Thromb Haemost 2003; 90(03): 465-475
DOI: 10.1160/TH03-02-0072
Platelets and Blood Cells
Schattauer GmbH

A tetrameric glycoprotein Ib-binding protein, agglucetin, from Formosan pit viper: structure and interaction with human platelets

Wen-Jeng Wang
1   Division of Biomedical Science, Department of Nursing, Chang-Gung Institute of Technology, Kwei-Shan, Tao-Yuan, Taiwan
,
Qing-Dong Ling
2   Cathay Medical Research Institute, Cathay General Hospital, Taipei, Taiwan
,
Ming-Yi Liau
3   Department of Biotechnology, Fooyin Institute of Technology, Ta-Liao, Kaohsiung Taiwan
,
Tur-Fu Huang
4   Department of Pharmacology, College of Medicine, National Taiwan University, Taipei, Taiwan
› Author Affiliations

Financial support: This work was financially supported by grants from the National Science Council of Taiwan (NSC91-2320-B002-156) and Chang Gung Medical Research foundation (CMRPF32001).
Further Information

Publication History

Received 04 February 2003

Accepted after revision 25 May 2003

Publication Date:
05 December 2017 (online)

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Summary

Agglucetin, a tetrameric agglutination inducer from the Formosan pit viper, has been identified as a platelet membrane glycoprotein (GP) Ib agonist and directly agglutinated fixed-platelets in the absence of von Willebrand factor (vWf). Here, we resolved the complete cDNA sequences of agglucetin subunits (α1, α2, β1 and β2) by molecular cloning. Each cloned cDNA encoding the leader peptide (23 residues) and the mature subunit (131/135/123/126 residues) shares a high degree of homology to each other and the C-type lectin-like GP Ib-binding proteins (BPs). Furthermore, agglucetin specifically caused platelet agglutination and surface exposure of integrin αIIbβ3 with a GPIb-dependent manner in washed platelets, based on the observation that the enhanced expression of functional αIIbβ3 was suppressed by a GPIb-cleaving metalloproteinase, crotalin. Pretreating platelets with staurosporine or BAPTA-AM also completely blocked the exposure of functional αIIbβ3, suggesting that the activation of protein kinase C and intracellular calcium mobilization are involved in the GPIb-dependent signaling. In human platelet-rich plasma (PRP), agglucetin elicited sequential biphasic responses of platelet agglutination and aggregation in a GPIb- and αIIbβ3-dependent manner, respectively, implying that other cofactors may amplify platelet activation to trigger aggregation.

The nucleotide sequences reported in Figs. 1 and 2 have deposited in the GenBank, EMBL and DDBJ Nucleotide Sequence Databases under the accession numbers: AF540645 for agglucetin-α1 subunit, AF540646 for agglucetin-α2 subunit, AF540647 for agglucetin-β1 subunit and AF540648 for agglucetin-β2 subunit.