Angiotensin II Activates Cholesterol Ester Hydrolase in Bovine Adrenal Glomerulosa Cells through Phosphorylation Mediated by p42/p44 Mitogen-Activated Protein Kinase

Abstract

In adrenal glomerulosa cells, the stimulation of aldosterone biosynthesis by angiotensin II (Ang II) occurs via activation of the Ca2+ messenger system, increased expression of the steroidogenic acute regulatory protein, and enhanced transfer of cholesterol to the inner mitochondrial membrane. We examined here whether Ang II affects the activity of cholesterol ester hydrolase (CEH), also named hormone-sensitive lipase, the enzyme recruiting cholesterol from intracellular pools, in bovine adrenal glomerulosa cells. In bovine adrenal tissue, CEH activity was detected with characteristics similar to those reported in other tissues (Michaelis constant = 46.3 +/- 6.7 microM, n = 3; maximal velocity = 1 nmol/mg.min). This activity was significantly enhanced in isolated bovine glomerulosa cells challenged for 2 h with 10 nM Ang II (to 149 +/- 11% of controls, n = 3). Similarly, 25 microM forskolin raised CEH activity to 151 +/- 5% of controls (n = 3). This increase in activity of CEH was not due to an increase in the amount of enzyme protein but was associated with an increased phosphorylation of the enzyme to 337 +/- 33% of controls (n = 9, P < 0.0001). Potassium ion (K+) and forskolin also stimulated [32P]orthophosphate incorporation, although to a lesser extent (to 157 +/- 18% and 186 +/- 25% of controls, respectively). On SDS-PAGE, the majority of this radioactivity was associated with a species of 172 kDa, corresponding to a CEH dimer. Both Ang II-induced CEH phosphorylation and pregnenolone production were significantly reduced (to 47 +/- 6% and 50 +/- 8% of controls with Ang II alone, respectively) in the presence of PD098059, an inhibitor of p42/p44 MAPK. Indeed, Ang II challenge led to a rapid 32P incorporation into p42/p44 MAPK. These results demonstrate that, in addition to its known effects on intramitochondrial cholesterol transfer, Ang II also promotes aldosterone biosynthesis by rapidly increasing cholesterol supply to the outer mitochondrial membrane.

Regulation of aldosterone production from zona glomerulosa cells by ANG II and cAMP: evidence for PKA-independent activation of CaMK by cAMP

“…Activation of ERK and p38 MAP kinases plays an important role in the regulation of aldosterone production. ERK and p38 MAPKs have been shown to stimulate CEH activity (8) and regulate [Ca 2ϩ ] i by the inhibition of the Na ϩ /Ca 2ϩ exchanger (48). Therefore, we investigated the activation of all three major MAPK pathways (JNK, ERK, and p38) using phosphospecific antibodies in response to ANG II and forskolin stimulation.…”

“…Stimulation of steroidproducing cells results in prompt mobilization of cholesterol esters from intracellular lipid droplets and their enzymatic hydrolysis to free cholesterol by cholesterol ester hydrolase (CEH) (8). Free cholesterol is then transported to the outer mitochondrial membrane (28,29,50,57), where it is transferred to the side-chain cleavage enzyme system that is localized at the inner mitochondrial membranes.…”

Extramitochondrial OPA1 and adrenocortical function

“…ACTH,59 through cAMP-PKA, phosphorylates and thus activates the enzyme 60 (Hirsch and Rosen, 1984;Holm et al, 2000;Kraemer et al, 2004; 61 Trzeciak and Boyd, 1974) and also induces its expression eman and Moore, 2008;Holysz et al, 2011). Calcium ion, the sec-63 ond messenger of angiotensin II, acts via CaMKII to activate 64 (Cherradi et al, 1998) and through p42/p44 mitogen-activated 65 protein kinase (Cherradi et al, 2003) to increase the expression 66 of HSL.…”

Very low-density lipoprotein (VLDL)-induced signals mediating aldosterone production

“…At the same time, the other signal formed within minutes is DAG; DAG activates protein kinase C (PKC) isoforms to stimulate the activity of extracellular signal-regulated kinase (ERK), again within minutes of VLDL treatment. VLDL-stimulated ERK, like the angiotensin II (AngII)-activated enzyme, may, in turn, phosphorylate and activate cholesterol ester hydrolase (Cherradi et al 2003), also known as hormone-sensitive lipase, to release cholesterol esters stored in lipid droplets. ERK also likely phosphorylates StAR, thereby enhancing its cholesterol transport activity (Poderoso et al 2008).…”