Abstract
Rab7 has been shown to regulate the late steps of the endocytic pathway. In bone-resorbing osteoclasts, it is involved in formation of the ruffled border, which is a late endosomal-like compartment in the plasma membrane. Here we report a new Rab7-interacting protein, Rac1, another small GTPase protein that binds to the GTP-form of Rab7 as found with a two-hybrid system. We demonstrate further that Rab7 colocalizes with Rac1 at the fusion zone of the ruffled border in bone-resorbing osteoclasts. In other cell types, such as fibroblast-like cells, partial colocalization is perinuclear. Because Rac1 is known to control the actin cytoskeleton through its effectors, the Rab7-Rac1 interaction may mediate late endosomal transport between microtubules and microfilaments enabling endosomal vesicles to switch tracks and may thus also regulate ruffled border formation in osteoclasts.
MeSH terms
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Actins / metabolism
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Amino Acid Sequence
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Animals
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Base Sequence
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Biological Transport
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Bone Marrow Cells / cytology
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Bone Resorption
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Cell Membrane / metabolism
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Cytoskeleton / metabolism
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DNA, Complementary / metabolism
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Endocytosis
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Endosomes / metabolism
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Fibroblasts / metabolism
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Fluorescent Antibody Technique, Indirect
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GTP Phosphohydrolases / chemistry
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Gene Library
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Glutathione Transferase / metabolism
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Histidine / chemistry
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Intracellular Membranes / metabolism
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Microscopy, Confocal
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Models, Biological
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Molecular Sequence Data
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Osteoclasts / metabolism*
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Plasmids / metabolism
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Protein Binding
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Rats
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Two-Hybrid System Techniques
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rab GTP-Binding Proteins / chemistry*
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rab7 GTP-Binding Proteins
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rac1 GTP-Binding Protein / chemistry*
Substances
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Actins
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DNA, Complementary
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rab7 GTP-Binding Proteins
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rab7 GTP-binding proteins, rat
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Histidine
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Glutathione Transferase
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GTP Phosphohydrolases
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rab GTP-Binding Proteins
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rac1 GTP-Binding Protein