title: To stabilize neutrophil polarity, PIP3 and Cdc42 augment RhoA activity at the back as well as signals at the front.
abstract: Chemoattractants like f-Met-Leu-Phe (fMLP) induce neutrophils to polarize by triggering divergent signals that promote the formation of protrusive filamentous actin (F-actin; frontness) and RhoA-dependent actomyosin contraction (backness). Frontness locally inhibits backness and vice versa. In neutrophil-like HL60 cells, blocking phosphatidylinositol-3,4,5-tris-phosphate (PIP3) accumulation with selective inhibitors of PIP3 synthesis completely prevents fMLP from activating a PIP3-dependent kinase and Cdc42 but not from stimulating F-actin accumulation. PIP3-deficient cells show reduced fMLP-dependent Rac activity and unstable pseudopods, which is consistent with the established role of PIP3 as a mediator of positive feedback pathways that augment Rac activation at the front. Surprisingly, such cells also show reduced RhoA activation and RhoA-dependent contraction at the trailing edge, leading to the formation of multiple lateral pseudopods. Cdc42 mediates PIP3's positive effect on RhoA activity. Thus, PIP3 and Cdc42 maintain stable polarity with a single front and a single back not only by strengthening pseudopods but also, at longer range, by promoting RhoA-dependent actomyosin contraction at the trailing edge.
authors.affiliation: Department of Cellular and Molecular Pharmacology, and Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94143, USA.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Van Keymeulen
authors.forename: Kit
authors.initials: K
authors.lastname: Wong
authors.forename: Zachary A
authors.initials: ZA
authors.lastname: Knight
authors.forename: Cedric
authors.initials: C
authors.lastname: Govaerts
authors.forename: Klaus M
authors.initials: KM
authors.lastname: Hahn
authors.forename: Kevan M
authors.initials: KM
authors.lastname: Shokat
authors.forename: Henry R
authors.initials: HR
authors.lastname: Bourne
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D016764:Cell Polarity / Q000187:drug effects; D002478:Cells, Cultured; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000166:cytology*; D010641:Phenotype; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D011554:Pseudopodia / Q000187:drug effects; D015398:Signal Transduction; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018129:Phosphatidylinositol Phosphates; D000081082:Phosphoinositide-3 Kinase Inhibitors; D013844:Thiazoles; D053778:Thiazolidines; C060974:phosphatidylinositol 3,4,5-triphosphate; D009240:N-Formylmethionine Leucyl-Phenylalanine; D020764:cdc42 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein; C037068:latrunculin B