title: Migration and retraction of endothelial and epithelial cells require PHI-1, a specific protein-phosphatase-1 inhibitor protein.
abstract: Cell migration and retraction are interrelated activities that are crucial for a range of physiological processes such as wound healing and vascular permeability. Immunostaining of brain sections for the specific inhibitor of type-1 protein Ser/Thr phosphatase called PHI-1 showed high expression levels in smooth muscle and especially in vascular endothelial cells. During migration of cultured human lung microvascular endothelial cells, endogenous PHI-1 was concentrated to the trailing edge of the cells. Knockdown of PHI-1 using small interfering RNAs reduced by 45% the rate of HeLa cell migration in a wound-healing assay. These cells exhibited an extremely elongated phenotype relative to controls and time-lapse movies revealed a defect in retraction of the trailing edge. Both HeLa and human vascular endothelial cells depleted of PHI-1 showed increased surface areas relative to controls during cell spreading in a replating assay. Analysis of sequential microscopic images demonstrated this was due to a significant decrease in the number of retraction events, whereas protrusive action was unaffected. The Ser/Thr phosphorylation of several signaling, cytoskeletal and focal-adhesion proteins was unchanged in PHI-1-depleted cells, so the target of PHI-1 inhibited protein-phosphatase 1 remains unidentified. Nonetheless, the results show that PHI-1 participates in regulatory events at the trailing edge of migrating cells and modulates retraction of endothelial and epithelial cells.
authors.affiliation: Center for Cell Signaling, University of Virginia School of Medicine, PO Box 800577, Charlottesville, VA 22908, USA.
authors.forename: Nikolaos A
authors.initials: NA
authors.lastname: Tountas
authors.forename: David L
authors.initials: DL
authors.lastname: Brautigan
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002465:Cell Movement; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology*; D004847:Epithelial Cells / Q000166:cytology*; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D008168:Lung / Q000098:blood supply; D008214:Lymphocytes / Q000166:cytology; D008833:Microcirculation; D008856:Microscopy, Fluorescence; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D012694:Serine / Q000737:chemistry; D013912:Threonine / Q000737:chemistry; D013997:Time Factors; D014162:Transfection; D014945:Wound Healing
chemical_list: D011506:Proteins; D034741:RNA, Small Interfering; C073882:phosphoprotein phosphatase inhibitor 1; D013912:Threonine; D012694:Serine; D010749:Phosphoprotein Phosphatases