Dances with leukocytes: how tetraspanin-enriched microdomains assemble to form endothelial adhesive platforms

Abstract

Rather than just providing an unstructured adhesive surface for leukocytes, cytokine-activated endothelial cells assemble preexisting tetraspanin-enriched microdomains to form endothelial adhesive platforms (EAPs) and endothelial docking structures. In this issue of the Journal of Cell Biology, Barreiro et al. (Barreiro, O., M. Zamai, M. Yáñez-Mó, E. Tejera, P. López-Romero, P.N. Monk, E. Gratton, V.R. Caiolfa, and F. Sánchez-Madrid. 2008. J. Cell Biol. 183:527-542) show how the immunoglobulin superfamily adhesion molecules intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 form nanoclusters with the tetraspanins CD9 and CD151 in a physiologically relevant system. Furthermore, convincing biochemical data suggest that these structures are distinct from lipid rafts.

Figure 1.

Preexisting TEMs assemble to form docking structure for adherent leukocytes. TNF-α–stimulated endothelial cells show preassembled TEMs (left) that contain ICAM-1 (red), VCAM-1 (yellow), and the tetraspanins CD9 (blue) and CD151 (pink) as well as other molecules (not depicted). When an activated lymphoblast with activated integrins (light blue and purple heterodimers) adheres to the endothelial cell (right), the TEMs assemble into a characteristic docking structure that forms an elevated ring of microvilli.