[Effect of the defect of integrin alpha II b beta 3 on the inside-out signal transduction in platelets].
OBJECTIVE
To investigate the effect of the defect of integrin alpha II b beta 3 on the inside-out signal transduction in platelets.


METHODS
The transfected cDNA, its expression and the ability of cells binding to PAC-1 and fibrinogen were investigated by RT-PCR, DNA sequence analysis, flow cytometry and Western blotting.


RESULTS
The integrin alpha II b beta 3 level in the patients with Glanzmann's thrombasthenia was significantly lower than that of the normal subjects and the platelets of the patients failed to bind PAC-1 activated by ADP. There were both C3077G and G3078C mutations in exon 30 of mutant alpha II bR995A beta 3 cDNA, which resulted in an amino acid substitution arginine (R) 995 to alanine (A). CHO cells transfected with wild-type alpha II b beta 3 or mutant alpha II bR995A beta 3 cDNA respectively expressed normal alpha II b beta 3 and mutant alpha II bR995A beta 3. When cells were not activated, wild-type alpha II b beta 3 CHO cells failed to bind PAC-1, but could adhere to fibrinogen, but mutant chimera alpha II bR995A beta 3 CHO cells were able to bind PAC-1 and exhibited high affinity binding fibrinogen.


CONCLUSIONS
The point mutation in integrin alpha II bR995A can induce the inside-out signal transduction in platelets, and have integrin alpha II bR995A beta 3 locked into an activation state; the defect of alpha II b beta 3 in patients with GT impairs the inside-out signal transduction mediated by alpha II b beta 3 in platelets and the adhesive functions of platelets.
Tang
Xue-yuan
XY
Department of Hematology, Xiangya Hospital, Central South University, Changsha 410008, China.
Chen
Fang-ping
FP
Jian
Zai-fu
ZF
D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D016466:CHO Cells / Q000378:metabolism; D002648:Child; D006224:Cricetinae; D018076:DNA, Complementary / Q000235:genetics; D006801:Humans; D008297:Male; D010973:Platelet Adhesiveness / Q000502:physiology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics / Q000502:physiology*; D017354:Point Mutation; D015398:Signal Transduction; D013915:Thrombasthenia / Q000097:blood; D014162:Transfection
D018076:DNA, Complementary; D019039:Platelet Glycoprotein GPIIb-IIIa Complex