Molecular dissection of radixin: distinct and interdependent functions of the amino- and carboxy-terminal domains.
The ERM proteins--ezrin, radixin, and moesin--occur in particular cortical cytoskeletal structures. Several lines of evidence suggest that they interact with both cytoskeletal elements and plasma membrane components. Here we described the properties of full-length and truncated radixin polypeptides expressed in transfected cells. In stable transfectants, exogenous full-length radixin behaves much like endogenous ERM proteins, localizing to the same cortical structures. However, the presence of full-length radixin or its carboxy-terminal domain in cortical structures correlates with greatly diminished staining of endogenous moesin in those structures, suggesting that radixin and moesin compete for a limiting factor required for normal associations in the cell. The results also reveal distinct roles for the amino- and carboxy-terminal domains. At low levels relative to endogenous radixin, the carboxy-terminal polypeptide is associated with most of the correct cortical targets except cleavage furrows. In contrast, the amino-terminal polypeptide is diffusely localized throughout the cell. Low level expression of full-length radixin or either of the truncated polypeptides has no detectable effect on cell physiology. However, high level expression of the carboxy-terminal domain dramatically disrupts normal cytoskeletal structures and functions. At these high levels, the amino-terminal polypeptide does localize to cortical structures, but does not affect the cells. We conclude that the behavior of radixin in cells depends upon activities contributed by separate domains of the protein, but also requires modulating interactions between those domains.
Henry
M D
MD
Department of Biology and Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139, USA.
Gonzalez Agosti
C
C
Solomon
F
F
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D001798:Blood Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002451:Cell Compartmentation; D002455:Cell Division / Q000502:physiology*; D003598:Cytoskeletal Proteins; D004252:DNA Mutational Analysis; D005455:Fluorescent Antibody Technique; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D015151:Immunoblotting; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D051379:Mice; D008840:Microfilament Proteins; D008969:Molecular Sequence Data; D009024:Morphogenesis; D010446:Peptide Fragments / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection; D000099149:Ezrin
D001798:Blood Proteins; D003598:Cytoskeletal Proteins; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D006389:Hemagglutinins, Viral; D008565:Membrane Proteins; D008840:Microfilament Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D000099149:Ezrin; C071058:moesin; C071776:radixin