title: AMP-activated protein kinase phosphorylates R5/PTG, the glycogen targeting subunit of the R5/PTG-protein phosphatase 1 holoenzyme, and accelerates its down-regulation by the laforin-malin complex.
abstract: R5/PTG is one of the glycogen targeting subunits of type 1 protein phosphatase, a master regulator of glycogen synthesis. R5/PTG recruits the phosphatase to the places where glycogen synthesis occurs, allowing the activation of glycogen synthase and the inactivation of glycogen phosphorylase, thus increasing glycogen synthesis and decreasing its degradation. In this report, we show that the activity of R5/PTG is regulated by AMP-activated protein kinase (AMPK). We demonstrate that AMPK interacts physically with R5/PTG and modifies its basal phosphorylation status. We have also mapped the major phosphorylation sites of R5/PTG by mass spectrometry analysis, observing that phosphorylation of Ser-8 and Ser-268 increased upon activation of AMPK. We have recently described that the activity of R5/PTG is down-regulated by the laforin-malin complex, composed of a dual specificity phosphatase (laforin) and an E3-ubiquitin ligase (malin). We now demonstrate that phosphorylation of R5/PTG at Ser-8 by AMPK accelerates its laforin/malin-dependent ubiquitination and subsequent proteasomal degradation, which results in a decrease of its glycogenic activity. Thus, our results define a novel role of AMPK in glycogen homeostasis.
authors.affiliation: Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas (CSIC) and CIBER de Enfermedades Raras (CIBERER), Jaime Roig 11, Valencia 46010, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Vernia
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Solaz-Fuster
authors.forename: José Vicente
authors.initials: JV
authors.lastname: Gimeno-Alcañiz
authors.forename: Teresa
authors.initials: T
authors.lastname: Rubio
authors.forename: Luisa
authors.initials: L
authors.lastname: García-Haro
authors.forename: Marc
authors.initials: M
authors.lastname: Foretz
authors.forename: Santiago Rodríguez
authors.initials: SR
authors.lastname: de Córdoba
authors.forename: Pascual
authors.initials: P
authors.lastname: Sanz
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D015536:Down-Regulation / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D006003:Glycogen / Q000235:genetics / Q000378:metabolism*; D024981:Glycogen Phosphorylase / Q000235:genetics / Q000378:metabolism; D006006:Glycogen Synthase / Q000235:genetics / Q000378:metabolism; D020035:Holoenzymes / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D054558:Protein Tyrosine Phosphatases, Non-Receptor / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination / Q000502:physiology
chemical_list: D002352:Carrier Proteins; D020035:Holoenzymes; D047908:Intracellular Signaling Peptides and Proteins; D009097:Multienzyme Complexes; C491294:PPP1R3C protein, human; D006003:Glycogen; C478960:NHLRC1 protein, human; D044767:Ubiquitin-Protein Ligases; D024981:Glycogen Phosphorylase; D006006:Glycogen Synthase; D055372:AMP-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054558:Protein Tyrosine Phosphatases, Non-Receptor; C114990:EPM2A protein, human; D046988:Proteasome Endopeptidase Complex