Angiotensin II (AngII) and elevated extracellular K+ levels [(K+) e] are the primary physiologic regulators of the synthesis and secretion of aldosterone, the hormone responsible for maintaining normal salt balance in the body. Previous studies have indicated that elevated (K+)e stimulates steroidogenesis by depolarizing the glomerulosa cell, thereby activating voltage-dependent Ca2+ channels and increasing Ca2+ influx. This enhanced influx, in turn, activates Ca2+-dependent processes, such as Ca2+/calmodulin-dependent protein kinases. In novel findings we have recently shown that elevated (K+) e also activates phospholipase D (PLD) and increases the phosphorylation of an endogenous protein kinase C (PKC) substrate (myristoylated alanine-rich C kinase substrate or MARCKS). PLD-mediated hydrolysis of membrane phosphatidylcholine generates phosphatidic acid, which can be dephosphorylated to produce diacylglycerol, the natural activator of PKC. Thus, we propose that the elevated (K+)e-induced increase in Ca2+ influx activates PLD to stimulate PKC activity, thereby eliciting MARCKS phosphorylation and sustained aldosterone secretion. Our data also suggest an involvement of PLD in the process of priming. Priming refers to the ability of a pretreatment with AngII to sensitize glomerulosa cells to respond to agents that stimulate Ca2+ influx, including small elevations in (K+) e, with enhanced aldosterone secretion relative to """"""""naive"""""""" unpretreated cells. We have postulated that priming is the result of the observed persistent elevation in PLD-generated diacylglycerol retaining PKC at the plasma membrane, a site at which the enzyme is poised to activate in response to increased Ca2+ influx. Using two-dimensional polyacrylamide gel electrophoretic analysis, proteomics and mass spectrometric identification of phosphorylation sites, PLD activity measurements, overexpression of PLD isoforms, aldosterone radioimmunoassays and western blot analysis, we wish to test the hypothesis that a PLD-generated signal retains PKC at the plasma membrane to result in the induction of priming. We will also define the mechanism of elevated (K+)e-induced PLD activation and examine the hypothesis that this activation stimulates PKC activity, MARCKS phosphorylation and aldosterone secretion. Since priming would allow enhanced aldosterone secretion to multiple AngII or sequential AngII and elevated (K+)e exposures, this research may provide novel insights into normal and pathological changes in steroidogenesis under conditions of altered sodium intake. The complex interactions between AngII and serum K+ levels suggest that abnormalities in the glomerulosa cell response to either agonist, or both, may contribute to the development of some forms of hypertension. ? ?

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Cardiovascular and Renal Study Section (CVB)
Program Officer
Lin, Michael
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Georgia Health Sciences University
Internal Medicine/Medicine
Schools of Medicine
United States
Zip Code
Seremwe, Mutsa; Schnellmann, Rick G; Bollag, Wendy B (2015) Calpain-10 Activity Underlies Angiotensin II-Induced Aldosterone Production in an Adrenal Glomerulosa Cell Model. Endocrinology 156:2138-49
Pan, Zhi-qiang; Xie, Ding; Choudhary, Vivek et al. (2014) The effect of pioglitazone on aldosterone and cortisol production in HAC15 human adrenocortical carcinoma cells. Mol Cell Endocrinol 394:119-28
Olala, Lawrence O; Choudhary, Vivek; Johnson, Maribeth H et al. (2014) Angiotensin II-induced protein kinase D activates the ATF/CREB family of transcription factors and promotes StAR mRNA expression. Endocrinology 155:2524-33
Olala, Lawrence O; Shapiro, Brian A; Merchen, Todd C et al. (2014) Protein kinase C and Src family kinases mediate angiotensin II-induced protein kinase D activation and acute aldosterone production. Mol Cell Endocrinol 392:173-81
Olala, Lawrence O; Seremwe, Mutsa; Tsai, Ying-Ying et al. (2013) A role for phospholipase D in angiotensin II-induced protein kinase D activation in adrenal glomerulosa cell models. Mol Cell Endocrinol 366:31-7
Hattangady, Namita G; Olala, Lawrence O; Bollag, Wendy B et al. (2012) Acute and chronic regulation of aldosterone production. Mol Cell Endocrinol 350:151-62
Shapiro, Brian A; Olala, Lawrence; Arun, Senthil Nathan et al. (2010) Angiotensin II-activated protein kinase D mediates acute aldosterone secretion. Mol Cell Endocrinol 317:99-105
Qin, Haixia; Frohman, Michael A; Bollag, Wendy B (2010) Phospholipase D2 mediates acute aldosterone secretion in response to angiotensin II in adrenal glomerulosa cells. Endocrinology 151:2162-70
Nogueira, Edson F; Bollag, Wendy B; Rainey, William E (2009) Angiotensin II regulation of adrenocortical gene transcription. Mol Cell Endocrinol 302:230-6
Qin, Haixia; Kent, Patricia; Isales, Carlos M et al. (2009) The role of calcium influx pathways in phospholipase D activation in bovine adrenal glomerulosa cells. J Endocrinol 202:77-86

Showing the most recent 10 out of 14 publications