title: Phospholipase C-related catalytically inactive protein (PRIP) regulates lipolysis in adipose tissue by modulating the phosphorylation of hormone-sensitive lipase.
abstract: Phosphorylation of hormone-sensitive lipase (HSL) and perilipin by protein kinase A (PKA) promotes the hydrolysis of lipids in adipocytes. Although activation of lipolysis by PKA has been well studied, inactivation via protein phosphatases is poorly understood. Here, we investigated whether phospholipase C-related catalytically inactive protein (PRIP), a binding partner for protein phosphatase 1 and protein phosphatase 2A (PP2A), is involved in lipolysis by regulating phosphatase activity. PRIP knockout (PRIP-KO) mice displayed reduced body-fat mass as compared with wild-type mice fed with standard chow ad libitum. Most other organs appeared normal, suggesting that mutant mice had aberrant fat metabolism in adipocytes. HSL in PRIP-KO adipose tissue was highly phosphorylated compared to that in wild-type mice. Starvation of wild-type mice or stimulation of adipose tissue explants with the catabolic hormone, adrenaline, translocated both PRIP and PP2A from the cytosol to lipid droplets, but the translocation of PP2A was significantly reduced in PRIP-KO adipocytes. Consistently, the phosphatase activity associated with lipid droplet fraction in PRIP-KO adipocytes was significantly reduced and was independent of adrenaline stimulation. Lipolysis activity, as assessed by measurement of non-esterified fatty acids and glycerol, was higher in PRIP-KO adipocytes. When wild-type adipocytes were treated with a phosphatase inhibitor, they showed a high lipolysis activity at the similar level to PRIP-KO adipocytes. Collectively, these results suggest that PRIP promotes the translocation of phosphatases to lipid droplets to trigger the dephosphorylation of HSL and perilipin A, thus reducing PKA-mediated lipolysis.
authors.affiliation: Department of Cellular and Molecular Pharmacology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan; Department of Oral Surgery, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Toshiya
authors.initials: T
authors.lastname: Okumura
authors.affiliation: Department of Cellular and Molecular Pharmacology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Kae
authors.initials: K
authors.lastname: Harada
authors.affiliation: Department of Cellular and Molecular Pharmacology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan; Department of Dental Anesthesiology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Kana
authors.initials: K
authors.lastname: Oue
authors.affiliation: Department of Cellular and Molecular Pharmacology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Cellular and Molecular Pharmacology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Asano
authors.affiliation: Department of Cellular and Molecular Pharmacology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Hayashiuchi
authors.affiliation: Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Mizokami
authors.affiliation: Department of Cellular and Molecular Pharmacology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan; Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Department of Dental Anesthesiology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Irifune
authors.affiliation: Department of Oral Surgery, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kamata
authors.affiliation: Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Hirata
authors.affiliation: Department of Cellular and Molecular Pharmacology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kanematsu
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D066292:Lipid Droplets / Q000187:drug effects / Q000378:metabolism; D008066:Lipolysis / Q000187:drug effects; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008954:Models, Biological; D000070778:Perilipin-1; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D054645:Protein Phosphatase 1 / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D002787:Sterol Esterase / Q000378:metabolism*; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; C513987:PRIP-1 phospholipase C-related protein, mouse; D000070778:Perilipin-1; D010750:Phosphoproteins; D002787:Sterol Esterase; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D004837:Epinephrine