Honors Theses
Date of Award
Fall 5-11-2024
Document Type
Undergraduate Thesis
Department
Biology
First Advisor
Mika Jekabsons
Second Advisor
Bradley Jones
Third Advisor
Joshua Bloomekatz
Relational Format
Dissertation/Thesis
Abstract
Members of the Bcl-2 family are responsible for regulating the intrinsic pathway of apoptosis through Bcl-2 homology 3 (BH3) domain interactions of pro- and anti-apoptotic members. Apoptosis occurs when BH3-only pro-death members overwhelm the pro-survival ones, leading to oligomerization of the multi-BH domain pro-death protein Bax to signal death by releasing cytochrome c from mitochondria into the cytoplasm. This process is essential for proper embryonic tissue development as well as maintenance of mature tissues. While BH3-only proteins such as Bim and Bid bind to and activate Bax through their BH3 domains, other regulators of this mitochondrial permeabilizer may exist. Two such candidates are the voltage-dependent anion channels (VDACs) 1 and 2, which were recently discovered to have strong sequence homology at their N-termini with BH3 domains. This study tested the hypothesis that VDACs 1 and 2 are Bax activators through their N-terminal BH3-like domains. Recombinant Bax lacking a-helix 9 was treated with synthetic 26-mer peptides corresponding to the N-terminal sequence of VDACs 1 or 2 and its conformational state assessed by blue native poly acrylamide gel electrophoresis (BN-PAGE). As a positive control, a Bim BH3-domain peptide consistently induced a ~15 kDa altered monomeric Bax conformation that was resolved from the ~20 kDa inactive form. Bim inconsistently (2 of 15 experiments) triggered a modest increase in dimers. VDAC 1 and 2 peptides modestly induced dimers (~40 kDa) and trimers (~60 kDa) in ~30-40 % of experiments, but unlike Bim, they did not trigger a detectable ~15 kDa monomer. This may indicate that the VDAC peptides trigger a slightly different conformation of Bax monomer with a greater propensity to form dimers than Bim. Together, these findings support the hypothesis that the N-terminal BH3-like domains of VDAC 1 and 2 are potential Bax activators involved in apoptosis regulation.
Recommended Citation
Dupree, Allison G., "Effects of VDAC 1 and 2 N-terminal peptides on Bax conformation assessed by blue native gel electrophoresis" (2024). Honors Theses. 3119.
https://egrove.olemiss.edu/hon_thesis/3119