Dynamics of Z-band based proteins in developing skeletal muscle cells.
During myofibril formation, Z-bodies, small complexes of alpha-actinin and associated proteins, grow in size, fuse and align to produce Z-bands. To determine if there were changes in protein dynamics during the assembly process, Fluorescence Recovery after Photobleaching was used to measure the exchange of Z-body and Z-band proteins with cytoplasmic pools in cultures of quail myotubes. Myotubes were transfected with plasmids encoding Yellow, Green, or Cyan Fluorescent Protein linked to the Z-band proteins: actin, alpha-actinin, cypher, FATZ, myotilin, and telethonin. Each Z-band protein showed a characteristic recovery rate and mobility. All except telethonin were localized in both Z-bodies and Z-bands. Proteins that were present both early in development in Z-bodies and later in Z-bands had faster exchange rates in Z-bodies. These results suggest that during myofibrillogenesis, molecular interactions develop between the Z-band proteins that decrease their mobility and increase the stability of the Z-bands. A truncated construct of alpha-actinin, which localized in Z-bands in myotubes and exhibited a very low rate of exchange, led to disruption of myofibrils, suggesting the importance of dynamic, intact alpha-actinin molecules for the formation and maintenance of Z-bands. Our experiments reveal the Z-band to be a much more dynamic structure than its appearance in electron micrographs of cross-striated muscle cells might suggest.
Wang
Jushuo
J
Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia 19104-6058, USA.
Shaner
Nathan
N
Mittal
Balraj
B
Zhou
Qiang
Q
Chen
Ju
J
Sanger
Jean M
JM
Sanger
Joseph W
JW
D000818:Animals; D002478:Cells, Cultured; D036681:Fluorescence Recovery After Photobleaching; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000166:cytology* / Q000502:physiology*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism; D011784:Quail; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
D008164:Luminescent Proteins; D009124:Muscle Proteins; D011993:Recombinant Fusion Proteins