GHRP-6 induces CREB phosphorylation and growth hormone secretion via a protein kinase Csigma-dependent pathway in GH3 cells.
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.
Tian
Chunlei
C
Department of Neurosurgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China. chunleit.0223@yahoo.com.cn
Ye
Fei
F
Xu
Tongjiang
T
Wang
Sheng
S
Wang
Xiaodan
X
Wang
Heping
H
Wan
Feng
F
Lei
Ting
T
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
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
J Neurochem. 2003 Mar;84(6):1367-77
12614337
Science. 1996 Aug 16;273(5277):974-7
8688086
Endocrinology. 2007 Sep;148(9):4440-9
17540720
Endocrinology. 1994 Sep;135(3):1073-6
7915227
J Tongji Med Univ. 2000;20(3):214-6
11215052
Mol Endocrinol. 1996 Apr;10(4):432-8
8721987
Endocrinology. 2003 Dec;144(12):5372-80
12960033
Proc Natl Acad Sci U S A. 2008 Dec 23;105(51):20452-7
19088192
Neurosurgery. 1996 Sep;39(3):569-75; discussion 575-6
8875488
J Clin Endocrinol Metab. 2001 Sep;86(9):4552
11549707
Endocr Rev. 2005 May;26(3):346-60
15814848
IDrugs. 2002 Aug;5(8):804-14
12802697
Endocr Rev. 2004 Jun;25(3):426-57
15180951
J Mol Endocrinol. 1995 Feb;14(1):135-8
7772238
J Biol Chem. 2004 Jul 16;279(29):30123-32
15138267
Endocrinology. 2004 Aug;145(8):3731-8
15087428
Mol Cell Endocrinol. 2006 Jun 27;252(1-2):184-90
16682115
Endocrinology. 2007 Mar;148(3):1099-107
17185372
J Tongji Med Univ. 1999;19(4):277-9
12938517
J Cell Biochem. 2007 Dec 1;102(5):1245-55
17455223
J Gerontol A Biol Sci Med Sci. 2007 Jun;62(6):585-97
17595414
J Tongji Med Univ. 1997;17(3):132-5
9812762