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Spaulding SC, Bollag WB. The role of lipid second messengers in aldosterone synthesis and secretion. J Lipid Res 2022; 63:100191. [PMID: 35278411 PMCID: PMC9020094 DOI: 10.1016/j.jlr.2022.100191] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 11/23/2022] Open
Abstract
Second messengers are small rapidly diffusing molecules or ions that relay signals between receptors and effector proteins to produce a physiological effect. Lipid messengers constitute one of the four major classes of second messengers. The hydrolysis of two main classes of lipids, glycerophospholipids and sphingolipids, generate parallel profiles of lipid second messengers: phosphatidic acid (PA), diacylglycerol (DAG), and lysophosphatidic acid versus ceramide, ceramide-1-phosphate, sphingosine, and sphingosine-1-phosphate, respectively. In this review, we examine the mechanisms by which these lipid second messengers modulate aldosterone production at multiple levels. Aldosterone is a mineralocorticoid hormone responsible for maintaining fluid volume, electrolyte balance, and blood pressure homeostasis. Primary aldosteronism is a frequent endocrine cause of secondary hypertension. A thorough understanding of the signaling events regulating aldosterone biosynthesis may lead to the identification of novel therapeutic targets. The cumulative evidence in this literature emphasizes the critical roles of PA, DAG, and sphingolipid metabolites in aldosterone synthesis and secretion. However, it also highlights the gaps in our knowledge, such as the preference for phospholipase D-generated PA or DAG, as well as the need for further investigation to elucidate the precise mechanisms by which these lipid second messengers regulate optimal aldosterone production.
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Affiliation(s)
- Shinjini C Spaulding
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Wendy B Bollag
- Department of Physiology, Medical College of Georgia at Augusta University, Augusta, GA, USA; Research Department, Charlie Norwood VA Medical Center, Augusta, GA, USA.
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Tsai YY, Rainey WE, Bollag WB. Very low-density lipoprotein (VLDL)-induced signals mediating aldosterone production. J Endocrinol 2017; 232:R115-R129. [PMID: 27913572 PMCID: PMC8310676 DOI: 10.1530/joe-16-0237] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 12/02/2016] [Indexed: 01/14/2023]
Abstract
Aldosterone, secreted by the adrenal zona glomerulosa, enhances sodium retention, thus increasing blood volume and pressure. Excessive production of aldosterone results in high blood pressure and contributes to cardiovascular and renal disease, stroke and visual loss. Hypertension is also associated with obesity, which is correlated with other serious health risks as well. Although weight gain is associated with increased blood pressure, the mechanism by which excess fat deposits increase blood pressure remains unclear. Several studies have suggested that aldosterone levels are elevated with obesity and may represent a link between obesity and hypertension. In addition to hypertension, obese patients typically have dyslipidemia, including elevated serum levels of very low-density lipoprotein (VLDL). VLDL, which functions to transport triglycerides from the liver to peripheral tissues, has been demonstrated to stimulate aldosterone production. Recent studies suggest that the signaling pathways activated by VLDL are similar to those utilized by AngII. Thus, VLDL increases cytosolic calcium levels and stimulates phospholipase D (PLD) activity to result in the induction of steroidogenic acute regulatory (StAR) protein and aldosterone synthase (CYP11B2) expression. These effects seem to be mediated by the ability of VLDL to increase the phosphorylation (activation) of their regulatory transcription factors, such as the cAMP response element-binding (CREB) protein family of transcription factors. Thus, research into the pathways by which VLDL stimulates aldosterone production may identify novel targets for the development of therapies for the treatment of hypertension, particularly those associated with obesity, and other aldosterone-modulated pathologies.
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Affiliation(s)
- Ying-Ying Tsai
- Department of PhysiologyMedical College of Georgia at Augusta University (formerly Georgia Regents University), Augusta, Georgia, USA
| | - William E Rainey
- Departments of Molecular & Integrative Physiology and Internal MedicineUniversity of Michigan, Ann Arbor, Michigan, USA
| | - Wendy B Bollag
- Department of PhysiologyMedical College of Georgia at Augusta University (formerly Georgia Regents University), Augusta, Georgia, USA
- Charlie Norwood VA Medical CenterOne Freedom Way, Augusta, Georgia, USA
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3
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Abstract
Phospholipases are lipid-metabolizing enzymes that hydrolyze phospholipids. In some cases, their activity results in remodeling of lipids and/or allows the synthesis of other lipids. In other cases, however, and of interest to the topic of adrenal steroidogenesis, phospholipases produce second messengers that modify the function of a cell. In this review, the enzymatic reactions, products, and effectors of three phospholipases, phospholipase C, phospholipase D, and phospholipase A2, are discussed. Although much data have been obtained concerning the role of phospholipases C and D in regulating adrenal steroid hormone production, there are still many gaps in our knowledge. Furthermore, little is known about the involvement of phospholipase A2, perhaps, in part, because this enzyme comprises a large family of related enzymes that are differentially regulated and with different functions. This review presents the evidence supporting the role of each of these phospholipases in steroidogenesis in the adrenal cortex.
