Myosin heavy chain isoforms influence stretch activation and cross-bridge kinetics of Drosophila muscles

Loading...
Thumbnail Image
Authors
Zhao, Cuiping
Issue Date
2013-05
Type
Electronic thesis
Thesis
Language
ENG
Keywords
Biology
Research Projects
Organizational Units
Journal Issue
Alternative Title
Abstract
Myosin is the molecular motor that powers muscle contraction. Variation between myosin isoforms is a major determinant of muscle mechanical properties including shortening velocity and perhaps stretch activation (SA). We investigated the effect of Ca2+ concentration and myosin heavy chain (MHC) isoforms on SA, and attempted to determine the rate-limiting step of the myosin cross-bridge cycle for maximum shortening velocity. First, to understand the relationship between Ca2+ concentration, stretch-activated tension (FSA) and Ca2+-activated tension (FO), we measured FSA and power generation in skinned Drosophila indirect flight muscles (IFMs). We found that a large SA response was induced in Ca2+ activated IFMs upon a 1% muscle length increase. At pCa 4.5, FSA and FO made up ~70% and 30% of total active tension (FO+FSA), respectively. We found that IFM power output increased with increasing [Ca2+], indicating that Drosophila may regulate power output by varying Ca2+ levels instead of adjusting the number of motor units recruited. The contribution to power enhancement over the physiological Ca2+ range of pCa 5.7 to pCa 5.4 from FSA was 4-fold greater than from FO, suggesting that FSA plays a major role in regulating IFM power output during insect flight.
Description
May 2013
School of Science
Full Citation
Publisher
Rensselaer Polytechnic Institute, Troy, NY
Terms of Use
Journal
Volume
Issue
PubMed ID
DOI
ISSN
EISSN