PMID: 8468464Apr 15, 1993Paper

Invariant chain retains MHC class II molecules in the endocytic pathway

The Journal of Immunology : Official Journal of the American Association of Immunologists
G E Loss, A J Sant

Abstract

During exocytosis of MHC class II, the class II alpha beta heterodimer associates with a third polypeptide termed invariant chain (Ii). Class II and Ii are coordinately processed and transported until proteolytic cleavage of Ii in an acidic compartment immediately before class II surface expression. Although the lysosomotropic agent chloroquine (CQ) prevents dissociation of class II/Ii within the cell, the ultimate fate of these complexes has not been determined. We considered two alternative possibilities. If Ii encodes an intracellular retention signal, then persistent association of Ii with class II could lead to intracellular accumulation of class II/Ii complexes. Alternatively, if Ii does not block further transport of class II, then CQ treatment should result in aberrant expression of class II/Ii complexes at the cell surface. Ltk- and EL4 cells transfected with I-A(d) alone or I-A(d) plus Ii were treated with CQ and examined for changes in surface class II and Ii expression. Anti-Ii mAb surface staining did not increase with prolonged CQ treatment, but a dramatic decrease in surface class II staining was observed. This decrease in class II was observed both with genomic Ii and p31 cDNA transfectants and was rapidly rever...Continue Reading

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