PKA and AMPK Signaling Pathways Differentially Regulate Luteal Steroidogenesis

Abstract Luteinizing hormone (LH) via protein kinase A (PKA) triggers ovulation and formation of the corpus luteum, which arises from the differentiation of follicular granulosa and theca cells into large and small luteal cells, respectively. The small and large luteal cells produce progesterone, a steroid hormone required for establishment and maintenance of pregnancy. We recently reported on the importance of hormone-sensitive lipase (HSL, also known as LIPE) and lipid droplets for appropriate secretory function of the corpus luteum. These lipid-rich intracellular organelles store cholesteryl esters, which can be hydrolyzed by HSL to provide cholesterol, the main substrate necessary for progesterone synthesis. In the present study, we analyzed dynamic posttranslational modifications of HSL mediated by PKA and AMP-activated protein kinase (AMPK) as well as their effects on steroidogenesis in luteal cells. Our results revealed that AMPK acutely inhibits the stimulatory effects of LH/PKA on progesterone production without reducing levels of STAR, CYP11A1, and HSD3B proteins. Exogenous cholesterol reversed the negative effects of AMPK on LH-stimulated steroidogenesis, suggesting that AMPK regulates cholesterol availability in luteal cells. AMPK evoked inhibitory phosphorylation of HSL (Ser565). In contrast, LH/PKA decreased phosphorylation of AMPK at Thr172, a residue required for its activation. Additionally, LH/PKA increased phosphorylation of HSL at Ser563, which is crucial for enzyme activation, and decreased inhibitory phosphorylation of HSL at Ser565. The findings indicate that LH and AMPK exert opposite posttranslational modifications of HSL, presumptively regulating cholesterol availability for steroidogenesis.

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Control of Steroidogenesis in Small and Large Bovine Luteal. Cells

Australian Journal of Biological Sciences ◽

10.1071/bi9870331 ◽

1987 ◽

Vol 40 (3) ◽

pp. 331 ◽

Cited By ~ 45

Author(s):

William Hansel ◽

Hector W Alila ◽

Joseph P Dowd ◽

Xiangzhong Yang

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Corpus Luteum ◽

Luteal Cell ◽

Lipoxygenase Pathway ◽

Luteal Cells ◽

Kinase C ◽

Bovine Corpus Luteum ◽

Progesterone Synthesis

Evidence was cited to show that: (1) prostacyclin (PGI2) plays a luteotrophic role in the bovine corpus luteum and that products of the lipoxygenase pathway of arachidonic acid metabolism, especially 5-hydroxyeicosatetraenoic acid play luteolytic roles; (2) oxytocin of luteal cell origin plays a role in development, and possibly in regression, of the bovine corpus luteum; and (3) luteal cells arise from two sources; the characteristic small luteal cells at all stages of the o~strous cycle and pregnancy are of theca cell origin; the large cells are of granulosa cell origin early in the cycle, but a population of theca-derived large cells appears later in the cycle. Results of in vitro studies with total dispersed cells and essentially pure preparations of large and small luteal cells indicate that : (1) the recently described Ca2+ -polyphosphoinositol-protein kinase C second messenger system is involved in progesterone synthesis in the bovine corpus luteum; (2) activation of protein kinase C is stimulatory to progesterone synthesis in the small luteal cells; (3) activation of protein kinase C has no effect on progesterone synthesis in the large luteal cells; and (4) protein kinase C exerts its luteotrophic effect in total cell preparations, in part at least, by stimulating the production of prostacyclin. The protein kinase C system may cause down regulation of LH receptors in the large cells.

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Protein Kinase A and 5′ AMP-Activated Protein Kinase Signaling Pathways Exert Opposite Effects on Induction of Autophagy in Luteal Cells

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.723563 ◽

2021 ◽

Vol 9 ◽

Author(s):

Emilia Przygrodzka ◽

Corrine F. Monaco ◽

Michele R. Plewes ◽

Guojuan Li ◽

Jennifer R. Wood ◽

...

