title: 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.
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.
authors.affiliation: Center for Cardiovascular Sciences, Albany Medical College, 47 New Scotland Avenue, MC-8, ME-424, Albany, NY 12208, USA. tangd@mail.amc.edu
authors.forename: Dale D
authors.initials: DD
authors.lastname: Tang
authors.forename: Ying
authors.initials: Y
authors.lastname: Bai
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Gunst
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D004285:Dogs; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic; D007382:Intermediate Filaments / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012701:Serotonin / Q000494:pharmacology*; D012995:Solubility; D014132:Trachea; D014746:Vimentin / Q000737:chemistry / Q000378:metabolism*; D054462:p21-Activated Kinases
chemical_list: D034741:RNA, Small Interfering; D014746:Vimentin; D010768:Phosphoserine; D012701:Serotonin; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases