Abstract
The Ras-related small GTPases Rac, Rho, Cdc42, and RalA bind filamin, an actin filament-crosslinking protein that also links membrane and other intracellular proteins to actin. Of these GTPases only RalA binds filamin in a GTP-specific manner, and GTP-RalA elicits actin-rich filopods on surfaces of Swiss 3T3 cells and recruits filamin into the filopodial cytoskeleton. Either a dominant negative RalA construct or the RalA-binding domain of filamin 1 specifically block Cdc42-induced filopod formation, but a Cdc42 inhibitor does not impair RalA's effects, which, unlike Cdc42, are Rac independent. RalA does not generate filopodia in filamin-deficient human melanoma cells, whereas transfection of filamin 1 restores the functional response. RalA therefore is a downstream intermediate in Cdc42-mediated filopod production and uses filamin in this pathway.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3T3 Cells
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Actins / metabolism
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Animals
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COS Cells
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Carrier Proteins / metabolism
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Cloning, Molecular
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Contractile Proteins / metabolism*
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Cytoskeleton / physiology
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Cytoskeleton / ultrastructure
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Escherichia coli
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Filamins
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GTP Phosphohydrolases / genetics
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GTP Phosphohydrolases / metabolism*
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Humans
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Kinetics
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Membrane Proteins / metabolism
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Mice
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Microfilament Proteins / metabolism*
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Microscopy, Video
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Pseudopodia / physiology*
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Pseudopodia / ultrastructure
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Recombinant Fusion Proteins / biosynthesis
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Recombinant Proteins / metabolism
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Time Factors
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Transfection
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ral GTP-Binding Proteins*
Substances
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Actins
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Carrier Proteins
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Contractile Proteins
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Filamins
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Membrane Proteins
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Microfilament Proteins
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Recombinant Fusion Proteins
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Recombinant Proteins
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GTP Phosphohydrolases
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RALA protein, human
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Rala protein, mouse
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ral GTP-Binding Proteins