Structural analysis of class I MHC molecules: The cytoplasmic domain is not required for cytoskeletal association, aggregation and internalization

The role of the cytoplasmic domain in a variety of the functional activities of class I MHC molecules has not been documented. To address this question, Jurkat cells were transfected with genes for either native class I MHC molecules or constructs in which all but four cytoplasmic amino acids were deleted. Antibody-induced aggregation and internalization of class I MHC molecules were examined by flow cytometry, and cytoskeletal association was determined by analyzing the detergent-resistant fraction of FITC- labeled mAb to class I molecules. The results indicate that the truncated class I MHC molecules are comparable to native class I MHC molecules in the ability to move in the plane of the membrane and aggregate, to associate with the cytoskeleton and to undergo mAb-induced internalization at 37 C. Thus, the cyloplasmic domain of class I MHC molecules is not required for these functional activities.