title: Paxillin associates with poly(A)-binding protein 1 at the dense endoplasmic reticulum and the leading edge of migrating cells.
abstract: Using mass spectrometry we have identified proteins which co-immunoprecipitate with paxillin, an adaptor protein implicated in the integrin-mediated signaling pathways of cell motility. A major component of paxillin immunoprecipitates was poly(A)-binding protein 1, a 70-kDa mRNA-binding protein. Poly(A)-binding protein 1 associated with both the alpha and beta isoforms of paxillin, and this was unaffected by RNase treatment consistent with a protein-protein interaction. The NH(2)-terminal region of paxillin (residues 54-313) associated directly with poly(A)-binding protein 1 in cell lysates, and with His-poly(A)-binding protein 1 immobilized in microtiter wells. Binding was specific, saturable and of high affinity (K(d) of approximately 10 nm). Cell fractionation studies showed that at steady state, the bulk of paxillin and poly(A)-binding protein 1 was present in the "dense" polyribosome-associated endoplasmic reticulum. However, inhibition of nuclear export with leptomycin B caused paxillin and poly(A)-binding protein 1 to accumulate in the nucleus, indicating that they shuttle between the nuclear and cytoplasmic compartments. When cells migrate, poly(A)-binding protein 1 colocalized with paxillin-beta at the tips of lamellipodia. Our results suggest a new mechanism whereby a paxillin x poly(A)-binding protein 1 complex facilitates transport of mRNA from the nucleus to sites of protein synthesis at the endoplasmic reticulum and the leading lamella during cell migration.
authors.affiliation: Department of Biochemistry, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom.
authors.forename: Alison J
authors.initials: AJ
authors.lastname: Woods
authors.forename: Marnie S
authors.initials: MS
authors.lastname: Roberts
authors.forename: Jyoti
authors.initials: J
authors.lastname: Choudhary
authors.forename: Simon T
authors.initials: ST
authors.lastname: Barry
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Mazaki
authors.forename: Hisataka
authors.initials: H
authors.lastname: Sabe
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Morley
authors.forename: David R
authors.initials: DR
authors.lastname: Critchley
authors.forename: Jim C
authors.initials: JC
authors.lastname: Norman
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D051419:Paxillin; D010446:Peptide Fragments / Q000737:chemistry; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D039102:Poly(A)-Binding Proteins; D020033:Protein Isoforms / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014162:Transfection
chemical_list: D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D051419:Paxillin; D010446:Peptide Fragments; D010750:Phosphoproteins; D039102:Poly(A)-Binding Proteins; D020033:Protein Isoforms; C496062:Pxn protein, mouse; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins