Polyubiquitination is required for US11-dependent movement of MHC class I heavy chain from endoplasmic reticulum into cytosol

C. E. Shamu, D. Flierman, H. L. Ploegh, T. A. Rapoport, V. Chau

    Research output: Contribution to journalArticlepeer-review

    114 Scopus citations

    Abstract

    The human cytomegalovirus protein US11 induces the dislocation of MHC class I heavy chains from the endoplasmic reticulum (ER) into the cytosol for degradation by the proteasome. With the use of a fractionated, permeabilized cell system, we find that US11 activity is needed only in the cell membranes and that additional cytosolic factors are required for heavy chain dislocation. We identify ubiquitin as one of the required cytosolic factors. Cytosol depleted of ubiquitin does not support heavy chain dislocation from the ER, and activity can be restored by adding back purified ubiquitin. Methylated-ubiquitin or a ubiquitin mutant lacking all lysine residues does not substitute for wild-type ubiquitin, suggesting that polyubiquitination is required for US11-dependent dislocation. We propose a new function for ubiquitin in which polyubiquitination prevents the lumenal domain of the MHC class I heavy chain from moving back into the ER lumen. A similar mechanism may be operating in the dislocation of misfolded proteins from the ER in the cellular quality control pathway.

    Original languageEnglish (US)
    Pages (from-to)2546-2555
    Number of pages10
    JournalMolecular biology of the cell
    Volume12
    Issue number8
    DOIs
    StatePublished - 2001

    All Science Journal Classification (ASJC) codes

    • Molecular Biology
    • Cell Biology

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