Senior Honors Projects, 2010-current

Date of Award

Winter 2016

Document Type

Thesis

Degree Name

Bachelor of Science (BS)

Department

Department of Biology

Advisor(s)

Tim Bloss, Ph.D.

Kim Slekar, Ph.D.

Abstract

Severe misfolded protein stress initiates cellular responses that often result in the death of the affected cell, typically by apoptosis. An essential aspect of apoptosis is caspase-mediated cleavage of proteins that, once cleaved, further propagate death. One heterodimeric structure putatively targeted in this process in the nascent polypeptide-associated complex (NAC), a translational chaperone thought to help prevent misfolded protein stress in the ER. The purpose of this investigation was to determine whether the beta subunit of the NAC in C. elegans (ICD-1) is cleaved during the induction of apoptosis, with the hypothesis that ICD-1 is cleaved during stressed-induced apoptosis to propagate cell death. To test this hypothesis, I performed Western analyses of ICD-1 obtained from stressed and un-stressed populations of wild-type C. elegans to determine any stress-correlated differences in the protein length of ICD-1. To determine the possible structure of ICD-1 during this cleavage, I used protein modelling to evaluate the position of the putative caspase-cleavage site of monomeric ICD-1, the form the protein is thought to take during misfolded protein stress. Optimization of western blotting conditions for detecting ICD-1 were developed, but the final western blots on stressed and unstressed worms were inconclusive due to bacterial contamination of protein lysates. The amino acid sequence analyses and protein modelling algorithm analyses revealed the putative caspase cleavage site on monomeric ICD-1 is exposed and accessible to cleavage by a caspase. Sequence alignments and bioinformatics analyses for conservation revealed a high degree of variability localized to the region surrounding the putative caspase cleavage site, indicating evolutionary specialization that optimizes the cleavage of this site by the specific caspases found in the worm. Further investigation should develop uncontaminated western analysis results of the state of ICD-1 in stressed and unstressed worms. Further structural analyses could assess the nature of ICD-1 when bound by ICD-2 as well as x-ray crystallography to reliably resolve the structures of the ICD-1/ICD-2 heterodimer.

Available for download on Thursday, May 03, 2018

Share

COinS