scholarly journals Protein kinase G-mediated stimulation of basal Leydig cell steroidogenesis

2007 ◽  
Vol 293 (5) ◽  
pp. E1399-E1408 ◽  
Author(s):  
Silvana A. Andric ◽  
Marija M. Janjic ◽  
Natasa J. Stojkov ◽  
Tatjana S. Kostic
Keyword(s):  
Protein Kinase ◽  
Leydig Cells ◽  
Regulatory Protein ◽  
Nitric Oxide Donor ◽  
Stimulatory Action ◽  
Guanylyl Cyclases ◽  
Androgen Synthesis ◽  
Dependent Protein ◽  
Phosphodiesterase 5 ◽  
Stimulation Of

The androgen-secreting Leydig cells produce cGMP, but the pathways responsible for generation and actions of this intracellular messenger have been incompletely characterized in these cells. Here, we show the presence of mRNA transcripts for the membrane-bound and soluble guanylyl cyclases (sGC), the cGMP-specific phosphodiesterase 5, and the cGMP-dependent protein kinase I (PKG I) and PKG II in purified rat Leydig cells from adult animals. Stimulation of both guanylyl cyclases and inhibition of phosphodiesterase 5 in vitro were accompanied by elevations in cGMP and androgen production, whereas inhibition of sGC and PKG led to a decrease in steroidogenesis. The stimulatory action of cGMP on steroidogenesis was preserved in cells with inhibited cAMP-dependent protein kinases. Experiments with exogenously added substrates revealed the dependence of cGMP-induced progesterone and androgen synthesis on cholesterol but not on 22-OH cholesterol, pregnenolone, progesterone, and Δ4-androstenedione. Treatment with nitric oxide donor increased phosphorylation of the steroidogenic acute regulatory protein (StAR). In contrast, inhibition of sGC and PKG, but not protein kinase A, significantly reduced StAR phosphorylation. These results suggest that cGMP contributes to the control of basal steroidogenesis in Leydig cells through the PKG-dependent modification of the StAR protein.

Regulation of calcium mobilization and entry in human platelets by endothelium-derived factors

1994 ◽  
Vol 267 (1) ◽  
pp. C236-C244 ◽  
Author(s):  
J. Geiger ◽  
C. Nolte ◽  
U. Walter
Keyword(s):  
Endothelial Cells ◽  
Protein Kinase ◽  
Human Platelets ◽  
Dependent Protein Kinase ◽  
Rapid Phase ◽  
No Donor ◽  
Cyclic Monophosphate ◽  
Dependent Protein ◽  
Camp And Cgmp ◽  
Stimulation Of

Stimulation of Ca2+ mobilization and entry by agonists such as ADP, thrombin, and thromboxane is an early step of platelet activation. Here, we compared the effects of adenosine 3',5'-cyclic monophosphate (cAMP)-elevating prostaglandins, guanosine 3',5'-cyclic monophosphate (cGMP)-elevating nitrovasodilators, membrane-permeant selective activators of cAMP- or cGMP-dependent protein kinases, and physiological endothelium-derived factors on the agonist-evoked Ca2+ mobilization and entry in human platelets. Prostaglandin E1, the prostacyclin analogue Iloprost, the nitric oxide (NO) donor 3-morpholinosydnonimine hydrochloride, and selective activators of cGMP- or cAMP-dependent protein kinase strongly inhibited the agonist-evoked Ca2+ mobilization from intracellular stores and associated late Ca2+ entry but had little effects on the rapid (1st) phase of ADP-evoked Ca2+ entry. During coincubation of platelets with endothelial cells, endothelium-derived factors that were released strongly inhibited platelet agonist-evoked Ca2+ mobilization and only moderately affected the rapid phase of ADP-evoked Ca2+ entry. These effects were partially prevented when endothelial cells were preincubated with cyclooxygenase and/or NO synthase inhibitors. Endothelial cells therefore produce sufficient quantities of labile platelet inhibitors whose effects on the platelet Ca2+ response resemble those observed with selective cAMP- and cGMP-dependent protein kinase activators.

scholarly journals Inhibition of diuretic stimulation of an insect secretory epithelium by a cGMP-dependent protein kinase

2013 ◽  
Vol 304 (9) ◽  
pp. F1210-F1216 ◽  
Author(s):  
Kristen A. Ruka ◽  
Anna P. Miller ◽  
Edward M. Blumenthal
Keyword(s):  
Protein Kinase ◽  
Stellate Cells ◽  
Malpighian Tubules ◽  
Microelectrode Recording ◽  
Dependent Protein Kinase ◽  
Rnai Construct ◽  
Cgmp Dependent Protein Kinase ◽  
Dependent Protein ◽  
Diuretic Agents ◽  
Stimulation Of

The rate of urine secretion by insect Malpighian tubules (MTs) is regulated by multiple diuretic and antidiuretic hormones, often working either synergistically or antagonistically. In the Drosophila melanogaster MT, only diuretic factors have been reported. Two such agents are the biogenic amine tyramine (TA) and the peptide drosokinin (DK), both of which act on the stellate cells of the tubule to increase transepithelial chloride conductance. In the current study, TA and DK signaling was quantified by microelectrode recording of the transepithelial potential in isolated Drosophila MTs. Treatment of tubules with cGMP caused a significant reduction in the depolarizing responses to both TA and DK, while cAMP had no effect on these responses. To determine whether a specific cGMP-dependent protein kinase (PKG) was mediating this inhibition, PKG expression was knocked down by RNAi in either the principal cells or the stellate cells. Knockdown of Pkg21D in the stellate cells eliminated the modulation of TA and DK signaling. Knockdown of Pkg21D with a second RNAi construct also reduced the modulation of TA signaling. In contrast, knockdown of the expression of foraging or CG4839, which encodes a known and a putative PKG, respectively, had no effect. These data indicate that cGMP, acting through the Pkg21D gene product in the stellate cells, can inhibit signaling by the diuretic agents TA and DK. This represents a novel function for cGMP and PKG in the Drosophila MT and suggests the existence of an antidiuretic hormone in Drosophila .

scholarly journals LH/chorionic gonadotropin signaling pathway involves protein tyrosine phosphatase activity downstream of protein kinase A activation: evidence of an obligatory step in steroid production by Leydig cells

2001 ◽  
Vol 170 (2) ◽  
pp. 403-411 ◽  
Author(s):  
FC Maciel ◽  
C Poderoso ◽  
A Gorostizaga ◽  
C Paz ◽  
EJ Podesta
Keyword(s):  
Protein Kinase ◽  
Chorionic Gonadotropin ◽  
Leydig Cell ◽  
Protein Tyrosine Phosphatase ◽  
Leydig Cells ◽  
Tyrosine Phosphatase ◽  
Zona Fasciculata ◽  
Stimulatory Action ◽  
Protein Tyrosine ◽  
Cell Functions

Our recent reports indicate that protein tyrosine phosphorylation is an obligatory component of the mechanism of action of ACTH in its stimulatory action of corticosteroid production in adrenal zona fasciculata (ZF). The role of protein tyrosine phosphatase (PTP) activity in the regulation of steroidogenesis by LH/chorionic gonadotropin (CG) was tested using cell-permeable PTP inhibitors. Thus, PTP inhibition blocks LH- and 8-bromo-cAMP-stimulated testosterone production by Leydig cells without affecting 22(R)OH-cholesterol-supported steroidogenesis, similar results to those obtained in the adrenal ZF/ACTH system, leading us to propose that PTP action is an obligatory and common step in the cascade triggered by both hormones. Then, we continued the study testing whether LH modulates PTP activity in MA-10 cells, a Leydig cell line. In this regard, we observed by an in-gel PTP assay two PTPs of 110 and 50 kDa that are activated by hormone and 8-bromo-cAMP activation of the cells. Moreover, there is a transient increase by the second messenger in total PTP activity that correlates with the higher activity displayed by the 110 and 50 kDa proteins in the in-gel assay. In accordance with these results, analysis of tyrosine phosphorylated proteins showed the LH-induced dephosphorylation of proteins of 120, 68 and 50 kDa. The results of this study indicate that PTPs play an important role in the regulation of Leydig cell functions and that there exists a cross talk between serine/threonine phosphorylation and tyrosine dephosphorylation mediated by hormone-activated cAMP-dependent protein kinase and PTPs. These results are the first evidence of PTP having a role in LH/CG-stimulated steroidogenesis.

Nitric oxide and cGMP protein kinase activity in aged ventricular myocytes

2001 ◽  
Vol 281 (6) ◽  
pp. H2304-H2309 ◽  
Author(s):  
Qihang Zhang ◽  
Bruno Molino ◽  
Lin Yan ◽  
Todd Haim ◽  
Yakir Vaks ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Protein Kinase ◽  
Kinase Activity ◽  
Kinase Inhibitor ◽  
Ventricular Myocytes ◽  
Nitric Oxide Donor ◽  
Protein Kinase Activity ◽  
Edge Detector ◽  
Negative Effects ◽  
Dependent Protein

We tested the hypothesis that nitric oxide-induced negative functional effects through cGMP would be reduced in aged cardiac myocytes. Maximum rate of shortening ( R max) and percent shortening of ventricular myocytes from young (6 mo) and old (3 y) rabbits were studied using a video edge detector. cGMP-dependent phosphorylation was examined by electrophoresis and autoradiography. Myocytes received a nitric oxide donor S-nitroso- N-acetyl-penicillamine (SNAP, 10−7, 10−6, and 10−5 M) followed by KT-5823 (10−6 M), a cGMP protein kinase inhibitor. Baseline function was similar in young and old myocytes (89.1 ± 4.5 young vs. 86.4 ± 8.3 μm/s old R max, 5.6 ± 0.3 vs. 5.2 ± 0.7%shortening). SNAP (10−5 M) decreased R max in both young (25%, n = 6) and old myocytes (24%, n = 7). SNAP also reduced percent shortening by 28% in young and 23% in old myocytes. The negative effects of SNAP were partially reversed by KT-5823 only in young myocytes. Multiple proteins were phosphorylated by cGMP, and KT-5823 could reduce this effect. The degree of phosphorylation was significantly less in old myocytes. These results suggest that the functional response of ventricular myocytes to nitric oxide was preserved during aging. However, the importance of cGMP-dependent protein phosphorylation was decreased, indicating a shift to other pathways.

scholarly journals Stimulation of neuronal KATP channels by cGMP-dependent protein kinase: involvement of ROS and 5-hydroxydecanoate-sensitive factors in signal transduction

2010 ◽  
Vol 298 (4) ◽  
pp. C875-C892 ◽  
Author(s):  
Yongping Chai ◽  
Yu-Fung Lin
Keyword(s):  
Protein Kinase ◽  
Signaling Pathway ◽  
Neuronal Excitability ◽  
Single Channel ◽  
Katp Channels ◽  
Membrane Excitability ◽  
Dependent Protein Kinase ◽  
Cgmp Dependent Protein Kinase ◽  
Dependent Protein ◽  
Stimulation Of

The ATP-sensitive potassium (KATP) channel couples intracellular metabolic state to membrane excitability. Recently, we demonstrated that neuronal KATP channels are functionally enhanced by activation of a nitric oxide (NO)/cGMP/cGMP-dependent protein kinase (PKG) signaling cascade. In this study, we further investigated the intracellular mechanism underlying PKG stimulation of neuronal KATP channels. By performing single-channel recordings in transfected HEK293 and neuroblastoma SH-SY5Y cells, we found that the increase of Kir6.2/SUR1 (i.e., the neuronal-type KATP) channel currents by PKG activation in cell-attached patches was diminished by 5-hydroxydecanoate (5-HD), an inhibitor of the putative mitochondrial KATP channel; N-(2-mercaptopropionyl)glycine, a reactive oxygen species (ROS) scavenger, and catalase, a hydrogen peroxide (H2O2)-decomposing enzyme. These reagents also ablated NO-induced KATP channel stimulation and prevented the shifts in the single-channel open- and closed-time distributions resulting from PKG activation and NO induction. Bath application of H2O2 reproduced PKG stimulation of Kir6.2/SUR1 but did not activate tetrameric Kir6.2LRKR368/369/370/371AAAA channels. Moreover, neither the PKG activator nor exogenous H2O2 was able to enhance the function of KATP channels in the presence of Ca2+ chelators and calmodulin antagonists, whereas the stimulatory effect of H2O2 was unaffected by 5-HD. Altogether, in this report we provide novel evidence that activation of PKG stimulates neuronal KATP channels by modulating intrinsic channel gating via a 5-HD-sensitive factor(s)/ROS/Ca2+/calmodulin signaling pathway that requires the presence of the SUR1 subunit. This signaling pathway may contribute to neuroprotection against ischemic injury and regulation of neuronal excitability and neurotransmitter release by modulating the function of neuronal KATP channels.

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