title: Exclusion of exogenous phosphatidylinositol-3,4,5-trisphosphate from neutrophil-polarizing pseudopodia: stabilization of the uropod and cell polarity.
abstract: Although there is accumulating evidence that the generation and localization of phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P(3)) have important functions in neutrophil polarization and chemotaxis, the mechanism of this linkage has yet to be established. Here, using exogenous fluorescent PtdIns(3,4,5)P(3) introduced into the inner leaflet of the neutrophil plasma membrane by a cationic carrier, we show that: first, PtdIns(3,4,5)P(3) uniformly delivered to the neutrophil plasma membrane is excluded from newly forming pseudopodia; second, PtdIns(3,4,5)P(3) translocates to and is immobilized at the pole opposite a stable polarizing pseudopod; third, asymmetric delivery of PtdIns(3,4,5)P(3) to the neutrophil triggers the generation of polarizing pseudopodia at the opposite pole; and finally, PtdIns(3,4,5)P(3) triggers repetitive Ca(2+) signals, the onset of which precedes morphological polarization. These data suggest that translocation and immobilization of PtdIns(3,4,5)P(3) or a 3,x-phosphorylated metabolite in the uropod functions as an important polarization cue that defines neutrophil polarity and stabilizes the generation of pseudopodia at the opposite pole.
authors.affiliation: Neutrophil Signalling Group, University Department of Surgery, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK.
authors.forename: Wei
authors.initials: W
authors.lastname: Tian
authors.forename: Iraj
authors.initials: I
authors.lastname: Laffafian
authors.forename: Sharon
authors.initials: S
authors.lastname: Dewitt
authors.forename: Maurice B
authors.initials: MB
authors.lastname: Hallett
mesh_terms: D001692:Biological Transport / Q000502:physiology; D001896:Boron Compounds / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D016764:Cell Polarity; D048429:Cell Size; D036681:Fluorescence Recovery After Photobleaching; D005456:Fluorescent Dyes / Q000378:metabolism; D006801:Humans; D009504:Neutrophils / Q000166:cytology / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000737:chemistry / Q000378:metabolism*; D011554:Pseudopodia / Q000737:chemistry* / Q000378:metabolism*
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D005456:Fluorescent Dyes; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate