title: Macrophage/microglia-specific protein Iba1 enhances membrane ruffling and Rac activation via phospholipase C-gamma -dependent pathway.
abstract: Iba1 is a macrophage/microglia-specific calcium-binding protein that is involved in RacGTPase-dependent membrane ruffling and phagocytosis. In this study, we introduced Iba1 into Swiss 3T3 fibroblasts and demonstrated the enhancement of platelet-derived growth factor (PDGF)-induced membrane ruffling and chemotaxis. Wortmannin treatment did not completely suppressed this enhanced membrane ruffling in Iba1-expressing cells, whereas it did in Iba1-nonexpressing cells, suggesting that the enhancement is mediated through a phosphatidylinositol 3-kinase (PI3K)-independent signaling pathway. Porcine aorta endothelial cells transfected with expression constructs of Iba1 and PDGF receptor add-back mutants were used to analyze the signaling pathway responsible for the Iba1-induced enhancement of membrane ruffling. In the absence of Iba1 expression, PDGF did not induced membrane ruffling in cells expressing the Tyr-1021 receptor mutant, which is capable of activating phospholipase C-gamma (PLC-gamma) but not PI3K. In contrast, in the presence of Iba1 expression, membrane ruffling was formed in cells expressing the Tyr-1021 mutant. In addition, Rac was shown to be activated during membrane ruffling in cells expressing Iba1 and the Tyr-1021 mutant. Furthermore, dominant negative forms of PLC-gamma completely suppressed PDGF-induced Iba1-dependent membrane ruffling and Rac activation. These results indicate the existence of a novel signaling pathway where PLC-gamma activates Rac in a manner dependent on Iba1.
authors.affiliation: Department of Neurochemistry, National Institute of Neuroscience, 4-1-1 Ogawahigashi, Kodaira, Tokyo 187-8502, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kanazawa
authors.forename: Keiko
authors.initials: K
authors.lastname: Ohsawa
authors.forename: Yo
authors.initials: Y
authors.lastname: Sasaki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kohsaka
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Imai
mesh_terms: D016475:3T3 Cells; D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002633:Chemotaxis; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry; D007527:Isoenzymes / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins; D017628:Microglia / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D010590:Phalloidine / Q000494:pharmacology; D051966:Phospholipase C gamma; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011233:Precipitin Tests; D015398:Signal Transduction; D013552:Swine; D013997:Time Factors; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: C491049:Aif1 protein, mouse; D002135:Calcium-Binding Proteins; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008840:Microfilament Proteins; D010982:Platelet-Derived Growth Factor; D010590:Phalloidine; D010738:Type C Phospholipases; D051966:Phospholipase C gamma; D020744:rac GTP-Binding Proteins