8-CPT-2Me-cAMP, sodium salt

8-CPT-2Me-cAMP, sodium salt is a selective agonist of EPAC [1].

Cyclic AMP guanine nucleotide exchange factors (EPACs) are intracellular sensors for cAMP and function as nucleotide exchange factors for the Ras GTPase homologues Rap1 and Rap2 [1].

8-CPT-2Me-cAMP, sodium salt is a selective EPAC agonist. 8-CPT-2Me-cAMP increased Rap1 activation by EPAC1. Meantime, light chain 2 (LC2) of the microtubule-associated protein MAP1A increased this response. In LC2- and EPAC1-transfected cells, 8-CPT-2Me-cAMP increased cell adhesion to laminin [1]. In Jurkat Tcells, 8-CPT-2Me-cAMP (100 μM) activated Rap1, which was not affected by H-89, a PKA inhibitor [2]. In 1-LN prostate cancer cells, 8-CPT-2Me-cAMP increased Epac1, p-AktS473 and p-AktT308 in a dose-dependent way. 8-CPT-2Me-cAMP increased p-AktS473 and AktS473 kinase activity by two-three fold. Also, 8-CPT-2Me-cAMP activated mTORC1 and mTORC2 [3].

In human prostate cancer cells, 8-CPT-2Me-cAMP increased the levels of p-cPLA2S505, COX-2 and PGE2. However, COX-2, EP4 or mTOR inhibitors inhibited this effect and reduced protein and DNA synthesis induced by Epac1. These results suggested Epac1 was a pro-inflammatory modulator and promoted cell proliferation [4].

References:
[1].  Gupta M, Yarwood SJ. MAP1A light chain 2 interacts with exchange protein activated by cyclic AMP 1 (EPAC1) to enhance Rap1 GTPase activity and cell adhesion. J Biol Chem, 2005, 280(9): 8109-8116.
[2].  Fuld S, Borland G, Yarwood SJ. Elevation of cyclic AMP in Jurkat T-cells provokes distinct transcriptional responses through the protein kinase A (PKA) and exchange protein activated by cyclic AMP (EPAC) pathways. Exp Cell Res, 2005, 309(1): 161-173.
[3].  Misra UK, Pizzo SV. Upregulation of mTORC2 activation by the selective agonist of EPAC, 8-CPT-2Me-cAMP, in prostate cancer cells: assembly of a multiprotein signaling complex. J Cell Biochem, 2012, 113(5): 1488-1500.
[4].  Misra UK, Pizzo SV. Evidence for a pro-proliferative feedback loop in prostate cancer: the role of Epac1 and COX-2-dependent pathways. PLoS One, 2013, 8(4): e63150.

Epac-selective cAMP analog 8-pCPT-2'-O-Me-cAMP as a stimulus for Ca2+-induced Ca2+ release and exocytosis in pancreatic beta-cells.[Pubmed:12496249]

J Biol Chem. 2003 Mar 7;278(10):8279-85.

The second messenger cAMP exerts powerful stimulatory effects on Ca(2+) signaling and insulin secretion in pancreatic beta-cells. Previous studies of beta-cells focused on protein kinase A (PKA) as a downstream effector of cAMP action. However, it is now apparent that cAMP also exerts its effects by binding to cAMP-regulated guanine nucleotide exchange factors (Epac). Although one effector of Epac is the Ras-related G protein Rap1, it is not fully understood what the functional consequences of Epac-mediated signal transduction are at the cellular level. 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate (8-pCPT-2'-O-Me-cAMP) is a newly described cAMP analog, and it activates Epac but not PKA. Here we demonstrate that 8-pCPT-2'-O-Me-cAMP acts in human pancreatic beta-cells and INS-1 insulin-secreting cells to mobilize Ca(2+) from intracellular Ca(2+) stores via Epac-mediated Ca(2+)-induced Ca(2+) release (CICR). The cAMP-dependent increase of [Ca(2+)](i) that accompanies CICR is shown to be coupled to exocytosis. We propose that the interaction of cAMP and Epac to trigger CICR explains, at least in part, the blood glucose-lowering properties of an insulinotropic hormone (glucagon-like peptide-1, also known as GLP-1) now under investigation for use in the treatment of type-2 diabetes mellitus.

A novel Epac-specific cAMP analogue demonstrates independent regulation of Rap1 and ERK.[Pubmed:12402047]

Nat Cell Biol. 2002 Nov;4(11):901-6.

cAMP is involved in a wide variety of cellular processes that were thought to be mediated by protein kinase A (PKA). However, cAMP also directly regulates Epac1 and Epac2, guanine nucleotide-exchange factors (GEFs) for the small GTPases Rap1 and Rap2 (refs 2,3). Unfortunately, there is an absence of tools to discriminate between PKA- and Epac-mediated effects. Therefore, through rational drug design we have developed a novel cAMP analogue, 8-(4-chloro-phenylthio)-2'-O-methyladenosine-3',5'-cyclic monophosphate (8CPT-2Me-cAMP), which activates Epac, but not PKA, both in vitro and in vivo. Using this analogue, we tested the widespread model that Rap1 mediates cAMP-induced regulation of the extracellular signal-regulated kinase (ERK). However, both in cell lines in which cAMP inhibits growth-factor-induced ERK activation and in which cAMP activates ERK, 8CPT-2Me-cAMP did not affect ERK activity. Moreover, in cell lines in which cAMP activates ERK, inhibition of PKA and Ras, but not Rap1, abolished cAMP-mediated ERK activation. We conclude that cAMP-induced regulation of ERK and activation of Rap1 are independent processes.

A family of cAMP-binding proteins that directly activate Rap1.[Pubmed:9856955]

Science. 1998 Dec 18;282(5397):2275-9.

cAMP (3',5' cyclic adenosine monophosphate) is a second messenger that in eukaryotic cells induces physiological responses ranging from growth, differentiation, and gene expression to secretion and neurotransmission. Most of these effects have been attributed to the binding of cAMP to cAMP-dependent protein kinase A (PKA). Here, a family of cAMP-binding proteins that are differentially distributed in the mammalian brain and body organs and that exhibit both cAMP-binding and guanine nucleotide exchange factor (GEF) domains is reported. These cAMP-regulated GEFs (cAMP-GEFs) bind cAMP and selectively activate the Ras superfamily guanine nucleotide binding protein Rap1A in a cAMP-dependent but PKA-independent manner. Our findings suggest the need to reformulate concepts of cAMP-mediated signaling to include direct coupling to Ras superfamily signaling.