scholarly journals Functional Roles of Protein Kinase A (PKA) and Exchange Protein Directly Activated by 3′,5′-Cyclic Adenosine 5′-Monophosphate (cAMP) 2 (EPAC2) in cAMP-Mediated Actions in Adrenocortical Cells

Endocrinology ◽  
2010 ◽  
Vol 151 (5) ◽  
pp. 2151-2161 ◽  
Author(s):  
Linda Aumo ◽  
Marte Rusten ◽  
Gunnar Mellgren ◽  
Marit Bakke ◽  
Aurélia E. Lewis
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Steroid Hormones ◽  
Steroid Hormone ◽  
Regulatory Protein ◽  
Adrenocortical Cancer ◽  
Hormone Production ◽  
Genes Encoding ◽  
And Migration ◽  
Kinase A

In the adrenal cortex, the biosynthesis of steroid hormones is controlled by the pituitary-derived hormone ACTH. The functions of ACTH are principally relayed by activating cAMP-dependent signaling pathways leading to the induction of genes encoding enzymes involved in the conversion of cholesterol to steroid hormones. Previously, protein kinase A (PKA) was thought to be the only direct effector of cAMP. However, the discovery of the cAMP sensors, exchange proteins directly activated by cAMP (EPAC1 and 2), has led to a reevaluation of this assumption. In the present study, we demonstrate the occurrence of the EPAC2 splicing variant EPAC2B in adrenocortical cancer cells. Immunocytochemistry demonstrated that EPAC2B is localized predominantly in the nucleus. EPAC2B is functional because it activates Rap1 in these cells. Using the cAMP analogs 8-p-chlorophenylthio-2′-O-methyl-cAMP and N6-benzoyl-cAMP, which specifically activate EPAC1/2 and PKA, respectively, we evaluated the contribution of these factors in steroid hormone production, cell morphology, actin reorganization, and migration. We demonstrate that the expression of cAMP-inducible factors involved in steroidogenesis (steroidogenic acute regulatory protein, cytochrome P450 11A1 and 17, and nerve growth factor-induced clone B) and the cAMP-induced biosynthesis of steroid hormones (cortisol and aldosterone) are mediated by PKA and not by EPAC2B. In contrast, both PKA- and EPAC-specific cAMP analogs induced cell rounding, loss of stress fibers, and blocked migration. Taken together, the presented data confirm PKA as the central cAMP mediator in steroid hormone production and reveal the involvement of EPAC2B in cAMP-induced effects on cytoskeleton integrity and cell migration.

scholarly journals Cysteine Sulfoxides Enhance Steroid Hormone Production via Activation of the Protein Kinase A Pathway in Testis-Derived I-10 Tumor Cells

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4694
Author(s):  
Yuya Nakayama ◽  
Hsin-Jung Ho ◽  
Miki Yamagishi ◽  
Hiroyuki Ikemoto ◽  
Michio Komai ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Tumor Cells ◽  
Steroid Hormone ◽  
Hormone Production ◽  
Onion Extract ◽  
Testosterone Levels ◽  
Age Related ◽  
Cysteine Sulfoxides ◽  
Kinase A

Testosterone plays an important role in male sexual characteristics and maturation, and decreased testosterone levels increase the risk of several diseases. Recently, onion extract rich in cysteine sulfoxides, which are amino acids unique to onions, has been reported to alleviate age-related symptoms resulting from decreased testosterone levels in males. However, the mechanism underlying the suppression of low testosterone levels by cysteine sulfoxides has not been elucidated. In this study, we found that onion extract containing cysteine sulfoxides enhanced progesterone, a precursor of testosterone, in mouse testis-derived I-10 tumor cells. Furthermore, cysteine sulfoxides activated protein kinase A (PKA) and cyclic adenosine monophosphate response element-binding protein, which are key factors in steroidogenesis. These results suggest that cysteine sulfoxides enhance steroid hormone production via activation of the PKA signaling pathway.

scholarly journals Protein Kinase A-Mediated Septin7 Phosphorylation Disrupts Septin Filaments and Ciliogenesis

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 361
Author(s):  
Han-Yu Wang ◽  
Chun-Hsiang Lin ◽  
Yi-Ru Shen ◽  
Ting-Yu Chen ◽  
Chia-Yih Wang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Primary Cilia ◽  
Cell Growth And Migration ◽  
Filament Dynamics ◽  
Gtp Binding ◽  
Cilia Formation ◽  
And Migration ◽  
Septin Filament ◽  
Kinase A

