The Carboxyl-terminal Region of Biliary Glycoprotein Controls Its Tyrosine Phosphorylation and Association with Protein-tyrosine Phosphatases SHP-1 and SHP-2 in Epithelial Cells*
- Maria Huber‡§,
- Luisa Izzi‡¶,
- Philippe Grondin‡‖,
- Caroline Houde‡‖,
- Tilo Kunath‡**‡,
- André Veillette‡§§¶¶ and
- Nicole Beaucheminत,166
- From the ‡McGill Cancer Centre and the§§Departments of Biochemistry, Medicine, and Oncology, McGill University, Montreal, Quebec H3G 1Y6, Canada and the**Samuel Lunenfeld Institute, Toronto, Ontario M5G 1X5, Canada
Abstract
Biliary glycoprotein (Bgp, C-CAM, or CD66a) is an immunoglobulin-like cell adhesion molecule and functions as a tumor suppressor protein. We have previously shown that the Bgp1 isoform responsible for inhibition of colonic, liver, prostate, and breast tumor cell growth contains within its cytoplasmic domain two tyrosine residues positioned in immunoreceptortyrosine-based inhibition motif (ITIM) consensus sequences. Moreover, we determined that these residues, upon phosphorylation, associate with the protein-tyrosine phosphatase SHP-1. In this report, we have further evaluated the structural bases of the association of Bgp1 with Tyr phosphatases. First, we demonstrate that Bgp1 also associates with the SHP-2 Tyr phosphatase, but not with an unrelated Tyr phosphatase, PTP-PEST. Association of Bgp1 and SHP-2 involves the Tyr residues within the Bgp1 ITIM sequences, Val at position +3 relative to the second Tyr (Tyr-515), and the SHP-2 N-terminal SH2 domain. In addition, our results indicate that residues +4, +5, and +6 relative to Tyr-515 in the Bgp1 cytoplasmic domain play a significant role in these interactions, as their deletion reduced Bgp1 Tyr phosphorylation and association with SHP-1 and SHP-2 by as much as 80%. Together, these results indicate that both SHP-1 and SHP-2 interact with the Bgp1 cytoplasmic domain via ITIM-like sequences. Furthermore, they reveal that the C-terminal amino acids of Bgp1 are critical for these interactions.
Footnotes
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↵* This work was supported in part by Grant MT-13911 from the Medical Research Council of Canada (to N. B.) and by a grant from the National Cancer Institute of Canada (to A. V.).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.
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↵§ Recipient of a Medical Research Council of Canada fellowship.
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↵¶ Recipient of a Fonds pour la Formation de Chercheurs et l’Aide á la Recherche Centre studentship.
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↵‖ Recipient of a “Fonds de la Recherche en Santé du Québec” studentship.
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↵‡ Recipient of a Medical Research Council of Canada studentship.
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↵¶¶ Recipient of a Medical Research Council of Canada Scientist award.
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↵166 Recipient of a “Fonds de la Recherche en Santé du Québec” Senior Scientist award. To whom correspondence should be addressed: McGill Cancer Centre, McGill University, 3655 Drummond St., Montreal, Quebec H3G 1Y6, Canada. Tel.: 514-398-3541; Fax: 514-398-6769; E-mail: nicoleb{at}med.mcgill.ca.
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↵2 S. Sadekova and N. Beauchemin, manuscript in preparation.
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↵3 L. Izzi and N. Beauchemin, manuscript in preparation.
- Abbreviations:
- Bgp or BGP
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biliary glycoprotein
- ITIM
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immunoreceptortyrosine-based inhibition motif
- PCR
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polymerase chain reaction
- GST
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glutathioneS-transferase.
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- Received August 6, 1998.
- Revision received October 7, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
