A biochemical investigation of actin disassembly mechanisms

The dynamic nature of the actin cytoskeleton enables the rapid shape changes that are necessary for processes such as wound healing, motility and division of cells. Disassembly of actin filaments is extremely critical for the reorganization of cell shape. The cell possesses several factors that depolymerize actin filaments in an environment that has a high concentration of polymerizable monomer. However current microscopic techniques preclude the direct observation of the dynamics of individual actin filaments that usually exist as part of highly crosslinked networks inside cells. Therefore, the mechanism(s) by which actin filaments disassemble inside cells remains unclear. In this work we use a combination of single filament imaging of fluorescently labeled actin filaments as well as pyrene and FRET-based spectroscopy in order to reconstitute cellular disassembly in vitro in the presence of three factors: cofilin, coronin and Aip1. These three factors have been shown to be principally responsible for the disassembly activity of thymus extract. We describe here our discoveries regarding catastrophic whole filament destabilization of actin in the presence of the three factors. We also reinvestigated the role of Aip1 alone in cofilin-mediated depolymerization of actin filaments. We showed that Aip1 is not an actin capping protein as was previously thought, however it can destabilize cofilin-saturated stable filaments and potentiate cofilin’s severing and depolymerization activity. During the course of our work we also uncovered some insights on the biophysics of filament severing in the presence of cofilin.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Cell and Developmental Biology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2016

Author dc:creator

• Nadkarni, Ambika Vithal

Contributors dc:contributor

• Brieher, William M.
• Newmark, Phillip A.
• Gillette, Martha U.
• Raetzman, Lori T.

• Actin depolymerization
• cofilin
• Aip1

Statement dc:rights

• Copyright 2016 Ambika Nadkarni

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/92945

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/92945