title: Pathological shear stress stimulates the tyrosine phosphorylation of alpha-actinin associated with the glycoprotein Ib-IX complex.
abstract: Shear-induced platelet responses are triggered by VWF binding to the platelet GpIb-IX complex, and there is evidence that this ligand-receptor coupling stimulates transmembranous signaling through the cytoplasmic tail of glycoprotein (Gp) Ib alpha. To investigate the mechanism by which signaling is effected, new molecular interactions involving GpIb-IX that develop in response to pathological shearing stress were examined in intact human platelets. Exposure to shear, but not alpha-thrombin, results in the co-immunoprecipitation of the actin cross-linking protein alpha-actinin with the GpIb-IX complex. Blockers of VWF binding to GpIb alpha or actin polymerization inhibit the association of alpha-actinin with the GpIb-IX complex, but the association of alpha-actinin with the GpIb-IX complex is not affected by inhibiting VWF binding to platelet integrin alpha IIb beta 3 (GpIIb-IIIa). alpha-Actinin becomes tyrosine phosphorylated in response to pathological shear stress, and phosphorylated alpha-actinin associates with GpIb-IX. In resting platelets, class IA heterodimeric phosphatidylinositol 3-kinase (PI 3-K) and protein kinase N (PKN) associate with nonphosphorylated alpha-actinin. Shear stress causes PI 3-K to disassociate from alpha-actinin, while it stimulates PKN binding to alpha-actinin. These results demonstrate that shear-induced VWF binding to GpIb alpha causes enhanced binding of cytoskeletal alpha-actinin to GpIb-IX and suggest that alpha-actinin, perhaps through tyrosine phosphorylation, serves as an adapter for a signaling complex that could regulate VWF-induced platelet aggregation.
authors.affiliation: Veterans' Affairs Medical Center, Baylor College of Medicine and Rice University, Houston, Texas 77030, USA.
authors.forename: Shuju
authors.initials: S
authors.lastname: Feng
authors.forename: Julio C
authors.initials: JC
authors.lastname: Reséndiz
authors.forename: Nicolaos
authors.initials: N
authors.lastname: Christodoulides
authors.forename: Xin
authors.initials: X
authors.lastname: Lu
authors.forename: David
authors.initials: D
authors.lastname: Arboleda
authors.forename: Michael C
authors.initials: MC
authors.lastname: Berndt
authors.forename: Michael H
authors.initials: MH
authors.lastname: Kroll
mesh_terms: D000185:Actinin / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D014783:Viscosity
chemical_list: D019038:Platelet Glycoprotein GPIb-IX Complex; D000185:Actinin; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; C061570:protein kinase N; D011493:Protein Kinase C