Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Diethylumbelliferyl phosphate (DEUP) is an organophosphate cholesteryl ester hydrolase inhibitor that blocks steroidogenesis mainly by preventing cholesterol transport into the mitochondria of steroidogenic cells. In the present study, we show that DEUP blocks the cAMP-stimulated mitochondrial accumulation of the 30-kDa mitochondrial proteins (recently named steroidogenic acute regulatory StAR proteins) that are believed to be the cycloheximide-sensitive factors induced by trophic hormones and cAMP. Inhibition of mitochondrial StAR accumulation by DEUP is dose dependent and closely parallels inhibition of progesterone synthesis. Stimulated lactate production, another cAMP-dependent process in MA-10 cells, is also inhibited by DEUP. Inhibition of protein kinase A (PKA) action would explain the inhibition of these two unrelated processes. However, the cytosolic PKA activity of DEUP-treated MA-10 10 cells was normal. Moreover, the activity of purified PKA was unaffected by DEUP. The inhibition of StAR synthesis was not caused by a direct effect of DEUP on the labile proteins since DEUP-treated cells required more than 24 h to recover steroidogenic capacity after DEUP treatment. Further evidence that the synthesis of StAR was not directly affected was obtained using the constitutively active R2C cells. Progesterone synthesis by these cells also involves StAR, but neither StAR synthesis or steroid synthesis is sensitive to DEUP. Lactate formation in dibutyryl-cAMP-stimulated R2C cells is, however, sensitive to inhibition by DEUP. These data can be best explained by DEUP acting on a long-lived factor involved in the cAMP/PKA response pathway, but not involved in constitutive steroidogenesis.
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PMID:Diethylumbelliferyl phosphate inhibits steroidogenesis by interfering with a long-lived factor acting between protein kinase A activation and induction of the steroidogenic acute regulatory protein (StAR). 853 19

DAX-1 is an unusual member of the nuclear hormone receptor superfamily whose expression is mainly, but not uniquely, restricted to steroidogenic tissues. We have recently shown that DAX-1 can block the first and rate-limiting step in steroid biosynthesis by repressing StAR (steroidogenic acute regulatory protein) expression. Here we show that DAX-1 blocks steroid production at multiple levels in the Y-1 mouse adrenocortical tumor cell line. Expression of DAX-1 in Y-1 cells significantly impairs both basal and cAMP-stimulated steroid production, without affecting the functionality of the cAMP-responsive PKA pathway. Experiments using an hydroxylated cholesterol derivative show that biochemical steps in steroidogenesis subsequent to cholesterol delivery to mitochondria are also impaired in Y-1 cells expressing DAX-1. This is explained by the repression of P450scc and 3beta-HSD expression, in addition to StAR. DAX-1 expression in Y-1 cells results in the inhibition of the activity of the StAR, P450scc and 3beta-HSD promoters. An inappropriate steroidogenic block in the male fetus might have an important role in the pathogenesis of sex reversal syndromes caused by a duplication of the genomic region of the X chromosome containing the DAX-1 gene.
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PMID:DAX-1 blocks steroid production at multiple levels. 975 5

Primary cultures of bovine ZF cells were incubated for 1 h or 6h with the agonists 8-bromo-cyclic AMP (8-Br-cAMP) an activator of protein kinase A (PKA), the phorbol ester phorbol 12-myristate 13-acetate (PMA) a protein kinase C (PKC) activator, the Ca2+ ionophore, A23187, or the L-type Ca2+ channel agonist Bay K8644. Both cortisol secretion (determined by radioimmunoassay of cell medium) and cellular StAR protein levels (quantified by western blotting) were significantly increased at 6h, by all agonists. However, while all agonists stimulated cortisol secretion at 1h, StAR protein levels remained unchanged by these treatments. We conclude that in bovine ZF cells, StAR protein synthesis can be regulated by mechanisms involving activation of PKA, PKC and Ca2+ influx. However, a net increase in cellular StAR protein does not appear to be essential for the initiation for the first stage of acute steroidogenesis.
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PMID:Effects of cellular mediator agonists on cortisol and steroid acute regulatory (StAR) protein in bovine zona fasciculata (ZF) cells. 1119 36

