Glycosylphosphatidylinositol (GPI)-anchored proteins expressed on lymphocytes

Glycosylphosphatidylinositol (GPI)-anchored proteins are a fascinating and diverse group of integral membrane proteins. The core structure of the GPI-anchor is conserved in all eukaryotes, and the process of GPI-anchor synthesis and attachment to nascent protein chains is as highly regulated as it is conserved. GPI-anchors vary in both species and cell-type. This variation may reflect one mechanism of controlling the effector functions of GPI-anchored proteins. In mammals GPI-anchored proteins have shared properties which stem from the common anchor moiety. These properties include signal transduction, src kinase association, detergent insolubility, sorting in polarized cells and increased lateral mobility. In lymphocytes many GPI-anchored proteins are involved in adhesion and in complement regulation. The studies presented here demonstrate: that T cells can be differentiated from NK cells, and NK cell subpopulations can be differentiated from one another by the levels at which GPI-anchored proteins are expressed on the cell surface, suggesting developmental control of GPI-anchoring in man; that CDw109, a novel T cell activation antigen, is GPI-anchored; that GPI-anchored proteins in T cells are associated with heterotrimeric G protein {dollar}alpha{dollar} subunits, which may help explain various signal transduction phenomena associated with GPI-anchored proteins; and that the cytoplasmic tail of TCR {dollar}beta{dollar} may help regulate the attachment of GPI-anchors, implying a role for the short cytoplasmic tails found in many immunologically significant transmembrane proteins. In total, these experiments further our understanding of GPI-anchored proteins and help reveal the form and function of GPI-anchored proteins and the anchoring process in lymphocytes.