Pathological shear stress stimulates the tyrosine phosphorylation of alpha-actinin associated with the glycoprotein Ib-IX complex.
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.
Feng
Shuju
S
Veterans' Affairs Medical Center, Baylor College of Medicine and Rice University, Houston, Texas 77030, USA.
Reséndiz
Julio C
JC
Christodoulides
Nicolaos
N
Lu
Xin
X
Arboleda
David
D
Berndt
Michael C
MC
Kroll
Michael H
MH
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
D019038:Platelet Glycoprotein GPIb-IX Complex; D000185:Actinin; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; C061570:protein kinase N; D011493:Protein Kinase C