Possible involvement of salt-inducible kinase (SIK), a serine/threonine protein kinase first cloned from high K+-diet treated rat adrenal glands, in the regulation of steroidogenesis was investigated. Y-1 cells, when treated with ACTH, underwent a rapid change in SIK's mRNA content. It reached the maximum within a few hours and returned to the base after 8 h. In contrast, the levels of mRNAs for CYP11A and StAR protein reached the maxima after 8 h. The SIK's mRNA induction failed to occur in ACTH-, forskolin- or 8-Br-cAMP-treated Kin-7 cells, a mutant cell line of Y-1 with defective cAMP-dependent protein kinase A (PKA). Y-1 cells that overexpress SIK, when treated with ACTH, had significantly repressed levels of mRNAs for CYP11A and StAR protein. Therefore, SIK might have a negative effect on the CYP11A- and StAR protein-gene expression in the early phase of ACTH-mediated steroidogenesis. To further explore the mechanisms underlying this phenomenon, we examined intracellular distribution of the green fluorescence protein (GFP)-tagged SIK. When GFP-SIK was introduced into HeLa cells, the fluorescent signals were detected in the nucleus. In Y-1 cells GFP-SIK was detected both in the nucleus and cytosol, and the signal in the former moved to the latter after ACTH-treatment. The nuclear/cytosol re-distribution of GFP-SIK was also observed in forskolin- or 8-Br-cAMP-treated Y-1 cells, but not in Kin-7 cells. These results suggest that the intracellular re-distribution of SIK in Y-1 cells may depend on the cAMP/PKA signaling pathway and has an important regulatory role in the ACTH-mediated steroidogenic gene expression.
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PMID:SIK (Salt-inducible kinase): regulation of ACTH-mediated steroidogenic gene expression and nuclear/cytosol redistribution. 1119 81

The gonadotropic hormones, FSH and LH exert a major effect on ovarian and testicular function through interaction with specific seven-transmembrane domain glycoprotein receptors. Desensitization to the hormones, which can occur both in vivo and in vitro, is essential for prevention of overstimulation of the gonadal cells. The long-term process of desensitization to the gonadotropic hormones is probably mediated, in part, by extensive clustering and internalization of the hormone-receptor complex. Short-term desensitization may occur as a result of phosphorylation of serine or threonine residues on the receptor molecules, although a specific receptor kinase has not yet been identified. Recently, we have discovered a novel mechanism of gonadotropin desensitization, which is exerted by down-regulation of StAR expression and steroidogenesis mediated by MAPK activation as a result of hormone-receptor interaction, cAMP accumulation and PKA activation. Thus, PKA not only mediates gonadotropin-induced steroidogenesis, it also activates the down-regulation mechanism that can silence steroidogenesis under certain conditions. Moreover, our findings raise the possibility that activation or inhibition of ERK by other pathways could be an important mechanism for diminution or amplification of gonadotropin-stimulated steroidogenesis. This could contribute to functional luteolysis, a process in which luteinized granulosa cells show reduced sensitivity to LH despite maintenance of LH receptors, or to up-regulation of the steroidogenic machinery during luteinization of granulosa cells.
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PMID:Mechanisms of gonadotropin desensitization. 1198 13

Salt-inducible kinase (SIK), expressed in Y1 mouse adrenocortical tumor cells at an early stage of adrenocorticotropic hormone (ACTH)-stimulation, represses the cAMP-responsive element (CRE)-dependent gene expression of CYP11A and StAR by acting on bZIP domain of CRE-binding protein. ACTH induced the SIK's nuclear to cytosolic translocation in a PKA-dependent manner. A mutant SIK in which the PKA-dependently phosphorylatable Ser577 had been replaced with Ala could not move out of the nucleus. The degree of CRE-reporter repression by SIK was strong as long as SIK was present in the nucleus. These indicated that intracellular translocation of SIK might be an important factor to determine the time-dependent change in the level of steroidogenic gene expression in ACTH-stimulated cells. Promoter analyses suggested that SIK repressed gene expressions not only of CYP11A and StAR but also of CYP11B1, CYP11B2 and SIK itself. We propose here that SIK is one of important molecule regulating expression of steroidogenic genes in the early phase of ACTH treatment.
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PMID:Salt-inducible kinase-mediated regulation of steroidogenesis at the early stage of ACTH-stimulation. 1294 28

The cloning of salt-inducible kinase-1 (SIK1) that was specifically expressed in the adrenal glands of high-salt diet-fed rats led to subsequent cloning of adipose-specific SIK2 and rather ubiquitous SIK3. The three enzymes constitute a novel serine/threonine kinase subfamily, a member of AMP-activated protein kinase (PKA) family. Physiological roles of SIK1 and SIK2 have been investigated. The SIK1 transcript was expressed very early in the ACTH-stimulated Y1 cells, even before the expression of transcripts for CYP11A and StAR protein. Forced expression of SIK1 inhibited the ACTH-dependent expression of CYP11A- and StAR protein-genes. Cotransfection assays employing CRE-reporter gene showed that SIK1 could repress the PKA-dependent activation of CRE by acting on the bZIP domain of the CRE-binding protein (CREB), though the target site of SIK1-mediated phosphorylation has yet to be determined. ACTH/PKA-dependent nucleocytoplasmic shuttling of SIK1 took place in Y1 cells, implying that the intracellular movement of SIK1 might be a physiologically important determining factor for regulation of steroidogenic gene expression in the early phase of ACTH-stimulation. The SIK2 gene was expressed in 3T3-L1 cells at a very early stage of adipogenesis. SIK2 could phosphorylate Ser-794 of human insulin-receptor-substrate-1 (IRS-1) in vitro as well as in vivo. In addition, the SIK2 activity in db/db mice adipose tissues was significantly higher than that in wild-type adipose. These results strongly suggest that SIK2 may play important role(s) in modulating the insulin-signaling cascade of adipocytes, and thus, may be involved in the development of insulin resistance. Taken together, these results suggest that the SIK isoforms regulate hormonal signal transduction in both adrenal and adipose tissues.
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PMID:Salt-inducible kinase (SIK) isoforms: their involvement in steroidogenesis and adipogenesis. 1513 8

