Transcriptional regulation of transcriptional Mediator complexes in cardiovascular development and disease.

During the development of the mammalian cardiovascular system, the formation of a mature and fully functional cardiovascular system needs the fine coordination of the morphogenesis of various molecules, cells, tissues, and organs. Abnormalities in these processes usually lead to serious congenital heart defects. The determination and maintenance of cell fate in multicellular organisms depend to a large extent on the precise timing and control of RNA polymerase II (Pol II) transcription, and the transcription Mediator complex plays an irreplaceable role in the Pol II transcription process. Mediator is an evolutionarily conserved multi-subunit protein complex, including four parts: head, middle, tail, and kinase. It is a functional bridge between transcription factors and basic transcription machines. In recent years, due to the key role of Mediator in the transcriptional regulation of gene expression, many of human heart diseases have been confirmed to be related to specific Mediator gene mutations, such as heart valve defects, translocation of the great arteries, DiGeorge syndrome and some cardiovascular diseases related to energy homeostasis. In this review, we summarize the role of Mediator in cardiovascular development and disease, focusing on the role of Mediator in the development of cardiovascular disease, and provides a broad idea for the research on Mediator-related cardiovascular system development and diseases.

Beta-arrestin-1 protein represses adipogenesis and inflammatory responses through its interaction with peroxisome proliferator-activated receptor-gamma (PPARgamma).

One of the master regulators of adipogenesis and macrophage function is peroxisome proliferator-activated receptor-γ (PPARγ). Here, we report that a deficiency of ß-arrestin-1 expression affects PPARγ-mediated expression of lipid metabolic genes and inflammatory genes. Further mechanistic studies revealed that ß-arrestin-1 interacts with PPARγ. ß-Arrestin-1 suppressed the formation of a complex between PPARγ and 9-cis-retinoic acid receptor-α through its direct interaction with PPARγ. The interaction of ß-arrestin-1 with PPARγ repressed PPARγ/9-cis-retinoic acid receptor-α function but promoted PPARγ/nuclear receptor corepressor function in PPARγ-mediated adipogenesis and inflammatory gene expression. Consistent with these results, a deficiency of ß-arrestin-1 binding to PPARγ abolished its suppression of PPARγ-dependent adipogenesis and inflammatory responses. These results indicate that the regulation of PPARγ by ß-arrestin-1 is critical. Furthermore, in vivo expression of ß-arrestin-1 (but not the binding-deficient mutant) significantly repressed adipogenesis, macrophage infiltration, and diet-induced obesity and improved glucose tolerance and systemic insulin sensitivity. Therefore, our findings not only reveal a molecular mechanism for the modulation of obesity by ß-arrestin-1 but also suggest a potential tactical approach against obesity and its associated metabolic disorders.

Beta-arrestin-1 protein represses diet-induced obesity.

Diet-related obesity is a major metabolic disorder. Excessive fat mass is associated with type 2 diabetes, hepatic steatosis, and arteriosclerosis. Dysregulation of lipid metabolism and adipose tissue function contributes to diet-induced obesity. Here, we report that ß-arrestin-1 knock-out mice are susceptible to diet-induced obesity. Knock-out of the gene encoding ß-arrestin-1 caused increased fat mass accumulation and decreased whole-body insulin sensitivity in mice fed a high-fat diet. In ß-arrestin-1 knock-out mice, we observed disrupted food intake and energy expenditure and increased macrophage infiltration in white adipose tissue. At the molecular level, ß-arrestin-1 deficiency affected the expression of many lipid metabolic genes and inflammatory genes in adipose tissue. Consistently, transgenic overexpression of ß-arrestin-1 repressed diet-induced obesity and improved glucose tolerance and systemic insulin sensitivity. Thus, our findings reveal that ß-arrestin-1 plays a role in metabolism regulation.