title: Association of leupaxin with Src in osteoclasts.
abstract: Leupaxin (LPXN), which belongs to the paxillin extended family of adaptor proteins, was previously identified as a component of the sealing zone in osteoclasts. LPXN was found to associate with several podosomal proteins, such as the protein tyrosine kinase Pyk2, the protein-tyrosine phosphatase-PEST (PTP-PEST), actin-binding proteins, and regulators of actin cytoskeletal reorganization. It was previously demonstrated that inhibition of LPXN expression resulted in reduced osteoclast-mediated resorption. In the current study, overexpression of LPXN in murine osteoclasts resulted in both enhanced resorptive activity and cell adhesion, as assessed by in vitro resorption assays. The overexpression of LPXN resulted in an increased association of Pyk2 with LPXN. In an attempt to determine an additional biochemical basis for the observed phenomenon in increased osteoclast activity, a coimmunoprecipitation screen for additional binding partners revealed that Src, a protein tyrosine kinase that is critical to both podosome formation and osteoclast function, was also associated with LPXN. After exposure to the pro-inflammatory and osteoclastogenic cytokine TNF-alpha, there was an increase in the level of Src that coimmunoprecipitated with LPXN. Our data indicate that association of the scaffold protein LPXN with Src adds further complexity to the organization of the podosomal signaling complex in osteoclasts.
authors.affiliation: Department of Biomedical Sciences, 4G-29, Dental School, University of Maryland-Baltimore, 666 West Baltimore St., Baltimore, MD 21201, USA.
authors.forename: Surasri Nandan
authors.initials: SN
authors.lastname: Sahu
authors.forename: Mohammed Abdul
authors.initials: MA
authors.lastname: Khadeer
authors.forename: Brian W
authors.initials: BW
authors.lastname: Robertson
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Núñez
authors.forename: Guang
authors.initials: G
authors.lastname: Bai
authors.forename: Anandarup
authors.initials: A
authors.lastname: Gupta
mesh_terms: D000818:Animals; D001862:Bone Resorption; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D051418:Focal Adhesion Kinase 2 / Q000378:metabolism; D066298:In Vitro Techniques; D051379:Mice; D010010:Osteoclasts / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000378:metabolism; D014157:Transcription Factors; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D015815:Cell Adhesion Molecules; C504469:Lpxn protein, mouse; D010750:Phosphoproteins; D014157:Transcription Factors; D051418:Focal Adhesion Kinase 2; C496053:Ptk2b protein, mouse; D019061:src-Family Kinases