Ssz1 restores endoplasmic reticulum-associated protein degradation in cells expressing defective cdc48-ufd1-npl4 complex by upregulating cdc48.
The endoplasmic reticulum (ER)-associated protein degradation (ERAD) pathway eliminates aberrant proteins from the ER. The key role of Cdc48p-Ufd1p-Npl4p is indicated by impaired ERAD in Saccharomyces cerevisiae with mutations in any of this complex's genes. We identified SSZ1 in genetic screens for cdc48-10 suppressors and show that it upregulates Cdc48p via the pleiotropic drug resistance (PDR) network. A pSSZ1 plasmid restored impaired ERAD-M of 6myc-Hmg2 in cdc48-10, ufd1-2, and npl4-1, while SSZ1 deletion had no effect. Ssz1p activates Pdr1p, the PDR master regulator. Indeed, plasmids of PDR1 or its target gene RPN4 increased cdc48-10p levels and restored ERAD-M in cdc48-10. Rpn4p regulates transcription of proteasome subunits and CDC48, thus RPN4 deletion abolished ERAD. However, the diminished proteasome level in Deltarpn4 was sufficient for degrading a cytosolic substrate, whereas the impaired ERAD-M was the result of diminished Cdc48p and was restored by expression of pCDC48. The corrected ERAD-M in the hypomorphic strains of the Cdc48 partners ufd1-2 and npl4-1 by the pCDC48 plasmid, and in cdc48-10 cells by the pcdc48-10 plasmid, combined with the finding that neither pSSZ1 nor pcdc48-10 restored ERAD-L of CPY*-HA, support our conclusion that Ssz1p suppressing effects is brought about by upregulating Cdc48p.
Bosis
Eran
E
Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
Salomon
Dor
D
Ohayon
Orit
O
Sivan
Gilad
G
Bar-Nun
Shoshana
S
Rabinovich
Efrat
E
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D025141:Drug Resistance, Fungal / Q000502:physiology; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000096:biosynthesis / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology; D000074405:Valosin Containing Protein; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
D018797:Cell Cycle Proteins; D018840:HSP70 Heat-Shock Proteins; C104361:NPL4 protein, S cerevisiae; D029543:Nucleocytoplasmic Transport Proteins; C424445:SSZ1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C444652:UFD1 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C000614177:CDC48 protein, S cerevisiae; D000074405:Valosin Containing Protein