Pharmacological disintegration of lipid rafts decreases specific tetramer binding and disrupts the CD3 complex and CD8 heterodimer in human cytotoxic T lymphocytes

Abstract

Accumulating evidence strongly supports the role of lipid rafts in the regulation of T-lymphocyte activation, but the organization and molecular composition of these cholesterol- and sphingolipid-rich membrane microdomains in different subsets of T cells remain poorly investigated. Here, we show that pharmacological disruption of lipid rafts in human CD8+ cytotoxic T-lymphocyte (CTL) clones disturbs the integrity of CD3 complex and CD8 heterodimer, without affecting the reactivity with T-cell receptor (TCR)-specific antibodies. This demonstrates that interaction with completely assembled CD3 complex is not required for the stable expression of TCR at the cell surface. The effect of raft disruption on CD3 and CD8 expression correlates with failure to bind specific tetrameric complexes by a proportion of surface TCR molecules. However, the interaction of specific tetramer with the rest of surface TCR pools appears to be unaffected, demonstrating that TCR-signalling complexes may differ in their requirement for cholesterol to stably maintain their composition and to rearrange for efficient tetramer binding. Together with previously published data, our results support the existence of molecular and/or structural heterogeneity of lipid rafts that may play an important role in controlling distinct functional properties of T-cell subsets.