DETERGENT-INSOLUBLE GLYCOLIPID MICRODOMAINS IN LYMPHOCYTES IN THE ABSENCE OF CAVEOLAE

Antibody binding to glycolipids and glycophosphatidylinositol (GPI)-an chored proteins of lymphocytes can trigger activation of specific sign al transduction pathways. The finding that GPI-anchored proteins are p resent in detergent-insoluble complexes with several tyrosine kinases of the Src family suggested that these complexes may represent membran e microdomains involved in the transduction of signals to the cell int erior. Recent work has suggested a link between detergent-insoluble mi crodomains and plasma membrane in vaginations termed caveolae. Here we show that lymphocytes lack plasma membrane domains with the character istic features of caveolae. Furthermore, VIP21-caveolin was not detect able in four different lymphocyte cell lines at the protein or mRNA le vel. In addition to the lack of caveolar domains, capping experiments suggested that the bulk of the GPI-anchored protein Thy1 and the glyco sphingolipid G(M1) were not stably associated in the lymphocyte plasma membrane. Despite this, Thy1 and G(M1) were present in detergent-inso luble complexes. We conclude that detergent insolubility does not corr elate with the presence of caveolae or of VIP21-caveolin and that cave olae, as defined by a number of different markers, are not involved in signal transduction in lymphocytes.