Inhibition of tBid-promoted cytochrome c release by the antimicrobial peptide tritrpticin: effects on membrane structure

• Grant number: 13/19491-4
• Support type: Scholarships abroad - Research Internship - Doctorate
• Effective date (Start): January 01, 2014
• Effective date (End): December 31, 2014
• Field of knowledge: Biological Sciences - Biophysics - Molecular Biophysics
• Principal Investigator: Shirley Schreier
• Grantee: José Carlos Bozelli Junior
• Supervisor abroad: Richard M. Epand
• Home Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Research place: McMaster University, Canada

Abstract

Mitochondria perform crucial roles in vital cellular functions, including life/death decisions. Mitochondria outer membrane permeabilization (MOMP) is considered the point of no return in programmed cell death, namely apoptosis. Proteins of the B cell lymphoma 2 (Bcl-2) family regulate MOMP. Yet, the members Bax and Bak are known to be the executioners of MOMP. Activation of Bax could be triggered by tBid , another member of the Bcl-2 family, among other stimuli. Although many of the key apoptotic proteins that are activated or inactivated in the apoptotic pathways have been identified, the molecular mechanisms of action or activation of these proteins are not fully understood. The mitochondria-specific lipid, cardiolipin (CL), has been shown to be required for tBid-induced Bax oligomerization, and therefore MOMP. Changes in intrinsic membrane curvature have also been related with this process. Cardiolipin (CL) is a conically shaped molecule with propensity to form hexagonal II (HII) phase. Indeed, it has been described that tBid promotes hexagonal phase formation in liposomes containing CL. The antimicrobial peptide tritrpticin (TRP3) which presents activity at the membrane level and is able to induce positive membrane curvature has been shown to inhibit tBid-promoted cytochrome c release in mitochondria in vitro. However, the molecular details of TRP3 inhibtion of tBid-promoted cytochrome c release is not know. Our aim is to understand how TRP3 inhibits MOMP; this knowledge should contribute to the understanding of the molecular mechanisms involved in the apoptotic pathways. In addition, these studies might shed light on the antimicrobial mechanism of action of TRP3, which is not completely understood at present. In order to achieve this goal we propose to study the interaction of TRP3 with mitochondria in vitro and with model membranes containing variable amounts of the mitochondria-specific lipid CL in the absence and presence of Bax and/or tBid. (AU)