title: G protein beta subunit-null mutants are impaired in phagocytosis and chemotaxis due to inappropriate regulation of the actin cytoskeleton.
abstract: Chemotaxis and phagocytosis are basically similar in cells of the immune system and in Dictyostelium amebae. Deletion of the unique G protein beta subunit in D. discoideum impaired phagocytosis but had little effect on fluid-phase endocytosis, cytokinesis, or random motility. Constitutive expression of wild-type beta subunit restored phagocytosis and normal development. Chemoattractants released by cells or bacteria trigger typical transient actin polymerization responses in wild-type cells. In beta subunit-null cells, and in a series of beta subunit point mutants, these responses were impaired to a degree that correlated with the defect in phagocytosis. Image analysis of green fluorescent protein-actin transfected cells showed that beta subunit- null cells were defective in reshaping the actin network into a phagocytic cup, and eventually a phagosome, in response to particle attachment. Our results indicate that signaling through heterotrimeric G proteins is required for regulating the actin cytoskeleton during phagocytic uptake, as previously shown for chemotaxis. Inhibitors of phospholipase C and intracellular Ca2+ mobilization inhibited phagocytosis, suggesting the possible involvement of these effectors in the process.
authors.affiliation: Dipartimento di Scienze Cliniche e Biologiche, Università di Torino, Ospedale S. Luigi, 10043 Orbassano, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Peracino
authors.forename: J
authors.initials: J
authors.lastname: Borleis
authors.forename: T
authors.initials: T
authors.lastname: Jin
authors.forename: M
authors.initials: M
authors.lastname: Westphal
authors.forename: J M
authors.initials: JM
authors.lastname: Schwartz
authors.forename: L
authors.initials: L
authors.lastname: Wu
authors.forename: E
authors.initials: E
authors.lastname: Bracco
authors.forename: G
authors.initials: G
authors.lastname: Gerisch
authors.forename: P
authors.initials: P
authors.lastname: Devreotes
authors.forename: S
authors.initials: S
authors.lastname: Bozzaro
mesh_terms: D000199:Actins / Q000502:physiology*; D000818:Animals; D002455:Cell Division; D002465:Cell Movement; D002630:Chemotactic Factors / Q000494:pharmacology; D002633:Chemotaxis / Q000502:physiology*; D003599:Cytoskeleton / Q000502:physiology; D004023:Dictyostelium / Q000378:metabolism / Q000502:physiology; D004926:Escherichia coli / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D016296:Mutagenesis; D010587:Phagocytosis / Q000502:physiology*; D010873:Pinocytosis; D012475:Salmonella / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000199:Actins; D002630:Chemotactic Factors; D019204:GTP-Binding Proteins