Following hormonal stimulation of a neuroendocrine cell, for
example, increased cAMP levels activate cAMP-dependent protein kinase A, which phosphorylates 1 or more
DNA-binding proteins. These in turn stimulate transcription of an array of cAMP-responsive genes. All
cAMP-responsive gene promoters have in common an 8-base enhancer known as the cAMP-response element (CRE)
containing a conserved core sequence, 5-prime-TGACG-3-prime, first described in the somatostatin gene by Montminy et al. (1986). Montminy and Bilezikjian (1987) purified a 43-kD nuclear phosphoprotein, which binds to CRE with high
affinity.
Transcriptional activity of CREB requires phosphorylation of the protein on a serine residue at position 119.
NCBI Summary:
This gene encodes a transcription factor that is a member of the leucine zipper family of DNA binding proteins. This protein binds as a homodimer to the cAMP-responsive element, an octameric palindrome. The protein is phosphorylated by several protein kinases, and induces transcription of genes in response to hormonal stimulation of the cAMP pathway. Alternate splicing of this gene results in several transcript variants encoding different isoforms. [provided by RefSeq, Mar 2016]
CREB Non-autonomously Controls Reproductive Aging through Hedgehog/Patched Signaling. Templeman NM et al. (2020) Evolutionarily conserved signaling pathways are crucial for adjusting growth, reproduction, and cell maintenance in response to altered environmental conditions or energy balance. However, we have an incomplete understanding of the signaling networks and mechanistic changes that coordinate physiological changes across tissues. We found that loss of the cAMP response element-binding protein (CREB) transcription factor significantly slows Caenorhabditis elegans' reproductive decline, an early hallmark of aging in many animals. Our results indicate that CREB acts downstream of the transforming growth factor β (TGF-β) Sma/Mab pathway in the hypodermis to control reproductive aging, and that it does so by regulating a Hedgehog-related signaling factor, WRT-10. Overexpression of hypodermal wrt-10 is sufficient to delay reproductive decline and oocyte quality deterioration, potentially acting via Patched-related receptors in the germline. This TGF-β-CREB-Hedgehog signaling axis allows a key metabolic tissue to communicate with the reproductive system to regulate oocyte quality and the rate of reproductive decline.//////////////////CREB activity is required for mTORC1 signaling-induced primordial follicle activation in mice. Li J et al. (2020) In mammals, progressive activation of primordial follicles is essential for maintenance of the reproductive lifespan. Several reports have demonstrated that mitogen-activated protein kinases 3 and 1 (MAPK3/1)-mammalian target of rapamycin complex 1 (mTORC1) signaling in pre-granulosa cells promotes primordial follicle activation by increasing KIT ligand (KITL) expression and then stimulating phosphatidylinositol 3 kinase signaling in oocytes. However, the mechanism of mTORC1 signaling in the promotion of KITL expression is unclear. Immunofluorescence staining results showed that phosphorylated cyclic AMP response element-binding protein (CREB) was mainly expressed in pre-granulosa cells. The CREB inhibitor KG-501 and CREB knockdown by Creb siRNA significantly suppressed primordial follicle activation, reduced pre-granulosa cell proliferation and dramatically increased oocyte apoptosis. Western blotting results demonstrated that both the MAPK3/1 inhibitor U0126 and mTORC1 inhibitor rapamycin significantly decreased the levels of phosphorylated CREB, indicating that MAPK3/1-mTORC1 signaling is required for CREB activation. Furthermore, CREB could bind to the Kitl promoter region, and KG-501 significantly decreased the expression levels of KITL. In addition, KG-501 and CREB knockdown significantly decreased the levels of phosphorylated Akt, leading to a reduced number of oocytes with Foxo3a nuclear export. KG-501 also inhibited bpV (HOpic)-stimulated primordial follicle activation. Taken together, the results show that CREB is required for MAPK3/1-mTORC1 signaling-promoted KITL expression followed by the activation of primordial follicles.//////////////////
