title: A snake venom metalloproteinase, kistomin, cleaves platelet glycoprotein VI and impairs platelet functions.
abstract: OBJECTIVE
  Injuries to the vessel wall and subsequent exposure of the matrix of the subendothelial layer resulted in thrombus formation. Platelet glycoprotein (GP) Ib and VI play a crucial role in matrix-induced activation and aggregation of platelets.
  
  
  RESULTS
  In the present study, we reported that the GPIb-cleaving snake venom metalloproteinase (SVMP), kistomin, inhibited collagen-induced platelet aggregation. Moreover, kistomin inhibited platelet aggregation induced by convulxin (CVX, a GPVI agonist) and a GPVI-specific antibody in a concentration and time-dependent manner. Kistomin treatment decreased platelet GPVI but not integrin alpha2beta1 and alphaIIbbeta3, accompanied with the formation of GPVI cleavage fragments, as determined by flow cytometric and Western blot analyses. In addition, intact platelet GPVI and recombinant GPVI were digested by kistomin to release 25- and 35-kDa fragments, suggesting that kistomin cleaved GPVI near the mucin-like region. We designed four synthetic peptides ranging from Leu180 to Asn249 as the substrates for kistomin and found that kistomin cleaved these synthetic peptides at FSE205/A206TA and NKV218/F219TT, as analyzed by MALDI-TOF-MS. In addition, GPVI-specific antibody-induced tyrosine kinase phosphorylation in platelets was reduced after kistomin pretreatment, and platelet adhesion to collagen but not to fibrinogen was attenuated by kistomin.
  
  
  CONCLUSIONS
  We provided here the first evidence that a P-I snake venom metalloproteinase, kistomin, inhibits the interaction between collagen and platelet GPVI through its proteolytic activity on GPVI, thus providing an alternative strategy for developing new anti-thrombotic agents.
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: C C
authors.initials: CC
authors.lastname: Hsu
authors.forename: W B
authors.initials: WB
authors.lastname: Wu
authors.forename: T F
authors.initials: TF
authors.lastname: Huang
mesh_terms: D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018955:CD36 Antigens / Q000378:metabolism*; D002448:Cell Adhesion; D003094:Collagen / Q000378:metabolism; D003435:Crotalid Venoms / Q000378:metabolism / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D006868:Hydrolysis; D045726:Metalloproteases / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D010975:Platelet Aggregation Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
chemical_list: D018955:CD36 Antigens; D003435:Crotalid Venoms; D010975:Platelet Aggregation Inhibitors; D011994:Recombinant Proteins; D014443:Tyrosine; D003094:Collagen; D045726:Metalloproteases; C524409:kistomin protein, Calloselasma rhodostoma