Author ORCID Identifier

0000-0002-0533-7687

Date of Graduation

8-2019

Document Type

Thesis (MS)

Program Affiliation

Biomedical Sciences

Degree Name

Masters of Science (MS)

Advisor/Committee Chair

Dr. Shane Cunha

Committee Member

Dr. Carmen Dessauer

Committee Member

Dr. Jeff Frost

Committee Member

Dr. Darren Boehning

Committee Member

Dr. Neal Waxham

Abstract

Distinctly organized domains of receptors, ion channels, transporters, signaling molecules, cell adhesion molecules, and contractile proteins are crucial to cardiac function. Interactions between adaptor proteins such as ankyrins and cytoskeletal proteins such as obscurin play a pivotal role in organizing these functional domains in cardiomyocytes. Therefore, dysfunction of both ankyrin as well as obscurin lead to a host of cardiovascular diseases such as arrhythmias and cardiomyopathies. Alternative splicing of ankyrin yields numerous isoforms that interact with obscurin at various sub-cellular domains. And while some of these obscurin-ankyrin complexes have been studied, many others have not been characterized. Further, previous studies have focused on these ankyrin-obscurin complexes individually; however, how ankyrin-mediated macromolecular complexes are integrated together within the cardiomyocyte is not clear. Thus, the work in this thesis describes mechanisms by which obscurin organizes two separate ankyrin-mediated macromolecular complexes simultaneously. Two muscle-specific ankyrin isoforms, sAnk1.5 and AnkG107/130, which do not interact with each other, were used to test if obscurin could serve to bridge these ankyrins. Through a series of in vitro binding assays, co-precipitation assays, and FLIM-FRET analysis we demonstrate that obscurin binds both isoforms simultaneously via interactions with two ankyrin binding sites in its C-terminus. We also show that β1-spectrin, a protein that does not directly interact with obscurin or sAnk1.5, can be recruited to a macromolecular complex via an interaction with AnkG107/130. Lastly, both ankyrin isoforms localize to the M-line of cardiomyocytes suggesting that obscurin could serve to target two separate ankyrin protein complexes to the same domain (M-line). In sum, this work provides a novel, compelling mechanism for ankyrin complex integration and coordination in cardiomyocytes.

Keywords

ankyrin, obscurin, cardiomyocytes, domain organization

Available for download on Tuesday, August 11, 2020

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