RESUMO
Conversion of mesenchymal stem cells into terminally differentiated adipocytes progresses sequentially through regulated transcriptional steps. While it is clear that the late phases of adipocyte maturation are governed by the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ), less is known about the transcriptional control of the initial stages of differentiation. To identify early regulators, we performed a small interfering RNA (siRNA) screen of Forkhead-box genes in adipocytes and show here for the first time that the winged helix factor Foxa3 promotes adipocyte differentiation by cooperating with C/EBPß and -δ to transcriptionally induce PPARγ expression. Furthermore, we demonstrate that mice with genetic ablation of Foxa3 have a selective decrease in epididymal fat depot and a cell-autonomous defect to induce PPARγ specifically in their visceral adipocytes. In obese subjects, FOXA3 is differentially expressed in visceral and subcutaneous adipose depots. Overall, our study implicates Foxa3 in the regulation of adipocyte differentiation and depot-selective adipose tissue expansion.
Assuntos
Adipócitos/citologia , Adipogenia , Tecido Adiposo/crescimento & desenvolvimento , Fator 3-gama Nuclear de Hepatócito/metabolismo , PPAR gama/genética , Ativação Transcricional , Células 3T3-L1 , Adipócitos/metabolismo , Tecido Adiposo/metabolismo , Adulto , Animais , Proteína beta Intensificadora de Ligação a CCAAT/metabolismo , Proteína delta de Ligação ao Facilitador CCAAT/metabolismo , Dieta Hiperlipídica , Feminino , Deleção de Genes , Regulação da Expressão Gênica no Desenvolvimento , Fator 3-gama Nuclear de Hepatócito/genética , Humanos , Resistência à Insulina/genética , Camundongos , Camundongos Endogâmicos C57BL , Pessoa de Meia-Idade , Obesidade/genética , Obesidade/metabolismo , PPAR gama/metabolismo , Interferência de RNA , Adulto JovemRESUMO
The serum and glucocorticoid-inducible kinase 1 (SGK1) is an inducible kinase the physiological function of which has been characterized primarily in the kidney. Here we show that SGK1 is expressed in white adipose tissue and that its levels are induced in the conversion of preadipocytes into fat cells. Adipocyte differentiation is significantly diminished via small interfering RNA inhibition of endogenous SGK1 expression, whereas ectopic expression of SGK1 in mesenchymal precursor cells promotes adipogenesis. The SGK1-mediated phenotypic effects on differentiation parallel changes in the mRNA levels for critical regulators and markers of adipogenesis, such as peroxisome proliferator-activated receptor gamma, CCAAT enhancer binding protein alpha, and fatty acid binding protein aP2. We demonstrate that SGK1 affects differentiation by direct phosphorylation of Foxo1, thereby changing its cellular localization from the nucleus to the cytosol. In addition we show that SGK1-/- cells are unable to relocalize Foxo1 to the cytosol in response to dexamethasone. Together these results show that SGK1 influences adipocyte differentiation by regulating Foxo1 phosphorylation and reveal a potentially important function for this kinase in the control of fat mass and function.
Assuntos
Adipócitos Brancos/metabolismo , Adipogenia , Fatores de Transcrição Forkhead/metabolismo , Glucocorticoides/farmacologia , Proteínas Imediatamente Precoces/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Células 3T3-L1 , Adipócitos Brancos/citologia , Adipócitos Brancos/efeitos dos fármacos , Adipogenia/efeitos dos fármacos , Adipogenia/genética , Animais , Animais Geneticamente Modificados , Biomarcadores/metabolismo , Linhagem Celular , Células Cultivadas , Embrião de Mamíferos , Feminino , Fibroblastos , Proteína Forkhead Box O1 , Fatores de Transcrição Forkhead/genética , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Humanos , Proteínas Imediatamente Precoces/antagonistas & inibidores , Proteínas Imediatamente Precoces/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Especificidade de Órgãos , Fosforilação/efeitos dos fármacos , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Serina-Treonina Quinases/genética , Transporte Proteico/efeitos dos fármacos , RNA Mensageiro/metabolismo , RNA Interferente PequenoRESUMO
Cytoplasmic phospholipase A2 (cPLA2) has a key role in prostaglandin production. The role of cPLA2 in intestinal tumorigenesis has been suggested, however, contradictory data are found in the literature. We evaluated cPLA2 and cyclooxygenase-2 (COX-2) protein expression in 65 colon carcinomas by immunohistochemistry, and in eight colorectal cancer cell lines by Western Blot. PGE2 production was evaluated by enzyme-immunoassay in the cell lines. We demonstrate that cPLA2 is overexpressed in approximately 50% of colon cancers and cell lines. cPLA2 expression is correlated with COX-2 expression. Both cPLA2 and COX-2 expressions are important in regard to PGE2 production. Our data suggest that cPLA2 might be involved in colon tumor development.
Assuntos
Adenocarcinoma/patologia , Neoplasias Colorretais/patologia , Ciclo-Oxigenase 2/genética , Dinoprostona/biossíntese , Fosfolipases A/genética , Adenocarcinoma/genética , Adenocarcinoma/metabolismo , Western Blotting , Células CACO-2 , Linhagem Celular Tumoral , Neoplasias Colorretais/genética , Neoplasias Colorretais/metabolismo , Ciclo-Oxigenase 2/metabolismo , Citoplasma/enzimologia , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Células HCT116 , Células HT29 , Humanos , Imuno-Histoquímica , Instabilidade de Microssatélites , Estadiamento de Neoplasias , Fosfolipases A/metabolismo , Fosfolipases A2 , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Emerging data indicate that serine proteases of the kallikrein family (KLK) are implicated in various human diseases, including carcinoma; however, kallikrein gene expression has never been investigated in lung cancer. Using RT-PCR and Western blotting, we demonstrated the expression of both KLK5 and KLK7, and their respective proteins (hK5 and hK7) in tumoral and nontumoral lung tissues. Quantitative gene expression was then analyzed in a cohort of 56 patients with non-small cell lung cancer by real-time RT-PCR. KLK5 expression is significantly more expressed in squamous cell carcinoma than in matched nonmalignant lung tissue (P=0.02), whereas expression of KLK7 was decreased in adenocarcinoma (P=0.003). Multivariate analysis revealed diverse correlations between the KLK5 and KLK7 expression levels in nonmalignant and malignant tissues, and clinical parameters, including histotype, metastatic status, and grade. Our findings provide new insight into kallikrein gene expression in hormone-independent carcinoma. Altogether, our results suggest that variability in KLK5 and KLK7 gene expression might be involved in lung tumorigenesis and useful for clinical purposes.
