Protein stabilization by RSUME accounts for PTTG pituitary tumor abundance and oncogenicity.

Increased levels of the proto-oncogene pituitary tumor-transforming gene 1 (PTTG) have been repeatedly reported in several human solid tumors, especially in endocrine-related tumors such as pituitary adenomas. Securin PTTG has a critical role in pituitary tumorigenesis. However, the cause of upregulation has not been found yet, despite analyses made at the gene, promoter and mRNA level that show that no mutations, epigenetic modifications or other mechanisms that deregulate its expression may explain its overexpression and action as an oncogene. We describe that high PTTG protein levels are induced by the RWD-containing sumoylation enhancer (RWDD3 or RSUME), a protein originally identified in the same pituitary tumor cell line in which PTTG was also cloned. We demonstrate that PTTG and RSUME have a positive expression correlation in human pituitary adenomas. RSUME increases PTTG protein in pituitary tumor cell lines, prolongs the half-life of PTTG protein and regulates the PTTG induction by estradiol. As a consequence, RSUME enhances PTTG transcription factor and securin activities. PTTG hyperactivity on the cell cycle resulted in recurrent and unequal divisions without cytokinesis, and the consequential appearance of aneuploidies and multinucleated cells in the tumor. RSUME knockdown diminishes securin PTTG and reduces its tumorigenic potential in a xenograft mouse model. Taken together, our findings show that PTTG high protein steady state levels account for PTTG tumor abundance and demonstrate a critical role of RSUME in this process in pituitary tumor cells.

The activity of the glucocorticoid receptor is regulated by SUMO conjugation to FKBP51.

FK506-binding protein 51 (FKBP51) regulates the activity of the glucocorticoid receptor (GR), and is therefore a key mediator of the biological actions of glucocorticoids. However, the understanding of the molecular mechanisms that govern its activity remains limited. Here, we uncover a novel regulatory switch for GR activity by the post-translational modification of FKBP51 with small ubiquitin-like modifier (SUMO). The major SUMO-attachment site, lysine 422, is required for FKBP51-mediated inhibition of GR activity in hippocampal neuronal cells. Importantly, impairment of SUMO conjugation to FKBP51 impacts on GR-dependent neuronal signaling and differentiation. We demonstrate that SUMO conjugation to FKBP51 is enhanced by the E3 ligase PIAS4 and by environmental stresses such as heat shock, which impact on GR-dependent transcription. SUMO conjugation to FKBP51 regulates GR hormone-binding affinity and nuclear translocation by promoting FKBP51 interaction within the GR complex. SUMOylation-deficient FKBP51 fails to interact with Hsp90 and GR thus facilitating the recruitment of the closely related protein, FKBP52, which enhances GR transcriptional activity. Moreover, we show that the modification of FKBP51 with SUMO modulates its binding to Hsp90. Our data establish SUMO conjugation as a novel regulatory mechanism in the Hsp90 cochaperone activity of FKBP51 with a functional impact on GR signaling in a neuronal context.

[Stress-responsive systems in the rat pancreas upon long-term gastric hypochlorhydria and administration of multiprobiotic "Symbiter"].

The intensity of free-radical processes upon long-term omeprazole-induced hypoacidity in the rat pancreas was investigated. Significant violation of oxidative-antioxidative balance in pancreatic tissue upon gastric hypochlorhydria was established: overproduction of superoxide anion, quantitative changes of lipid functional groups, increased level of lipid peroxidation products, augmentation of xanthine oxidase, superoxide dismutase and glutathione transferase activity, as well as depletion of catalase, glutathione peroxidase activity and reduced glutathione content. The inflected expression of Cckbr gene in the rat pancreas upon these conditions was also observed, thus suggesting an increased risk of pathological changes development in the gland. Abovementioned parameters were only partially restored to control values in the case of simultaneous administration of multiprobiotic "Symbiter" with omeprazole, thus indicating the ability of this preparation to efficiently counteract the development of oxidative damages in pancreatic tissues upon long-term hypoacidic conditions.

[Influence of oxidative stress on the level of genes expression Tgfb1 and Hgf in rat liver upon long-term gastric hypochlorhydria and administration of multiprobiotic Symbiter].

Free-radical processes upon long-term omeprazole-induced gastric hypochlorhydria in the rat liver were researched. Intensification of oxidative processes in the liver tissue upon gastric hypoacid state was established: overproduction of superoxide anion, hydrogen peroxide, the quantitative changes of lipid functional groups, increased level of lipid peroxidation products, and augmentation of xanthine oxidase activity. The expression of Tgfb1 gene increased, while the expression of Hgf gene was not detected upon long-term suppression of gastric acid secretion of hydrochloric acid by omeprazole that indicated possible development of liver fibrosis. Abovementioned parameters were only partially restored to control values in the case of simultaneous administration of multiprobiotic "Symbiter acidophilic" concentrated with omeprazole, thus indicating the ability of this preparation to counteract the development of oxidative damages in liver tissues upon long-term gastric hypoacidic conditions.

Amygdaloid pERK1/2 in corticotropin-releasing hormone overexpressing mice under basal and acute stress conditions.

Corticotropin-releasing hormone (CRH) coordinates neuroendocrine and behavioral adaptations to stress. Acute CRH administration in vivo activates extracellular signal-regulated kinase 1/2 (ERK1/2) in limbic brain areas, acting through the CRH receptor type 1 (CRH-R1). In the present study, we used CRH-COE-Cam mice that overexpress CRH in limbic-restricted areas, to analyze the effect of chronic CRH overexpression on ERK1/2 activation. By immunohistochemistry and confocal microscopy analysis we found that pERK1/2 levels in the basolateral amygdala (BLA) were similar in control and CRH overexpressing mice under basal conditions. Acute stress caused comparably increased levels of corticosterone in both control (CRH-COEcon-Cam) and CRH overexpressing (CRH-COEhom-Cam) animals. CRH-COEhom-Cam mice after stress showed reduced pERK1/2 immunoreactivity in the BLA compared to CRH-COEhom-Cam animals under basal conditions. Radioligand binding and in situ hybridization revealed higher density of CRH-R1 in the amygdala of CRH-COEhom mice under basal conditions compared to control littermates. A significant reduction of the receptor levels was observed in this area after acute stress, suggesting that stress may trigger CRH-R1 internalization/downregulation in these CRH overexpressing mice. Chronic CRH overexpression leads to reduced ERK1/2 activation in response to acute stress in the BLA.