Septins are GTP-binding proteins that form heteromeric filaments for proper cell growth and migration. Among the septins, septin7 (SEPT7) is an important component of all septin filaments. Here we show that protein kinase A (PKA) phosphorylates SEPT7 at Thr197, thus disrupting septin filament dynamics and ciliogenesis. The Thr197 residue of SEPT7, a PKA phosphorylating site, was conserved among different species. Treatment with cAMP or overexpression of PKA catalytic subunit (PKACA2) induced SEPT7 phosphorylation, followed by disruption of septin filament formation. Constitutive phosphorylation of SEPT7 at Thr197 reduced SEPT7‒SEPT7 interaction, but did not affect SEPT7‒SEPT6‒SEPT2 or SEPT4 interaction. Moreover, we noted that SEPT7 interacted with PKACA2 via its GTP-binding domain. Furthermore, PKA-mediated SEPT7 phosphorylation disrupted primary cilia formation. Thus, our data uncover the novel biological function of SEPT7 phosphorylation in septin filament polymerization and primary cilia formation.

scholarly journals Spatial targeting of type II protein kinase A to filopodia mediates the regulation of growth cone guidance by cAMP

2007 ◽  
Vol 176 (1) ◽  
pp. 101-111 ◽  
Author(s):  
Jianzhong Han ◽  
Liang Han ◽  
Priyanka Tiwari ◽  
Zhexing Wen ◽  
James Q. Zheng
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Growth Cone ◽  
Regulatory Protein ◽  
Cyclic Adenosine Monophosphate ◽  
Spatial Localization ◽  
Adenosine Monophosphate ◽  
Type Ii ◽  
Regulation Of Growth ◽  
Kinase A

The second messenger cyclic adenosine monophosphate (cAMP) plays a pivotal role in axonal growth and guidance, but its downstream mechanisms remain elusive. In this study, we report that type II protein kinase A (PKA) is highly enriched in growth cone filopodia, and this spatial localization enables the coupling of cAMP signaling to its specific effectors to regulate guidance responses. Disrupting the localization of PKA to filopodia impairs cAMP-mediated growth cone attraction and prevents the switching of repulsive responses to attraction by elevated cAMP. Our data further show that PKA targets protein phosphatase-1 (PP1) through the phosphorylation of a regulatory protein inhibitor-1 (I-1) to promote growth cone attraction. Finally, we find that I-1 and PP1 mediate growth cone repulsion induced by myelin-associated glycoprotein. These findings demonstrate that the spatial localization of type II PKA to growth cone filopodia plays an important role in the regulation of growth cone motility and guidance by cAMP.

scholarly journals Genes encoding catalytic subunits of protein kinase a and risk of spina bifida

2005 ◽  
Vol 73 (9) ◽  
pp. 591-596 ◽  
Author(s):  
Huiping Zhu ◽  
Wei Lu ◽  
Cecile Laurent ◽  
Gary M. Shaw ◽  
Edward J. Lammer ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Spina Bifida ◽  
Protein Kinase A ◽  
Catalytic Subunits ◽  
Genes Encoding ◽  
Kinase A

scholarly journals Convergence of 3′,5′-Cyclic Adenosine 5′-Monophosphate/Protein Kinase A and Glycogen Synthase Kinase-3β/β-Catenin Signaling in Corpus Luteum Progesterone Synthesis

Endocrinology ◽  
2009 ◽  
Vol 150 (11) ◽  
pp. 5036-5045 ◽  
Author(s):  
Lynn Roy ◽  
Claudia A. McDonald ◽  
Chao Jiang ◽  
Dulce Maroni ◽  
Anthony J. Zeleznik ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Corpus Luteum ◽  
Glycogen Synthase ◽  
Regulatory Protein ◽  
Glycogen Synthase Kinase ◽  
Proximal Promoter ◽  
Progesterone Secretion ◽  
Progesterone Synthesis ◽  
Kinase A

Progesterone secretion by the steroidogenic cells of the corpus luteum (CL) is essential for reproduction. Progesterone synthesis is under the control of LH, but the exact mechanism of this regulation is unknown. It is established that LH stimulates the LH receptor/choriogonadotropin receptor, a G-protein coupled receptor, to increase cAMP and activate cAMP-dependent protein kinase A (PKA). In the present study, we tested the hypothesis that cAMP/PKA-dependent regulation of the Wnt pathway components glycogen synthase kinase (GSK)-3β and β-catenin contributes to LH-dependent steroidogenesis in luteal cells. We observed that LH via a cAMP/PKA-dependent mechanism stimulated the phosphorylation of GSK3β at N-terminal Ser9 causing its inactivation and resulted in the accumulation of β-catenin. Overexpression of N-terminal truncated β-catenin (Δ90 β-catenin), which lacks the phosphorylation sites responsible for its destruction, significantly augmented LH-stimulated progesterone secretion. In contrast, overexpression of a constitutively active mutant of GSK3β (GSK-S9A) reduced β-catenin levels and inhibited LH-stimulated steroidogenesis. Chromatin immunoprecipitation assays demonstrated the association of β-catenin with the proximal promoter of the StAR gene, a gene that expresses the steroidogenic acute regulatory protein, which is a cholesterol transport protein that controls a rate-limiting step in steroidogenesis. Collectively these data suggest that cAMP/PKA regulation of GSK3β/β-catenin signaling may contribute to the acute increase in progesterone production in response to LH.

