Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously reported the Ras-dependent activation of the mitogen-activated protein kinases p44 and p42, also termed extracellular signal-regulated kinases (ERK)1 and 2 (ERK1/2), mediated through Gs-coupled serotonin receptors transiently expressed in human embryonic kidney (HEK) 293 cells. Whereas Gi- and Gq-coupled receptors have been shown to activate Ras through the guanine nucleotide exchange factor (GEF) called Ras-GRF1 (CDC25Mm) by binding of Ca2+/calmodulin to its N-terminal IQ domain, the mechanism of Ras activation through Gs-coupled receptors is not fully understood. We report the endogenous expression of Ras-GRF1 in HEK293 cells. Serotonin stimulation of HEK293 cells transiently expressing Gs-coupled 5-HT7 receptors induced protein kinase A-dependent phosphorylation of the endogenous human Ras-GRF1 on Ser927 and of transfected mouse Ras-GRF1 on Ser916. Ras-GRF1 overexpression increased basal and serotonin-stimulated ERK1/2 phosphorylation. Mutations of Ser916 inhibiting (Ser916Ala) or mimicking (Ser916Asp/Glu) phosphorylation did not alter these effects. However, the deletion of amino acids 1-225, including the Ca2+/calmodulin-binding IQ domain, from Ras-GRF1 reduced both basal and serotonin-stimulated ERK1/2 phosphorylation. Furthermore, serotonin treatment of HEK293 cells stably expressing 5-HT7 receptors increased [Ca2+]i, and the serotonin-induced ERK1/2 phosphorylation was Ca2+-dependent. Therefore, both cAMP and Ca2+ may contribute to the Ras-dependent ERK1/2 activation after 5-HT7 receptor stimulation, through activation of a guanine nucleotide exchange factor with activity towards Ras.
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PMID:Endogenous expression and protein kinase A-dependent phosphorylation of the guanine nucleotide exchange factor Ras-GRF1 in human embryonic kidney 293 cells. 1585 14

Sequences in Drug Discovery is a new series of distinct brief reports on breaking topics in the field of drug R&D. This month's Sequences in Drug Discovery contains the following reports: Spotlight on West Nile virus vaccines. p38alpha MAPK--a dynamic target in rheumatoid arthritis. The need for new contraceptives: targeting PDE3. Vasopeptidase inhibition with a triple mode of action. Current advances in the development of 5-HT(6) receptor antagonists.
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PMID:Sequences in drug discovery. 1591 21

Serotonin 5-HT2C receptors (5-HT(2C)Rs) are almost exclusively expressed in the CNS, and implicated in disorders such as obesity, depression, and schizophrenia. The present study investigated the mechanisms governing the coupling of the 5-HT(2C)R to the extracellular signal-regulated kinases (ERKs) 1/2, using a Chinese hamster ovary (CHO) cell line stably expressing the receptor at levels comparable to those found in the brain. Using the non-RNA-edited isoform of the 5-HT(2C)R, constitutive ERK1/2 phosphorylation was observed and found to be modulated by full, partial and inverse agonists. Interestingly, agonist-directed trafficking of receptor stimulus was also observed when comparing effects on phosphoinositide accumulation and intracellular Ca2+ elevation to ERK1/2 phosphorylation, whereby the agonists, [+/-]-2,5-dimethoxy-4-iodoamphetamine (DOI) and quipazine, showed reversal of efficacy between the phosphoinositide/Ca2+ pathways, on the one hand, and the ERK1/2 pathway on the other. Subsequent molecular characterization found that 5-HT-stimulated ERK1/2 phosphorylation in this cellular background requires phospholipase D, protein kinase C, and activation of the Raf/MEK/ERK module, but is independent of both receptor- and non-receptor tyrosine kinases, phospholipase C, phosphoinositide 3-kinase, and endocytosis. Our findings underscore the potential for exploiting pathway-selective receptor states in the differential modulation of signaling pathways that play prominent roles in normal and abnormal neuronal signaling.
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PMID:Characterization of serotonin 5-HT2C receptor signaling to extracellular signal-regulated kinases 1 and 2. 1593 77

