New COP1-binding motifs involved in ER retrieval.
Coatomer-mediated sorting of proteins is based on the physical interaction between coatomer (COP1) and targeting motifs found in the cytoplasmic domains of membrane proteins. For example, binding of COP1 to dilysine (KKXX) motifs induces specific retrieval of tagged proteins from the Golgi back to the endoplasmic reticulum (ER). Making use of the two-hybrid system, we characterized a new sequence (deltaL) which interacts specifically with the delta-COP subunit of the COP1 complex. Transfer of deltaL to the cytoplasmic domain of a reporter membrane protein resulted in its localization in the ER, in yeast and mammalian cells. This was due to continuous retrieval of tagged proteins from the Golgi back to the ER, in a manner similar to the ER retrieval of KKXX-tagged proteins. Extensive mutagenesis of deltaL identified an aromatic residue as a critical determinant of the interaction with COP1. Similar COP1-binding motifs containing an essential aromatic residue were identified in the cytoplasmic domain of an ER-resident protein, Sec71p, and in an ER retention motif previously characterized in the CD3epsilon chain of the T-cell receptor. These results emphasize the role of the COP1 complex in retrograde Golgi-to-ER transport and highlight its functional similarity with clathrin-adaptor complexes.
Cosson
P
P
Centre Médical Universitaire, Département de Morphologie, Genève, Switzerland.
Lefkir
Y
Y
Démollière
C
C
Letourneur
F
F
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D017252:CD3 Complex; D016466:CHO Cells; D019556:COS Cells; D020756:Coatomer Protein; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014443:Tyrosine
D017252:CD3 Complex; C115335:CD3E protein, human; D020756:Coatomer Protein; D005656:Fungal Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; C084842:SEC66 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014443:Tyrosine