Association of leupaxin with Src in osteoclasts

• Published in: American Journal of Physiology: Cell Physiology 2007-01, Vol.292 (1), p.C581-C590
• Main Authors: Sahu, Surasri Nandan, Khadeer, Mohammed Abdul, Robertson, Brian W, Nunez, Stephanie M, Bai, Guang, Gupta, Anandarup
• Format: Article
• Language: English
• Subjects: Animals; Bone Resorption; Bones; Cell Adhesion; Cell adhesion & migration; Cell Adhesion Molecules - genetics; Cell Adhesion Molecules - metabolism; Cells, Cultured; Cloning, Molecular; Focal Adhesion Kinase 2 - metabolism; Gene expression; In Vitro Techniques; Mice; Osteoclasts - metabolism; Phosphoproteins - genetics; Phosphoproteins - metabolism; Protein Structure, Tertiary; Proteins; Signal Transduction; src-Family Kinases - metabolism; Subcellular Fractions - metabolism
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00636.2005

1 Department of Biomedical Sciences, Dental School, University of Maryland, Baltimore; and 2 Biochemistry and Molecular Biology, University of Maryland, Baltimore County, Maryland Submitted 19 December 2005 ; accepted in final form 11 August 2006 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- , 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. LPXN; sealing zone; podosomes; LD2 domain Address for reprint requests and other correspondence: A. Gupta, Dept. of Biomedical Sciences, 4G-29, Dental School, Univ. of Maryland, Baltimore, 666 West Baltimore St., Baltimore, MD 21201 (e-mail: agupta{at}umaryland.edu )