Effects of brefeldin A on cleavage of invariant chain to p21 and p10 and the appearance of Ii-freed class II MHC dimers.
Intracellular cleavage of class II MHC-associated Ii to p21 and p10 and the appearance of Ii-freed alpha, beta dimers were concurrent events lasting from 1 to 6 hr after synthesis of alpha, beta, Ii trimers, possibly related to charging of foreign peptides to the class II MHC antigen-binding site. Sequential immunoprecipitations of pulse-chase radiolabeled cells were made four times with anti-Ii monoclonal antibody to remove Ii and alpha, beta, Ii trimers and then with anti-class II antibody to detect the time-dependent appearance of Ii-freed alpha, beta dimers. The cleavage of Ii to p21 and p10 was revealed in leupeptin-treated cells. Cell treatment with Brefeldin A (BFA) was associated with a decrease in Ii-freed alpha, beta dimers, with inhibition of leupeptin-revealed cleavage of Ii to p21 and p10, and with persistence of endoglycosidase H susceptibility of Ii and class II alpha, beta chains. We conclude that in untreated cells, cleavage and release of Ii from class II MHC alpha and beta chains occur after those complexes traverse a BFA-sensitive step in the Golgi apparatus.
Nguyen
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QV
Department of Pediatrics, University of Massachusetts Medical School, Worcester 01655.
Roskey
A M
AM
Humphreys
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RE
D000938:Antigen-Presenting Cells / Q000737:chemistry* / Q000187:drug effects; D000944:Antigens, Differentiation, B-Lymphocyte; D001665:Binding Sites; D020126:Brefeldin A; D002451:Cell Compartmentation / Q000187:drug effects; D003517:Cyclopentanes / Q000494:pharmacology*; D006056:Golgi Apparatus / Q000378:metabolism*; D000949:Histocompatibility Antigens Class II / Q000737:chemistry*; D007976:Leupeptins / Q000037:antagonists & inhibitors; D014407:Tumor Cells, Cultured / Q000187:drug effects
D000944:Antigens, Differentiation, B-Lymphocyte; D003517:Cyclopentanes; D000949:Histocompatibility Antigens Class II; D007976:Leupeptins; C045084:invariant chain; D020126:Brefeldin A; C032854:leupeptin