Trimucytin, a collagen-like snake venom protein, activates platelets independent of I-domain within alpha2 subunit of alpha2beta1 integrin.
Trimucytin is a powerful platelet aggregation inducer isolated from the venom of Taiwan habu snake (Trimeresurus mucrosquamatus). In this study, we found that the snake venom protein, crovidisin, which prevents collagen-platelet interaction through its high-affinity binding to collagen, inhibited competitively trimucytin-induced aggregation of washed human platelets with a pA(2) value of 6.65. The ability of trimucytin in triggering platelet aggregation was suppressed by a monoclonal antibody (A2-IIE10) raised against the alpha2 subunit of alpha2beta1 integrin (glycoprotein Ia/IIa), indicating that platelet alpha2beta1 integrin plays a central role in trimucytin's platelet reactivity. Many studies have localized the major reactive site of alpha2beta1 integrin to the I-domain of alpha2 subunit. However, Escherichia coli-produced recombinant alpha2 I-domain (GST-alpha2 fusion protein) blocking collagen-induced platelet aggregation failed to inhibit aggregation of platelets in response to trimucytin. Based on these findings, it is concluded that the platelet reactivity of trimucytin is alpha2beta1 integrin-dependent, while the I-domain present in the alpha2 subunit is not involved. This novel snake venom protein would be useful for mapping the functional domain of alpha2beta1 integrin.
Liu
Chao-Zong
CZ
Department of Pharmacology, College of Medicine, Tzu Chi University, Number 701, Section 3, Chung-Yang Road, Hualien 970, Taiwan, ROC. czliu33@mail.tcu.edu.tw
Wu
Ting-Feng
TF
Huang
Tur-Fu
TF
Wu
Dung-Ho
DH
Lin
Guan-Ling
GL
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive; D001792:Blood Platelets / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D002352:Carrier Proteins / Q000494:pharmacology; D024042:Collagen Type I / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003435:Crotalid Venoms / Q000494:pharmacology*; D006801:Humans; D039421:Integrin alpha2 / Q000276:immunology / Q000378:metabolism / Q000502:physiology; D045726:Metalloproteases; D015539:Platelet Activation / Q000187:drug effects*; D017434:Protein Structure, Tertiary; D011509:Proteoglycans / Q000494:pharmacology*; D038981:Receptors, Collagen / Q000037:antagonists & inhibitors / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000502:physiology; D030162:Reptilian Proteins
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D024042:Collagen Type I; D003435:Crotalid Venoms; D039421:Integrin alpha2; D011509:Proteoglycans; D038981:Receptors, Collagen; D011993:Recombinant Fusion Proteins; D030162:Reptilian Proteins; C029748:Trimeresurus venoms; C026064:aggregoserpentin; D045726:Metalloproteases; C103975:crovidisin protein, Crotalus viridis