Tropomyosin assembly intermediates in the control of microfilament system turnover

Tropomyosin is a coiled-coil α-helical protein, which self-associates in a head-to-tail fashion along polymers of actin to produce thin filaments. Mammalian non-muscle cells express a large number of tropomyosin isoforms, which are differentially regulated during embryogenesis and associated with sp...

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Bibliographic Details
Published in:European journal of cell biology 2008-11, Vol.87 (11), p.905-920
Main Authors: Grenklo, Staffan, Hillberg, Louise, Zhao Rathje, Li-Sophie, Pinaev, George, Schutt, Clarence. E., Lindberg, Uno
Format: Article
Language:English
Subjects:
Actin
Actin Cytoskeleton - genetics
Actin Cytoskeleton - metabolism
Actins - genetics
Actins - metabolism
Animals
Cell Line, Transformed
Cell Line, Tumor
Cell Movement
Filopodia
Humans
Lamellipodia
Protein Isoforms - genetics
Protein Isoforms - metabolism
Pseudopodia - genetics
Pseudopodia - metabolism
Rats
Tropomyosin
Tropomyosin - genetics
Tropomyosin - metabolism
Tropomyosin multimers
Tumorigenesis
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Summary:Tropomyosin is a coiled-coil α-helical protein, which self-associates in a head-to-tail fashion along polymers of actin to produce thin filaments. Mammalian non-muscle cells express a large number of tropomyosin isoforms, which are differentially regulated during embryogenesis and associated with specialized actin microfilament ensembles in cells. The function of tropomyosin in specifying form and localization of these subcellular structures, and the precise mechanism(s) by which they carry out their functions, is unclear. This paper reports that, while the major fraction of non-muscle cell tropomyosin resides in actin thin filaments of the cytomatrix, the soluble part of the cytoplasm contains tropomyosins in the form of actin-free multimers, which are isoform specific and of high molecular weight (MW app 180,000–250,000). Stimulation of motile cells with growth factors induces a rapid, actin polymerization-dependent outgrowth of lamellipodia and filopodia. Concomitantly, the levels of tropomyosin isoform-specific multimers decrease, suggesting their involvement in actin thin filament formation. Malignant tumor cells have drastically altered levels and composition of tropomyosin isoform-specific multimers as well as tropomyosin in the cytomatrix.
ISSN:0171-9335
1618-1298
DOI:10.1016/j.ejcb.2008.06.006