Combining Bioinformatics and Experiments to Identify CREB1 as a Key Regulator in Senescent Granulosa Cells. Lin PH et al. (2020) Aging of functional ovaries occurs many years before aging of other organs in the female body. In recent years, a greater number of women continue to postpone their pregnancies to later stages in their lives, raising concerns of the effect of ovarian aging. Mitochondria play an important role in the connection between the aging granulosa cells and oocytes. However, the underlying mechanisms of mitochondrial dysfunction in these cells remain poorly understood. Therefore, we evaluated the molecular mechanism of the aging granulosa cells, including aspects such as accumulation of mitochondrial reactive oxygen species, reduction of mtDNA, imbalance of mitochondrial dynamics, and diminished cell proliferation. Here, we applied bioinformatics approaches, and integrated publicly available resources, to investigate the role of CREB1 gene expression in reproduction. Senescence hallmark enrichment and pathway analysis suggested that the downregulation of bioenergetic-related genes in CREB1. Gene expression analyses showed alterations in genes related to energy metabolism and ROS production in ovary tissue. We also demonstrate that the biogenesis of aging granulosa cells is subject to CREB1 binding to the PRKAA1 and PRKAA2 upstream promoters. In addition, cofactors that regulate biogenesis significantly increase the levels of SIRT1 and PPARGC1A mRNA in the aging granulosa cells. These findings demonstrate that CREB1 elevates an oxidative stress-induced senescence in granulosa cells by reducing the mitochondrial function.//////////////////CREB activity is required for epidermal growth factor-induced mouse cumulus expansion. Zhang Y et al. (2019) The release of a fertilizable oocyte from the ovary is dependent upon the expansion of the cumulus cells. The expansion requires cooperation between epidermal growth factor (EGF) family peptide-activated mitogen-activated protein kinase (MAPK)3/1 and oocyte paracrine factor-activated-Sma- and Mad-related protein (SMAD)2/3 signaling in cumulus cells. However, the mechanism underlying (MAPK)3/1 signaling is unclear. In the present study, the EGF-activation of EGF receptor (EGFR) induced cyclic adenosine 3',5'-monophosphate (cAMP) response element-binding protein (CREB) phosphorylation in cumulus cells, and the interruption of CREB functional complex formation by naphthol AS-E phosphate (KG-501) completely blocked the EGF-stimulated expansion-related gene expression. EGF-stimulated phosphorylation of CREB was completely inhibited by MAPK3/1 inhibitor U0126, suggesting that EGF-activated MAPK3/1 results in the activation of CREB for cumulus expansion. Also, the role of EGF-stimulated calcium signaling was studied. Calcium-elevating reagents ionomycin and sphingosine-1-phosphate mimicked, but calcium chelators bis-(o'aminophenoxy)-ethane-N,N,N,N-tetraacetic acid, tetra(acetoxymethyl)-ester, and 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate abolished the activity of EGF on CREB phosphorylation, cumulus expansion, and expansion-related gene expression. Furthermore, EGF-induced cumulus expansion was inhibited by calmodulin (CaM)-dependent protein kinase II (CaMKII) inhibitors, KN-93 and autocamtide-2-related inhibitory peptide. However, the inhibition of SMAD2/3 activity by removal of oocyte from cumulus-oocyte complexes did not affect the EGF-induced CREB phosphorylation, indicating that EGF-activated CREB is independent of oocyte-activated SMAD2/3 signaling. Therefore, EGF-induced CREB activity by MAPK3/1 and Ca2+ /CaMKII signaling pathways promotes the expansion-related gene expression and consequent cumulus expansion.//////////////////
Somers JP et al reported that adenovirus-directed expression of a nonphosphorylatable mutant of CREB (cAMP response element-binding protein) adversely affects the survival, but not
the differentiation, of rat granulosa cells. These
results demonstrate that the trophic effects of cAMP (proliferation and survival)
on ovarian granulosa cells are functionally separate from the effects of cAMP on
differentiation and provide novel evidence that CREB may function as a cell
survival factor in the ovary. The separation of signaling pathways that govern
differentiation and survival in the ovary thereby provides a mechanism by which
progesterone production, which is absolutely essential for the maintenance of
pregnancy, can continue despite the cessation of proliferation of luteal cells and
their commitment to cell death (luteolysis).
