E3 Ligase FBXW2 Is a New Therapeutic Target in Obesity and Atherosclerosis

Ubiquitous regulation of cerebrovascular diseases by ubiquitin-modifying enzymes

Cerebrovascular diseases (CVDs) are a major threat to global health. Elucidation of the molecular mechanisms underlying the pathology of CVDs is critical for the development of efficacious preventative and therapeutic approaches. Accumulating studies have highlighted the significance of ubiquitin-modifying enzymes (UMEs) in the regulation of CVDs. UMEs are a group of enzymes that orchestrate ubiquitination, a post-translational modification tightly involved in CVDs. Functionally, UMEs regulate multiple pathological processes in ischemic and hemorrhagic stroke, moyamoya disease, and atherosclerosis. Considering the important roles of UMEs in CVDs, they may become novel druggable targets for these diseases. Besides, techniques applying UMEs, such as proteolysis-targeting chimera and deubiquitinase-targeting chimera, may also revolutionize the therapy of CVDs in the future.

Targeting protein modifications in metabolic diseases: molecular mechanisms and targeted therapies

The ever-increasing prevalence of noncommunicable diseases (NCDs) represents a major public health burden worldwide. The most common form of NCD is metabolic diseases, which affect people of all ages and usually manifest their pathobiology through life-threatening cardiovascular complications. A comprehensive understanding of the pathobiology of metabolic diseases will generate novel targets for improved therapies across the common metabolic spectrum. Protein posttranslational modification (PTM) is an important term that refers to biochemical modification of specific amino acid residues in target proteins, which immensely increases the functional diversity of the proteome. The range of PTMs includes phosphorylation, acetylation, methylation, ubiquitination, SUMOylation, neddylation, glycosylation, palmitoylation, myristoylation, prenylation, cholesterylation, glutathionylation, S-nitrosylation, sulfhydration, citrullination, ADP ribosylation, and several novel PTMs. Here, we offer a comprehensive review of PTMs and their roles in common metabolic diseases and pathological consequences, including diabetes, obesity, fatty liver diseases, hyperlipidemia, and atherosclerosis. Building upon this framework, we afford a through description of proteins and pathways involved in metabolic diseases by focusing on PTM-based protein modifications, showcase the pharmaceutical intervention of PTMs in preclinical studies and clinical trials, and offer future perspectives. Fundamental research defining the mechanisms whereby PTMs of proteins regulate metabolic diseases will open new avenues for therapeutic intervention.

AMP-activated protein kinase α1 phosphorylates PHD2 to maintain systemic iron homeostasis

BACKGROUND

Iron is essential for all mammalian life, and either a deficiency or excess of iron can cause diseases. AMP-activated protein kinase (AMPK) is a critical regulator of metabolic homeostasis; however, it has not been established whether AMPK regulates iron metabolism.

METHODS

Iron, hepcidin and ferroportin levels were examined in mice with global and hepatocyte-specific knockout of AMPKα1 and AMPKα2. Primary AMPKα1 or AMPKα2 deleted hepatocytes were isolated and cultured in hypoxia condition to explore PHD2, HIF and hydroxylated HIF1α levels. We performed immunoprecipitation, in vitro AMPK kinase assay and site-direct mutant assay to detect phosphorylation sites of PHD2. We also obtained liver tissues from patients with anaemia of chronic disease undergoing surgery, AMPKα1 and hydroxylated HIF1α levels were measured by immunohistochemical analysis.

RESULTS

We found that mice with global deficiency of AMPKα1, but not AMPKα2, exhibited hypoferraemia as well as iron sequestration in the spleen and liver. Hepatocyte-specific, but not myeloid-specific, ablation of AMPKα1 also reduced serum iron levels in association with increased hepcidin and decreased ferroportin protein levels. Mechanistically, AMPKα1 directly phosphorylated prolyl hydroxylase domain-containing (PHD)2 at serines 61 and 136, which suppressed PHD2-dependent hydroxylation of hypoxia-inducible factor (HIF)1α and subsequent regulation of hepatic hepcidin-related iron signalling. Inhibition of PHD2 hydroxylation ameliorated abnormal iron metabolism in hepatic AMPKα1-deficient mice. Furthermore, we found hepatic AMPKα/PHD2/HIFα/ hepcidin axes were highly clinically relevant to anaemia of chronic disease.