Keyword(s):

Protein Kinase ◽

Corpus Luteum ◽

Signaling Pathways ◽

Luteal Cell ◽

Luteal Cells ◽

Mediated Effects ◽

Luteal Tissue ◽

Amp Activated Protein Kinase

In the absence of pregnancy the ovarian corpus luteum undergoes regression, a process characterized by decreased production of progesterone and structural luteolysis involving apoptosis. Autophagy has been observed in the corpus luteum during luteal regression. Autophagy is a self-degradative process important for balancing sources of cellular energy at critical times in development and in response to nutrient stress, but it can also lead to apoptosis. Mechanistic target of rapamycin (MTOR) and 5′ AMP-activated protein kinase (AMPK), key players in autophagy, are known to inhibit or activate autophagy, respectively. Here, we analyzed the signaling pathways regulating the initiation of autophagy in bovine luteal cells. In vivo studies showed increased activating phosphorylation of AMPKα (Thr172) and elevated content of LC3B, a known marker of autophagy, in luteal tissue during PGF2α-induced luteolysis. In vitro, AMPK activators 1) stimulated phosphorylation of regulatory associated protein of MTOR (RPTOR) leading to decreased activity of MTOR, 2) increased phosphorylation of Unc-51-Like Kinase 1 (ULK1) and Beclin 1 (BECN1), at sites specific for AMPK and required for autophagy initiation, 3) increased levels of LC3B, and 4) enhanced colocalization of autophagosomes with lysosomes indicating elevated autophagy. In contrast, LH/PKA signaling in luteal cells 1) reduced activation of AMPKα and phosphorylation of RPTOR, 2) elevated MTOR activity, 3) stimulated phosphorylation of ULK1 at site required for ULK1 inactivation, and 4) inhibited autophagosome formation as reflected by reduced content of LC3B-II. Pretreatment with AICAR, a pharmacological activator of AMPK, inhibited LH-mediated effects on RPTOR, ULK1 and BECN1. Our results indicate that luteotrophic signaling via LH/PKA/MTOR inhibits, while luteolytic signaling via PGF2α/Ca2+/AMPK activates key signaling pathways involved in luteal cell autophagy.

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Myeloid deletion and therapeutic activation of AMP-activated protein kinase (AMPK) do not alter atherosclerosis in male or female mice

10.1101/2020.07.15.204487 ◽

2020 ◽

Author(s):

Nicholas D. LeBlond ◽

Peyman Ghorbani ◽

Conor O’Dwyer ◽

Nia Ambursley ◽

Julia R. C. Nunes ◽

...

Keyword(s):

Protein Kinase ◽

First Generation ◽

Western Diet ◽

Daily Injection ◽

Catalytic Subunits ◽

Male And Female ◽

Ampk Signaling ◽

Female Mice ◽

Amp Activated Protein Kinase ◽

Progression Of Atherosclerosis

AbstractObjectiveThe dysregulation of myeloid-derived cell metabolism can drive atherosclerosis. AMP-activated protein kinase (AMPK) controls various aspects of macrophage dynamics and lipid homeostasis, which are important during atherogenesis.Approach and ResultsWe aimed to clarify the role of myeloid-specific AMPK signaling by using LysM-Cre to drive the deletion of both the α1 and α2 catalytic subunits (MacKO), in male and female mice made acutely atherosclerotic by PCSK9-AAV and Western diet-feeding. After 6 weeks of Western diet feeding, half received daily injection of either the AMPK activator, A-769662 or a vehicle control for a further 6 weeks. After 12 weeks, myeloid cell populations were not different between genotype or sex. Similarly, aortic sinus plaque size, lipid staining and necrotic area were not different in male and female MacKO mice compared to their littermate floxed controls. Moreover, therapeutic intervention with A-769662 had no effect. There were no differences in the amount of circulating total cholesterol or triglyceride, and only minor differences in the levels of inflammatory cytokines between groups. Finally, CD68+ area or markers of autophagy showed no effect of either lacking AMPK signaling or systemic AMPK activation.ConclusionsOur data suggest that while defined roles for each catalytic AMPK subunit have been identified, global deletion of myeloid AMPK signaling does not significantly impact atherosclerosis. Moreover, we show that intervention with the first-generation AMPK activator, A-769662, was not able to stem the progression of atherosclerosis.Highlights- The deletion of both catalytic subunits of AMPK in myeloid cells has no significant effect on the progression of atherosclerosis in either male or female mice- Therapeutic delivery of a first-generation AMPK activator (A-769662) for the last 6 weeks of 12-week study had no beneficial effect in either male or female mice- Studying total AMPK deletion may mask specific effects of each isoform and highlights the need for targeted disruption of AMPK phosphorylation sites via knock-in mutations, rather than the traditional “sledgehammer” knockout approach

