Identification and characterization of the unique guanine nucleotide exchange factor, SmgGDS, in vascular smooth muscle cells. J Cell Biochem 2008 Aug 01;104(5):1760-70
Date
03/19/2008Pubmed ID
18348285DOI
10.1002/jcb.21740Scopus ID
2-s2.0-50249171006 (requires institutional sign-in at Scopus site) 6 CitationsAbstract
The guanine nucleotide exchange factor (GEF), SmgGDS, promotes nucleotide exchange by several GTPases in both the Ras and Rho families, especially by RhoA. Because RhoA plays an important role in regulating the contraction of vascular smooth muscle cells (VSMC), we examined the expression and function of SmgGDS in VSMC. SmgGDS is expressed in primary rat aortic smooth muscle (ASM) cells, primary bovine coronary artery smooth muscle (BCASM) cells, and the immortalized A7r5 line of rat ASM cells. Down regulation of SmgGDS expression by siRNA transfection resulted in a decrease of RhoA-GTP levels, enhanced cell spreading, and loss of the characteristic elongated morphology of VSMC. A similar morphology was also observed following treatment with the Rho-kinase inhibitor, Y27632. In contrast, cells with reduced RhoA expression exhibit an elongated shape. Subsequent immunofluorescent staining revealed a disruption of the myosin filament organization in the cells with reduced SmgGDS expression. Further studies analyzed the effect of SmgGDS siRNA transfection on the contraction of A7r5 cells and BCASM cells, which is also a Rho-regulated pathway. Transfection of SmgGDS siRNA or RhoA siRNA resulted in an impaired ability of the A7r5 and BCASM cells to undergo contraction in a collagen gel matrix. However, phosphorylation of the myosin-binding subunit of myosin phosphatase (MYPT1) or the light chain of myosin II (MLC) was not altered by downregulating expression of either SmgGDS or RhoA GTPase. Taken together these results identify SmgGDS as a novel regulator of myosin organization and contraction in VSMC.
Author List
Thill R, Campbell WB, Williams CLAuthors
William B. Campbell PhD Professor in the Pharmacology and Toxicology department at Medical College of WisconsinCarol L. Williams PhD Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
AnimalsCattle
Cell Shape
Cells, Cultured
Down-Regulation
Gene Silencing
Guanine Nucleotide Exchange Factors
Models, Biological
Muscle Contraction
Muscle, Smooth, Vascular
Myocytes, Smooth Muscle
Myosin Light Chains
Myosins
Phosphorylation
Protein Phosphatase 1
RNA, Small Interfering
Rats
Transfection
rhoA GTP-Binding Protein
