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Biochem J. 2005 Jun 15;388(Pt 3):773-83.

Silencing of p21-activated kinase attenuates vimentin phosphorylation on Ser-56 and reorientation of the vimentin network during stimulation of smooth muscle cells by 5-hydroxytryptamine.

Author information

  • 1Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, ME-424, Albany, NY 12208, USA. tangd@mail.amc.edu

Abstract

Vimentin intermediate filaments undergo spatial reorganization in endothelial cells and fibroblasts in response to stimulation with platelet-derived growth factor and epidermal growth factor. In the present study, the vimentin network exhibited a curved filamentous structure in unstimulated smooth muscle cells. Vimentin filaments became straight and were arranged along the long axis of cells upon stimulation with 5-hydroxytryptamine (5-HT; serotonin). Stimulation of smooth muscle cells with 5-HT also induced phosphorylation of vimentin on Ser-56. Treatment of cells with small interfering RNA selectively down-regulated the expression of PAK1 (p21-activated kinase 1) without affecting the content of smooth muscle alpha-actin. The silencing of PAK1 inhibited the site-specific phosphorylation and spatial rearrangement of the vimentin network in response to stimulation with 5-HT. Neither the disruption of stress fibres by cytochalasin D nor the inhibition of protein tyrosine phosphorylation affects the spatial reorganization of vimentin intermediate filaments in response to stimulation with 5-HT. In addition, stimulation of smooth muscle cells with 5-HT increased the ratio of soluble to insoluble vimentin. PAK1 silencing attenuated increases in the ratio of soluble to insoluble vimentin upon stimulation with 5-HT. These results suggest that the PAK-mediated site-specific phosphorylation of vimentin may play a role in regulating the reorganization of vimentin intermediate filaments during stimulation of smooth muscle cells with 5-HT.

PMID:
15766329
[PubMed - indexed for MEDLINE]
PMCID:
PMC1183456
Free PMC Article

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