Alpha-galactosyl-mediated activation of porcine endothelial cells: studies on CD31 and VE-cadherin in adhesion and signaling

Transplantation. 1999 Sep 27;68(6):861-7. doi: 10.1097/00007890-199909270-00020.

Abstract

Background: Ligation of alpha-galactosyl epitopes on endothelial cells by naturally occurring human antibodies causes hyperacute rejection in porcine-to-human xenotransplantation. The alpha-galactosyl-specific lectin Bandeiraea simplicifolia isolectin B4 (IB4) has been reported to trigger endothelial "gap" formation and tyrosine phosphorylation of an unidentified 130-kDa protein. We have studied two 130-kDa junctional adhesion molecules, CD31 and VE-cadherin, in porcine aortic endothelial cells (PAECs) during IB4-mediated activation. The cellular distribution of these molecules, their susceptibility to tyrosine phosphorylation, and their capacity to bind IB4 or natural human antibodies have been determined.

Methods: Porcine CD31 and VE-cadherin were cloned. Recombinant proteins and monoclonal antibodies were prepared. The distribution and phosphorylation of CD31 and VE-cadherin in confluent PAECs activated with IB4 or human serum were studied by confocal microscopy and Western blotting, respectively.

Results: IB4 caused rapid redistribution of CD31 and VE-cadherin away from cell junctions and tyrosine-phosphorylation of CD31 but not VE-cadherin. A monoclonal antibody to CD31 also triggered tyrosine phosphorylation of this molecule, but brief exposure of PAECs to normal human serum did not. Tyrosine-phosphorylated CD31 complexed with SHP2 and other unidentified phosphoproteins. Both IB4 and natural human antibodies bound to porcine CD31 but not to VE-cadherin. Cell adhesion tests showed that porcine and human CD31 are functionally incompatible.

Conclusions: Endothelial cell retraction during IB4-mediated activation of PAECs is associated with rapid loss of CD31 and VE-cadherin from cell junctions. CD31 becomes strongly tyrosine-phosphorylated and forms a cell signaling complex, which may have a significant role in the response of the xenograft vascular endothelium.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigen-Antibody Reactions
  • Antigens, CD
  • Cadherins / pharmacology
  • Cell Adhesion / drug effects
  • Endothelium, Vascular / cytology*
  • Humans
  • Immunoglobulin G / immunology
  • Lectins / immunology
  • Lectins / pharmacology
  • Plant Lectins*
  • Platelet Endothelial Cell Adhesion Molecule-1 / physiology
  • Signal Transduction / drug effects
  • Swine
  • Transplantation, Heterologous / immunology
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • Antigens, CD
  • Cadherins
  • Griffonia simplicifolia lectins
  • Immunoglobulin G
  • Lectins
  • Plant Lectins
  • Platelet Endothelial Cell Adhesion Molecule-1
  • Tumor Necrosis Factor-alpha
  • cadherin 5