SCAP/SREBP pathway is required for the full steroidogenic response to cyclic AMP

Abstract

Luteinizing hormone (LH) stimulates steroidogenesis largely through a surge in cyclic AMP (cAMP). Steroidogenic rates are also critically dependent on the availability of cholesterol at mitochondrial sites of synthesis. This cholesterol is provided by cellular uptake of lipoproteins, mobilization of intracellular lipid, and de novo synthesis. Whether and how these pathways are coordinated by cAMP are poorly understood. Recent phosphoproteomic analyses of cAMP-dependent phosphorylation sites in MA10 Leydig cells suggested that cAMP regulates multiple steps in these processes, including activation of the SCAP/SREBP pathway. SCAP [sterol-regulatory element-binding protein (SREBP) cleavage-activating protein] acts as a cholesterol sensor responsible for regulating intracellular cholesterol balance. Its role in cAMP-mediated control of steroidogenesis has not been explored. We used two CRISPR (clustered regularly interspaced short palindromic repeat)-Cas9 (CRISPR associated protein 9) knockout approaches to test the role of SCAP in steroidogenesis. Our results demonstrate that SCAP is required for progesterone production induced by concurrent inhibition of the cAMP phosphodiesterases PDE4 and PDE8. These inhibitors increased SCAP phosphorylation, SREBP2 activation, and subsequent expression of cholesterol biosynthetic genes, whereas SCAP deficiency largely prevented these effects. Reexpression of SCAP in SCAP-deficient cells restored SREBP2 protein expression and partially restored steroidogenic responses, confirming the requirement of SCAP-SREBP2 in steroidogenesis. Inhibitors of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase and isoprenylation attenuated, whereas exogenously provided cholesterol augmented, PDE inhibitor-induced steroidogenesis, suggesting that the cholesterol substrate needed for steroidogenesis is provided by both de novo synthesis and isoprenylation-dependent mechanisms.Overall, these results demonstrate a novel role for LH/cAMP in SCAP/ SREBP activation and subsequent regulation of steroidogenesis.

GDF15-Mediated Cholesterol Metabolism Promotes EMT and Metastasis in Esophageal Cancer

“…We observed an interaction between GDF15 and SCAP (Fig.3A-3B). TGFβ1 has been reported to activate SREBF2 in kidney mesangial cells, and SREBF2 activation was dependent on SCAP [29,30]. In this study, knockdown of GDF15 decreased expression of SCAP, SREBF2, and HMGCR in siRNA-GDF15 ESCCs (Fig.3C), while SCAP overexpression could increase SREBF2 and HMGCR expression levels (Fig.4A) and reverse the migration, invasion, and EMT of GDF15-siRNA ESCCs (Fig.4B-4D).…”

SCAP Mediated GDF15-Induced Invasion and EMT of Esophageal Cancer

“…However, the role of GDF15 in the invasion and metastasis of EC remains poorly understood. Both TGFβ1 and GDF15 belongs to TGF-β superfamily, TGFβ1 was reported to activate SREBP2 in kidney mesangial cells, SREBF2 activation was dependent on SCAP ( 11 , 12 ), SCAP or SREBPs promoted tumor progression in various cancer ( 13 ). Therefore, we speculated that GDF15 may also regulate the invasion and metastasis of EC through SCAP/SREBF2 axis, which involved cholesterol synthesis and uptake.…”

“…TGFβ1 has been reported to activate the sterol regulatory element-binding protein 2 (SREBP2) in kidney mesangial cells, and SREBF2 activation was dependent on sterol regulatory element-binding protein cleavage-activating protein (SCAP) ( 11 , 12 ), inhibition of SCAP or SREBPs significantly suppressed tumor growth in various cancer ( 13 ). As a divergent member of the TGF-β superfamily, GDF15 may also promote the progression of EC through SCAP/SREBPs pathway.…”

An in vitro test system for evaluation of SCAP–SREBP pathway inhibitory activities of Traditional Chinese Medicines

“…10,16,32 Targeting SREBPs pathway critical for cholesterol biosynthesis provides an promising strategy to improve therapeutic option of lipid metabolic diseases. 1,14,15 In this study, we established a stable HepG2 cell line transfected with a vector containing the human pGL3-promoter coupled to rey luciferase reporter gene. The activity of luciferase varies with the expression levels of SREBPs in the transfected cells.…”

“…[11][12][13] Masami Shimizu-Albergine et al demonstrated that SCAP/SREBP pathway was required for maximal steroid hormone biosynthesis. 14 Tang et al suggested that botulin could be a promising lead compound for treatment of hyperlipidemia by inhibition SREBP pathway. 15 Inhibition of SREBP pathway could be employed as an alternative strategy to treat metabolic diseases.…”