Document Detail

Time-dependent cleavage of a high-mannose form of Ii to p25 in an intracellular compartment.
MedLine Citation:
PMID:  2816909     Owner:  NLM     Status:  MEDLINE    
The cleavage of a high-mannose form of Ii to p25 was demonstrated in an intracellular compartment of B cells. Subcellular fractions of 72 hr-activated B cells, separated by Percoll density gradient centrifugation, were immunoprecipitated with anti-class II or anti-Ii serum and characterized for 5'-nucleotidase, acid phosphatase, and radiolabeled transferrin. The cleavage of p25 from Ii as a C-terminal fragment occurred from 20 to 60 min after synthesis in an intracellular compartment which was intermediate in density between lysosomal and plasma membrane fractions and coincided with the lighter to two internalized transferrin compartments. Chloroquine or monensin treatments, at maximal nontoxic doses, which block Golgi and lysosomal functions, did not seem to alter the cleavage of Ii to p25. p25 molecules were reduced to about 10,500 daltons by treatment with endoglycosidases F or H. We conclude that p25 was generated from a high mannose form of Ii in the endoplasmic reticulum or cis-Golgi. This finding could either implicate that site for class II MHC desetope charging with foreign peptides or reflect a mechanism for degradation of "excess" Ii molecules.
L J Thomas; R E Humphreys; W Knapp; Q V Nguyen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American journal of hematology     Volume:  32     ISSN:  0361-8609     ISO Abbreviation:  Am. J. Hematol.     Publication Date:  1989 Nov 
Date Detail:
Created Date:  1989-11-30     Completed Date:  1989-11-30     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  7610369     Medline TA:  Am J Hematol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  167-77     Citation Subset:  IM    
Department of Pediatrics, University of Massachusetts Medical School, Worcester 01655.
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MeSH Terms
Chemical Phenomena
Chloroquine / pharmacology
Electrophoresis, Polyacrylamide Gel
Glycoproteins / biosynthesis,  metabolism*
Histocompatibility Antigens Class II / physiology*
Intracellular Membranes / metabolism*
Molecular Weight
Monensin / pharmacology
Precipitin Tests
Time Factors
Grant Support
Reg. No./Substance:
0/Glycoproteins; 0/Histocompatibility Antigens Class II; 17090-79-8/Monensin; 31103-86-3/Mannose; 54-05-7/Chloroquine

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