Internalization of MHC class I molecules is a prerequisite for endocytosis of endorphin by lymphocytes.
The nature of the interaction between gamma-type endorphins and the HLA class I molecules was studied by immunoelectronmicroscopy. The HLA molecules were not involved in the actual binding of endorphin to the cell. In contrast, for the endocytosis of gamma-endorphin, co-internalization of the HLA class I molecules is essential. The internalization process starts with clustering of gamma-endorphin and HLA class I molecules in coated pits. Cells that do not carry HLA class I molecules (Daudi) or do not internalize HLA class I molecules (EBV-transformed B cells) bind but do not internalize gamma-endorphin. On the basis of these observations, we suggest that the MHC class I molecules may function as transport molecules. Whether it is a general phenomenon that non-immunological ligands use the HLA class I molecules to get into the cell and immunological ligands (viral proteins) to reach the cell surface, remains to be established.
Mommaas
A M
AM
Department of Dermatology, University of Leiden, The Netherlands.
Wijsman
M C
MC
Verduijn
W
W
Vermeer
B J
BJ
Claas
F M
FM
D000911:Antibodies, Monoclonal; D002461:Cell Line, Transformed; D004705:Endocytosis / Q000502:physiology*; D004723:Endorphins / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D008213:Lymphocyte Activation / Q000187:drug effects; D008214:Lymphocytes / Q000378:metabolism*; D016253:Microscopy, Immunoelectron; D010446:Peptide Fragments / Q000378:metabolism*; D010835:Phytohemagglutinins / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D004723:Endorphins; D015395:Histocompatibility Antigens Class I; D010446:Peptide Fragments; D010835:Phytohemagglutinins; C018903:gamma-endorphin, des-Tyr(1)-