Stejnihagin, a novel snake metalloproteinase from Trimeresurus stejnegeri venom, inhibited L-type Ca2+ channels

Snake venom metalloproteinases (SVMPs) mainly distribute in Crotalid and Viperid snake venom and are classified into the Reprolysin subfamily of the M12 family of metalloproteinases. Previous function investigations have suggested that SVMPs are the key toxins involved in a variety of snake venom-induced pathogenesis including systemic injury, local damage, hemorrhage, edema, hypotension, hypovolemia, inflammation and necrosis. However, up to now, there is no report on ion channels blocking activity about SVMPs. Here, from Trimeresurus stejnegeri venom we purified a component Stejnihagin containing a mixture of Stejnihagin-A and -B, with 86% sequences identity, both as members of SVMPs. In the study, whole-cell patch clamp and vessel tension measurement were employed to identify the effect of Stejnihagin on L-type Ca2+ channels and vessel contraction. The results show that Stejnihagin inhibited L-type Ca2+channels in A7r5 cells with an IC50 about 37 nM and simultaneously blocked 60 mM K+-induced vessel contraction. Besides, the inhibitory effect of Stejnihagin on L-type Ca2+ channels was also independent of the enzymatic activity. This finding offers new insight into the snake venom metalloproteinase functions and provides a novel pathogenesis of T. stejnegeri venom. Furthermore, it may also provide a clue to study the structure–function relationship of animal toxins and voltage-gated Ca2+ channel.