title: The SHP-1 protein tyrosine phosphatase negatively modulates Akt signaling in the ghrelin/GHSR1a system.
abstract: The aim of the present study was to identify the signaling mechanism(s) responsible for the modulation of growth hormone secretagogue receptor type 1a (GHSR1a)-associated Akt activity. Ghrelin leads to the activation of Akt through the interplay of distinct signaling mechanisms: an early G(i/o) protein-dependent pathway and a late pathway mediated by β-arrestins. We found that the Src homology 2-containing protein tyrosine phosphatase (SHP-1) was an essential molecule in both G(i/o) protein-dependent and β-arrestin-mediated pathways. More specifically, the role of SHP-1 in the G(i/o) protein-dependent pathway was demonstrated by the fact that the overexpression of a catalytically defective SHP-1 augments tyrosine phosphorylation of the PI3K regulatory subunit p85, leading to an increase in the phosphorylation of cSrc and phosphoinositide-dependent protein kinase 1, and finally activating Akt. The presence of SHP-1 in the β-arrestin-scaffolded complex and its attenuating effect on the cSrc and Akt activities verified that SHP-1 regulates not only the G(i/o) protein-dependent pathway but also the β-arrestin-mediated pathway. Assays performed in preadipocyte and adipocyte 3T3-L1 cells showed SHP-1 expression. According to our results in HEK-GHSR1a cells, ghrelin stimulated SHP-1 phosphorylation in 3T3-L1 cells. The increase in ghrelin-induced Akt activity was enhanced by small interfering RNA of SHP-1 in preadipocyte 3T3-L1 cells. These results were reproduced in white adipose tissue obtained from mice, in which SHP-1 exhibited higher expression in omental than in subcutaneous tissue. Furthermore, this pattern of expression was inverted in mice fed a high-fat diet, suggesting a role for SHP-1 in controlling ghrelin sensitivity in adipose tissue. Indeed, SHP-1 deficiency was associated with augmented ghrelin-evoked Akt phosphorylation in omental tissue, as well as decreased phosphorylation under overexpression of SHP-1 in subcutaneous tissue. These findings showed a novel role for SHP-1 in the regulation of Akt activity through the modulation of the ghrelin/GHSR1a system signaling.
authors: Área de Endocrinología Molecular y Celular, Instituto de Investigación Sanitaria de Santiago, Hospital Clinico Universitario de Santiago, Servicio Gallego de Salud, 15706 Santiago de Compostela, Spain.
authors: Maria
authors: M
authors: Lodeiro
authors: Begoña O
authors: BO
authors: Alén
authors: Carlos S
authors: CS
authors: Mosteiro
authors: Daniel
authors: D
authors: Beiroa
authors: Rubén
authors: R
authors: Nogueiras
authors: Marily
authors: M
authors: Theodoropoulou
authors: María
authors: M
authors: Pardo
authors: Rosalía
authors: R
authors: Gallego
authors: Yolanda
authors: Y
authors: Pazos
authors: Felipe F
authors: FF
authors: Casanueva
authors: Jesus P
authors: JP
authors: Camiña
mesh_terms: D041721:3T3-L1 Cells; D000818:Animals; D019390:Arrestins / Q000378:metabolism; D000081247:CSK Tyrosine-Protein Kinase; D059305:Diet, High-Fat; D057075:Enzyme Assays; D054439:Ghrelin / Q000494:pharmacology / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D054440:Receptors, Ghrelin / Q000378:metabolism*; D015398:Signal Transduction; D050151:Subcutaneous Fat / Q000378:metabolism; D046509:Tissue Culture Techniques; D000071557:beta-Arrestins; D019061:src-Family Kinases
chemical_list: D019390:Arrestins; D000081247:CSK Tyrosine-Protein Kinase; D054439:Ghrelin; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D011505:Protein-Tyrosine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D054440:Receptors, Ghrelin; D000071557:beta-Arrestins; D019061:src-Family Kinases; C000631346:CSK protein, human; C509249:PTPN6 protein, human