The serotonin system and NMDA receptors (NMDARs) in prefrontal cortex (PFC) are both critically involved in the regulation of cognition and emotion under normal and pathological conditions; however, the interactions between them are essentially unknown. Here we show that serotonin, by activating 5-HT(1A) receptors, inhibited NMDA receptor-mediated ionic and synaptic currents in PFC pyramidal neurons, and the NR2B subunit-containing NMDA receptor is the primary target of 5-HT(1A) receptors. This effect of 5-HT(1A) receptors was blocked by agents that interfere with microtubule assembly, as well as by cellular knock-down of the kinesin motor protein KIF17 (kinesin superfamily member 17), which transports NR2B-containing vesicles along microtubule in neuronal dendrites. Inhibition of either CaMKII (calcium/calmodulin-dependent kinase II) or MEK/ERK (mitogen-activated protein kinase kinase/extracellular signal-regulated kinase) abolished the 5-HT(1A) modulation of NMDAR currents. Biochemical evidence also indicates that 5-HT(1A) activation reduced microtubule stability, which was abolished by CaMKII or MEK inhibitors. Moreover, immunocytochemical studies show that 5-HT(1A) activation decreased the number of surface NR2B subunits on dendrites, which was prevented by the microtubule stabilizer. Together, these results suggest that serotonin suppresses NMDAR function through a mechanism dependent on microtubule/kinesin-based dendritic transport of NMDA receptors that is regulated by CaMKII and ERK signaling pathways. The 5-HT(1A)-NMDAR interaction provides a potential mechanism underlying the role of serotonin in controlling emotional and cognitive processes subserved by PFC.
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PMID:Serotonin 5-HT1A receptors regulate NMDA receptor channels through a microtubule-dependent mechanism. 1594 77

Serotonin (5-HT) stimulates superoxide release, phosphorylation of p42/p44 mitogen-activated protein kinase (MAPK), and DNA synthesis in bovine pulmonary artery smooth muscle cells. Both p42/p44 MAPK and reactive oxygen species (ROS) generation are required for 5-HT-induced growth in SMC. Agents that block the production of ROS, or ROS scavengers, block MAPK activation by 5-HT. However, specific signal transduction by 5-HT leading to proteins that control entrance into the cell cycle are not well defined in smooth muscle cells. Here, we show by Western blot that 5-HT upregulates c-Fos, an immediate early gene product known to regulate the entrance of quiescent cells into the cell cycle. Northern blots showed that c-fos mRNA is induced by 5-HT in 30 min. This induction is blocked by PD98059, indicating that activation of MAPK is required. 5-HT-induced expression of a 350 bp c-fos promoter in a luciferase reporter is blocked by PD98059 and diphenyliodonium (DPI). The GTPases Rac1 and Ras have been implicated in growth factor-induced generation of ROS. Overexpression of either dominant negative (DN) Rac1 or DN Ras inhibited 5-HT-mediated c-fos promoter activation. 5-HT also induced expression from a truncated c-fos promoter containing an isolated serum response element. This activation was blocked by DPI and PD98059. Overexpression of activated Ras and Rac1 were additive for activation of the serum response element promoter. Regulation of cyclin D1, a protein shown to be regulated by c-fos and required for entry into the cell cycle, is upregulated by 5-HT and is blocked by DPI and PD98059. Nuclear factor-kappaB, which can also regulate cyclin D1, was not activated. We conclude that 5-HT stimulates c-fos and cyclin D1 expression through a ROS-dependent mechanism that requires Ras, Rac1, and MAPK.
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PMID:5-HT induction of c-fos gene expression requires reactive oxygen species and Rac1 and Ras GTPases. 1597 59

Acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) converts intracellular free cholesterol into cholesterol ester for storage in lipid droplets and plays an important role in the formation of macrophage-derived foam cells in atherosclerotic lesions. Serotonin (5-HT), a potent vasoconstrictor that is released from activated platelets, increases uptake of oxidized low-density lipoprotein (LDL) by macrophages, leading to foam cell formation, and contributes to the development of atherosclerotic plaque. However, it is not yet known whether 5-HT affects ACAT-1 expression in human monocyte-macrophages as the molecular mechanism of enhanced foam cell formation by 5-HT remains unclear. We examined the effects of 5-HT on ACAT-1 expression during differentiation of cultured human monocytes into macrophages. Expression of ACAT-1 protein but not 5-HT2A receptor increased in a time-dependent manner. 5-HT increased ACAT activity in a concentration-dependent manner after 7 days in primary monocyte culture. Immunoblotting analysis showed that 5-HT at 10 microM increased ACAT-1 protein expression level by two-fold, and this effect was abolished completely by a 5-HT2A receptor antagonist (sarpogrelate), its major metabolite (M-1), a G protein inactivator (GDP-beta-S), a protein kinase C (PKC) inhibitor (rottlerin), a Src family inhibitor (PP2), or a mitogen-activated protein kinase (MAPK) kinase inhibitor (PD98059). Northern blotting analysis indicated that among the four ACAT-1 mRNA transcripts (2.8-, 3.6-, 4.3-, and 7.0-kb), the levels of the 2.8- and 3.6-kb transcripts were selectively up-regulated by approximately 1.7-fold by 5-HT (10 microM). The results of the present study suggested that 5-HT may play a crucial role in macrophage-derived foam cell formation by up-regulating ACAT-1 expression via the 5-HT2A receptor/G protein/c-Src/PKC/MAPK pathway, contributing to the progression of atherosclerotic plaque.
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PMID:Serotonin acts as an up-regulator of acyl-coenzyme A:cholesterol acyltransferase-1 in human monocyte-macrophages. 1615 45

We have previously found that both mitogen-activated protein kinase (MAPK)- and Rho kinase (ROCK)-related signaling pathways are necessary for the induction of pulmonary artery smooth muscle cell (SMC) proliferation by serotonin (5-hydroxytryptamine [5-HT]). In the present study, we investigated the possible additional participation of a phosphatidylinositol 3-kinase (PI3K)/serine-threonine protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (S6K1) pathway in this growth response. We found transient activation of Akt (Ser473) and more prolonged activation of S6K1 by 5-HT. Inhibition of PI3K with Wortmannin and LY294002 completely blocked these activations, but not that of MAPK or the ROCK substrate myosin phosphatase targeting subunit. Similarly, inhibition of MAPK and ROCK failed to block the Akt activation. Inhibition of Akt with NL-71-101 and downregulation of Akt expression with Akt small interfering RNA blocked 5-HT-induced S6K1 phosphorylation. Wortmannin, LY294002, and NL-71-101 dose-dependently inhibited 5-HT-induced SMC proliferation. 5-HT stimulated mTOR phosphorylation and the mTOR inhibitor, rapamycin, blocked activations of S6K1 and S6 ribosomal protein, and inhibited 5-HT-induced SMC proliferation. Akt phosphorylation and cell proliferation were also blocked by the antioxidants, N-acetyl-l-cysteine, Ginko biloba 501, and tiron, the reduced nicotinamide adenine dinucleotide phosphate oxidase inhibitor, diphenyleneiodonium, and the 5-HT2 receptor antagonists ketanserin and mianserin, but not by the 5-HT serotonin transporter or 5-HT 1B/1D receptor antagonists. We conclude from these studies that a parallel PI3K- and reactive oxygen species-dependent Akt/mTOR/S6K1 pathway participates independently from MAPK and Rho/ROCK in the mitogenic effect of 5-HT on pulmonary artery SMCs. From these and other studies, we postulate that independent signaling pathways leading to 5-HT-induced SMC proliferation are initiated through multiple 5-HT receptors and serotonin transporter at the cell surface.
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PMID:Serotonin-induced growth of pulmonary artery smooth muscle requires activation of phosphatidylinositol 3-kinase/serine-threonine protein kinase B/mammalian target of rapamycin/p70 ribosomal S6 kinase 1. 1619 41

