Functional differences between L- and T-plastin isoforms.
Fimbrins/plastins are a family of highly conserved actin-bundling proteins. They are present in all eukaryotic cells including yeast, but each isoform displays a remarkable tissue specificity. T-plastin is normally found in epithelial and mesenchymal cells while L-plastin is present in hematopoietic cells. However, L-plastin has been also found in tumor cells of non-hematopoietic origin (Lin, C.-S., R. H. Aebersold, S. B. Kent, M. Varma, and J. Leavitt. 1988. Mol. Cell. Biol. 8:4659-4668; Lin, C.-S., R. H. Aebersold, and J. Leavitt. 1990. Mol. Cell. Biol. 10: 1818-1821). To learn more about the biological significance of their tissue specificity, we have overproduced the T- and L-plastin isoforms in a fibroblast-like cell line, CV-1, and in a polarized epithelial cell line, LLC-PK1. In CV-1 cells, overproduction of T- and L-plastins induces cell rounding and a concomitant reorganization of actin stress fibers into geodesic structures. L-plastin remains associated with microfilaments while T-plastin is almost completely extracted after treatment of the cells with non-ionic detergent. In LLC-PK1 cells, T-plastin induces shape changes in microvilli and remains associated with microvillar actin filaments after detergent extraction while L-plastin has no effect on these structures and is completely extracted. The effect of T-plastin on the organization of microvilli differs from that of villin, another actin-bundling protein. Our experiments indicate that these two isoforms play differing roles in actin filament organization, and do so in a cell type-specific fashion. Thus it is likely that these plastin isoforms play fundamentally different roles in cell function.
Arpin
M
M
Unité de Biologie des Membranes, URA CNRS, Département de Biologie Moléculaire, Institut Pasteur, Paris.
Friederich
E
E
Algrain
M
M
Vernel
F
F
Louvard
D
D
D008841:Actin Cytoskeleton / Q000502:physiology / Q000648:ultrastructure; D000199:Actins / Q000502:physiology / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology; D002448:Cell Adhesion / Q000502:physiology; D016764:Cell Polarity / Q000502:physiology; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000502:physiology* / Q000648:ultrastructure; D004847:Epithelial Cells; D004848:Epithelium / Q000648:ultrastructure; D005347:Fibroblasts / Q000166:cytology / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins / Q000235:genetics / Q000502:physiology; D008871:Microvilli / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D011994:Recombinant Proteins / Q000302:isolation & purification; D014162:Transfection
D000199:Actins; D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D010750:Phosphoproteins; D011994:Recombinant Proteins; C026742:plastin; C026615:villin