide exchange factor -1 inhibitor 1-(3-nitrophenyl)-1H-pyrrole-2,5-dione. With reduced Kalirin function, SMCs showed normal RhoA activation but diminished Rac1 activation, assessed as reduced Rac-GTP levels, p21-activated kinase autophosphorylation, and SMC migration. Kalrn(-/+) SMCs proliferated 30% less rapidly than wild-type SMCs. Neointimal hyperplasia engendered by carotid endothelial denudation was ≈60% less in Kalrn(-/+) and SMC-specific Kalrn(-/+) mice than in control mice.Conclusions
Kalirin functions as a guanine nucleotide exchange factor for Rac1 in SMCs, and promotes SMC migration and proliferation both in vitro and in vivo.Type
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Wu, Jiao-Hui, Alexander C Fanaroff, Krishn C Sharma, Liisa S Smith, Leigh Brian, Betty A Eipper, Richard E Mains, Neil J Freedman, et al. (2013). Kalirin promotes neointimal hyperplasia by activating Rac in smooth muscle cells. Arteriosclerosis, thrombosis, and vascular biology, 33(4). pp. 702–708. 10.1161/atvbaha.112.300234 Retrieved from https://hdl.handle.net/10161/31548.
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Scholars@Duke
Neil J. Freedman
Our work focuses on atherosclerosis-related signal transduction and the genetic bases of atherosclerosis and vein graft failure, both in vitro and in vivo. We investigate the regulation of receptor protein tyrosine kinases by G protein-coupled receptor kinases (GRKs), and the role of GRKs and β-arrestins in atherosclerosis; molecular mechanisms of atherogenesis associated with the dual Rho-GEF kalirin, the F-actin-binding protein Drebrin, and small nucleolar RNAs (snoRNAs) of the Rpl13a locus. For in vivo modeling of atherosclerosis and neointimal hyperplasia, we use mouse carotid artery bypass grafting with either veins or arteries from gene-deleted or congenic wild type mice, as well as aortic atherosclerosis studies and bone marrow transplantation. To study receptor phosphorylation, signal transduction, and intracellular trafficking, we employ primary smooth muscle cells, endothelial cells, and macrophages derived from knockout mice, as well as cells treated with RNA interference.
Key Words: atherosclerosis, G protein-coupled receptor kinases, arrestins, desensitization, phosphorylation, receptor protein tyrosine kinases, smooth muscle cells, neointimal hyperplasia, Rho-GEF, Drebrin, snoRNAs.
Lisheng Zhang
My research efforts involves studying the pathogenesis of vein graft neointimal hyperplasia and atherosclerosis.
The greatest amount of my time in the past years has been devoted to developing and characterizing our interposition vein graft model in mice. This model allows us to use IVC to carotid artery transplants between congenic mice. These transplants allow us to ask the questions about which gene products contribute to the pathogenesis of vein graft disease. In addition, I have used carotid artery to carotid artery transplants to study the role of TNF receptors in atherosclerosis. For these studies, we have used apolipoprotein E-deficient mice as graft recipients.
By using mouse vein graft model we demonstrate that most of the neointimal cells in vein grafts originate from cellular pools outside of the vein graft at the time of its implantation. The importance of this work relates to our persistent inability to treat vein graft disease in human beings. The second work demonstrates that expression of the tumor necrosis factor receptor-1, even in just in the vein graft cells themselves, contributes to the pathogenesis of vein graft neointimal hyperplasia. In this project, I surgically created chimeric mice to demonstrate molecular mechanisms by which the tumor necrosis factor receptor-1 aggravates neointimal hyperplasia, a process that is believed to lay the foundation for accelerated atherosclerosis in vein grafts.
I have also adapted my vein graft procedure in mice to ask questions about the arterial wall’s role in atherosclerosis. This atherosclerosis model involves making carotid interposition grafts not with veins, but with the carotid artery of congenic mice, and placing them into the carotid artery of spontaneously atherogenic mice that are deficient in apolipoprotein E.
I plan to continue our studies related to the role of inflammatory cytokine receptors in neointimal hyperplasia and atherosclerosis. In addition, I envision extending this work with the surgical models I have created in mice.
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