Molecular Diversity of Myofibrillar Proteins: Gene Regulation and
Functional Significance.
Schiaffino, Stefano, and Carlo Reggiani.
Dept. of Biomedical Sciences, University of Padova, Via Trieste 75, 35121
Padova, Italy.
APStracts 2:0028P, 1996.
ABSTRACT
Myofibrillar proteins exist as multiple isoforms that derive from multigene
(isogene) families. Additional isoforms, including products of tropomyosin,
myosin light chain 1 fast, troponin T, titin, and nebulin genes can be
generated from the same gene through alternative splicing or use of
alternative promoters. Myofibrillar protein isogenes are differentially
expressed in various muscle types and fiber types but can be coexpressed
within the same fiber. Isogenes are regulated by transcriptional and
posttranscriptional mechanisms; however, specific regulatory sequences and
transcription factors have not yet been identified. The pattern of isogene
expression varies during muscle development in relation to the different
origin of myogenic cells and primary/secondary fiber generations and is
affected by neural and hormonal influences. The variable expression of
myofibrillar protein isoforms is a major determinant of the contractile
properties of skeletal muscle fibers. The diversity among isomyosins is
related to the differences in the parameters of chemomechanical transduction
as ATP hydrolysis rate and shortening velocity. Troponin and tropomyosin
isoforms determine the variable sensitivity to calcium, whereas titin isoforms
dictate the elastic properties of muscle fibers at rest. Both myosin and
troponin isoforms contribute to the differences in the resistance to fatigue
of muscle fibers.
APS Manuscript Number P28-5.
Article publication pending April 1996, Physiological Reviews.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996