title: GHRP-6 induces CREB phosphorylation and growth hormone secretion via a protein kinase Csigma-dependent pathway in GH3 cells.
abstract: This study examined the effect of GHRP-6, a known GHSs receptor agonist, on the phosphorylation of cAMP-responsive element-binding protein (CREB) and the underly mechanism. GH3 cells were cultured and subjected to different treatments as follows: GHRP-6, GHRP-6 plus GHRH, phorbol ester (PMA), an activator of PKC, alone or in combination with GHRP-6, Gö6983, a general inhibitor of PKCs, in the presence or absence of GHRP-6, rottlerin, an inhibitor of PKCs, alone or plus GHRP-6. The cells were transiently transfected with PKCsigma-specific siRNA and then treated with GHRP-6. GH level was measured by enzyme-linked immunosorbent assay (ELISA). The expression of phosphor-CREB, PKCsigma, PKCtheta and phosphor-PKCsigma was determined by Western blotting. The results showed that GHRP-6 stimulated GH secretion in both time- and dose-dependent manners and enhanced the effect of GHRH on GH secretion. GHRP-6 was also found to induce CREB phosphorylation. Moreover, GH secretion was enhanced by the PKC activator PMA and reduced by the PKC inhibitors (Gö6983, rottlerin) and knockdown of PKCsigma. PKCsigma could be activated by GHRP-6. It is concluded that PKC, especially PKCsigma, mediates CREB phosphorylation and GHRP-6-induced GH secretion.
authors.affiliation: Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China. chunleit.0223@yahoo.com.cn
authors.forename: Chunlei
authors.initials: C
authors.lastname: Tian
authors.forename: Fei
authors.initials: F
authors.lastname: Ye
authors.forename: Tongjiang
authors.initials: T
authors.lastname: Xu
authors.forename: Sheng
authors.initials: S
authors.lastname: Wang
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Wang
authors.forename: Heping
authors.initials: H
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Wan
authors.forename: Ting
authors.initials: T
authors.lastname: Lei
mesh_terms: D045744:Cell Line, Tumor; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology*; D010766:Phosphorylation; D010911:Pituitary Neoplasms / Q000378:metabolism / Q000473:pathology*; D011493:Protein Kinase C / Q000378:metabolism*; D054440:Receptors, Ghrelin / Q000819:agonists; D015398:Signal Transduction
chemical_list: C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D009842:Oligopeptides; D054440:Receptors, Ghrelin; C041048:growth hormone releasing hexapeptide; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D011493:Protein Kinase C
references.citation: J Neurochem. 2003 Mar;84(6):1367-77
references.pmid: 12614337
references.citation: Science. 1996 Aug 16;273(5277):974-7
references.pmid: 8688086
references.citation: Endocrinology. 2007 Sep;148(9):4440-9
references.pmid: 17540720
references.citation: Endocrinology. 1994 Sep;135(3):1073-6
references.pmid: 7915227
references.citation: J Tongji Med Univ. 2000;20(3):214-6
references.pmid: 11215052
references.citation: Mol Endocrinol. 1996 Apr;10(4):432-8
references.pmid: 8721987
references.citation: Endocrinology. 2003 Dec;144(12):5372-80
references.pmid: 12960033
references.citation: Proc Natl Acad Sci U S A. 2008 Dec 23;105(51):20452-7
references.pmid: 19088192
references.citation: Neurosurgery. 1996 Sep;39(3):569-75; discussion 575-6
references.pmid: 8875488
references.citation: J Clin Endocrinol Metab. 2001 Sep;86(9):4552
references.pmid: 11549707
references.citation: Endocr Rev. 2005 May;26(3):346-60
references.pmid: 15814848
references.citation: IDrugs. 2002 Aug;5(8):804-14
references.pmid: 12802697
references.citation: Endocr Rev. 2004 Jun;25(3):426-57
references.pmid: 15180951
references.citation: J Mol Endocrinol. 1995 Feb;14(1):135-8
references.pmid: 7772238
references.citation: J Biol Chem. 2004 Jul 16;279(29):30123-32
references.pmid: 15138267
references.citation: Endocrinology. 2004 Aug;145(8):3731-8
references.pmid: 15087428
references.citation: Mol Cell Endocrinol. 2006 Jun 27;252(1-2):184-90
references.pmid: 16682115
references.citation: Endocrinology. 2007 Mar;148(3):1099-107
references.pmid: 17185372
references.citation: J Tongji Med Univ. 1999;19(4):277-9
references.pmid: 12938517
references.citation: J Cell Biochem. 2007 Dec 1;102(5):1245-55
references.pmid: 17455223
references.citation: J Gerontol A Biol Sci Med Sci. 2007 Jun;62(6):585-97
references.pmid: 17595414
references.citation: J Tongji Med Univ. 1997;17(3):132-5
references.pmid: 9812762