Monocyte Cells and Cancer Cells Express Novel Paxillin Isoforms with Different Binding Properties to Focal Adhesion Proteins*
- From the ‡ Institute for Virus Research, Kyoto University, Kyoto 606, Japan
- ∥ Precursory Research for Embryonic Science and Technology, Japan Science and Technology Corporation, Kyoto 619-02, Japan and
- § Center for Molecular and Cellular Biology, Osaka University, Suita, Osaka 565, Japan
- ** To whom correspondence should be addressed: Institute for Virus Research, Kyoto University, Kawaracho Shogoin, Sakyoku, Kyoto 606, Japan. Tel.: 81-75-751-4026; Fax: 81-75-761-5766.
Abstract
The versatility of integrin functions is mediated by engagement of a number of proteins that assemble with integrins. Among them, paxillin is one of the important molecules interacting with a variety of signaling molecules and cytoskeletal building blocks. We report here that paxillin is not a single molecule with a unique physiological property. We identified two human paxillin isoforms, β and γ. These isoforms have distinct amino acid insertions; each consists of a distinct exon, at the same site of previously reported paxillin (paxillin α). Several proteins were co-precipitated with paxillin, and we found that β bound to focal adhesion kinase but weakly to vinculin, and γ bound to vinculin but only weakly to focal adhesion kinase, although both bound equally to talin. No additional proteins were found to bind to β and γ over those binding to α. Unlike the α isoform, β and γ mRNAs were not detected in normal tissues, but several cancer cells expressed both α and β proteins simultaneously. All three isoform proteins were expressed in promonocytic cells with ratios comparable with each other, and the expression patterns were altered during differentiation of floating promonocytic cells into adherent macrophage-like cells. Therefore, each isoform of paxillin exhibits distinct expression and different biochemical as well as physiological properties and thereby appears to act as a distinct module involved in different functions of integrins.
Footnotes
-
↵* This work was supported by the Japan Science and Technology Corp., Precursory Research for Embryonic Science and Technology, and Grants-in-aid 07272220 and 08264216 from the Ministry of Education, Science, Sports and Culture of Japan (to H. S.). The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- ECM
-
extracellular matrix
- Fak
-
focal adhesion kinase
- GST
-
glutathione S-transferase
- SH
-
src homology
- PAGE
-
polyacrylamide gel electrophoresis
- FCS
-
fetal calf serum
- TPA
-
12-O-tetradecanoylphorbol acetate
- PCR
-
polymerase chain reaction
- Ab
-
antibody
- kb
-
kilobase.
-
↵2 H. Sabe and H. Hanafusa, submitted for publication.
-
↵3 Y. Mazaki and H. Sabe, unpublished data.
-
- Received May 30, 1996.
- Revision received November 18, 1996.
- © 1997 by The American Society for Biochemistry and Molecular Biology, Inc.
