A mutually inhibitory feedback loop between the 20S proteasome and its regulator, NQO1.
NAD(P)H:quinone-oxidoreductase-1 (NQO1) is a cytosolic enzyme that catalyzes the reduction of various quinones using flavin adenine dinucleotide (FAD) as a cofactor. NQO1 has been also shown to rescue proteins containing intrinsically unstructured domains, such as p53 and p73, from degradation by the 20S proteasome through an unknown mechanism. Here, we studied the nature of interaction between NQO1 and the 20S proteasome. Our study revealed a double negative feedback loop between NQO1 and the 20S proteasome, whereby NQO1 prevents the proteolytic activity of the 20S proteasome and the 20S proteasome degrades the apo form of NQO1. Furthermore, we demonstrate, both in vivo and in vitro, that NQO1 levels are highly dependent on FAD concentration. These observations suggest a link between 20S proteolysis and the metabolic cellular state. More generally, the results may represent a regulatory mechanism by which associated cofactors dictate the stability of proteins, thus coordinating protein levels with the metabolic status.
Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Oren
O
Moscovitz
Peter
P
Tsvetkov
Nimrod
N
Hazan
Izhak
I
Michaelevski
Hodaya
H
Keisar
Gili
G
Ben-Nissan
Yosef
Y
Shaul
Michal
M
Sharon
D000818:Animals; D001051:Apoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004795:Enzyme Stability; D025461:Feedback, Physiological; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry / Q000378:metabolism*; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D013058:Mass Spectrometry; D008954:Models, Biological; D008958:Models, Molecular; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D017510:Protein Folding; D059748:Proteolysis; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013696:Temperature
D001051:Apoenzymes; D011994:Recombinant Proteins; D005182:Flavin-Adenine Dinucleotide; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; D046988:Proteasome Endopeptidase Complex