Possible role of ILK-affixin complex in integrin-cytoskeleton linkage during platelet aggregation.
Integrin-mediated adhesion induces the formation of focal adhesions that link the extracellular matrix and intracellular actin cytoskeletal networks. We previously showed that integrin-linked kinase (ILK), which can interact with beta1 and beta3 integrins, and its interacting protein, affixin, play an essential role in the initial assembly of focal adhesion structures and actin stress fibers. Although the relevant structures are also observed in integrin alphaIIbbeta3 in platelets, the precise underlying molecular mechanism remains unclarified. Here, we found that ILK stably forms a complex with ss-affixin in platelets. Thrombin stimulation induces their association with integrin beta3, which is followed by their incorporation into the Triton-insoluble membrane-cytoskeletal fraction. During the course of thrombin-induced platelet aggregation, ILK activity was enhanced within 90s to 2.1-fold of the basal level, independent of phosphatidylinositol 3-kinase. Taken together with the observation that the treatment with an anti-integrin beta3 antibody stimulates ILK activity without inducing platelet aggregation, these results suggest that the outside-in signaling induced by fibrinogen binding to integrin enhances ILK activity and results in the initial phase to reorganize the actin cytoskeleton.
Yamaji
Satoshi
S
The First Department of Internal Medicine, Yokohama City University School of Medicine, 3-9 Fuku-ura, Kanazawa-ku, 236-0004, Yokohama, Japan.
Suzuki
Atsushi
A
Kanamori
Heiwa
H
Mishima
Wataru
W
Takabayashi
Maki
M
Fujimaki
Katsumichi
K
Tomita
Naoto
N
Fujisawa
Shin
S
Ohno
Shigeo
S
Ishigatsubo
Yoshiaki
Y
D000185:Actinin; D000199:Actins / Q000378:metabolism; D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D015153:Blotting, Western; D016466:CHO Cells; D019556:COS Cells; D006224:Cricetinae; D003599:Cytoskeleton / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D022001:Focal Adhesions; D006801:Humans; D039661:Integrin beta3 / Q000378:metabolism; D016023:Integrins / Q000378:metabolism; D008024:Ligands; D008840:Microfilament Proteins; D008856:Microscopy, Fluorescence; D010974:Platelet Aggregation; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D022502:Stress Fibers / Q000378:metabolism; D013917:Thrombin / Q000378:metabolism; D013997:Time Factors; D000099200:Scaffold Protein ILK; D000096985:Calponins
D000185:Actinin; D000199:Actins; D018076:DNA, Complementary; D039661:Integrin beta3; D016023:Integrins; D008024:Ligands; D008840:Microfilament Proteins; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D013917:Thrombin; D000099200:Scaffold Protein ILK; C486590:PARVA protein, human; D000096985:Calponins; C486591:PARVB protein, human