RESUMO
CD38 enzymatic activity regulates NAD+ and cADPR levels in mammalian tissues, and therefore has a prominent role in cellular metabolism and calcium homeostasis. Consequently, it is reasonable to hypothesize about its involvement in cardiovascular physiology as well as in heart related pathological conditions. AIM: To investigate the role of CD38 in cardiovascular performance, and its involvement in cardiac electrophysiology and calcium-handling. METHODS AND RESULTS: When submitted to a treadmill exhaustion test, a way of evaluating cardiovascular performance, adult male CD38KO mice showed better exercise capacity. This benefit was also obtained in genetically modified mice with catalytically inactive (CI) CD38 and in WT mice treated with antibody 68 (Ab68) which blocks CD38 activity. Hearts from these 3 groups (CD38KO, CD38CI and Ab68) showed increased NAD+ levels. When CD38KO mice were treated with FK866 which inhibits NAD+ biosynthesis, exercise capacity as well as NAD+ in heart tissue decreased to WT levels. Electrocardiograms of conscious unrestrained CD38KO and CD38CI mice showed lower basal heart rates and higher heart rate variability than WT mice. Although inactivation of CD38 in mice resulted in increased SERCA2a expression in the heart, the frequency of spontaneous calcium release from the sarcoplasmic reticulum under stressful conditions (high extracellular calcium concentration) was lower in CD38KO ventricular myocytes. When mice were challenged with caffeine-epinephrine, CD38KO mice had a lower incidence of bidirectional ventricular tachycardia when compared to WT ones. CONCLUSION: CD38 inhibition improves exercise performance by regulating NAD+ homeostasis. CD38 is involved in cardiovascular function since its genetic ablation decreases basal heart rate, increases heart rate variability and alters calcium handling in a way that protects mice from developing catecholamine induced ventricular arrhythmias.
Assuntos
ADP-Ribosil Ciclase 1/metabolismo , Cálcio , Glicoproteínas de Membrana/metabolismo , NAD , ADP-Ribosil Ciclase 1/genética , Animais , Arritmias Cardíacas/etiologia , Arritmias Cardíacas/metabolismo , Cálcio/metabolismo , Catecolaminas/metabolismo , Tolerância ao Exercício , Frequência Cardíaca , Masculino , Mamíferos/metabolismo , Camundongos , Miócitos Cardíacos/metabolismo , NAD/metabolismoRESUMO
The protein Deleted in Breast Cancer-1 is a regulator of several transcription factors and epigenetic regulators, including HDAC3, Rev-erb-alpha, PARP1 and SIRT1. It is well known that DBC1 regulates its targets, including SIRT1, by protein-protein interaction. However, little is known about how DBC1 biological activity is regulated. In this work, we show that in quiescent cells DBC1 is proteolytically cleaved, producing a protein (DN-DBC1) that misses the S1-like domain and no longer binds to SIRT1. DN-DBC1 is also found in vivo in mouse and human tissues. Interestingly, DN-DBC1 is cleared once quiescent cells re-enter to the cell cycle. Using a model of liver regeneration after partial hepatectomy, we found that DN-DBC1 is down-regulated in vivo during regeneration. In fact, WT mice show a decrease in SIRT1 activity during liver regeneration, coincidentally with DN-DBC1 downregulation and the appearance of full length DBC1. This effect on SIRT1 activity was not observed in DBC1 KO mice. Finally, we found that DBC1 KO mice have altered cell cycle progression and liver regeneration after partial hepatectomy, suggesting that DBC1/DN-DBC1 transitions play a role in normal cell cycle progression in vivo after cells leave quiescence. We propose that quiescent cells express DN-DBC1, which either replaces or coexist with the full-length protein, and that restoring of DBC1 is required for normal cell cycle progression in vitro and in vivo. Our results describe for the first time in vivo a naturally occurring form of DBC1, which does not bind SIRT1 and is dynamically regulated, thus contributing to redefine the knowledge about its function.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/química , Proteínas Adaptadoras de Transdução de Sinal/genética , Técnicas de Inativação de Genes , Proteínas Adaptadoras de Transdução de Sinal/deficiência , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Animais , Ciclo Celular/genética , Humanos , Regeneração Hepática/genética , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Peso Molecular , Ligação Proteica/genética , Domínios Proteicos , Proteólise , Sirtuína 1/metabolismoRESUMO
Obesity is often regarded as the primary cause of metabolic syndrome. However, many lines of evidence suggest that obesity may develop as a protective mechanism against tissue damage during caloric surplus and that it is only when the maximum fat accumulation capacity is reached and fatty acid spillover occurs into to peripheral tissues that metabolic diseases develop. In this regard, identifying the molecular mechanisms that modulate adipocyte fat accumulation and fatty acid spillover is imperative. Here we identify the deleted in breast cancer 1 (DBC1) protein as a key regulator of fat storage capacity of adipocytes. We found that knockout (KO) of DBC1 facilitated fat cell differentiation and lipid accumulation and increased fat storage capacity of adipocytes in vitro and in vivo. This effect resulted in a "healthy obesity" phenotype. DBC1 KO mice fed a high-fat diet, although obese, remained insulin sensitive, had lower free fatty acid in plasma, were protected against atherosclerosis and liver steatosis, and lived longer. We propose that DBC1 is part of the molecular machinery that regulates fat storage capacity in adipocytes and participates in the "turn-off" switch that limits adipocyte fat accumulation and leads to fat spillover into peripheral tissues, leading to the deleterious effects of caloric surplus.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Adipócitos/metabolismo , Aterosclerose/metabolismo , Células Endoteliais/metabolismo , Síndrome Metabólica/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Adipócitos/citologia , Animais , Aorta/citologia , Aterosclerose/genética , Diferenciação Celular/fisiologia , Células Cultivadas , Células Endoteliais/citologia , Ácidos Graxos não Esterificados/sangue , Fígado Gorduroso/genética , Fígado Gorduroso/metabolismo , Feminino , Glicerol/metabolismo , Humanos , Síndrome Metabólica/genética , Camundongos Knockout , Obesidade/genética , Obesidade/metabolismo , Fenótipo , Sirtuína 1/metabolismo , Células-Tronco/citologia , Células Estromais/citologiaRESUMO
Chronic obesity leads to inflammation, tissue dysfunction, and cellular senescence. It was proposed that cellular senescence during obesity and aging drives inflammation and dysfunction. Consistent with this, clearance of senescent cells increases healthspan in progeroid mice. Here, we show that the protein Deleted in Breast Cancer-1 (DBC1) regulates cellular senescence during obesity. Deletion of DBC1 protects preadipocytes against cellular senescence and senescence-driven inflammation. Furthermore, we show protection against cellular senescence in DBC1 KO mice during obesity. Finally, we found that DBC1 participates in the onset of cellular senescence in response to cell damage by mechanism that involves binding and inhibition of HDAC3. We propose that by regulating HDAC3 activity during cellular damage, DBC1 participates in the fate decision that leads to the establishment of cellular senescence and consequently to inflammation and tissue dysfunction during obesity.