The degradation (by distinct pathways) of human D-amino acid oxidase and its interacting partner pLG72--two key proteins in D-serine catabolism in the brain.
Human D-amino acid oxidase (EC 1.4.3.3; hDAAO) is a peroxisomal flavoenzyme significantly enriched in the mammalian brain. hDAAO has been proposed to play (with serine racemase; EC 5.1.1.18) an essential role in the catabolism of D-serine, an 'atypical' key signalling molecule that acts as allosteric activator of the N-methyl-D-aspartate-type glutamate receptor (NMDAr). hDAAO and its interacting partner pLG72 have been related to schizophrenia, a highly disabling psychiatric disorder in which a dysfunction of NMDA-mediated neurotransmission is widely assumed to occur. We previously demonstrated that the D-serine cellular concentration depends on hDAAO and pLG72 expression levels and that newly-synthesized hDAAO interacts with its modulator in the cytosol, being progressively destabilized and inactivated. To obtain insight into the mechanisms regulating cellular D-serine levels, we investigated the degradation pathways of hDAAO and pLG72 in U87 glioblastoma cells stably expressing enhanced yellow fluorescent protein-hDAAO (peroxisomal), hDAAO-enhanced yellow fluorescent protein (cytosolic) or pLG72-enhanced cyan fluorescent protein (mitochondrial) proteins. hDAAO is a long-lived protein: the peroxisomal fraction of this flavoprotein is degraded via the lysosomal/endosomal pathway (and blocking this pathway increases the cellular hDAAO activity and decreases D-serine levels), whereas the cytosolic portion is ubiquitinated and targeted to the proteasome. By contrast, pLG72 shows a rapid turnover (t(1/2) ≈ 25-40 min) and is degraded via the proteasome system, albeit not ubiquitinated. Overexpression of pLG72 increases the turnover of hDAAO, in turn playing a protective role against excessive D-serine depletion.
Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, Varese, Italy; Centro Interuniversitario di Ricerca in Biotecnologie Proteiche 'The Protein Factory', Politecnico di Milano, ICRM-CNR Milano and Università degli studi dell'Insubria, Varese, Italy.
Pamela
P
Cappelletti
Paola
P
Campomenosi
Loredano
L
Pollegioni
Silvia
S
Sacchi
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001921:Brain / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D003605:D-Amino-Acid Oxidase / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D020675:Peroxisomes / Q000201:enzymology / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects*; D055550:Protein Stability / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D011993:Recombinant Fusion Proteins; D054875:Ubiquitination / Q000187:drug effects
D001426:Bacterial Proteins; D002352:Carrier Proteins; C475071:DAOA protein, human; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D009419:Nerve Tissue Proteins; D011480:Protease Inhibitors; D011993:Recombinant Fusion Proteins; C527701:enhanced cyan fluorescent protein; C054562:yellow fluorescent protein, Bacteria; D049452:Green Fluorescent Proteins; C417983:DAO protein, human; D003605:D-Amino-Acid Oxidase; D046988:Proteasome Endopeptidase Complex
d-serine; degradation pathway; neuromodulator; regulation; schizophrenia