cAMP response element-binding protein is activated by Ca2+/calmodulin- as well as cAMP-dependent protein kinase.

Abstract

a convergence point for synaptic activity acting through kinase A and impulse activity acting through Cam kinase. Together the two kinases could activate transcription in a synergistic manner, which could allow CRE-binding protein to couple short-term to long-term associative forms of synaptic plasticity.Studies of neuronal plasticity in vertebrates and invertebrates indicate that long-term changes in the functional properties of nerve cells are often accompanied by and perhaps mediated through changes in gene expression (1-7). The changes in gene expression commonly result from signal transduction at the membrane produced either by impulse activity, by synaptic activity, or by both (5, 8). These two types of signals are then conveyed from the membrane to the nucleus by independent second-messenger pathways: (l) by Ca2" influx through voltage-gated ion channels activated by the action potential and (ii) by cAMP or other second-messenger systems activated by synaptic transmitters binding to receptors coupled to guanine nucleotide-binding proteins (G proteins) (9-12). We here ask: Can these pathways converge and interact on common transcription factors? Can transcription factors detect the independent but coincident occurrence at the membrane of synaptic activity on the one hand and impulse activity on the other?In neurons, it initially appeared as if these two pathways might be independent. For example, transmitter receptors coupled to adenylyl cyclase were found to induce the expression of c-fos by means of CREB transcriptional activators that bind as dimers to the cAMP response element (CRE) (12)(13)(14). Conversely, c-fos was found to be activated independently by membrane depolarization and the consequent Ca2+ influx (9, 10). However, recent studies in PC12 (rat pheochromocytoma) cells by Sheng et al. (15) Tryptic peptide analysis of the phosphorylated protein shows that the two kinases phosphorylate a common peptide. Moreover, in vitro transcription from a CRE-containing fos promoter is enhanced when the CRE-binding protein is phosphorylated either by Cam kinase or by kinase A. Phosphorylation by both the kinases increases transcription to a greater extent than phosphorylation by either one alone. METHODSProtein Purification and Blotting. Bovine brain nuclear extracts were prepared essentially by the method of Yamamoto et al. (12). Briefly, fresh brains were homogenized and the cell nuclei were centrifuged, washed, and frozen. The nuclei were lysed and centrifuged, DNA was removed with DEAE-cellulose resin, and the protein was precipitated with ammonium sulfate. The nuclear proteins were fractionated by heparin affinity chromatography and the fractions were assayed for CRE binding by gel retardation assay. Active fractions were further purified by affinity chromatography on oligonucleotide-agarose resins-sequentially CRE, API, and CRE sequence. These resins were synthesized according to Kadonaga and Tjian (16). For analysis the purified active fractions were concentrated and subjected to standard SDS/ PAGE....

The HMG box of SRY is a calmodulin binding domain

“…In the absence of CaM, peptides were not detected in the gel (result not shown). In the presence of CaM, peptides from two regions of the SRY HMG domain showed an interaction: residues 57-80 (lane 1) and a second, weakly binding region, 131-144, which gave multiple bands (lane 9). No CaM binding was detectable with the other six SRY peptides (lanes [3][4][5][6][7][8].…”

“…Many nuclear functions are under CaM control and some transcriptional activators are known to be modulated indirectly through CaM-dependent kinases [8,9]. CaM has more recently been shown to influence transcription by interacting directly with basic helix-loop-helix (bHLH) DNA binding proteins through differential inhibition of the DNA binding activity of these domains [10].…”

Involvement of cyclic AMP response element binding protein (CREB) and estrogen receptor phosphorylation in the synergistic activation of the estrogen receptor by estradiol and protein kinase activators

“…Because CREB is activated by PKA [32,33] and since CBP (CREB binding protein) is a coactivator for both CREB and ER [34][35][36], we examined whether CREB was involved in the synergistic activation of ER by E 2 and PKA. We found that CREB could enhance the activity of ER in CHO cells, and that when CREB was transfected into SK-BR-3 cells, we saw transcriptional synergy where this was not seen if CREB was not transfected into these cells.…”

Cross-talk in signal transduction: Ras-dependent induction of cAMP-responsive transcriptional repressor ICER by nerve growth factor

“…We discuss the possible physiological implications of these results. miny, 1989;Dash et al, 1991;Sheng et al, 1991;de Groot et al, 1993de Groot et al, , 1994Ginty et al, 1994). In particular, activation of transduction pathways independent from cAMP may also result in CREB phosphorylation, as for instance in PC12 cells upon NGF treatment (Ginty et al, 1994).…”