Cdc48p(Npl4p/Ufd1p) binds and segregates membrane-anchored/tethered complexes via a polyubiquitin signal present on the anchors.
Cdc48p is an abundant and conserved member of the AAA ATPase family of molecular chaperones. Cdc48p performs ubiquitin-selective functions, which are mediated by numerous ubiquitin binding adaptors, including the Npl4p-Ufd1p complex. Previous studies suggest that Cdc48p-containing complexes carry out many biochemical activities, including ubiquitination, deubiquitination, protein complex segregation, and targeting of ubiquitinated substrates to the proteasome. The molecular mechanisms by which Cdc48p-containing complexes participate in these processes remain poorly defined. We show here by using physiologically relevant Cdc48p substrates (i.e., endoplasmic membrane-associated/tethered dimers of Mga2p and Spt23p) and in vitro systems with purified proteins that Cdc48p(Npl4p/Ufd1p) binds to and promotes segregation of the tethered proteins via a polyubiquitin signal present on the membrane-bound proteins. Mobilization does not involve retrotranslocation of the associated anchors. These results provide biochemical evidence that Cdc48p(Npl4p/Ufd1p) functions as a polyubiquitin-selective segregase and that a polyubiquitin-Cdc48p pathway modulates protein interactions at cell membranes.
Shcherbik
Natalia
N
Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
Haines
Dale S
DS
D000251:Adenosine Triphosphatases / Q000378:metabolism / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000201:enzymology; D019281:Dimerization; D056827:Endosomal Sorting Complexes Required for Transport; D008565:Membrane Proteins; D008954:Models, Biological; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism / Q000502:physiology; D029543:Nucleocytoplasmic Transport Proteins; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors; D025801:Ubiquitin / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism; D000074405:Valosin Containing Protein; D033921:Vesicular Transport Proteins
D018797:Cell Cycle Proteins; D056827:Endosomal Sorting Complexes Required for Transport; D008565:Membrane Proteins; C104361:NPL4 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D029543:Nucleocytoplasmic Transport Proteins; C087570:SPT23 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C444652:UFD1 protein, S cerevisiae; D025801:Ubiquitin; D033921:Vesicular Transport Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D000251:Adenosine Triphosphatases; C000614177:CDC48 protein, S cerevisiae; D000074405:Valosin Containing Protein; C469287:RSP5 protein, S cerevisiae