Off-campus UMass Amherst users: To download campus access dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Dissertations that have an embargo placed on them will not be available to anyone until the embargo expires.

ORCID

Document Type

Open Access Thesis

Degree Program

Kinesiology

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2019

Month Degree Awarded

September

Abstract

Intracellular acidosis is a putative agent of skeletal muscle fatigue, in part, because acidosis depresses the calcium (Ca2+) sensitivity and force production of muscle (18, 50). However, the molecular mechanisms behind this depression in Ca2+ sensitivity and force production are unknown. This gap in knowledge poses a significant challenge in generating a complete understanding of the fatigue process. To close this gap, the ability of myosin to bind to a single actin filament was measured under acidic conditions, in a laser trap assay, with and without regulatory proteins. Decreasing pH from 7.4 to 6.5 reduced the frequency of single actomyosin binding events at submaximal (pCa 8 – pCa 6), but not at maximal (pCa 5 - 4) concentrations. To delineate whether this was due to a direct effect on myosin versus an indirect effect on the regulatory proteins, troponin (Tn) and tropomyosin (Tm), binding frequency was also quantified in the absence of Tn and Tm. Acidosis did not alter the frequency of actomyosin binding events in the absence of regulatory proteins (1.4 ± 0.05 vs 1.4 ± 0.13 events/sec for pH 7.4 and 6.5). Additionally, acidosis did not significantly affect the size of myosin’s powerstroke, or the duration of binding events in the presence of regulatory proteins, at every pCa. These data suggest that acidosis impedes activation of the thin filament by competitively inhibiting Ca2+ binding to TnC. This slows the rate at which myosin initially attaches to actin, therefore less cross-bridges will be bound and generating force at any given sub-maximal pCa.

First Advisor

Edward P. Debold, Ph.D.

Second Advisor

Mark S. Miller, Ph.D.

Third Advisor

Jennifer L. Ross, Ph.D.

Share

COinS