title: Roles for the tubulin- and PTP-PEST-binding paxillin LIM domains in cell adhesion and motility.
abstract: Cell dynamics mediated through cell-extracellular matrix contacts, such as adhesion and motility involve the precise regulation of large complexes of structural and signaling molecules called focal adhesions (FAs). Paxillin is a multi-domain FA adaptor protein containing five amino-terminal paxillin leucine-aspartate repeat (LD) motifs and four carboxyl-terminal Lin-11 Isl-1 and Mec-3 (LIM) domains. The LD motifs support paxillin binding to actopaxin, integrin linked kinase (ILK), FA kinase (FAK), paxillin kinase linker (PKL) and vinculin. Of the LIM domains, LIM2 and 3 comprise the paxillin FA-targeting motif, with phosphorylation of these domains modulating paxillin targeting and cell adhesion to fibronectin (Fn). The identity of the paxillin FA targeting partner remains to be determined; however, the LIM domains mediate interactions with tubulin and the protein-tyrosine phosphatase (PTP)-PEST. PTP-PEST binding requires both LIM3 and 4, whereas, the precise LIM target of tubulin binding is not known. In this report, we demonstrate that the individual paxillin LIM2 and 3 domains support specific binding to tubulin and suggest a potential role for this interaction in the regulation of paxillin sub-cellular compartmentalization. In addition, expression of paxillin molecules with mutations in the tubulin- and PTP-PEST-binding LIM domains differentially impaired Chinese hamster ovary K1 (CHO.K1) cell adhesion and migration to Fn. Perturbation of LIM3 or 4 inhibited adhesion while mutation of LIM2 or 4 decreased cell motility. Interestingly, expression of tandem LIM2-3 inhibited cell adhesion and spreading while LIM3-4 stimulated a well-spread polarized phenotype. These data offer further support for a critical role for paxillin in cell adhesion and motility.
authors.affiliation: Department of Cell & Developmental Biology, State University of New York Upstate Medical University, 750 East Adams Street Syracuse, New York, NY 13210-2306, USA. brownm@mail.upstate.edu
authors.forename: Michael C
authors.initials: MC
authors.lastname: Brown
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Turner
mesh_terms: D000818:Animals; D001665:Binding Sites; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology*; D006224:Cricetinae; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D005353:Fibronectins / Q000378:metabolism; D051419:Paxillin; D010750:Phosphoproteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary; D054594:Protein Tyrosine Phosphatase, Non-Receptor Type 12; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014404:Tubulin / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*
chemical_list: D003598:Cytoskeletal Proteins; D005353:Fibronectins; D051419:Paxillin; D010750:Phosphoproteins; D011994:Recombinant Proteins; D014404:Tubulin; D054594:Protein Tyrosine Phosphatase, Non-Receptor Type 12; D017027:Protein Tyrosine Phosphatases