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Affiliation(s)
- Wendy B Bollag
- Charlie Norwood VA Medical CenterOne Freedom Way, Augusta, GA, USA Department of PhysiologyMedical College of Georgia, Augusta University (formerly Georgia Regents University), Augusta, GA, USA
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4
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Abstract
Aldosterone is a steroid hormone synthesized in and secreted from the outer layer of the adrenal cortex, the zona glomerulosa. Aldosterone is responsible for regulating sodium homeostasis, thereby helping to control blood volume and blood pressure. Insufficient aldosterone secretion can lead to hypotension and circulatory shock, particularly in infancy. On the other hand, excessive aldosterone levels, or those too high for sodium status, can cause hypertension and exacerbate the effects of high blood pressure on multiple organs, contributing to renal disease, stroke, visual loss, and congestive heart failure. Aldosterone is also thought to directly induce end-organ damage, including in the kidneys and heart. Because of the significance of aldosterone to the physiology and pathophysiology of the cardiovascular system, it is important to understand the regulation of its biosynthesis and secretion from the adrenal cortex. Herein, the mechanisms regulating aldosterone production in zona glomerulosa cells are discussed, with a particular emphasis on signaling pathways involved in the secretory response to the main controllers of aldosterone production, the renin-angiotensin II system, serum potassium levels and adrenocorticotrophic hormone. The signaling pathways involved include phospholipase C-mediated phosphoinositide hydrolysis, inositol 1,4,5-trisphosphate, cytosolic calcium levels, calcium influx pathways, calcium/calmodulin-dependent protein kinases, diacylglycerol, protein kinases C and D, 12-hydroxyeicostetraenoic acid, phospholipase D, mitogen-activated protein kinase pathways, tyrosine kinases, adenylate cyclase, and cAMP-dependent protein kinase. A complete understanding of the signaling events regulating aldosterone biosynthesis may allow the identification of novel targets for therapeutic interventions in hypertension, primary aldosteronism, congestive heart failure, renal disease, and other cardiovascular disorders.
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Affiliation(s)
- Wendy B Bollag
- Charlie Norwood VA Medical Center, Augusta, Georgia; Department of Physiology, Medical College of Georgia at Georgia Regents University, Augusta, Georgia
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Hattangady N, Olala L, Bollag WB, Rainey WE. Acute and chronic regulation of aldosterone production. Mol Cell Endocrinol 2012; 350:151-62. [PMID: 21839803 PMCID: PMC3253327 DOI: 10.1016/j.mce.2011.07.034] [Citation(s) in RCA: 206] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 07/11/2011] [Accepted: 07/17/2011] [Indexed: 11/28/2022]
Abstract
Aldosterone is the major mineralocorticoid synthesized by the adrenal and plays an important role in the regulation of systemic blood pressure through the absorption of sodium and water. Aldosterone production is regulated tightly by selective expression of aldosterone synthase (CYP11B2) in the adrenal outermost zone, the zona glomerulosa. Angiotensin II (Ang II), potassium (K(+)) and adrenocorticotropin (ACTH) are the main physiological agonists which regulate aldosterone secretion. Aldosterone production is regulated within minutes of stimulation (acutely) through increased expression and phosphorylation of the steroidogenic acute regulatory (StAR) protein and over hours to days (chronically) by increased expression of the enzymes involved in the synthesis of aldosterone, particularly CYP11B2. Imbalance in any of these processes may lead to several disorders of aldosterone excess. In this review we attempt to summarize the key molecular events involved in the acute and chronic phases of aldosterone secretion.
