RESUMO
Pyroglutamylated RFamide peptide (QRFP), an important regulator of metabolism and energy homeostasis, has orexigenic effects. QRFP acts via a specific receptor, Gpr103. Gpr103 mRNA is expressed in the rat hypothalamic paraventricular nucleus (PVN). In the PVN, corticotropin-releasing factor (CRF), which plays a central role in regulating the stress response and is produced in response to stress, stimulates the release of adrenocorticotropic hormone from the anterior pituitary. We hypothesized that QRFP regulates CRF gene expression directly in the hypothalamus, and thus examined the direct effect of QRFP on the promoter activity and mRNA levels of CRF in hypothalamic cells. To examine these pathways, we used hypothalamic 4B cells, a homologous PVN neuronal cell line. Gpr103a and Gpr103b mRNA, and Gpr103 (a and b) proteins were expressed in the hypothalamic cells. The Gpr103 mRNA and protein levels were increased by QRFP. QRFP also stimulated CRF mRNA levels and CRF promoter activity directly in 4B cells following their transfection with the CRF promoter. The protein kinase A (PKA) and protein kinase C (PKC) pathways were involved in the QRFP-induced increases in CRF promoter activity. QRFP stimulated cAMP response element-binding protein (CREB) phosphorylation. CREB phosphorylation was inhibited by a PKC inhibitor. PKC-dependent signaling would be upstream of the CREB phosphorylation. Thus, QRFP-dependent pathways are involved in the regulation of CRF gene expression in the hypothalamus.
Assuntos
Hormônio Liberador da Corticotropina/genética , Hipotálamo/efeitos dos fármacos , Hipotálamo/metabolismo , Neuropeptídeos/farmacologia , Animais , Linhagem Celular , Hormônio Liberador da Corticotropina/metabolismo , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Neuropeptídeos/metabolismo , Fosforilação/efeitos dos fármacos , Regiões Promotoras Genéticas/efeitos dos fármacos , Ácido Pirrolidonocarboxílico/metabolismo , Ratos , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/genéticaRESUMO
BACKGROUND: A peptidyl prolyl cis/trans isomerase, Pin1, regulates insulin signal transduction. Pin1 reduces responses to insulin stimulation by binding CRTC2 (CREB-regulated transcriptional co-activator 2) and PPARγ (peroxisome prolifereator- activated receptor γ), but conversely enhances insulin signaling by binding IRS-1 (insulin receptor substrate-1), Akt kinase, and Smad3. Therefore, it is still unclear whether Pin1 inhibits or enhances adipose cell differentiation. METHODOLOGY/PRINCIPAL FINDINGS: Pin1(-/-) and wild-type mice were fed with high fat diets and adipose tissue weight was measured. Compared to wild-type mice, Pin1(-/-) mice had lower adipose tissue weight, while the weight of other tissues was similar. Mouse embryo fibroblasts (MEFs), prepared from both groups of mice, were induced to differentiate into adipose cells by stimulation with insulin. However, the rate of differentiation of MEFs from Pin1(-/-) mice was less than that of MEFs from wild-type mice. The rate of insulin-induced MEF cell differentiation in Pin1(-/-) mice was restored by increasing expression of Pin1. We found that Pin1 binds to phosphoThr172- and phosphoSer271-Pro sites in CREB suppress the activity in COS-7 cells. CONCLUSION AND SIGNIFICANCE: Pin1 enhanced the uptake of triglycerides and the differentiation of MEF cells into adipose cells in response to insulin stimulation. Results of this study suggest that Pin1 down-regulation could be a potential approach in obesity-related dysfunctions, such as high blood pressure, diabetes, non-alcoholic steatohepatitis.