title: High NaCl-induced inhibition of PTG contributes to activation of NFAT5 through attenuation of the negative effect of SHP-1.
abstract: Activation of the transcription factor NFAT5 by high NaCl involves changes in phosphorylation. By siRNA screening, we previously found that protein targeting to glycogen (PTG), a regulatory subunit of protein phosphatase1 (PP1), contributes to regulation of high NaCl-induced NFAT5 transcriptional activity. The present study addresses the mechanism involved. We find that high NaCl-induced inhibition of PTG elevates NFAT5 activity by increasing NFAT5 transactivating activity, protein abundance, and nuclear localization. PTG acts via a catalytic subunit PP1γ. PTG associates physically with PP1γ, and NaCl reduces both this association and remaining PTG-associated PP1γ activity. High NaCl-induced phosphorylation of p38, ERK, and SHP-1 contributes to activation of NFAT5. Knockdown of PTG does not affect phosphorylation of p38 or ERK. However, PTG and PP1γ bind to SHP-1, and knockdown of either PTG or PP1γ increases high NaCl-induced phosphorylation of SHP-1-S591, which inhibits SHP-1. Mutation of SHP-1-S591 to alanine, which cannot be phosphorylated, increases inhibition of NFAT5 by SHP-1. Thus high NaCl reduces the stimulatory effect of PTG and PP1γ on SHP-1, which in turn reduces the inhibitory effect of SHP-1 on NFAT5. Our findings add to the known functions of PTG, which was previously recognized only for its glycogenic activity.
authors.affiliation: Department of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA. xiaoming.zhou@usuhs.edu
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Zhou
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.forename: Maurice B
authors.initials: MB
authors.lastname: Burg
authors.forename: Joan D
authors.initials: JD
authors.lastname: Ferraris
mesh_terms: D015153:Blotting, Western; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D020935:MAP Kinase Signaling System / Q000502:physiology; D019913:Nuclear Localization Signals / Q000187:drug effects; D010957:Plasmids; D016133:Polymerase Chain Reaction; D054645:Protein Phosphatase 1 / Q000187:drug effects / Q000378:metabolism*; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering; D012965:Sodium Chloride / Q000494:pharmacology*; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C118125:NFAT5 protein, human; D019913:Nuclear Localization Signals; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014157:Transcription Factors; D012965:Sodium Chloride; D048051:p38 Mitogen-Activated Protein Kinases; D054645:Protein Phosphatase 1; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6
keywords: PP1γ; PPP1R3C; TonEBP; hypertonicity; protein phosphatase 1; protein targeting to glycogen