A Novel Protein with Homology to the Junctional Adhesion Molecule
CHARACTERIZATION OF LEUKOCYTE INTERACTIONS*
- Sonia A. Cunningham‡§,
- M. Pia Arrate‡,
- Jose M. Rodriguez‡,
- Robert J. Bjercke‡,
- Peter Vanderslice‡,
- Andrew P. Morris¶ and
- Tommy A. Brock‡
- From the ‡Department of Pharmacology, Texas Biotechnology Corporation and the ¶Department of Integrative Biology and Pharmacology, University of Texas Medical School, Houston, Texas 77030
Abstract
We have cloned a novel cDNA belonging to the Ig superfamily that shows 44% similarity to the junctional adhesion molecule (JAM) and maps to chromosome 21q21.2. The open reading frame of JAM2 predicts a 34-kDa type I integral membrane protein that features two Ig-like folds and three N-linked glycosylation sites in the extracellular domain. A single protein kinase C phosphorylation consensus site and a PDZ-binding motif are present in the short intracellular tail. Heterologous expression of JAM2 in Chinese hamster ovary cells defined a 48-kDa protein that localizes predominantly to the intercellular borders. Northern blot analysis showed that JAM2 is preferentially expressed in the heart. JAM2 homotypic interactions were demonstrated by the ability of JAM2-Fc to capture JAM2-expressing Chinese hamster ovary cells. We further showed that JAM2, but not JAM1, is capable of adhering to the HSB and HPB-ALL lymphocyte cell lines. Neutralizing mouse anti-JAM2 polyclonal antibodies provided evidence against homotypic interactions in this assay. Biotinylation of HSB cell membranes revealed a 43-kDa counter-receptor that precipitates specifically with JAM2-Fc. These characteristics of JAM2 led us to hypothesize a role for this novel protein in adhesion events associated with cardiac inflammatory conditions.
Footnotes
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↵* 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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↵§ To whom correspondence should be addressed: Dept. of Pharmacology, Texas Biotechnology Corp., 7000 Fannin, Suite 1920, Houston, TX 77030. Tel.: 713-796-8822 (ext. 144); Fax: 713-796-8232; E-mail: scunningham@tbc.com.
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Published, JBC Papers in Press, August 16, 2000, DOI 10.1074/jbc.M002718200
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↵2 S. A. Cunningham, M. P. Arrate, and J. M. Rodriguez, unpublished observations.
- Abbreviations:
- JAM
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junctional adhesion molecule
- VCAM
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vascular cell adhesion molecule
- ICAM
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intercellular adhesion molecule
- PECAM
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platelet endothelial cell adhesion molecule
- EST
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expressed sequence tag
- RACE
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rapid amplification of cDNA ends
- bp
-
base pairs
- CHO
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Chinese hamster ovary
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- Received March 30, 2000.
- Revision received July 27, 2000.
- The American Society for Biochemistry and Molecular Biology, Inc.
