Casein kinase I controls a late step in the endocytic trafficking of yeast uracil permease.
The modification of yeast uracil permease by phosphorylation at the plasma membrane is a key mechanism for regulating transporter endocytosis. Uracil permease is phosphorylated at several serine residues within a well characterized PEST sequence. The phosphorylation of these residues facilitates the ubiquitination and internalization of the permease. Following endocytosis, the permease is targeted to the lysosome/vacuole for proteolysis. We have shown that in casein kinase 1 (CK1)-deficient cells, the permease is poorly phosphorylated, poorly ubiquitinated and that Yck activity may play a direct role in phosphorylating the permease. We show here that CK1-deficient cells accumulated permease that was subjected to endocytosis in an internal compartment on its way to the vacuole. Uracil permease, produced as a fusion protein with green fluorescent protein in CK1-deficient cells, was detected in dots adjacent to the vacuole. These dots probably correspond to the late endosome/prevacuolar compartment because they were partially colocalized with the Pep12p marker. This accumulation was abolished by mutations affecting the adaptor-related complex, AP-3. The CPY and ALP pathways to the vacuole were both unaffected in CK1-deficient cells. Our analysis provides the first evidence that CK1 is important for the delivery of proteins to the vacuole after endocytosis.
Marchal
Christelle
C
Institut Jacques Monod, CNRS-UMRC9922, Université Paris 6 and Paris 7-Denis Diderot, 2 place Jussieu, 75251-Paris-cedex 05, France.
Dupré
Sophie
S
Urban-Grimal
Daniele
D
D001692:Biological Transport; D015415:Biomarkers / Q000032:analysis; D015153:Blotting, Western; D047388:Casein Kinases; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D005690:Galactose / Q000378:metabolism; D049452:Green Fluorescent Proteins; D007700:Kinetics; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D033704:Nucleotide Transport Proteins; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014498:Uracil / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
D015415:Biomarkers; C035528:FUR4 protein, S cerevisiae; D008164:Luminescent Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033704:Nucleotide Transport Proteins; C081224:PEP12 protein, S cerevisiae; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D014498:Uracil; D011494:Protein Kinases; D047388:Casein Kinases; D005690:Galactose