title: Ligation of cell surface-associated glucose-regulated protein 78 by receptor-recognized forms of alpha 2-macroglobulin: activation of p21-activated protein kinase-2-dependent signaling in murine peritoneal macrophages.
abstract: Previous studies of the plasma proteinase inhibitor alpha2-macroglobulin (alpha2M) demonstrated that alpha2M-proteinase complexes (alpha2M*) modulate immune responses and promotes macrophage locomotion and chemotaxis. Alpha2M* binds to cell surface-associated glucose-regulated protein 78 (GRP78), which activates downstream signaling events. The role of p21-activated protein kinase-1 and -2 (PAK-1 and -2) in promoting cellular motility is well documented. In the current study, we examined the ability of alpha2M* to activate PAK-1 and PAK-2. Upon macrophage stimulation with alpha2M*, PAK-2 is autophosphorylated, resulting in increased kinase activity; however, PAK-1 is negligibly affected. Alpha2M*-stimulated macrophages showed a marked elevation in the levels of Rac x GTP. Receptor tyrosine phosphorylation upon binding of alpha2M* to GRP78, recruits PAK-2 to the plasma membrane via the adaptor protein NCK. Consistent with this hypothesis, silencing of GRP78 gene expression greatly attenuated the levels of membrane-associated PAK-2 and NCK. PAK-2 activity was markedly decreased by inhibition of tyrosine kinases and PI3K before alpha2M* stimulation. We further demonstrate that phosphorylation of Lin-11, Isl-1, Mec-3 (LIM) kinase and cofilin is promoted by treating macrophages with alpha2M*. Thus, alpha2M* regulates activation of the PAK-2-dependent motility mechanism in these cells.
authors.affiliation: Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Uma Kant
authors.initials: UK
authors.lastname: Misra
authors.forename: Tushar
authors.initials: T
authors.lastname: Sharma
authors.forename: Salvatore Vincent
authors.initials: SV
authors.lastname: Pizzo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D051338:Cofilin 1 / Q000096:biosynthesis; D004306:Dose-Response Relationship, Immunologic; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation / Q000502:physiology; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D008024:Ligands; D054461:Lim Kinases; D017737:Macrophages, Peritoneal / Q000201:enzymology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018832:Molecular Chaperones / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D015513:Oncogene Proteins / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding / Q000502:physiology; D011494:Protein Kinases / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D034622:RNA Interference; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D014443:Tyrosine / Q000378:metabolism; D015854:Up-Regulation; D000511:alpha-Macroglobulins / Q000378:metabolism* / Q000502:physiology; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020703:ras GTPase-Activating Proteins / Q000096:biosynthesis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051338:Cofilin 1; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D008024:Ligands; D018832:Molecular Chaperones; C078332:Nck protein; D015513:Oncogene Proteins; D000511:alpha-Macroglobulins; D020703:ras GTPase-Activating Proteins; D014443:Tyrosine; D011494:Protein Kinases; D020794:Receptor Protein-Tyrosine Kinases; D054461:Lim Kinases; C515893:Limk1 protein, mouse; C515909:Pak2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein