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

---

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

Corticotropin (ACTH)-releasing factor, vasoactive intestinal peptide, and catecholamines--hormones that stimulate ACTH secretion and cAMP generation--increased cytosolic calcium in AtT-20 cells. The increase in intracellular calcium is presumably a consequence of the stimulated cAMP synthesis, since forskolin, an activator of the catalytic unit of adenylate cyclase, and the cAMP analog 8-bromoadenosine 3',5'-cyclic monophosphate (8Br-cAMP) also increased the cytosolic levels of this ion. Pretreatment with somatostatin, a neuropeptide that inhibits stimulation of the adenylate cyclase system and the secretion of ACTH blocked the increase of cytosolic calcium. The effect of 8Br-cAMP, which bypasses the cyclase, was not inhibited by somatostatin pretreatment. The source of the increased calcium appears to be mainly extracellular. This is indicated by the inability of the secretagogues to increase cytosolic calcium in a medium deprived of this ion or in the presence of blockers of voltage-gated calcium channels. The involvement of calcium channels in the calcium rise evoked by the secretagogues was supported by experiments using the whole-cell patch-clamp technique. In these experiments 8Br-cAMP increased voltage-dependent calcium currents. These results suggest the following chain of events in the receptor-mediated elevation of cytosolic calcium and the concomitant release of ACTH from AtT-20 cells: hormone-receptor binding----cAMP synthesis----protein kinase activation----calcium channel activation----increase in cytosolic calcium----many steps----ACTH release. Phorbol myristate acetate, a compound which does not stimulate cAMP generation but enhances the release of ACTH in AtT-20 cells, decreased the cytosolic calcium level.
...
PMID:Hormone secretagogues increase cytosolic calcium by increasing cAMP in corticotropin-secreting cells. 241 78

The mechanisms by which somatostatin (SRIF) inhibits CRF-induced ACTH secretion from AtT20 cells were characterized by comparing the effects of SRIF on cAMP production, adenylate cyclase activity, and activation of cAMP-dependent protein kinase isoenzymes with its effects on ACTH release. In isolated membranes, CRF (100 nM) stimulated adenylate cyclase activity 4- to 5-fold. SRIF inhibited CRF-stimulated adenylate cyclase in a concentration-dependent manner. However, maximal inhibition was 50%. SRIF did not inhibit basal adenylate cyclase or forskolin-stimulated cyclase in the absence of guanine nucleotides and had only small effects on forskolin-stimulated cyclase when assayed in the presence of guanine nucleotides. CRF (100 nM) induced small rises (2-fold) in intracellular cAMP levels which produced maximal ACTH release. SRIF inhibited basal and CRF-stimulated ACTH release in a concentration-dependent manner, and there was a good correlation between inhibition of ACTH release and inhibition of the activation of cAMP-dependent protein kinases in these cells. Thus, the effect of SRIF on CRF-induced ACTH release appeared to result from its effect on inhibition of adenylate cyclase. In the presence of 3-methylisobutylxanthine (MIX), CRF increased cAMP levels 20-fold and activated a greater proportion of cAMP-dependent protein kinase, but did not stimulate ACTH release more than CRF alone. Under these conditions, SRIF (100 nM) inhibited cAMP accumulation by 90%. ACTH release was also inhibited, but higher concentrations of SRIF were required to block ACTH release compared to cells incubated in the absence of MIX. Sufficient cAMP levels were achieved so that activation of cAMP-dependent protein kinases was only partially blocked. There was still sufficient cAMP to activate cAMP-dependent protein kinase to an extent equal to that seen with CRF without MIX. Similar effects of SRIF on cAMP accumulation and protein kinase activation were seen when cells were stimulated with forskolin. Our results demonstrate that SRIF inhibits ACTH release from AtT20 cells by inhibiting hormone-sensitive adenylate cyclase and thereby prevents the activation of cAMP-dependent protein kinases. However, under conditions where cAMP-dependent protein kinases are still sufficiently active to induce ACTH secretion, high concentrations of SRIF can inhibit ACTH release by a mechanism independent of cAMP-dependent protein kinase.
...
PMID:Somatostatin inhibits corticotropin-releasing factor-stimulated adrenocorticotropin release, adenylate cyclase, and activation of adenosine 3',5'-monophosphate-dependent protein kinase isoenzymes in AtT20 cells. 242 87

P19, a group of 19,000 mol wt cytosolic proteins, with apparent isoelectric points of pI 5.9, pI 5.7, and pI 5.4, respectively, was identified in three peptide hormone-producing cell types: AtT20 mouse pituitary tumor cells, RIN-1122 rat insulinoma cells, and hamster insulinoma cells. Secretagogue-dependent phosphorylation of P19 was analyzed in 32P-labeled cells by two-dimensional electrophoresis and autoradiography. The results were quantitated by computer-assisted densitometry. Cellular levels of cAMP and hormone release were measured in parallel incubations. In addition to stimulating ACTH release, CRF raised the cellular level of cAMP and increased the 32P labeling of all three 19,000 mol wt proteins in AtT20 cells. Other agents known to act through cAMP, which included isoproterenol, forskolin, and 8-bromo-cAMP, mimicked the effect of CRF on both ACTH release and phosphorylation of P19. 12-O-Tetra-decanoylphorbol-13-acetate, a tumor-promoting phorbol ester, also stimulated both ACTH release and phosphorylation of P19. In contrast, although 40 mM K+ promoted ACTH release, it did not affect the phosphorylation of P19. Analogous findings were observed in insulinoma cells. Glucagon stimulated insulin release, increased cellular cAMP and promoted phosphorylation of P19 in RIN 1122 cells. 12-O-Tetradecanoylphorbol-13-acetate also enhanced insulin release and the phosphorylation of P19 in these cells. The results obtained with hamster insulinoma cells closely resembled the observations in RIN-1122 cells. In conclusion, P19, an apparently homologous set of cytosolic proteins, undergoes phosphorylation in three peptide hormone-producing cells in response to two groups of secretagogues, the effect of which is probably mediated, in one case, by cAMP-dependent protein kinase and, in the other, by protein kinase C. The data suggest the possibility that P19 participates in a secretory pathway activated by these two effector systems.
...
PMID:P19, a hormonally regulated phosphoprotein of peptide hormone-producing cells: secretagogue-induced phosphorylation in AtT-20 mouse pituitary tumor cells and in rat and hamster insulinoma cells. 242 97

Two homologs of the gene encoding the adrenocortical 21-hydroxylase (21-OHase) are located within the S region of the mouse major histocompatibility complex. Only one of these homologs, however, encoded the full-length sequence of 21-OHase, directed the synthesis of 21-OHase RNA in the mouse adrenal gland, and was capable of restoring 21-OHase activity when transfected into 21-OHase-deficient Y1 adrenocortical tumor cells. Y1 cells transfected with the 21-OHase gene, when stimulated with ACTH, increased the number of 21-OHase transcripts up to 10-fold. The 21-OHase gene was not expressed when transfected into mouse fibroblast L cells, and was poorly expressed and poorly regulated by ACTH when transfected into a Y1 mutant harboring a defective cAMP-dependent protein kinase. Marked decreases in expression of the 21-OHase gene were noted when DNA constructs that contained fewer than 230 base pairs in the 5' flanking region of the gene were transfected into Y1 cells. These results indicate that the 21-OHase gene encodes information required for the tissue-specific expression and hormonal regulation of 21-OHase. The cAMP-dependent protein kinase is important for both aspects of gene expression. At most, 230 base pairs of 5' non-coding information are required for efficient expression of the 21-OHase gene in Y1 cells.
...
PMID:Molecular analysis of 21-hydroxylase gene expression in mouse adrenal cells. 243 43

Arginine vasopressin (AVP) potentiates corticotrope responses to CRH by increasing the percentage of target cells that secrete in a reverse hemolytic plaque assay for ACTH. The present studies were designed to test more specific effects of AVP and its second messengers on CRH binding to individual corticotropes. Spectrophotometric analyses of 560 corticotropes from fractions enriched to 90% by counterflow centrifugation showed a 30% increase in the average area of the dark blue label for biotinylated CRH after a 1-h exposure to 10 nM AVP or after activation of protein kinase-C [by 12-O-tetradecanoyl-phorbol-13-acetate (TPA) or L calcium channels (by Bay K 8644). In addition, computer analysis of the color of the label (wavelength 476-483) showed a 13% increase in saturation (intensity of the blue) and a 23% decrease in brightness (amount of white) after stimulation. The gray level readings of the blue color were also 18% lower after stimulation, which indicates an increase in density (less light transmitted). Taken together, the increases in label area and intensity indicated that activation of L calcium channels or protein kinase-C enhanced CRH binding by individual corticotropes. When mixed pituitary cell populations were analyzed for percentages of labeled cells, exposure to Bay K 8644, TPA, angiotensin II, or AVP resulted in 30-40% increases in the percentage of CRH-bound cells. Dual reactions for biotinylated CRH and ACTH showed that most of the added CRH-bound cells stored ACTH. The effect of exposure to two of the activators was not additive, however. If L calcium channels were blocked with nimodipine, the protein kinase-C-mediated enhancement in CRH binding and ACTH release was blocked, indicating that these actions are dependent on extracellular calcium. In contrast, nimodipine did not block the TPA-mediated enhancement of ACTH storage. These studies show that the potentiation of CRH-mediated ACTH release by AVP or angiotensin II may occur by the enhancement of CRH binding to individual corticotropes. This appears to promote the cytochemical detection of additional CRH-bound corticotropes which may stem from a reserve cell population that normally has levels of CRH receptors or ACTH stores below thresholds needed for detection. The source of these cells (from stem cells or multipotential cells) remains to be determined.
...
PMID:Activation of protein kinase C and L calcium channels enhances binding of biotinylated corticotropin-releasing hormone by anterior pituitary corticotropes. 246 51

Mouse clonal ACTH-secreting corticotrophs (AtT-20 cells) possess a membrane Ca2+-activated Cl- conductance which is partially blocked by the disulfonic stilbene derivative 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS). In the current study the effect of SITS on the ACTH secretory process was evaluated. SITS markedly blocked basal and forskolin-stimulated ACTH secretion from AtT-20 cells (IC50 = 2.7 x 10(-4) M). Both CRF-induced ACTH secretion and forskolin-stimulated GH secretion from acutely dispersed rat anterior pituitary cells were inhibited by SITS (IC50 = 2.4 and 1.3 x 10(-4) M, respectively). SITS did not alter unstimulated or forskolin-elicited cAMP synthesis in AtT-20 cells, and in fact, could inhibit ACTH secretion in response to cAMP-independent agonists such as the calcium channel activator BAY-K-8644 or the protein kinase-C activator 12-tetradecanoyl-phorbol-13-acetate (IC50 = 2.6 and 2.4 x 10(-4) M, respectively). SITS did not alter the secretion of amylase from isolated exocrine pancreatic acinar cells. Its action was also fully reversible; after its removal from the incubation medium, cells secreted ACTH without a change in response to forskolin activation. Increasing extracellular Ca2+ or the addition of up to 10(-3) M tetraethylammonium or 4-aminopyridine did not reverse the inhibitory pattern of SITS action, suggesting that its inhibitory effect is most likely not due to hyperpolarization of AtT-20 cell membranes. The inability of amiloride to inhibit ACTH secretion further suggests that inhibition of ACTH secretion provoked by SITS is not due to a blockade of Cl-/HCO3- exchange. On the other hand, SITS was able to block 44% of basal 36Cl uptake by AtT-20 cells. Exchange of incubation medium chloride for gluconate or a reduction in the osmotic strength of the medium reduced both basal and secretagogue-stimulated ACTH secretion. The data suggest that SITS may modulate chloride-dependent, osmotically driven secretion from AtT-20 cells.
...
PMID:4-Acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid inhibits adrenocorticotropin secretion from anterior pituitary cells. 247 34

To examine the effects of the cAMP-independent protein kinase-C system and interleukin-1 (IL-1) on secretion of ACTH and POMC gene expression in cultured rat anterior pituitary (AP) cells, AP cells were incubated with CRF, 8-bromo-cAMP, arginine vasopressin, angiotensin II, norepinephrine, and phorbol 12-myristate 13-acetate. After 15 h of incubation, CRF and 8-bromo-cAMP increased both ACTH release and the POMC mRNA level. Arginine vasopressin, angiotensin II, norepinephrine, or phorbol 12-myristate 13-acetate stimulated ACTH release but failed to increase basal or CRF-stimulated POMC mRNA levels. Human recombinant IL-1 alpha and -beta increased neither ACTH release nor POMC mRNA levels after 3 h of incubation. After 15 h of incubation, 100 pM to 10 nM IL-1 alpha and -beta increased ACTH release. However, POMC mRNA levels were significantly elevated only by 10 pM IL-1 beta. These results suggest that the CRF-cAMP system plays a major role in both ACTH release and expression of the POMC gene in AP cells, but the cAMP-independent protein kinase-C system contributes only to ACTH release; that acute stimulation of ACTH release from AP with IL-1 administration is not due to direct action of IL-1 at the pituitary level; that chronic exposure of AP cells to IL-1 alpha or -beta can stimulate ACTH release; and that the direct effects of IL-1 alpha and -beta on POMC gene expression, if any, seem to be minimal.
...
PMID:Effects of protein kinase-C-related adrenocorticotropin secretagogues and interleukin-1 on proopiomelanocortin gene expression in rat anterior pituitary cells. 253 81

Forskolin, an activator of adenylate cyclase, stimulates adrenocorticotropin (ACTH) release and increases proopiomelanocortin mRNA levels in anterior pituitary cells by enhancing cyclic AMP (cAMP)-dependent protein kinase activity. The phorbol ester phorbol 12-myristate 13-acetate (PMA) evokes these same responses from anterior pituitary cells by activating protein kinase C. Both protein kinases most likely induce their cellular effects by catalyzing the phosphorylation of specific proteins. To elucidate the mechanisms by which cAMP-dependent protein kinase and protein kinase C promote ACTH secretion and synthesis, the phosphoproteins regulated by forskolin and PMA were identified in the cell line AtT-20, which consists of a homogeneous population of corticotrophs. Phosphoproteins were analyzed in different subcellular fractions by two-dimensional polyacrylamide gel electrophoresis and autoradiography. Forskolin increased phosphate incorporation into two proteins in the cytoplasmic fraction of 24 kilodaltons (kd) (pI 6.8) and 40 kd (pI 5.8), two proteins in the plasma membrane fraction of 32 kd (pI 8.3) and 60 kd (pI 8), and one protein in the nuclear fraction of 20 kd (pI 8.7). Insertion of the inhibitor of cAMP-dependent protein kinase into the AtT-20 cells, using a liposome technique, blocked the rise in phosphate incorporation induced by forskolin. PMA also stimulated phosphate incorporation into proteins in AtT-20 cells. PMA increased the phosphorylation of three cytoplasmic proteins of 25 kd (pI 7.6), 40 kd (pI 5.8), and 40 kd (pI 8.1) as well as two membrane proteins of 32 kd (pI 8.3) and 60 kd (pI 8) and one nuclear protein of 20 kd (pI 6.3).(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Protein phosphorylation induced by phorbol esters and cyclic AMP in anterior pituitary cells: possible role in adrenocorticotropin release and synthesis. 253 66

The action of forskolin on bovine and rat fasciculata cells was examined in freshly prepared cells. Bovine cells show a close parallelism between production of steroids and production of cAMP as a function of the concentration of ACTH up to 10(-8) M. By contrast, forskolin (10(-7)-10(-5) M) causes a similar increase in steroid synthesis but relatively little effect on the production of cAMP. cAMP-dependent protein kinase shows a similar response to ACTH but no response to forskolin in the same range of concentrations. ACTH and forskolin, at submaximal concentrations, cause greater steroid production when added together than when added separately, but the two agents at high concentrations produce the same response whether added together or separately. The inhibitors of voltage-dependent Ca2+ channels inhibit the steroidogenic response to forskolin (IC50 for nifedipine is 0.1 microM and for Py108-068 is 0.4 microM). A Ca2+ channel agonist (BAY K8644) increases the steroidogenic response of bovine adrenal cells to forskolin, but not that of ACTH. Finally, forskolin causes a concentration-dependent uptake of Ca2+ by these cells; in the concentration range of 0.1-10 microM, forskolin caused an increase in [Ca2+] from 185 nM to 345 nM. By contrast, forskolin caused some stimulation of the production of cAMP, but not that of steroids in rat fasciculata cells. It is concluded that in bovine fasciculata cells forskolin activates voltage-dependent Ca2+ channels with a consequent increase in steroid synthesis. This effect is independent of the well known action of forskolin on adenylate cyclase. Rat fasciculata cells, on the other hand, do not possess such Ca2+ channels and do not show a steroidogenic response to forskolin.
...
PMID:Forskolin activates voltage-dependent Ca2+ channels in bovine but not in rat fasciculata cells. 253 78

Some functional properties of highly enriched turkey poult adrenocortical cells were characterized. Cells were incubated with various mammalian and avian ACTH analogues, 8-Br-cAMP, and 25-hydroxycholesterol for 2 hr. Corticosterone production and, where appropriate, cyclic AMP (cAMP) production were measured by radioimmunoassay. Human ACTH-(1-24) was the most efficacious and potent ACTH analogue for stimulating corticosterone and cAMP production, whereas turkey ACTH-(1-39) was among the least efficacious and least potent analogues. Maximal corticosterone production induced by 8-Br-cAMP and supported by 25-hydroxycholesterol was 67-109% greater than that induced by ACTH analogues. The data suggest that intracellular concentrations of cAMP-dependent factors and steroidogenic enzymes exceed those which are accessible to ACTH-activated cellular processes. In addition, there were sex-dependent contrasts in some functional parameters, despite the immature status of the birds. Basal corticosterone production of female cells was 19% greater than that of male cells, albeit maximal ACTH analogue-induced corticosterone production was not different between male and female cells. In contrast, maximal 8-Br-cAMP-induced and 25-hydroxycholesterol-supported corticosterone production of male cells were, respectively, 72 and 45% greater than that of female cells, thus suggesting greater intracellular concentrations of protein kinase A-dependent factors and steroidogenic enzymes in male cells compared to female cells. However, maximal ACTH-induced cAMP production of female cells was 21% greater than those of male cells, thus suggesting a compensatory mechanism in female cells. In addition, there were sex-dependent differences in sensitivity to ACTH as indicated by corticosterone and cAMP responses to ACTH analogues: sensitivity to ACTH as indicated by corticosterone and cAMP responses to ACTH analogues: sensitivity of male cells was 1.2-3.2 times that of female cells. A sex-dependent difference in ACTH-cell interaction, possibly including ACTH receptors, is implicated since there were no sex differences in cellular sensitivities to 8-Br-cAMP and 25-hydroxycholesterol. These data indicate that the turkey adrenal gland is amenable for the preparation of isolated adrenocortical cells that have functional integrity. Thus, turkey adrenocortical cells expand the in vitro repertoire for elucidating the regulatory mechanisms of avian adrenocortical function.
...
PMID:Steroidogenic properties of isolated turkey adrenocortical cells. 254 38


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---