Participation of the proteasomal lid subunit Rpn11 in mitochondrial morphology and function is mapped to a distinct C-terminal domain.
Substrates destined for degradation by the 26 S proteasome are labelled with polyubiquitin chains. Rpn11/Mpr1, situated in the lid subcomplex, partakes in the processing of these chains or in their removal from substrates bound to the proteasome. Rpn11 also plays a role in maintaining mitochondrial integrity, tubular structure and proper function. The recent finding that Rpn11 participates in proteasome-associated deubiquitination focuses interest on the MPN+ (Mpr1, Pad1, N-terminal)/JAMM (JAB1/MPN/Mov34) metalloprotease site in its N-terminal domain. However, Rpn11 damaged at its C-terminus (the mpr1-1 mutant) causes pleiotropic effects, including proteasome instability and mitochondrial morphology defects, resulting in both proteolysis and respiratory malfunctions. We find that overexpression of WT (wild-type) RPN8, encoding a paralogous subunit that does not contain the catalytic MPN+ motif, corrects proteasome conformations and rescues cell cycle phenotypes, but is unable to correct defects in the mitochondrial tubular system or respiratory malfunctions associated with the mpr1-1 mutation. Transforming mpr1-1 with various RPN8-RPN11 chimaeras or with other rpn11 mutants reveals that a WT C-terminal region of Rpn11 is necessary, and more surprisingly sufficient, to rescue the mpr1-1 mitochondrial phenotype. Interestingly, single-site mutants in the catalytic MPN+ motif at the N-terminus of Rpn11 lead to reduced proteasome-dependent deubiquitination connected with proteolysis defects. Nevertheless, these rpn11 mutants suppress the mitochondrial phenotypes associated with mpr1-1 by intragene complementation. Together, these results point to a unique role for the C-terminal region of Rpn11 in mitochondrial maintenance that may be independent of its role in proteasome-associated deubiquitination.
Rinaldi
Teresa
T
Pasteur Institute Cenci Bolognetti Foundation and the Department of Cell and Developmental Biology, University of Rome I, 00185 Rome, Italy.
Pick
Elah
E
Gambadoro
Alessia
A
Zilli
Stefania
S
Maytal-Kivity
Vered
V
Frontali
Laura
L
Glickman
Michael H
MH
D000123:Acetyltransferases / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D002262:Carboxy-Lyases / Q000235:genetics / Q000502:physiology; D020134:Catalytic Domain / Q000235:genetics / Q000502:physiology; D010450:Endopeptidases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D005816:Genetic Complementation Test; D008928:Mitochondria / Q000502:physiology* / Q000648:ultrastructure*; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000502:physiology; D010449:Peptide Mapping / Q000379:methods; D010455:Peptides / Q000235:genetics / Q000502:physiology; D010641:Phenotype; D046988:Proteasome Endopeptidase Complex / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D025801:Ubiquitin / Q000378:metabolism
D010455:Peptides; C115451:RPN11 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D000123:Acetyltransferases; C492447:Mpr1 protein, S cerevisiae; D010450:Endopeptidases; D010447:Peptide Hydrolases; D046988:Proteasome Endopeptidase Complex; C573321:Rpn8 protein, S cerevisiae; C061553:ATP dependent 26S protease; D002262:Carboxy-Lyases; C087194:phenylacrylic acid decarboxylase