Protein phosphatase 2Cm is a critical  regulator of branched-chain amino acid  catabolism in mice and cultured cells.
The branched-chain amino acids (BCAA) are essential amino acids required for protein homeostasis, energy balance, and nutrient signaling. In individuals with deficiencies in BCAA, these amino acids can be preserved through inhibition of the branched-chain-alpha-ketoacid dehydrogenase (BCKD) complex, the rate-limiting step in their metabolism. BCKD is inhibited by phosphorylation of its E1alpha subunit at Ser293, which is catalyzed by BCKD kinase. During BCAA excess, phosphorylated Ser293 (pSer293) becomes dephosphorylated through the concerted inhibition of BCKD kinase and the activity of an unknown intramitochondrial phosphatase. Using unbiased, proteomic approaches, we have found that a mitochondrial-targeted phosphatase, PP2Cm, specifically binds the BCKD complex and induces dephosphorylation of Ser293 in the presence of BCKD substrates. Loss of PP2Cm completely abolished substrate-induced E1alpha dephosphorylation both in vitro and in vivo. PP2Cm-deficient mice exhibited BCAA catabolic defects and a metabolic phenotype similar to the intermittent or intermediate types of human maple syrup urine disease (MSUD), a hereditary disorder caused by defects in BCKD activity. These results indicate that PP2Cm is the endogenous BCKD phosphatase required for nutrient-mediated regulation of BCKD activity and suggest that defects in PP2Cm may be responsible for a subset of human MSUD.
Lu
Gang
G
Division of Molecular Medicine, Department of Anesthesiology, David Geffen School of Medicine, UCLA, Los Angeles, California 90095, USA.
Sun
Haipeng
H
She
Pengxiang
P
Youn
Ji-Youn
JY
Warburton
Sarah
S
Ping
Peipei
P
Vondriska
Thomas M
TM
Cai
Hua
H
Lynch
Christopher J
CJ
Wang
Yibin
Y
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) / Q000378:metabolism; D000597:Amino Acids, Branched-Chain / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D023421:Models, Animal; D010749:Phosphoprotein Phosphatases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013379:Substrate Specificity
D000597:Amino Acids, Branched-Chain; D021122:Protein Subunits; D017382:Reactive Oxygen Species; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D010749:Phosphoprotein Phosphatases