scholarly journals Inhibition of Thromboxane A Synthase Activity Enhances Steroidogenesis and Steroidogenic Acute Regulatory Gene Expression in MA-10 Mouse Leydig Cells

Endocrinology ◽  
2007 ◽  
Vol 149 (2) ◽  
pp. 851-857 ◽  
Author(s):  
XingJia Wang ◽  
Xiangling Yin ◽  
Randolph B. Schiffer ◽  
Steven R. King ◽  
Douglas M. Stocco ◽  
...  
Keyword(s):  
Rna Interference ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
Leydig Cells ◽  
Steroid Hormone ◽  
Mrna Levels ◽  
Star Protein ◽  
Steroidogenic Acute Regulatory ◽  
Star Gene ◽  
Kinase A

The cyclooxygenase-2 (COX2)-dependent inhibition of Leydig cell steroidogenesis has been demonstrated. To understand the mechanism for this effect of COX2, the present study examined the role of an enzyme downstream of COX2, namely thromboxane A synthase (TBXAS), in steroidogenesis. Inhibition of TBXAS activity with the inhibitor furegrelate induced a concentration-dependent increase in cAMP-induced steroidogenic acute regulatory (StAR) protein in MA-10 mouse Leydig cells. The increase in StAR protein occurred concomitantly with a significant increase in steroid hormone production. Similar results were obtained in StAR promoter activity assays and RT-PCR analyses of StAR mRNA levels, suggesting that inhibition of TBXAS activity enhanced StAR gene transcription. These observations were corroborated when TBXAS expression was specifically inhibited by RNA interference. Although the RNA interference reduced mRNA levels of TBXAS, it increased StAR mRNA levels, StAR protein, and steroidogenesis. Additional studies indicated that inhibition of TBXAS activity reduced DAX-1 protein, a repressor in StAR gene transcription. In the absence of cAMP, inhibition of TBXAS activity did not induce a significant increase in steroid hormone and StAR protein. However, addition of a low level of cAMP analogs dramatically increased steroidogenesis. Lastly, inhibition of protein kinase A activity essentially abolished the steroidogenic effect of the TBXAS inhibitor. Thus, the results from the present study suggest that a minimal level of protein kinase A activity is required for the steroidogenic effect of the TBXAS inhibitor and that inhibition of TBXAS activity or its expression increase the steroidogenic sensitivity of MA-10 mouse Leydig cells to cAMP stimulation.

scholarly journals A tripartite cooperative mechanism confers resistance of the protein kinase A catalytic subunit to dephosphorylation

2020 ◽  
Vol 295 (10) ◽  
pp. 3316-3329
Author(s):  
Tung O. Chan ◽  
Roger S. Armen ◽  
Santosh Yadav ◽  
Sushrut Shah ◽  
Jin Zhang ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Catalytic Subunit ◽  
Site Directed Mutagenesis ◽  
Airway Smooth Muscle Cells ◽  
Activation Loop ◽  
Allosteric Sites ◽  
And Migration ◽  
Kinase A ◽  
In Cells

Phosphorylation of specific residues in the activation loops of AGC kinase group (protein kinase A, G, and C families) is required for activity of most of these kinases, including the catalytic subunit of PKA (PKAc). Although many phosphorylated AGC kinases are sensitive to phosphatase-mediated dephosphorylation, the PKAc activation loop uniquely resists dephosphorylation, rendering it “constitutively” phosphorylated in cells. Previous biophysical experiments and structural modeling have suggested that the N-terminal myristoylation signal and the C-terminal FXXF motif in PKAc regulate its thermal stability and catalysis. Here, using site-directed mutagenesis, molecular modeling, and in cell-free and cell-based systems, we demonstrate that substitutions of either the PKAc myristoylation signal or the FXXF motif only modestly reduce phosphorylation and fail to affect PKAc function in cells. However, we observed that these two sites cooperate with an N-terminal FXXW motif to cooperatively establish phosphatase resistance of PKAc while not affecting kinase-dependent phosphorylation of the activation loop. We noted that this tripartite cooperative mechanism of phosphatase resistance is functionally relevant, as demonstrated by changes in morphology, adhesion, and migration of human airway smooth muscle cells transfected with PKAc variants containing amino acid substitutions in these three sites. These findings establish that three allosteric sites located at the PKAc N and C termini coordinately regulate the phosphatase sensitivity of this enzyme. This cooperative mechanism of phosphatase resistance of AGC kinase opens new perspectives toward therapeutic manipulation of kinase signaling in disease.

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