title: Integrin engagement modulates the phosphorylation of focal adhesion kinase, phagocytosis, and cell spreading in molluscan defence cells.
abstract: Integrins play a key role in cellular immune responses in a variety of organisms; however, knowledge of integrins and their effects on cell signalling and functional responses in molluscan defence reactions is poor. Using integrin-mediated cell adhesion kits, alphaVbeta3 and beta1 integrin-like subunits were identified on the surface of Lymnaea stagnalis haemocytes. Haemocyte binding via these integrins was found to be dependent on Ca2+/Mg2+. Western blotting with an anti-phospho (anti-active) focal adhesion kinase (FAK) antibody revealed a 120-125 kDa FAK-like protein in these cells; this protein was transiently phosphorylated upon haemocyte adhesion over 90 min, with maximal phosphorylation occurring after 30 min binding. Also, integrin engagement with the tetrapeptide Arg-Gly-Asp-Ser (RGDS) resulted in a rapid increase in phosphorylation of the FAK-like protein; however, RGDS did not affect the phosphorylation of extracellular signal-regulated kinase. Treatment of haemocytes with RGDS (2 mM) inhibited phagocytosis of E. coli bioparticles by 88%. Moreover, at this concentration, RGDS reduced cell spreading by 61%; stress fiber formation was also impaired. Taken together, these results demonstrate a role for integrins in L. stagnalis haemocyte adhesion and defence reactions and, for the first time, link integrin engagement to FAK activation in molluscs.
authors.affiliation: School of Life Sciences, Kingston University, Penrhyn Road, Kingston-upon-Thames, Surrey, KT1 2EE, UK.
authors.forename: Louise D
authors.initials: LD
authors.lastname: Plows
authors.forename: Richard T
authors.initials: RT
authors.lastname: Cook
authors.forename: Angela J
authors.initials: AJ
authors.lastname: Davies
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Walker
mesh_terms: D000818:Animals; D002465:Cell Movement; D004926:Escherichia coli / Q000276:immunology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D006434:Hemocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D007111:Immunity, Cellular; D066298:In Vitro Techniques; D016023:Integrins / Q000378:metabolism*; D008195:Lymnaea / Q000166:cytology* / Q000276:immunology / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism; D010587:Phagocytosis; D010766:Phosphorylation; D015398:Signal Transduction
chemical_list: D016023:Integrins; D009842:Oligopeptides; C046617:arginyl-glycyl-aspartyl-serine; D051416:Focal Adhesion Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases