Characterization of muscle filamin isoforms suggests a possible role of gamma-filamin/ABP-L in sarcomeric Z-disc formation.
Filamin, also called actin binding protein-280, is a dimeric protein that cross-links actin filaments in the cortical cytoplasm. In addition to this ubiquitously expressed isoform (FLN1), a second isoform (ABP-L/gamma-filamin) was recently identified that is highly expressed in mammalian striated muscles. A monoclonal antibody was developed, that enabled us to identify filamin as a Z-disc protein in mammalian striated muscles by immunocytochemistry and immunoelectron microscopy. In addition, filamin was identified as a component of intercalated discs in mammalian cardiac muscle and of myotendinous junctions in skeletal muscle. Northern and Western blots showed that both, ABP-L/gamma-filamin mRNA and protein, are absent from proliferating cultured human skeletal muscle cells. This muscle specific filamin isoform is, however, up-regulated immediately after the induction of differentiation. In cultured myotubes, ABP-L/gamma-filamin localises in Z-discs already at the first stages of Z-disc formation, suggesting that ABP-L/gamma-filamin might play a role in Z-disc assembly.
van der Ven
P F
PF
University of Potsdam, Department of Cell Biology, Potsdam, Germany.
Obermann
W M
WM
Lemke
B
B
Gautel
M
M
Weber
K
K
Fürst
D O
DO
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D002417:Cattle; D002454:Cell Differentiation; D002478:Cells, Cultured; D003285:Contractile Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D064448:Filamins; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D012518:Sarcomeres / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D017386:Sequence Homology, Amino Acid
D000906:Antibodies; D003285:Contractile Proteins; C578663:FLNA protein, human; C578661:FLNC protein, human; D064448:Filamins; D008840:Microfilament Proteins; D020033:Protein Isoforms