To investigate the functional consequences of cross-talk between multiple effectors of serotonin (5-HT) 1A receptor, we employed transfected Chinese hamster ovary cells. Activation of 5-HT 1A receptor stimulated extracellular signal-regulated kinase (ERK)1/2, Akt and nuclear transcription factor-kappaB (NF-kappaB). Stimulation of cells with 5-HT 1A receptor agonist induced a rapid but transient ERK1/2 phosphorylation followed by increased phosphorylation of Akt. Elevated Akt activity in turn suppressed Raf activity and induced a decline in ERK activation. The activation of ERK and Akt downstream of 5-HT 1A receptor was sensitive to inhibitors of Ras, Raf and phosphatidylinositol 3-kinase (PI3K). Stimulation of 5-HT 1A receptor also resulted in activation of NF-kappaB through a decrease in inhibitor of nuclear transcription factor-kappaB. In support of the importance of 5-HT 1A receptor signaling for cell survival, inhibition of NF-kappaB facilitated caspase 3 activation and cleavage of poly (ADP-ribose) polymerase, while treatment of cells with agonist inhibited caspase 3, DNA fragmentation and cell death. Both agonist-dependent NF-kappaB activation and cell survival were decreased by Akt Inhibitor II or by overexpression of dominant-negative Akt. These findings suggest a role for 5-HT 1A receptor signaling in the Ras/Raf-dependent regulation of multiple intracellular signaling pathways that include ERK and PI3K/Akt. Of these, only PI3K/Akt and NF-kappaB activation were required for 5-HT 1A receptor-dependent cell survival, implying that the relative distribution of signals between competing transduction pathways determines the functional outcome of 5-HT 1A receptor activation.
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PMID:Roles of extracellular signal-regulated kinase and Akt signaling in coordinating nuclear transcription factor-kappaB-dependent cell survival after serotonin 1A receptor activation. 1623 96

Upregulation of endothelin B (ET(B)) and 5-hydroxytryptamine 1B (5-HT(1B)) receptors via transcription has been found after experimental subarachnoid hemorrhage (SAH), and this is associated with enhanced phosphorylation of the mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase (ERK1/2). In the present study, we hypothesized that inhibition of ERK1/2 alters the ET(B) and 5-HT(1B) receptor upregulation and at the same time prevents the sustained cerebral blood flow (CBF) reduction associated with SAH. The ERK1/2 inhibitor SB386023-b was injected intracisternally in conjunction with and after the induced SAH in rats. At 2 days after the SAH, cerebral arteries were harvested for quantitative real-time polymerase chain reaction, immunohistochemistry and analysis of contractile responses to endothelin-1 (ET-1; ET(A) and ET(B) receptor agonist) and 5-carboxamidotryptamine (5-CT; 5-HT1 receptor agonist) in a sensitive myograph. To investigate if ERK1/2 inhibition had an influence on the local and global CBF after SAH, an autoradiographic technique was used. At 48 h after induced SAH, global and regional CBF were reduced by 50%. This reduction was prevented by treatment with SB386023-b. The ERK1/2 inhibition also decreased the maximum contraction elicited by application of ET-1 and 5-CT in cerebral arteries compared with SAH. In parallel, ERK1/2 inhibition downregulated ET(B) and 5-HT(1B) receptor messenger ribonucleic acid and protein levels compared with the SAH. Cerebral ischemia after SAH involves vasoconstriction and subsequent reduction in the CBF. The results suggest that ERK1/2 inhibition might be a potential treatment for the prevention of cerebral vasospasm and ischemia associated with SAH.
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PMID:ERK1/2 inhibition attenuates cerebral blood flow reduction and abolishes ET(B) and 5-HT(1B) receptor upregulation after subarachnoid hemorrhage in rat. 1625 86

The sensorimotor synapse of Aplysia exhibits long-term facilitation (LTF) and long-term depression (LTD) elicited by the neuromodulator serotonin (5-HT) and the peptide Phe-Met-Arg-Phe-NH(2), respectively. 5-HT-induced LTF engages extracellular-regulated kinase (Erk) and CREB1, whereas FMRFa-induced LTD engages p38 MAPK (mitogen-activated protein kinase) and CREB2. The interaction of the 5-HT and FMRFa pathways was recently investigated in Aplysia at the level of gene expression. However, little is known about crosstalk of these pathways at the level of the second messenger cascades. We investigated the potential interaction of the 5-HT and FMRFa pathways at the level of the Erk cascade. We found that FMRFa inhibited basal Erk activity through p38 MAPK. FMRFa also inhibited 5-HT-induced phosphorylation of Erk and nuclear accumulation of phospho-ERK, suggesting that FMRFa may place inhibitory constraints on memory formation through regulation of the Erk MAPK cascade.
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PMID:The 5-HT- and FMRFa-activated signaling pathways interact at the level of the Erk MAPK cascade: potential inhibitory constraints on memory formation. 1635 40


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