Follicular development is characterized by both proliferation and differentiation of granulosa cells (GCs) under the control of FSH. However, the cellular mechanism by FSH is not known. Using cultured GCs, we examined whether FSH activated ERK1/2 was involved in the regulation of the proliferation related gene proliferating cell nuclear antigen (PCNA) and steroidogenesis. GCs were obtained from the ovaries of DES treated immature rats and cultured in serum free medium. The results showed that FSH activated ERK1/2 in a time dependent manner, with a peak at 20 min. Such activation was PKA dependent as was inhibited by specific inhibitors. FSH induced PCNA expression in a time dependent manner, with a maximum stimulation at 2 h. Similarly, StAR and steroid levels increased as FSH treatment time extended, with a maximum progesterone and StAR production at 48 h. ERK1/2 inactivation by UO126 inhibited the stimulatory effects of FSH on both PCNA and StAR expression and steroid synthesis in the GCs (p less than 0.01). Immunocytochemical studies further revealed that ERK1/2 inhibition led to a reduction of mitochondrial StAR in the GCs by FSH. These observations suggested that the stimulation of FSH on PCNA expression and steroidogenesis in GCs was mediated at least partially by ERK1/2.
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PMID:Role of ERK1/2 in FSH induced PCNA expression and steroidogenesis in granulosa cells. 1556 28

This study investigated the roles of the protein kinase C (PKC) and protein kinase A (PKA) pathways in regulating constitutive steroidogenesis and steroidogenic acute regulatory (STAR; herein designated by its common name, StAR) protein in R2C Leydig tumor cells. Inhibition of PKC and phospholipase C resulted in significant decreases in steroid production, phosphorylation of cAMP-responsive element binding (CREB) protein, and Star gene transcription under basal conditions in R2C cells. These observations were corroborated in MA-10 and mLTC-1 Leydig tumor cell lines, in which activation of PKC by phorbol-12-myristate-13-acetate (PMA, 10 nM) increased CREB phosphorylation and total StAR (tot-StAR) protein expression. However, induction of StAR protein by PMA did not result in the expected concomitant increase in steroids because PKC failed to phosphorylate StAR, the biologically active form of the protein. However, in conjunction with PMA, minor increases in PKA activity using submaximal doses of (Bu)2cAMP (0.05-0.1 mM; a concentration range insufficient for induction of StAR), were able to stimulate dramatic increases in both phospho-StAR (P-StAR) and steroid production. Human chorionic gonadotropin stimulation also resulted in a further enhancement in P-StAR and progesterone production when added to PMA-treated MA-10 cells. Similar results for tot-StAR and P-StAR expression were observed in primary cultures of immature rat Leydig cells treated with PMA and submaximal doses of (Bu)2cAMP. In summary, the present study demonstrates that basal activities of both PKC and PKA play important roles in the constitutive steroidogenic characteristics of R2C cells. This study also demonstrates for the first time a role for PMA-induced PKC in StAR protein regulation and the requirement for submaximal doses of cAMP to produce steroids in Leydig cells.
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PMID:Involvement of protein kinase C and cyclic adenosine 3',5'-monophosphate-dependent kinase in steroidogenic acute regulatory protein expression and steroid biosynthesis in Leydig cells. 1581 1

The luteinizing hormone (LH) plays a critical role in steroidogenesis, by stimulating cAMP-dependent protein kinase A (PKA) and phospholipase A2 activity, and by mobilizing calcium and chloride ions. In contrast, whether the ERK 1, 2 mitogen-activated protein (MAP) kinases are involved in LH-induced steroidogenesis is less obvious. Here, we sought to clarify this point in rat primary Leydig cells, naturally bearing the LH receptor (LH-R) in male, and in the mouse tumoral Leydig cell line (MLTC 1). Pre-incubation of both cell types with the mitogen-activated protein kinase kinase (MEK) inhibitors U0126 and PD98059 reduced LH-induced steroidogenesis, and tonically enhanced the expression of the StAR protein. Furthermore, ERK1, 2 were inducibly phosphorylated following LH exposure of MLTC 1 cells. Altogether, our results indicate that in primary as well as in tumoral Leydig cells, inhibiting MEK dampened LH-induced steroidogenesis but enhanced basal as well as LH-induced StAR expression, suggesting that ERK1,2 could be involved in these responses.
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PMID:Extracellular signal-regulated kinases (ERK) 1, 2 are required for luteinizing hormone (LH)-induced steroidogenesis in primary Leydig cells and control steroidogenic acute regulatory (StAR) expression. 1586 56


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