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Orexins stimulate steroidogenic acute regulatory protein expression through multiple signaling pathways in human adrenal H295R cells.

ABSTRACT: Orexins mediate a variety of physiological processes, including feeding behavior, the circadian pathway, and cortisol secretion. Steroidogenesis is regulated by a variety of neuropeptides, and one of the key rate-limiting steps is cholesterol transport across the mitochondrial membrane by the steroidogenic acute regulatory protein (StAR). StAR expression can be regulated through several different signaling pathways. Despite the clear link between orexins and steroid production, the actions of the orexin family of hormones on steroid biosynthesis are not fully understood. We present data showing that 100 nm of both orexins A and B for 4 or 24 h significantly up-regulates StAR, in H295R pluripotent adrenocortical cells. We present the dose-dependent and time-dependent characteristics of StAR up-regulation at the protein level, showing significant increases after 4 h at a relatively low agonist concentration (1 nm). We have provided a key analysis of the precise G protein-coupled signaling pathways required for the up-regulation of StAR in response to orexins A and B. This has involved dominant-negative G protein analysis, and the direct inhibition of the protein kinase A, protein kinase C, ERK1/2, and p38 pathways. This shows a fundamental role for multiple G protein-coupled and MAPK-mediated signaling pathways leading to StAR expression. Antagonist analysis also showed that orexin effects on StAR were primarily, but not exclusively, acting through the orexin receptor type 1. This is the first study linking orexin action on StAR expression and comprehensively describes the signaling pathways involved in regulating the complexity of hormone biosynthesis.

SUBMITTER: Ramanjaneya M

PROVIDER: S-EPMC2488249 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Orexins stimulate steroidogenic acute regulatory protein expression through multiple signaling pathways in human adrenal H295R cells.

Ramanjaneya Manjunath M Conner Alex C AC Chen Jing J Stanfield Peter R PR Randeva Harpal S HS

Endocrinology 20080501 8

Orexins mediate a variety of physiological processes, including feeding behavior, the circadian pathway, and cortisol secretion. Steroidogenesis is regulated by a variety of neuropeptides, and one of the key rate-limiting steps is cholesterol transport across the mitochondrial membrane by the steroidogenic acute regulatory protein (StAR). StAR expression can be regulated through several different signaling pathways. Despite the clear link between orexins and steroid production, the actions of th ...[more]

PMID: 18450961

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Project description:Steroidogenic acute regulatory protein (Star) facilitates cholesterol transfer into the inner mitochondrial membrane in the acute and regulated production of steroid hormones. Mice lacking Star (Star-/-) share the phenotypes with patients with congenital lipoid adrenal hyperplasia such as compromised production of steroid hormones and florid accumulation of cholesterol esters in adrenal glands and gonads. To define specific patterns of molecular changes with disruption of Star, we performed a transcriptome analysis of steroidogenic cells in adrenal glands. We harvested adrenal glands at E17.5 or 18.5 from seven wild-type (Star+/+) mice or four Star-/- mice having the transgene targeting enhanced green fluorescent protein (eGFP) under the control of regulatory sequences of mouse Star gene. Steroidogenic cells were selectively isolated by fluorescent-activated cell sorting. The gene expression profile of the fluorescence-positive cells was obtained with Agilent Whole Mouse Genome Microarray and was confirmed by quantitative real-time PCR. We identified 961 and 622 genes that were significantly up-regulated and down-regulated, respectively, in Star-/- mice compared with Star+/+ mice (fold difference ≥2, p value of Student t test <0.05, and Benjamini-Hochberg false discovery rate of multiple comparison test <0.2). In Star-/- mice, expression levels of genes involved in cholesterol mobilization and efflux or immune response as antigen presenting cells were significantly increased, and transition from fetal to adult adrenocortical cells were significantly decreased, whereas those of genes related to steroid hormone biosynthesis or cholesterol biosynthesis and influx were not significantly changed. The trancriptome analysis revealed hitherto undescribed characteristic changes in adrenocortical cells and expanded our understanding of the pathophysiology of the steroidogenic cells with disruption of Star. Gene expression profiles of isolated adrenal steroidogenic cells were compared between seven wild-type mice and four knockout mice lacking steroidogenic acute regulatory protein at E17.5-18.5.

Dataset Information

Orexins stimulate steroidogenic acute regulatory protein expression through multiple signaling pathways in human adrenal H295R cells.

Publications

Orexins stimulate steroidogenic acute regulatory protein expression through multiple signaling pathways in human adrenal H295R cells.

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