Coatomer is essential for retrieval of dilysine-tagged proteins to the endoplasmic reticulum.
Dilysine motifs in cytoplasmic domains of transmembrane proteins are signals for their continuous retrieval from the Golgi back to the endoplasmic reticulum (ER). We describe a system to assess retrieval to the ER in yeast cells making use of a dilysine-tagged Ste2 protein. Whereas retrieval was unaffected in most sec mutants tested (sec7, sec12, sec13, sec16, sec17, sec18, sec19, sec22, and sec23), a defect in retrieval was observed in previously characterized coatomer mutants (sec21-1, sec27-1), as well as in newly isolated retrieval mutants (sec21-2, ret1-1). RET1 was cloned by complementation and found to encode the alpha subunit of coatomer. While temperature-sensitive for growth, the newly isolated coatomer mutants exhibited a very modest defect in secretion at the nonpermissive temperature. Coatomer from beta'-COP (sec27-1) and alpha-COP (ret1-1) mutants, but not from gamma-COP (sec21) mutants, had lost the ability to bind dilysine motifs in vitro. Together, these results suggest that coatomer plays an essential role in retrograde Golgi-to-ER transport and retrieval of dilysine-tagged proteins back to the ER.
Letourneur
F
F
Basel Institute for Immunology, Switzerland.
Gaynor
E C
EC
Hennecke
S
S
Démollière
C
C
Duden
R
R
Emr
S D
SD
Riezman
H
H
Cosson
P
P
D000595:Amino Acid Sequence; D001692:Biological Transport / Q000502:physiology; D020756:Coatomer Protein; D004151:Dipeptides; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005656:Fungal Proteins / Q000378:metabolism; D006602:Hexosyltransferases; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D021382:Protein Sorting Signals / Q000502:physiology; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D014157:Transcription Factors; D014166:Transferases / Q000378:metabolism
D020756:Coatomer Protein; D004151:Dipeptides; D005656:Fungal Proteins; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D051964:Receptors, Mating Factor; D018000:Receptors, Peptide; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C024575:lysyllysine; D014166:Transferases; D006602:Hexosyltransferases; C025620:dolichyl-diphosphooligosaccharide - protein glycotransferase