Reexpression of alpha-smooth muscle actin isoform in cultured adult rat cardiomyocytes.
Expression of alpha-smooth muscle (sm) actin in regenerating adult cardiomyocytes in culture was investigated. No alpha-sm-actin could be detected in adult ventricular tissue or in newly dissociated rod-shaped cells, whereas a fraction of the polymorphic flattened out adult cardiac cells in culture did express the protein. Immunofluorescence studies revealed a characteristic staining pattern, suggesting the preferential presence of alpha-sm-actin in stress fiber-like structures, while newly formed myofibrils contained only little alpha-sm-actin isoprotein. Cell-cell contacts were resumed, but formation of new gap junctions, as revealed by microinjecting Lucifer yellow, was not dependent on alpha-sm-actin expression. The behavior corresponds to fetal cardiomyocytes either in tissue or as single cells in culture where expression of alpha-sm-actin can be observed. Such immunofluorescence staining patterns with corresponding immunoblot data can be expected when a return to a less differentiated, more fetal state of the adult cardiomyocyte in culture is assumed. The possible role of the alpha-sm-actin and alpha-sarcomeric actin isoforms during reformation of myofibrillar sarcomeres is discussed.
Institute for Cell Biology, Swiss Federal Institute of Technology, Zurich.
M
M
Eppenberger-Eberhardt
I
I
Flamme
V
V
Kurer
H M
HM
Eppenberger
D000199:Actins / Q000032:analysis / Q000096:biosynthesis* / Q000302:isolation & purification; D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex / Q000032:analysis; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D015151:Immunoblotting; D008970:Molecular Weight; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000199:Actins; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex