Changes in myosin heavy chain mRNA and protein isoforms in single fibers of unloaded rat soleus muscle

Abstract

Changes in myosin heavy chain (MHC) mRNA and protein isoforms were investigated in single fibers from rat soleus muscle unloaded by hindlimb suspension for 4 and 7 days. Dramatic changes were seen after 4 days, when all fibers coexpressed slow and fast MHC mRNAs. Most fibers contained mRNAs for MHCIL L, MHCIIa, MHCIId(x), and MHCIIb. The up-regulation of the fast isoforms was only partially transmitted to the protein level. Atypical combinations of MHC mRNA isoforms, which deviated from the`next-neighbor rule', were frequent in fibers from unloaded soleus. These atypical combinations increased with time and were not observed in the controls. The results suggest that hindlimb suspension elicits in soleus muscle pronounced perturbations in the expression of MHC isoforms by disrupting transcriptional and translational activities.z 1999 Federation of European Biochemical Societies.

Analysis of myofibrillar proteins and transcripts in adult skeletal muscles of the American lobsterHomarus americanus: variable expression of myosins, actin and troponins in fast, slow-twitch and slow-tonic fibres

“…The amounts of S1 and S2 MHC isoforms in fibers from the distal region of the cutter claw are present in reciprocal levels, with some fibers possessing a near 1:1 ratio of the S1 and S2 isoforms (Fig.·4). Single fibers from other species under control conditions also contain multiple MHC isoforms, indicating that these mixtures are not only present in transitional fibers but represent the normal state of the muscles (Peuker and Pette, 1997;Lutz et al, 1998;Stevens et al, 1999;Lutz et al, 2001). In frog muscle, MHC isoform composition changes along the length of the fiber and is correlated with characteristic proportions of myosin light chain isoforms (Lutz et al, 2001).…”

“…However, analysis of individual muscle fibers from the fast region of the cutter claw and from the crusher claw muscles reveals co-expression within single fibers. A significant number of fibers from rabbit, rat and frog muscles possess multiple MHC mRNAs, most of which are 'next neighbor' isoforms (Peuker and Pette, 1997;Lutz et al, 1998;Stevens et al, 1999). However, in some cases, MHC mRNA sequences were found in fibers that did not contain detectable levels of the corresponding proteins (Peuker and Pette, 1997;Stevens et al, 1999).…”

“…A significant number of fibers from rabbit, rat and frog muscles possess multiple MHC mRNAs, most of which are 'next neighbor' isoforms (Peuker and Pette, 1997;Lutz et al, 1998;Stevens et al, 1999). However, in some cases, MHC mRNA sequences were found in fibers that did not contain detectable levels of the corresponding proteins (Peuker and Pette, 1997;Stevens et al, 1999). Unloading of rat soleus muscle increases the proportion of these mismatched fibers (Stevens et al, 1999).…”

“…However, in some cases, MHC mRNA sequences were found in fibers that did not contain detectable levels of the corresponding proteins (Peuker and Pette, 1997;Stevens et al, 1999). Unloading of rat soleus muscle increases the proportion of these mismatched fibers (Stevens et al, 1999). It has been suggested that these discrepancies are evidence for both transcriptional and translational control of muscle phenotype (Peuker and Pette, 1997;Stevens et al, 1999).…”

Muscle plasticity related to changes in tubulin and αB-crystallin levels induced by eccentric contraction in rat skeletal muscles

“…Low-frequency stimulated muscles increase the combination of slower myosin heavy chain (MHC) isoforms (7). Unloaded soleus muscle fibers show slow-to-fast MHC transition in a time-dependent manner during atrophy (34). Muscle hypertrophy can be artificially induced in animal models using eccentric contraction (22,23).…”