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Affiliation(s)
- Namita Hattangady
- Department of Physiology, Georgia Health Sciences University (formerly the Medical College of Georgia), 1120 15 Street, Augusta, GA 30912
| | - Lawrence Olala
- Department of Physiology, Georgia Health Sciences University (formerly the Medical College of Georgia), 1120 15 Street, Augusta, GA 30912
| | - Wendy B. Bollag
- Department of Physiology, Georgia Health Sciences University (formerly the Medical College of Georgia), 1120 15 Street, Augusta, GA 30912
- Charlie Norwood VA Medical Center, One Freedom Way, Augusta, GA 30904
| | - William E. Rainey
- Department of Physiology, Georgia Health Sciences University (formerly the Medical College of Georgia), 1120 15 Street, Augusta, GA 30912
- To whom correspondence should be addressed: William E. Rainey, Department of Physiology, Georgia Health Sciences University, 1120 15 Street, Augusta, GA 30912, , Tel: (706) 721-7665, Fax: (706) 721-7299
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Shapiro BA, Olala L, Arun SN, Parker PM, George MV, Bollag WB. Angiotensin II-activated protein kinase D mediates acute aldosterone secretion. Mol Cell Endocrinol 2010; 317:99-105. [PMID: 19961896 PMCID: PMC2814994 DOI: 10.1016/j.mce.2009.11.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Revised: 10/21/2009] [Accepted: 11/27/2009] [Indexed: 11/23/2022]
Abstract
Dysregulation of the renin-angiotensin II (AngII)-aldosterone system can contribute to cardiovascular disease, such that an understanding of this system is critical. Diacylglycerol-sensitive serine/threonine protein kinase D (PKD) is activated by AngII in several systems, including the human adrenocortical carcinoma cell line NCI H295R, where this enzyme enhances chronic (24h) AngII-evoked aldosterone secretion. However, the role of PKD in acute AngII-elicited aldosterone secretion has not been previously examined. In primary cultures of bovine adrenal glomerulosa cells, which secrete detectable quantities of aldosterone in response to secretagogues within minutes, PKD was activated in response to AngII, but not an elevated potassium concentration or adrenocorticotrophic hormone. This activation was time- and dose-dependent and occurred through the AT1, but not the AT2, receptor. Adenovirus-mediated overexpression of constitutively active PKD resulted in enhanced AngII-induced aldosterone secretion; whereas overexpression of a dominant-negative PKD construct decreased AngII-stimulated aldosterone secretion. Thus, we demonstrate for the first time that PKD mediates acute AngII-induced aldosterone secretion.
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Affiliation(s)
- Brian A. Shapiro
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912
| | - Lawrence Olala
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912
| | - Senthil Nathan Arun
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912
| | - Peter M. Parker
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912
| | - Mariya V. George
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912
| | - Wendy B. Bollag
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912
- Charlie Norwood VA Medical Center, One Freedom Way, Augusta, GA 30904
- Departments of Physiolgy, Medicine, Cell Biology and Anatomy and Orthopaedic Surgery, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912
- To whom correspondence should be addressed: Wendy B. Bollag, Department of Physiology, Medical College of Georgia, 1120 15th Street, Augusta, Georgia 30912, TEL: (706) 721-0698, FAX: (706) 721-7299,
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Qin H, Kent P, Isales CM, Parker PM, Wilson MV, Bollag WB. The role of calcium influx pathways in phospholipase D activation in bovine adrenal glomerulosa cells. J Endocrinol 2009; 202:77-86. [PMID: 19372190 PMCID: PMC3743046 DOI: 10.1677/joe-09-0119] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The steroid hormone aldosterone maintains sodium homeostasis and is therefore important in the control of blood volume and pressure. Angiotensin II (AngII) and elevated extracellular potassium concentrations ([K(+)](e)), the prime physiologic regulators of aldosterone secretion from adrenal glomerulosa cells, activate phospholipase D (PLD) in these cells. The role of Ca(2+) in the activation by these agents is unknown, although nitrendipine, a voltage-dependent Ca(2+) channel antagonist, does not inhibit AngII-elicited PLD activation, despite the fact that this compound blocked elevated [K(+)](e)-stimulated PLD activity. PLD activation triggered by AngII was also unaffected by the T-type calcium channel inhibitor nickel. Nevertheless, Ca(2+) influx was required for AngII-induced PLD activation in both primary cultures of bovine adrenal glomerulosa cells and a glomerulosa cell model, the NCI H295R adrenocortical carcinoma cell line. The involvement of store-operated Ca(2+) (SOC) influx and Ca(2+) release-activated Ca(2+) (CRAC) influx pathways in PLD activation was investigated using thapsigargin, an endoplasmic reticulum Ca(2+) pump inhibitor that empties the store to induce SOC influx, and the SOC inhibitor YM-58483 (BTP2), as well as a CRAC inhibitor, tyrphostin A9. In bovine glomerulosa cells, tyrphostin A9 inhibited AngII-induced PLD activation without affecting elevated [K(+)](e)-stimulated enzyme activity. On the other hand, differences were observed between the bovine adrenal glomerulosa and H295R cells in the involvement of Ca(2+) influx pathways in PLD activation, with the involvement of the SOC pathway suggested in the H295R cells. In summary, our results indicate that Ca(2+) entry only through certain Ca(2+) influx pathways is linked to PLD activation.
