Alternative Splicing of a Specific Cytoplasmic Exon Alters the Binding Characteristics of Murine Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1)

doi:10.1074/jbc.270.40.23672

Alternative Splicing of a Specific Cytoplasmic Exon Alters the Binding Characteristics of Murine Platelet/Endothelial Cell Adhesion Molecule-1 (PECAM-1) (*)

From the (1)Department of Medicine, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104-4283,
(2)The Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104,
the (3)Cardiology Division, Department of Pediatrics, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, 19104-4283, and
the (4)Pulmonary Division, Department of Medicine, Tri-Service General Hospital, Taipei, Taiwan

^¶ To whom correspondence should be addressed:
894 Maloney Bldg., University of Pennsylvania Medical Center, 3600 Spruce St., Philadelphia, PA. 19104.
Tel.: 215-349-8362; Fax: 215-349-5172.

Abstract

Platelet/endothelial cell adhesion molecule-1 (PECAM-1, CD31) is a membrane glycoprotein expressed on endothelial cells, platelets, and leukocytes. Analysis of PECAM-1 expression in the developing mouse embryo has revealed the presence of multiple isoforms of murine PECAM-1 (muPECAM-1) that appeared to result from the alternative splicing of exons encoding cytoplasmic domain sequences (exons 10-16) (Baldwin, H. S., Shen, H. M., Yan, H., DeLisser, H. M., Chung, A., Mickanin, C., Trask, T., Kirschbaum, N. E. Newman, P. J., Albelda, S., and Buck, C. A.(1994) Development 120, 2539-2553). To investigate the functional consequences of alternatively spliced muPECAM-1 cytoplasmic domains, L-cells were transfected with cDNA for each variant and their ability to promote cell aggregation was compared. In this assay, full-length muPECAM-1 and all three isoforms containing exon 14 behaved like human PECAM-1 in that they mediated calcium- and heparin-dependent heterophilic aggregation. In contrast, three muPECAM-1 variants, all missing exon 14, mediated calcium- and heparin-independent homophilic aggregation. Exon 14 thus appears to modulate the ligand and adhesive interactions of the extracellular domain of PECAM-1. These findings suggest that alternative splicing may represent a mode of regulating the adhesive function of PECAM-1 in vivo and provides direct evidence that alternative splicing involving the cytoplasmic domain affects the ligand specificity and binding properties of a cell adhesion receptor.

Footnotes

↵^§ Established Investigator of the American Heart Association.
↵* This work was supported by grants from the Robert Wood Johnson Foundation Minority Faculty Development Program, W. W. Smith Charitable Trust Grant, and National Institutes of Health Grants HL-46311, HL-51533, HL-39023, HL47670, CA 19144, and CA10815. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

PECAM-1

platelet/endothelial cell adhesion molecule-1

hu

human

mu

murine

HBSS

Hanks' balanced salt solution

mAb

monoclonal antibody

FACS

fluorescence-activated cell sorting.
↵² H. M. DeLisser, J. Sun, H. Yan, and S. M. Albelda, unpublished data.
↵³ H. M. DeLisser, unpublished observations.
- Received June 5, 1995.
- Revision received July 26, 1995.