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AMP-activated protein kinase (AMPK) signaling in GnRH neurons links energy status and reproduction

Metabolism ◽

10.1016/j.metabol.2020.154460 ◽

2021 ◽

Vol 115 ◽

pp. 154460

Author(s):

D. Franssen ◽

A. Barroso ◽

F. Ruiz-Pino ◽

M.J. Vázquez ◽

D. García-Galiano ◽

...

Keyword(s):

Protein Kinase ◽

Energy Status ◽

Ampk Signaling ◽

Gnrh Neurons ◽

Amp Activated Protein Kinase

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AMP-activated Protein Kinase (AMPK) Signaling in Endothelial Cells Is Essential for Angiogenesis in Response to Hypoxic Stress

Journal of Biological Chemistry ◽

10.1074/jbc.m300643200 ◽

2003 ◽

Vol 278 (33) ◽

pp. 31000-31006 ◽

Cited By ~ 259

Author(s):

Daisuke Nagata ◽

Masaki Mogi ◽

Kenneth Walsh

Keyword(s):

Endothelial Cells ◽

Protein Kinase ◽

Hypoxic Stress ◽

Ampk Signaling ◽

Amp Activated Protein Kinase

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P2-316: Disturbance in AMP-activated protein kinase (AMPK) signaling pathway in Alzheimer's disease

Alzheimer s & Dementia ◽

10.1016/j.jalz.2010.05.1367 ◽

2010 ◽

Vol 6 ◽

pp. S406-S406

Author(s):

Hyoung-Gon Lee ◽

Hyun-Pil Lee ◽

Wataru Kudo ◽

Xiongwei Zhu ◽

George Perry ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Protein Kinase ◽

Signaling Pathway ◽

Ampk Signaling ◽

Amp Activated Protein Kinase

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AMP-activated protein kinase pathway and bone metabolism

Journal of Endocrinology ◽

10.1530/joe-11-0306 ◽

2011 ◽

Vol 212 (3) ◽

pp. 277-290 ◽

Cited By ~ 58

Author(s):

J Jeyabalan ◽

M Shah ◽

B Viollet ◽

C Chenu

Keyword(s):

Protein Kinase ◽

Energy Homeostasis ◽

Bone Cells ◽

Peripheral Tissues ◽

Ampk Signaling ◽

Obesity And Diabetes ◽

Regulate Food Intake ◽

Ampk Activity ◽

Amp Activated Protein Kinase

There is increasing evidence that osteoporosis, similarly to obesity and diabetes, could be another disorder of energy metabolism. AMP-activated protein kinase (AMPK) has emerged over the last decade as a key sensing mechanism in the regulation of cellular energy homeostasis and is an essential mediator of the central and peripheral effects of many hormones on the metabolism of appetite, fat and glucose. Novel work demonstrates that the AMPK signaling pathway also plays a role in bone physiology. Activation of AMPK promotes bone formationin vitroand the deletion of α or β subunit of AMPK decreases bone mass in mice. Furthermore, AMPK activity in bone cells is regulated by the same hormones that regulate food intake and energy expenditure through AMPK activation in the brain and peripheral tissues. AMPK is also activated by antidiabetic drugs such as metformin and thiazolidinediones (TZDs), which also impact on skeletal metabolism. Interestingly, TZDs have detrimental skeletal side effects, causing bone loss and increasing the risk of fractures, although the role of AMPK mediation is still unclear. These data are presented in this review that also discusses the potential roles of AMPK in bone as well as the possibility for AMPK to be a future therapeutic target for intervention in osteoporosis.

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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 ◽

10.1210/en.2009-0771 ◽

2009 ◽

Vol 150 (11) ◽

pp. 5036-5045 ◽

Cited By ~ 37

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.

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