A Heterodimeric Metalloprotease from Vipera Lebetina Venom Induces Human Endothelial Cell Apoptosis

Abstract number: P1158

Siigur¹ E, TrummalTõnismägi¹¹ KK, Aaspõllu¹ A, Lopp¹ A, Sillat¹ T, Saat¹ R, Kasak¹ L, Tammiste¹ I, Kogerman¹ P, Kalkkinen² N, Siigur¹ J

¹¹National Institute of Chemical Physics and Biophysics, Tallinn, Estonia ¹¹National Institute of Chemical Physics and Biophysics, Tallinn, Estonia ¹¹¹National Institute of Chemical Physics and Biophysics, Tallinn, Estonia ²²Institute of Biotechnology, Protein Facility, University of Helsinki, Finland

A novel endothelial cell apoptosis inducing metalloprotease (VLAIP) was found in the snake venom of Vipera lebetina. This metalloprotease is a heterodimeric glycoprotein with molecular mass of about 106 kDa. The protease hydrolyzes azocasein, fibrinogen and oxidized insulin B-chain. The enzyme readily hydrolyzes the Aa-chain and more slowly Bb-chain of fibrinogen. VLAIP does not cleave fibrin. The complete amino acid sequences of the two different monomers of VLAIP are deduced from the nucleotide sequences of cDNAs encoding these proteins. The full-length cDNA sequences of the VLAIP-A and VLAIP-B encode open reading frames of 616 and 614 amino acids that include signal peptide, propeptide and mature metalloprotease with disintegrin-like and cysteine-rich domains. VLAIP belongs to the metalloprotease/disintegrin family of reprolysins and has high identity with the proteins that induce apoptosis of endothelial cells. Treatment of HUVEC cells with VLAIP induces changes in the attachment of cells to the substrate and causes cell death. We demonstrated that VLAIP inhibits endothelial cell adhesion to extracellular matrix proteins fibrinogen, fibronectin, vitronectin, collagen I, and collagen IV. The induction of apoptosis by VLAIP was shown by means of a typical DNA fragmentation pattern of apoptotic cells as well as by monitoring phosphatidylserine externalization using annexin V-FITC staining and flow cytometric analysis.