Haemolytic and cytotoxic action of latarcin Ltc2a

Abstract

Activity and action mechanisms of latarcin 2a (Ltc2a), an antimicrobial peptide from the venom of the spider Lachesana tarabaevi ( Zodariidae), were studied in vitro on human cells. Cytotoxicity of Ltc2a for erythrocytes (EC 50 = 3.4 μM), leukocytes (EC 50 = 19.5 μM) and erythroleukemia K562 cells (EC 50 = 3.3 μM) has been found to be primary related to plasma membrane destabilization. Using fluorescently labeled Ltc2a, three common features are found for erythrocytes and K562 cells: pronounced inhomogeneity of cellular response to Ltc2a; complex multistage character of Ltc2a-cell interactions; a positive feedback between Ltc2a binding to plasma membrane and development of toxic effects. Discocyte – echinocyte – spherocyte – ghost is a sequence of Ltc2a-induced transformations of erythrocytes that are accompanied by multistage enhancement of Ltc2a membrane binding, formation of small ( ca. 2.0 nm) membrane pores, osmotic imbalance development and reorganization of the pores into large ( ca. 13 nm) membrane openings that are preserved in ghosts. Ltc2a induces membrane blebbing and swelling of K562 cells followed by cell death. Cytotoxic action occurs through formation of membrane pores ( ca. 3.7 nm) which show greater permeability for anionic than cationic molecules. The pore formation is accompanied with self-assisted Ltc2a internalization and accumulation in mitochondria, mitochondrion inactivation and apoptosis-independent phosphatidylserine externalization.