Abstract
Cardiotoxins (CTXs), a major component of snake venom from Taiwan cobra Naja atra, are structurally homologues beta-sheet basic polypeptides that are known to manifest cytotoxicity in cells, but the mechanism of their action remains obsecure. Using the confocal imaging technique, we show that cardiotoxins can get into H9C2 cells and accumulate markedly in lysosomes. And the previous study has shown that CTX A2 and CTXA4 internalize through dynamin-dependent macropinocytosis and it has proved that they can also internalize through clathrin mediated pathway. However, lipid rafts are implicated in endocytosis. So membrane lipid raft is needed to further investigate if it affects cargo internalization. In this study, we found that cholesterol incorporation can enhance the internalization of CTX A2 and CTXA4. And we observe that CTXA2 and CTXA4 can target to lysosome at higher level compared to normal and cholesterol deplete condition. On the basis of the results obtained, we propose that lysosomes may be the primary target of CTX A2 and CTXA4. CTXs may not degraded in lysosomes, it has possibility to make lysosome damage to release lysosomal extracts. So we try to test the lysosomal integrity and check the relative effects of CTXs on lysosmes of living cultured cells. And these data indicate that CTXA2 and CTXA4 may inhibits the acidification of lysosome. This may provide us some possibility of how CTXs make H9C2 cells toxicity.