Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

When quiescent dog thyroid epithelial cells in primary culture are stimulated for 48 h with thyrotropin (TSH), forskolin acting through cAMP, or with cAMP-independent mitogens including epidermal growth factor (EGF), hepatocyte growth factor (HGF), and a tumor promoting phorbol ester (TPA), only 30-60% of cells progress through the cell cycle. A more general growth response requires the combination of EGF and TSH or forskolin. In this study we ask whether this intercellular heterogeneity in mitogen sensitivity could depend on a similar heterogeneity at early stages of the mitogenic stimulation process, i.e., at the levels of p42/p44 MAP kinase nuclear translocation and c-Fos protein appearance. We used indirect immunofluorescence microscopy with photometric quantitation and corroborated data using Western blotting. We analyzed the double staining of c-Fos and p42/p44 MAP kinases, since the nuclear translocation of these MAP kinases has been suggested as a key step for the stimulation of c-fos transcription. (i) EGF and HGF induced c-Fos accumulation and MAP kinase translocation in variable fractions of the cell population that corresponded to their relative potency as mitogens. c-Fos appearance and MAP kinase translocation poorly correlated in individual cells. Many cells accumulated c-Fos without any detectable p42/p44 MAP kinase translocation. The heterogeneity of proliferative responses to EGF could be due to the lack of c-Fos or MAP kinase responsiveness of many cells. (ii) TPA induced c-Fos accumulation and MAP kinase translocation within the whole cell population, which did not explain the heterogeneity of the growth response to this factor and showed that these events are not sufficient to elicit DNA synthesis, (iii) TSH and forskolin induced a weak c-Fos accumulation in only a minority of cells but, as previously shown, no p42/p44 MAP kinase phosphorylation and translocation. An important c-Fos expression was thus dispensable for the strong DNA synthesis stimulation exerted by cAMP-dependent mitogens. (iv) Forskolin potentiated the EGF effect on c-Fos expression but not on p42/p44 MAP kinase phosphorylation and translocation. This reflected the fact that EGF induced c-Fos accumulation in 90% of cells in the presence of forskolin but in 30-50% of cells in its absence. This kind of potentiation, which specifically implies an increase in the fraction of responding cells, is termed "generalization" in the present study.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Intercellular heterogeneity of early mitogenic events: cAMP generalizes the EGF effect on c-Fos protein appearance but not on MAP kinase phosphorylation and nuclear translocation in dog thyroid epithelial cells. 758 41

Cholecystokinin (CCK) is a potent neuropeptide expressed in the small intestine and in the central nervous system. We have examined the effect of basic fibroblast factor (bFGF) and forskolin on CCK gene transcription and depicted the signaling pathways that lead to promoter activation. bFGF and forskolin stimulated promoter activity via a cAMP response element (CRE)/12-O-tetradecanoylphorbol-13-acetate response element (TRE) located 80 bp upstream from the transcription initiation site. In nuclear extracts from unstimulated as well as stimulated cells, only CRE-binding protein (CREB) and activating transcription factor-1 (ATF-1) bound to the CRE/TRE, and activation was associated with phosphorylation of CREB serine-133 and ATF-1 serine-63. In murine F9 cells, CREB stimulated promoter activity 10-fold in the presence of protein kinase A (PKA), and in SK-N-MC cells activation was inhibited 60-70% by a dominant negative CREB mutant. In contrast, ATF-1 had no effect in F9 cells and exhibited a dominant negative effect in SK-N-MC cells. bFGF stimulation led to phosphorylation of the p38 mitogen-activated protein kinase (MAPK), and the extracellular signal-regulated kinase (ERK) MAPK and promoter activation, phosphorylation of CREB, and GAL4-CREB-dependent transcription were selectively prevented by a dominant negative Ras-mutant, the p38 MAPK-specific inhibitor SB203580, and the MAP/ERK kinase 1 (MEK1) inhibitor PD098059. Forskolin stimulation proceeded via the PKA pathway, and to a minor extent via the p38 and ERK MAPK pathways. We conclude that bFGF and forskolin stimulate the CCK gene promoter via the CRE/TRE(-80) in the proximal promoter region. Signaling proceeds through the p38 MAPK, the ERK MAPK, and the PKA-signaling pathways, which leads to cumulative phosphorylation and activation of CREB. We propose that bFGF in combination with neurotransmitters/neuropeptides coupling to the PKA-signaling pathway play an important role in the control of CCK gene expression.
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PMID:Mitogen-activated protein kinase and protein kinase A signaling pathways stimulate cholecystokinin transcription via activation of cyclic adenosine 3',5'-monophosphate response element-binding protein. 1007 3

Myosin light chain kinase (MLCK) and the kinase-related protein (KRP), also known as telokin, are the major independent protein products of the smooth muscle/non-muscle MLCK genetic locus. They share a common C-terminal part and major sites phosphorylated in vivo. Whereas MLCK is critically involved in myosin activation and contraction initiation in smooth muscle, KRP is thought to antagonize MLCK and to exert relaxation activity. Phosphorylation controls the MLCK and KRP activities. We generated two phosphorylation and site-specific antibodies to individually monitor levels of MLCK and KRP phosphorylation on critical sites. We quantified the level of KRP phosphorylation in smooth muscle before and after an increase in intracellular free Ca2+ and stimulation of adenylate cyclase, protein kinase C, and mitogen-activated protein kinases (MAP-kinases). Forskolin and phorbol-12,13-dibutyrate increased KRP phosphorylation at Ser13 from 25 to 100% but did not produce contraction in rat ileum. The level of Ser13 phosphorylation was not altered during Ca2+-dependent contraction evoked by KCl depolarization or carbachol, but subsequently increased to maximum during forskolin-induced relaxation. These data suggest that several intracellular signaling pathways control phosphorylation of KRP on Ser13 in smooth muscle and thus may contribute to relaxation. In contrast, phosphorylation level of Ser19 of KRP increased only slightly (from 30 to 40-45%) and only in response to MAP-kinase activation, arguing against its regulatory function in smooth muscle.
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PMID:Novel phosphospecific antibodies for monitoring phosphorylation of proteins encoded by the myosin light chain kinase genetic locus. 1531 Feb 80