Effects of integrin alpha IIb(R995A) mutation on receptor affinity and pp125 (FAK) phosphorylation.
OBJECTIVE
To investigate the role of cytoplasmic domain of integrin alpha IIb in platelet signal transduction.


METHODS
Binding capacity of integrin alpha IIb(R995A) to antibody platelet activation complex-1 (PAC-1) and pp125 focal adhesion kinase (FAK) phosphorylation of cells were detected by flow cytometry, immune precipitation, and Western blotting.


RESULTS
Without activation, wild-type alpha IIb beta3 Chinese hamster ovary (CHO) cells failed to bind to PAC-1, but mutant chimera alpha IIb(R995A)beta3 CHO cells were able to bind with PAC-1. Furthermore, phosphorylation of pp125 (FAK) in wild-type alpha IIb beta3 CHO cells occured only when cells were adhered to fibrinogen, but could not be detected in bovine serum albumin suspension. However in the mutant chimera group, it could be detected in both conditions.


CONCLUSIONS
The mutation in integrin alpha IIb(R995A) alters its affinity state as a receptor, thus also mediating cytoplasmic signal transduction leading to the phosphorylation of pp125 (FAK) without ligand binding.
Tang
Xue-yuan
XY
Department of Hematology, the Third Xiangya Hospital, Central South University, Changsha 410013. tangxueyuan2003@yahoo.com.cn
Jian
Zai-fu
ZF
Wang
Guo-ping
GP
Yang
Hong-hui
HH
Liu
Wei
W
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D016466:CHO Cells; D002448:Cell Adhesion; D006224:Cricetinae; D003412:Cricetulus; D003593:Cytoplasm / Q000378:metabolism; D054641:Dual Specificity Phosphatase 2; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D010766:Phosphorylation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017354:Point Mutation; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection
D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D054648:Protein Phosphatase 2; C517032:DUSP2 protein, human; D054641:Dual Specificity Phosphatase 2; D017027:Protein Tyrosine Phosphatases