Translocation of TCR Alpha Chains into the Lumen of the Endoplasmic Reticulum and Their Degradation

After synthesis, the alpha chain of the T cell antigen receptor (TCR alpha) can form a complex with other TCR chains and move to the cell surface, or TCR alpha can undergo degradation in the endoplasmic reticulum (ER) if it remains unassembled. The mechanism of translocation and degradation in the ER is unclear. It was found that the putative transmembrane region of TCR alpha (alpha tm) was incompetent on its own to act as a transmembrane region. Molecules that contained alpha tm were translocated into the ER lumen and then underwent either rapid degradation or secretion, depending on the sequence of the cytoplasmic domain. A specific signal for ER degradation within alpha tm does not appear to be present.