Calcium Controls Gene Expression via Three Distinct Pathways That Can Function Independently of the Ras/Mitogen-Activated Protein Kinases (ERKs) Signaling Cascade

Abstract

Calcium ions are the principal second messenger in the control of gene expression by electrical activation of neurons. However, the full complexity of calcium-signaling pathways leading to transcriptional activation and the cellular machinery involved are not known. Using the c-fos gene as a model system, we show here that the activity of its complex promoter is controlled by three independently operating signaling mechanisms and that their functional significance is cell type-dependent. The serum response element (SRE), which is composed of a ternary complex factor (TCF) and a serum response factor (SRF) binding site, integrates two calcium-signaling pathways. In PC12 cells, calcium-regulated transcription mediated by the SRE requires the TCF site and is not inhibited by expression of the dominant-negative Ras mutant, RasN17, nor by the MAP kinase kinase 1 inhibitor PD 98059. In contrast, TCF-dependent transcriptional regulation by nerve growth factor or epidermal growth factor is mediated by a Ras/MAP kinases (ERKs) pathway targeting the TCF Elk-1. In AtT20 cells and hippocampal neurons, calcium signals can stimulate transcription via a TCFindependent mechanism that requires the SRF binding site. The cyclic AMP response element (CRE), which cooperates with the TCF site in growth factor-regulated transcription, is a target of a third calcium-regulated pathway that is little affected by the expression of RasN17 or by PD 98059. Thus, calcium can stimulate gene expression via a TCF-, SRF-, and CRE-linked pathway that can operate independently of the Ras/MAP kinases (ERKs) signaling cascade in a cell type-dependent manner.

Osteoblast calcium‐sensing receptor has characteristics of ANF/7TM receptors

“…We used the previously described c-fos promoter luciferase reporter construct (SRE-luc) as a read out of extracellular cation sensing response in various cell lines [Yamauchi et al, 1993;Quarles et al, 1997]. This promoter reporter construct contains two growth factor-regulated promoter elements: the SRE, which binds a ternary complex comprising serum response factor (SRF) and a ternary complex factor (TCF) Price et al, 1996;Johnson et al, 1997;Shaw and Saxton, 2003;Selvaraj and Prywes, 2004]. Both CASR and the putative Ob.CASR can activate the SRE-luc construct Pi et al, 2002].…”

“…To determine if TCF or SRF mediated the responses to CASR and Ob.CASR, we created inactivating mutations of TCF and SRF. Briefly, we synthesized a oligomers containing inactivating mutations sequences for either the TCF binding domain (tacacagga → tgtactgta) or SRF binding domain (catattag → ccaatcgg), as previously described [Johnson et al, 1997]. The 3′ end containing a Bgl II site was ligated to the 5′ end containing a Bcl I site to create a tandem insert containing two copies of the mutated TCF or SRF regions, which were then subcloned into the BamH I and BstY I site of the pGL2-Luciferase vector to replace the wildtype SRE.…”

The roles of signaling by the p42/p44 mitogen-activated protein (MAP) kinase pathway; a potential route to radio- and chemo-sensitization of tumor cells resulting in the induction of apoptosis and loss of clonogenicity

“…39,40 The relative ability of MAP kinase signaling to mediate increased activity of a variety of transcription factors is still under intensive study, potentially because it appears that many signaling pathways under the control of mitogens, eg c-Jun NH 2 -terminal kinase and p38-reactivating kinase pathways, can co-ordinately regulate transcription factor activities and gene expression along with the classical MAP kinase pathway in an agonist and cell-type specific manner. [41][42][43][44] …”

Noggin upregulates Fos expression by a calcium‐mediated pathway in amphibian embryos

“…protein upregulation were also unable to increase intracellular free calcium (Moreau et al 1994 Johnson et al 1997) (Tokumitsu et al 1990;Ishii et al 1991;Enslen & Soderling 1994). In stage 8a animal cap explants that were incubated with 10-50 µmol/L KN-62 for 30 min prior to treatment with Con A or S-(-)BayK 8644 there was no increase in immunoreactivity for the FOS-related protein (Fig.…”