Acute effects of desmin mutations on cytoskeletal and cellular integrity in cardiac myocytes.
Mutations in desmin have been associated with a subset of human myopathies. Symptoms typically appear in the second to third decades of life, but in the most severe cases can manifest themselves earlier. How desmin mutations lead to aberrant muscle function, however, remains poorly defined. We created a series of four mutations in rat desmin and tested their in vitro filament assembly properties. RDM-G, a chimera between desmin and green fluorescent protein, formed protofilament-like structures in vitro. RDM-1 and RDM-2 blocked in vitro assembly at the unit-length filament stage, while RDM-3 had more subtle effects on assembly. When expressed in cultured rat neonatal cardiac myocytes via adenovirus infection, these mutant proteins disrupted the endogenous desmin filament to an extent that correlated with their defects in in vitro assembly properties. Disruption of the desmin network by RDM-1 was also associated with disruption of plectin, myosin, and alpha-actinin organization in a significant percentage of infected cells. In contrast, expression of RDM-2, which is similar to previously characterized human mutant desmins, took longer to disrupt desmin and plectin organization and had no significant effect on myosin or alpha-actinin organization over the 5-day time course of our studies. RDM-3 had the mildest effect on in vitro assembly and no discernable effect on either desmin, plectin, myosin, or alpha-actinin organization in vivo. These results indicate that mutations in desmin have both direct and indirect effects on the cytoarchitecture of cardiac myocytes.
Haubold
Kurt
K
Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309-0347, USA.
Herrmann
Harald
H
Langer
Stephen J
SJ
Evans
Robert M
RM
Leinwand
Leslie A
LA
Klymkowsky
Michael W
MW
D000256:Adenoviridae / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000502:physiology* / Q000648:ultrastructure; D003893:Desmin / Q000235:genetics*; D017353:Gene Deletion; D015870:Gene Expression; D007381:Intermediate Filament Proteins / Q000502:physiology; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000502:physiology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D051190:Plectin; D051381:Rats; D012518:Sarcomeres / Q000502:physiology
D003893:Desmin; D007381:Intermediate Filament Proteins; C495334:Plec protein, rat; D051190:Plectin