title: Treponema denticola major outer sheath protein impairs the cellular phosphoinositide balance that regulates neutrophil chemotaxis.
abstract: The major outer sheath protein (Msp) of Treponema denticola inhibits neutrophil polarization and directed chemotaxis together with actin dynamics in vitro in response to the chemoattractant N-formyl-methionine-leucine-phenylanine (fMLP). Msp disorients chemotaxis through inhibition of a Rac1-dependent signaling pathway, but the upstream mechanisms are unknown. We challenged murine bone marrow neutrophils with enriched native Msp to determine the role of phospholipid modifying enzymes in chemotaxis and actin assembly downstream of fMLP-stimulation. Msp modulated cellular phosphoinositide levels through inhibition of phosphatidylinositol 3-kinase (PI3-kinase) together with activation of the lipid phosphatase, phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Impaired phosphatidylinositol[(3,4,5)]-triphosphate (PIP3) levels prevented recruitment and activation of the downstream mediator Akt. Release of the actin capping proteins gelsolin and CapZ in response to fMLP was also inhibited by Msp exposure. Chemical inhibition of PTEN restored PIP3 signaling, as measured by Akt activation, Rac1 activation, actin uncapping, neutrophil polarization and chemotaxis in response to fMLP-stimulation, even in the presence of Msp. Transduction with active Rac1 also restored fMLP-mediated actin uncapping, suggesting that Msp acts at the level of PIP3 in the hierarchical feedback loop of PIP3 and Rac1 activation. Taken together, Msp alters the phosphoinositide balance in neutrophils, impairing the cell "compass", which leads to inhibition of downstream chemotactic events.
authors.affiliation: Matrix Dynamics Group, Dental Research Institute, University of Toronto, Toronto, Ontario, Canada. michelle.visser@utoronto.ca
authors.forename: Michelle B
authors.initials: MB
authors.lastname: Visser
authors.forename: Chun-Xiang
authors.initials: CX
authors.lastname: Sun
authors.forename: Adeline
authors.initials: A
authors.lastname: Koh
authors.forename: Richard P
authors.initials: RP
authors.lastname: Ellen
authors.forename: Michael
authors.initials: M
authors.lastname: Glogauer
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D051347:CapZ Actin Capping Protein / Q000235:genetics / Q000378:metabolism; D016764:Cell Polarity / Q000187:drug effects; D002630:Chemotactic Factors / Q000494:pharmacology; D002634:Chemotaxis, Leukocyte / Q000187:drug effects* / Q000235:genetics; D018260:Gelsolin / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051059:PTEN Phosphohydrolase / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D018272:Porins / Q000302:isolation & purification / Q000494:pharmacology*; D061251:Primary Cell Culture; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D048373:Treponema denticola / Q000737:chemistry*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D051347:CapZ Actin Capping Protein; D002630:Chemotactic Factors; D018260:Gelsolin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009479:Neuropeptides; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D000081082:Phosphoinositide-3 Kinase Inhibitors; D018272:Porins; D051057:Proto-Oncogene Proteins c-akt; D020830:rac1 GTP-Binding Protein; C484602:Rac1 protein, mouse; C099361:major outer sheath protein, Treponema; C060974:phosphatidylinositol 3,4,5-triphosphate; C487757:Pten protein, mouse