Michael MD et al 1997 reported that a CRE-like sequence that binds CREB and contributes to cAMP-dependent
regulation of the proximal promoter of the human aromatase P450 (CYP19) gene.
Carlone DL,et al presented evidence that functional interactions of CREB and SF-1 mediate hormone
regulated expression of the aromatase gene in granulosa cells.
Expression regulated by
FSH, LH, Growth Factors/ cytokines
Comment
Although usually considered to be a constitutively expressed protein, in the
primate ovary the expression of CREB (cAMP response element-binding protein)
is extinguished after ovulation, and its loss is temporally associated with the
cessation of proliferation of luteal cells and the ultimate commitment of the corpus
luteum to undergo regression. Somers JP et al reported that luteinization in primates is accompanied by loss of a 43-kilodalton adenosine
3',5'-monophosphate response element-binding protein isoform.
Real-time monitoring of cAMP response element binding protein signaling in porcine granulosa cells modulated by ovarian factors. He PJ et al. The present study was performed to establish a real-time monitoring of the cAMP response element binding protein (CREB) signalling using granulosa cells, and to assess the modulation of CREB activity by potential ovarian autocrine/paracrine and oocyte-derived factors. Granulosa cells were isolated from porcine follicles and cultured for 2 days, and then transfected with CRE-containing pGL3. The cells were directly stimulated or cultured with FSH, LH, forskolin, or a permeable cAMP analog, and/or IGF-I, EGF, bFGF, TGF-beta2 or TNF-alpha, or cumulus-oocyte complex (COCs) for the real-time monitoring of CREB signaling. The activation pattern of CREB signaling consisted of three distinct phases, i.e., burst, attenuation and refractory. In contrast to FSH, LH, and forskolin, a cAMP analog induced the prolonged activation, although three distinct phases were observed at its high concentration. Of all the autocrine/paracrine factors, only IGF-I slightly induced CREB activity. On the other hand, TGF-beta2 and TNF-alpha significantly repressed FSH-stimulated transcriptional activation of CREB by 30% (P < 0.05) and 45% (P < 0.05), respectively. Additionally, coculture with COCs caused a significant suppression of transcriptional activation of CREB signaling stimulated by FSH. These results indicate that ovarian autocrine/paracrine factors such as IGF-I, TGF-beta2, TNF-alpha and oocyte-derived factors modulate the CREB signaling. The present study provides a new approach for direct signaling study on transcription factors under the influences of potential factors.
Mukherjee A et al reported that gonadotropins induce rapid phosphorylation of the 3',5'-cyclic
adenosine monophosphate response element binding protein in
ovarian granulosa cells. In situ hybridization,
RNA blot analysis and RT-PCR RNA quantification demonstrated that CREB
messenger RNA (mRNA) is expressed at low levels throughout the ovary, and that
CREB mRNA levels do not change appreciably after gonadotropin stimulation.
Similar results were obtained using immunohistochemistry and Western protein
blotting to examine CREB protein in ovaries isolated from immature animals
treated with gonadotropins or immunocytochemistry and Western protein blotting
to examine the CREB protein in cultured granulosa cells after gonadotropin
treatment. In contrast, immunocytochemistry and Western protein blotting using an
antipeptide antibody specific to CREB phosphorylated at serine 133 (P-CREB),
which is the activated from of the CREB protein, revealed a dramatic increase in
the phosphorylated form of CREB within 20 min of gonadotropin treatment of
granulosa cells that was transient and was decreased by 60 min after gonadotropin
treatment. Stimulation of P-CREB was observed using granulosa cells isolated
from immature animals and treated with recombinant human FSH in vitro, or using
granulosa cells isolated from immature animals primed with PMSG in vivo and
treated with human CG (hCG) in vitro. Stimulation of P-CREB was also observed
in ovarian granulosa cells isolated from animals treated with PMSG in vivo.