title: Leupaxin is a novel LIM domain protein that forms a complex with PYK2.
abstract: We have identified a novel cytoplasmic protein, leupaxin, that is preferentially expressed in hematopoietic cells and is most homologous to the focal adhesion protein, paxillin. Leupaxin possesses two types of protein interaction domains. There are four carboxyl-terminal LIM domains in leupaxin that share 70% amino acid identity and 80% similarity with those in paxillin. Paxillin LIM domains mediate localization to focal contacts. In the amino-terminal region of leupaxin there are three short stretches of approximately 13 amino acids that share 70-90% similarity with paxillin LD motifs. Paxillin LD motifs have been implicated in focal adhesion kinase (FAK) and vinculin binding resulting in the localization of FAK to focal adhesions. Leupaxin is expressed in cell types, such as macrophage, that lack FAK. We demonstrate here that leupaxin associates with a second FAK family member, PYK2. As leupaxin and PYK2 are both preferentially expressed in leukocytes they may therefore form a cell type-specific signaling complex. We also demonstrate that leupaxin is a substrate for a tyrosine kinase in lymphoid cells and thus may function in and be regulated by tyrosine kinase activity. Leupaxin is thus a phosphotyrosine protein with LD and LIM binding motifs most homologous to paxillin that may assemble and regulate PYK2 signaling complexes in leukocytes.
authors.affiliation: ICOS Corporation, Bothell, Washington 98021, USA.
authors.forename: B P
authors.initials: BP
authors.lastname: Lipsky
authors.forename: C R
authors.initials: CR
authors.lastname: Beals
authors.forename: D E
authors.initials: DE
authors.lastname: Staunton
mesh_terms: D000595:Amino Acid Sequence; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism* / Q000502:physiology*; D016384:Consensus Sequence; D003593:Cytoplasm / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D051418:Focal Adhesion Kinase 2; D006412:Hematopoietic Stem Cells / Q000378:metabolism; D006801:Humans; D008221:Lymphoid Tissue / Q000378:metabolism; D008264:Macrophages / Q000737:chemistry; D008969:Molecular Sequence Data; D051419:Paxillin; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014018:Tissue Distribution
chemical_list: D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; C112251:LPXN protein, human; C496061:PXN protein, human; D051419:Paxillin; D010750:Phosphoproteins; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2