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Affiliation(s)
- Haixia Qin
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
| | - Patricia Kent
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
| | - Carlos M. Isales
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
- Department of Orthopaedic Surgery, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
| | - Peter M. Parker
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
| | - Mariya V. Wilson
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
| | - Wendy B. Bollag
- Charlie Norwood VA Medical Center, One Freedom Way, Augusta, GA 30904
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
- Departments of Medicine and Cell Biology and Anatomy, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
- Department of Orthopaedic Surgery, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912
- Address correspondence to: Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15 Street, Augusta, GA 30912, Tel. 706-721-0698; Fax 706-721-7915;
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8
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Brizuela L, Rábano M, Peña A, Gangoiti P, Macarulla JM, Trueba M, Gómez-Muñoz A. Sphingosine 1-phosphate: a novel stimulator of aldosterone secretion. J Lipid Res 2006; 47:1238-49. [PMID: 16554657 DOI: 10.1194/jlr.m500510-jlr200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid capable of regulating critical physiological and pathological functions. Here, we report for the first time that S1P stimulates aldosterone secretion in cells of the zona glomerulosa of the adrenal gland. Regulation of aldosterone secretion is important because this hormone controls electrolyte and fluid balance and is implicated in cardiovascular homeostasis. S1P-stimulated aldosterone secretion was dependent upon the protein kinase C (PKC) isoforms alpha and delta and extracellular Ca2+, and it was inhibited by pertussis toxin (PTX). S1P activated phospholipase D (PLD) through a PTX-sensitive mechanism, also involving PKC alpha and delta and extracellular Ca2+. Primary alcohols, which attenuate the formation of phosphatidic acid (the product of PLD), and cell-permeable ceramides, which inhibit PLD activity, blocked S1P-stimulated aldosterone secretion. Furthermore, propranolol, chlorpromazine, and sphingosine, which are potent inhibitors of phosphatidate phosphohydrolase (PAP) (the enzyme that produces diacylglycerol from phosphatidate), also blocked aldosterone secretion. These data suggest that the PLD/PAP pathway plays a crucial role in the regulation of aldosterone secretion by S1P and that Gi protein-coupled receptors, extracellular Ca2+, and the PKC isoforms alpha and delta are all important components in the cascade of events controlling this process.
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Affiliation(s)
- Leyre Brizuela
- Department of Biochemistry and Molecular Biology, Faculty of Science and Technology, University of the Basque Country, 48080 Bilbao, Spain
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9
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Sundaram M, Cook HW, Byers DM. The MARCKS family of phospholipid binding proteins: regulation of phospholipase D and other cellular components. Biochem Cell Biol 2004; 82:191-200. [PMID: 15052337 DOI: 10.1139/o03-087] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP) are essential proteins that are implicated in coordination of membrane-cytoskeletal signalling events, such as cell adhesion, migration, secretion, and phagocytosis in a variety of cell types. The most prominent structural feature of MARCKS and MRP is a central basic effector domain (ED) that binds F-actin, Ca2+-calmodulin, and acidic phospholipids; phosphorylation of key serine residues within the ED by protein kinase C (PKC) prevents the above interactions. While the precise roles of MARCKS and MRP have not been established, recent attention has focussed on the high affinity of the MARCKS ED for phosphatidylinositol 4,5-bisphosphate (PIP2), and a model has emerged in which calmodulin- or PKC-mediated regulation of these proteins at specific membrane sites could in turn control spatial availability of PIP2. The present review summarizes recent progress in this area and discusses how the above model might explain a role for MARCKS and MRP in activation of phospholipase D and other PIP2-dependent cellular processes.
