RESUMO
Hormone-sensitive lipase (HSL) hydrolyzes triglyceride (TG) in adipose tissue. HSL is also expressed in heart. To explore the actions of cardiac HSL, heart-specific, tetracycline (Tc)-controlled HSL-overexpressing mice were generated. Tc-responsive element-HSL transgenic (Tg) mice were generated and crossed with myosin heavy chain (MHC)alpha-tTA Tg mice, which express the Tc-responsive transactivator (tTA) in the heart. The double-Tg mice (MHC-HSL) were maintained with doxycycline (Dox) to suppress Tg HSL. Upon removal of Dox, cardiac HSL activity and protein increased 12- and 8-fold, respectively, and the expression was heart specific. Although cardiac TG content increased twofold in control mice after an overnight fast, it did not increase in HSL-induced mice. Electron microscopy showed numerous lipid droplets in the myocardium of fasted control mice, whereas fasted HSL-induced mice showed virtually no droplets. Microarray analysis showed altered expression of cardiac genes for fatty acid oxidation, transcription factors, signaling molecules, cytoskeletal proteins, and histocompatibility antigens in HSL-induced mice. Thus cardiac HSL plays a role in controlling accumulation of triglyceride droplets and can affect the expression of a number of cardiac genes.
Assuntos
Metabolismo dos Lipídeos , Miocárdio/enzimologia , Esterol Esterase/genética , Esterol Esterase/metabolismo , Animais , Cruzamentos Genéticos , Primers do DNA , Doxiciclina/farmacologia , Ingestão de Alimentos , Indução Enzimática , Jejum , Regulação Enzimológica da Expressão Gênica , Genótipo , Ventrículos do Coração , Lipídeos/sangue , Fígado/enzimologia , Pulmão/enzimologia , Masculino , Camundongos , Camundongos Transgênicos , Músculo Esquelético/enzimologia , Cadeias Pesadas de Miosina/genética , Análise de Sequência com Séries de Oligonucleotídeos , Especificidade de Órgãos , Reação em Cadeia da Polimerase , Ratos , Proteínas Recombinantes de Fusão/metabolismo , Baço/enzimologia , Esterol Esterase/biossíntese , Testículo/enzimologia , Transativadores/genéticaRESUMO
Mammalian mitochondria are known to proliferate in response to several stimuli. Proliferation requires an increase in expression of genes encoding proteins involved in mitochondrial biogenesis, as well as in the replication and expression of mitochondrial DNA (mtDNA). In contrast, we report that inhibiting mitochondrial protein synthesis causes a modulation in mtDNA gene expression without the concomitant increase in proliferative markers. Further, inhibition results in the production of a previously unidentified light-strand mitochondrial RNA that spans the entire displacement loop, the function of which is currently unknown.
Assuntos
DNA Mitocondrial/biossíntese , Mitocôndrias Hepáticas/efeitos dos fármacos , Inibidores da Síntese de Proteínas/farmacologia , RNA/biossíntese , Sequência de Bases , Replicação do DNA/efeitos dos fármacos , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Mitocôndrias Hepáticas/genética , Mitocôndrias Hepáticas/metabolismo , Dados de Sequência Molecular , Fatores Nucleares Respiratórios , Biossíntese de Proteínas/efeitos dos fármacos , RNA/genética , RNA/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Mitocondrial , Tianfenicol/farmacologia , Transativadores/genética , Transativadores/metabolismo , Transcrição Gênica/efeitos dos fármacos , Células Tumorais CultivadasRESUMO
The mechanism of mitochondrial transcription is well documented although the method of regulation remains obscure. The mitochondrial transcription-termination complex, mTERF, holds a key position in determining the fate of heavy-strand promotor-initiated transcripts and has been suggested as a candidate in the regulation of mitochondrial DNA (mtDNA) transcription. We report here the first example of a modulation of mTERF-complex binding activity concomitant with a differential mtDNA transcription rate. We suggest that these observations are indicative of a method of intra-organellar transcriptional fine tuning.
