Leupaxin is a critical adaptor protein in the adhesion zone of the osteoclast.
Leupaxin is a cytoskeleton adaptor protein that was first identified in human macrophages and was found to share homology with the focal adhesion protein, paxillin. Leupaxin possesses several protein-binding domains that have been implicated in targeting proteins such as focal adhesion kinase (pp125FAK) to focal adhesions. Leupaxin can be detected ... in monocytes and osteoclasts, both cells of hematopoietic origin. We have identified leupaxin to be a component of the osteoclast podosomal signaling complex. We have found that leupaxin in murine osteoclasts is associated with both PYK2 and pp125FAK in the osteoclast. Treatment of osteoclasts with TNF-alpha and soluble osteopontin were found to stimulate tyrosine phosphorylation of both leupaxin and leupaxin-associated PYK2. Leupaxin was found to co-immunoprecipitate with the protein tyrosine phosphatase PTP-PEST. The cellular distribution of leupaxin, PYK2, and protein tyrosine phosphorylation-PEST co-localized at or near the osteoclast podosomal complex. Leupaxin was also found to associate with the ARF-GTPase-activating protein, paxillin kinase linker p95PKL, thereby providing a link to regulators of cytoskeletal dynamics in the osteoclast. Overexpression of leupaxin by transduction into osteoclasts evoked numerous cytoplasmic projections at the leading edge of the cell, resembling a motile phenotype. Finally, in vitro inhibition of leupaxin expression in the osteoclast led to a decrease in resorptive capacity. Our data suggest that leupaxin may be a critical nucleating component of the osteoclast podosomal signaling complex.
Mesh Terms:
Animals, Base Sequence, Cell Adhesion, Cell Adhesion Molecules, Cells, Cultured, Cloning, Molecular, Focal Adhesion Kinase 1, Focal Adhesion Kinase 2, Focal Adhesion Protein-Tyrosine Kinases, GTPase-Activating Proteins, Humans, Mice, Osteoclasts, Osteopontin, Phosphoproteins, Phosphorylation, Protein Tyrosine Phosphatase, Non-Receptor Type 12, Protein Tyrosine Phosphatases, Protein-Tyrosine Kinases, RNA, Messenger, Serine, Sialoglycoproteins, Signal Transduction, Subcellular Fractions, Transduction, Genetic, Tumor Necrosis Factor-alpha, Tyrosine
Animals, Base Sequence, Cell Adhesion, Cell Adhesion Molecules, Cells, Cultured, Cloning, Molecular, Focal Adhesion Kinase 1, Focal Adhesion Kinase 2, Focal Adhesion Protein-Tyrosine Kinases, GTPase-Activating Proteins, Humans, Mice, Osteoclasts, Osteopontin, Phosphoproteins, Phosphorylation, Protein Tyrosine Phosphatase, Non-Receptor Type 12, Protein Tyrosine Phosphatases, Protein-Tyrosine Kinases, RNA, Messenger, Serine, Sialoglycoproteins, Signal Transduction, Subcellular Fractions, Transduction, Genetic, Tumor Necrosis Factor-alpha, Tyrosine
J. Bone Miner. Res.
Date: Apr. 01, 2003
PubMed ID: 12674328
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