Expression of major histocompatibility complex class II molecules in HeLa cells promotes the recruitment of AP-1 Golgi-specific assembly proteins on Golgi membranes - PubMed (original) (raw)

. 1996 Nov 29;271(48):30318-21.

doi: 10.1074/jbc.271.48.30318.

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Expression of major histocompatibility complex class II molecules in HeLa cells promotes the recruitment of AP-1 Golgi-specific assembly proteins on Golgi membranes

J Salamero et al. J Biol Chem. 1996.

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Abstract

The newly synthesized major histocompatibility complex (MHC) class II molecules, an alphabeta dimer associated with the Ii invariant chain, must be targeted to endosomal, lysosomal enzyme-rich compartments in order to bind and present immunogenic peptides. The precise route followed by this complex at the exit of the trans-Golgi network, the last sorting station of the biosynthetic pathway, is poorly understood. We show here that overexpression of alphabetaIi complexes in HeLa cells promotes the first step of clathrin-coat assembly in vitro, that is the ARF-dependent translocation of AP-1 Golgi-specific assembly proteins on membranes. In contrast, alphabeta dimers alone or associated with Ii lacking most of its cytoplasmic domain fail to recruit AP-1. This study strongly suggests that the invariant chain (Ii) is responsible for the AP-1-dependent sorting of the alphabeta dimers in the trans-Golgi network of HeLa cells and that the MHC class II molecules are, like the mannose 6-phosphate receptors, transported directly from this compartment to endosomes via clathrin-coated vesicles.

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