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Affiliation(s)
- Meenakshi Sundaram
- Atlantic Research Centre, Department of Pediatrics, Dalhousie University, Halifax, NS, Canada
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Rábano M, Peña A, Brizuela L, Macarulla JM, Gómez-Muñoz A, Trueba M. Angiotensin II-stimulated cortisol secretion is mediated by phospholipase D. Mol Cell Endocrinol 2004; 222:9-20. [PMID: 15249121 DOI: 10.1016/j.mce.2004.05.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2004] [Accepted: 05/20/2004] [Indexed: 10/26/2022]
Abstract
Angiotensin II (Ang-II) regulates a variety of cellular functions including cortisol secretion. In the present report, we demonstrate that Ang-II activates phospholipase D (PLD) in zona fasciculata (ZF) cells of bovine adrenal glands, and that this effect is associated to the stimulation of cortisol secretion by this hormone. PLD activation was dependent upon extracellular Ca2+, and was blocked by inhibition of protein kinase C (PKC). Using the reverse transcription-polymerase chain reaction technique, we demonstrated that ZF cells express both PLD-1 and PLD-2 isozymes. Primary alcohols, which attenuate the formation of phosphatidate (the product of PLD), and cell-permeable ceramides, which inhibit PLD potently, blocked Ang-II-stimulated cortisol secretion. Furthermore, propranolol or chlorpromazine, which are potent inhibitors of phosphatidate phosphohydrolase (PAP) (the enzyme that produces diacylglycerol from phosphatidate), also blocked cortisol secretion. These data suggest that the PLD/PAP pathway plays an important role in the regulation of cortisol secretion by Ang-II in ZF cells.
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Affiliation(s)
- Miriam Rábano
- Department of Biochemistry and Molecular Biology, Faculty of Science and Technology, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
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Rábano M, Peña A, Brizuela L, Marino A, Macarulla JM, Trueba M, Gómez-Muñoz A. Sphingosine-1-phosphate stimulates cortisol secretion. FEBS Lett 2003; 535:101-5. [PMID: 12560086 DOI: 10.1016/s0014-5793(02)03882-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We show here for the first time that sphingosine-1-phosphate (Sph-1-P) stimulates cortisol secretion in zona fasciculata cells of bovine adrenal glands. This effect was dependent upon protein kinase C (PKC) and extracellular Ca2+, and was inhibited by pertussis toxin. Sph-1-P activated phospholipase D (PLD) through a pertussis toxin-sensitive mechanism, also involving extracellular Ca2+ and PKC. Primary alcohols, which attenuate formation of phosphatidic acid (the product of PLD), and cell-permeable ceramides, which inhibit PLD, blocked Sph-1-P-induced cortisol secretion. In conclusion, Sph-1-P stimulates cortisol secretion through a mechanism involving Gi/o protein-coupled receptors, extracellular Ca2+, PKC and PLD.
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Affiliation(s)
- Miriam Rábano
- Department of Biochemistry and Molecular Biology, Faculty of Sciences, University of the Basque Country, P.O. Box 644, 48080 Bilbao, Spain
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12
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Bollag WB, Jung E, Calle RA. Mechanism of angiotensin II-induced phospholipase D activation in bovine adrenal glomerulosa cells. Mol Cell Endocrinol 2002; 192:7-16. [PMID: 12088862 DOI: 10.1016/s0303-7207(02)00134-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Based on previous data demonstrating activation of phospholipase D (PLD) in response to angiotensin II (AngII), we have hypothesized a role for PLD in mediating aldosterone secretion from bovine adrenal glomerulosa cells. In this study we demonstrate that a PLD-generated signal(s) is required for the AngII-elicited secretory response, since interfering with lipid second messenger formation using a primary alcohol inhibited AngII-induced aldosterone secretion, but not that elicited by incubation with a hydrophilic cholesterol analog, 22(R)-hydroxycholesterol, which bypasses signaling pathways. Three mechanisms for hormonal activation of PLD have been described in other systems: direct receptor coupling, activation through protein kinase C (PKC) and a combination of these two mechanisms. Our results indicate that the PKC activator, phorbol 12-myristic 13-acetate (PMA), is able to activate PLD, and that receptor engagement is apparently not necessary for PLD activation in response to this agent. Maximal doses of AngII and PMA produced no additive effect on PLD activation, suggesting that these two agents function through a common PKC pathway. This interpretation was confirmed by the ability of a PKC inhibitor, Gö 6976, to inhibit partially AngII-induced PLD activation. Finally, treatment with the calcium ionophores A23187 or ionomycin or the calcium channel agonist BAY K8644 had no effect on PLD activity. Likewise, inhibiting calcium influx with high-dose nitrendipine affected neither basal PLD activity nor that stimulated by AngII. Thus, our results suggest a role for PKC, independent of calcium influx, in mediating AngII-induced PLD activation in glomerulosa cells.
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Affiliation(s)
- Wendy B Bollag
- Program in Cell Signaling, Department of Medicine, Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, 30912-2630, Augusta, GA, USA.
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