The Functional Pore Formation of Pro-apoptotic Proteins in Giant Unilamelar Vesicles as the Model System

Abstract

Apoptosis, also known as programmed cell death, is highly regulated mechanism in which the unwanted/damaged cells are removed in response to pro-apoptotic factors. The key step in intrinsic apoptosis pathway is the permeabilization of the mitochondrial outer membrane (MOM). Many proteins participate in the apoptotic pathway. To analyze the ability of pro-apoptotic proteins (Bid and Bax) to create functional pore into MOM-like membrane, we employ model membrane system - giant unilamelar vesicles (GUVs). The lipid composition of liposomes is phosphatidylcholine (PC), phosphatidylethanolamine (PE) and cardiolipin (CL). CL is a negatively charged lipid, which plays a crucial role in binding pro-apoptotic proteins to the membrane, where Bax tends to form pores. With the help of advanced fluorescent microscopy and the technique developed in our laboratory (dual+1 FCS) we correlate Bax/Bid in-membrane oligomerization to membrane permeabilization (pore formation).

By that we hope to shed light on the mechanism by which proapoptotic proteins induce apoptosis.