The role of the zeta chain in the expression, structure and function of the T cell receptor.

Abstract

The T Cell Antigen Receptor (TCR) is an extremely complex cell surface receptor that plays a key role in both the development and mature function of the immune system serving the dual functions of antigen recognition and transmembrane signaling1,2. The overall structure of the receptor and how it generates appropriate physiologic transmembrane signals is the object of studies in our laboatory. Two types of components make up the TCR: I) clonotypic chains (Ti alpha and beta or Ti gamma and delta) provide the recognition function and antigen-MHC specificity of the receptor; and 2) non-polymorphic chains (CD3) most likely determine the signalling capacity of the receptor. The receptor is defined structurally by the non-covalent assemblage of a clonotypic heterodimer with the complete set of CD3 chains. This requisite co-assembly is underscored by the fact that the lack of any of the above components leads to a deficiency in the surface expression of the multichain complex. The most recently characterized component of the receptor complex is the zeta chain3–5. This was first observed in murine and subsequently found in human T cells. Zeta is a 16 kD protein as determined by migration on SDS-PAGE. It is found only in T cells and exists primarily as a homodimer. Its pI of 8.2–8.3 makes it the most basic of all of the components of the surface TCR and it carries no N-linked carbohydrate as determined by both metabolic labeling and treatment with endoglycosaminidases.