title: Recognition of enzymes lacking bound cofactor by protein quality control.
abstract: Protein biogenesis is tightly linked to protein quality control (PQC). The role of PQC machinery in recognizing faulty polypeptides is becoming increasingly understood. Molecular chaperones and cytosolic and vacuolar degradation systems collaborate to detect, repair, or hydrolyze mutant, damaged, and mislocalized proteins. On the other hand, the contribution of PQC to cofactor binding-related enzyme maturation remains largely unexplored, although the loading of a cofactor represents an all-or-nothing transition in regard to the enzymatic function and thus must be surveyed carefully. Combining proteomics and biochemical analysis, we demonstrate here that cells are able to detect functionally immature wild-type enzymes. We show that PQC-dedicated ubiquitin ligase C-terminal Hsp70-interacting protein (CHIP) recognizes and marks for degradation not only a mutant protein but also its wild-type variant as long as the latter remains cofactor free. A distinct structural feature, the protruding C-terminal tail, which appears in both the mutant and wild-type polypeptides, contributes to recognition by CHIP. Our data suggest that relative insufficiency of apoprotein degradation caused by cofactor shortage can increase amyloidogenesis and aggravate protein aggregation disorders.
authors.affiliation: Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany; Institute of Biophysical Chemistry, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany.
authors.forename: Adrián
authors.initials: A
authors.lastname: Martínez-Limón
authors.affiliation: Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany; Institute of Biophysical Chemistry, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Alriquet
authors.affiliation: Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany; Institute of Biophysical Chemistry, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany.
authors.forename: Wei-Han
authors.initials: WH
authors.lastname: Lang
authors.affiliation: Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany; Institute of Biophysical Chemistry, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany.
authors.forename: Giulia
authors.initials: G
authors.lastname: Calloni
authors.affiliation: Functional Proteomics, Sonderforschungsbereich 815 Core Unit, School of Medicine, Goethe University Frankfurt, D-60590 Frankfurt am Main, Germany.
authors.forename: Ilka
authors.initials: I
authors.lastname: Wittig
authors.affiliation: Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany; Institute of Biophysical Chemistry, Goethe University Frankfurt, D-60438 Frankfurt am Main, Germany; vabulas@em.uni-frankfurt.de.
authors.forename: R Martin
authors.initials: RM
authors.lastname: Vabulas
mesh_terms: D000818:Animals; D003067:Coenzymes / Q000737:chemistry / Q000172:deficiency*; D005420:Flavoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D008546:Melanoma, Experimental; D051379:Mice; D008958:Models, Molecular; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D066329:Protein Aggregates; D017433:Protein Structure, Secondary; D059748:Proteolysis; D020543:Proteome / Q000235:genetics / Q000378:metabolism; D040901:Proteomics / Q000379:methods; D011732:Pyridoxal Phosphate / Q000737:chemistry / Q000378:metabolism; D012256:Riboflavin / Q000737:chemistry / Q000378:metabolism*; D013835:Thiamine Pyrophosphate / Q000737:chemistry / Q000378:metabolism; D014407:Tumor Cells, Cultured; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D003067:Coenzymes; D005420:Flavoproteins; D018840:HSP70 Heat-Shock Proteins; D066329:Protein Aggregates; D020543:Proteome; D009243:NAD; D011732:Pyridoxal Phosphate; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; C492951:Stub1 protein, mouse; D044767:Ubiquitin-Protein Ligases; D013835:Thiamine Pyrophosphate; D012256:Riboflavin
keywords: apoprotein; protein aggregation; ubiquitin ligase