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Autoregulation of pituitary corticotroph SOCS-3 expression: characterization of the murine SOCS-3 promoter.

ABSTRACT: Pituitary corticotroph SOCS-3 is a novel intracellular regulator of leukemia inhibitory factor (LIF)-mediated proopiomelanocortin gene expression and adrenocorticotropic hormone (ACTH) secretion, inhibiting LIF-activated Janus kinase-signal transducers and activators of transcription (STAT) signaling in a negative autoregulatory loop. We now demonstrate in corticotroph AtT-20 cells that LIF-stimulated endogenous SOCS-3 mRNA expression is blocked in stable transfectants of SOCS-3 wild type or in dominant negative STAT-3 mutants, respectively. We characterized approximately 3.8-kb genomic 5' sequence of murine SOCS-3, including approximately 2.9-kb sequence upstream of the transcription start site (+1), which was determined by 5' rapid amplification of cDNA ends and RNase protection assay. Different 5' constructs were cloned into the pGL3Basic vector, and luciferase activity was assayed in transiently transfected ACTH-secreting corticotroph AtT-20 cells. A STAT-1/STAT-3 binding element, located at nucleotides -72 to -64, was essential for LIF stimulation of SOCS-3 promoter activity. LIF induced 10-fold increased luciferase activity in a wild-type construct spanning -2757 to +929 bases. However, deletion or point mutation of the STAT-1/STAT-3 binding element abrogated LIF action (2- to 3-fold). Electrophoretic mobility-shift assay analysis confirmed specific binding of STAT-1 and STAT-3 to this region. These results characterize the genomic 5' region of murine SOCS-3 and identify an important STAT-1/STAT-3 binding element therein. Thus, LIF-stimulated SOCS-3 gene expression is at least in part mediated by STAT-3 and STAT-1. The cytokine inhibitor SOCS-3 acts in a negative loop to autoregulate its own gene expression, thus limiting its accumulation in the corticotroph cell. These results demonstrate a mechanism for corticotroph plasticity with rapid "on" and "off" ACTH induction in response to neuro-immuno-endocrine stimuli, such as LIF.

SUBMITTER: Auernhammer CJ

PROVIDER: S-EPMC22025 | biostudies-literature | 1999 Jun

REPOSITORIES: biostudies-literature

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Autoregulation of pituitary corticotroph SOCS-3 expression: characterization of the murine SOCS-3 promoter.

Auernhammer C J CJ Bousquet C C Melmed S S

Proceedings of the National Academy of Sciences of the United States of America 19990601 12

Pituitary corticotroph SOCS-3 is a novel intracellular regulator of leukemia inhibitory factor (LIF)-mediated proopiomelanocortin gene expression and adrenocorticotropic hormone (ACTH) secretion, inhibiting LIF-activated Janus kinase-signal transducers and activators of transcription (STAT) signaling in a negative autoregulatory loop. We now demonstrate in corticotroph AtT-20 cells that LIF-stimulated endogenous SOCS-3 mRNA expression is blocked in stable transfectants of SOCS-3 wild type or in ...[more]

PMID: 10359822

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Project description:Objective: Epidermal growth factor receptor (EGFR) has been found to localize in several human neoplasms and has been shown to have a significant correlation with adenomaigenesis and patient prognosis. EGFR is also overexpressed in pituitary corticotroph adenomas. However, its clinical significance and relationship with tumor behavior, especially tumor recurrence status, remain obscure. The purpose of the present study was to identify the expression patterns of EGFR and its downstream signaling pathway molecules in pituitary corticotroph adenomas and to investigate the association of EGFR with clinicopathological characteristics and tumor recurrence. Methods: Fifty-two sporadic pituitary adenoma specimens and six normal pituitary glands were collected. The expression levels of EGFR and its downstream signaling molecules in each sample were evaluated and quantified using immunohistochemistry and Western blot. The relationships of EGFR expression with clinicopathological characteristics and tumor recurrence status were analyzed. Results: EGFR was overexpressed in 55.8% of the pituitary corticotroph adenomas and in 1 of 6 of the normal adenohypophysial tissues. The expression degree was significantly higher in pituitary corticotroph adenomas than in normal adenohypophysial tissues. In EGFR-overexpressing adenomas, the downstream pathway phosphorylated Erk (p-Erk) was also significantly activated. Moreover, the expression levels of EGFR were positively correlated with the adrenocorticotropic hormone (ACTH) and cortisol levels but were not correlated with age, sex or symptom duration. The expression levels of EGFR, phosphorylated EGFR (p-EGFR) and p-Erk were significantly up-regulated in the recurrent adenoma group compared with those in the non-recurrent adenoma group (all p < 0.05). The expression levels of EGFR were strongly correlated with the recurrence-free interval (p = 0.005, CC = -0.31). Conclusion: The expression levels of EGFR and its downstream pathway components were significantly increased in pituitary corticotroph adenomas compared to the levels in normal adenohypophysial tissues. EGFR expression levels were positively associated with the ACTH and cortisol levels and with tumor recurrence status. Pituitary corticotroph adenomas with high EGFR expression levels were correlated with an increased recurrence rate and a decreased recurrence-free interval. EGFR could be used as a promising biomarker for predicting pituitary corticotroph tumor recurrence.

Dataset Information

Autoregulation of pituitary corticotroph SOCS-3 expression: characterization of the murine SOCS-3 promoter.

Publications

Autoregulation of pituitary corticotroph SOCS-3 expression: characterization of the murine SOCS-3 promoter.

Similar Datasets

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