CONCLUSION

In conclusion, these observations suggest that hepatic AMPKα1 has an essential role in maintaining iron homeostasis by PHD2-dependent regulation of hepcidin, thus providing a potentially promising approach for the treatment of iron disturbances in chronic diseases.

The Role of KH-Type Splicing Regulatory Protein (KSRP) for Immune Functions and Tumorigenesis

Post-transcriptional control of gene expression is one important mechanism that enables stringent and rapid modulation of cytokine, chemokines or growth factors expression, all relevant for immune or tumor cell function and communication. The RNA-binding protein KH-type splicing regulatory protein (KSRP) controls the mRNA stability of according genes by initiation of mRNA decay and inhibition of translation, and by enhancing the maturation of microRNAs. Therefore, KSRP plays a pivotal role in immune cell function and tumor progression. In this review, we summarize the current knowledge about KSRP with regard to the regulation of immunologically relevant targets, and the functional role of KSRP on immune responses and tumorigenesis. KSRP is involved in the control of myeloid hematopoiesis. Further, KSRP-mediated mRNA decay of pro-inflammatory factors is necessary to keep immune homeostasis. In case of infection, functional impairment of KSRP is important for the induction of robust immune responses. In this regard, KSRP seems to primarily dampen T helper cell 2 immune responses. In cancer, KSRP has often been associated with tumor growth and metastasis. In summary, aside of initiation of mRNA decay, the KSRP-mediated regulation of microRNA maturation seems to be especially important for its diverse biological functions, which warrants further in-depth examination.

Post-translational Control of RNA-Binding Proteins and Disease-Related Dysregulation

Cell signaling mechanisms modulate gene expression in response to internal and external stimuli. Cellular adaptation requires a precise and coordinated regulation of the transcription and translation processes. The post-transcriptional control of mRNA metabolism is mediated by the so-called RNA-binding proteins (RBPs), which assemble with specific transcripts forming messenger ribonucleoprotein particles of highly dynamic composition. RBPs constitute a class of trans-acting regulatory proteins with affinity for certain consensus elements present in mRNA molecules. However, these regulators are subjected to post-translational modifications (PTMs) that constantly adjust their activity to maintain cell homeostasis. PTMs can dramatically change the subcellular localization, the binding affinity for RNA and protein partners, and the turnover rate of RBPs. Moreover, the ability of many RBPs to undergo phase transition and/or their recruitment to previously formed membrane-less organelles, such as stress granules, is also regulated by specific PTMs. Interestingly, the dysregulation of PTMs in RBPs has been associated with the pathophysiology of many different diseases. Abnormal PTM patterns can lead to the distortion of the physiological role of RBPs due to mislocalization, loss or gain of function, and/or accelerated or disrupted degradation. This Mini Review offers a broad overview of the post-translational regulation of selected RBPs and the involvement of their dysregulation in neurodegenerative disorders, cancer and other pathologies.

Body mass index linked to short-term and long-term all-cause mortality in patients with acute myocardial infarction

PURPOSES OF STUDY

This study aimed to elucidate the relationship between obesity and short-term and long-term mortality in patients with acute myocardial infarction (AMI) by analysing the body mass index (BMI).

STUDY DESIGN

A retrospective cohort study was performed on adult intensive care unit (ICU) patients with AMI in the Medical Information Mart for Intensive Care III database. The WHO BMI classification was used in the study. The Kaplan-Meier curve was used to show the likelihood of survival in patients with AMI. The relationships of the BMI classification with short-term and long-term mortality were assessed using Cox proportional hazard regression models.

RESULTS

This study included 1295 ICU patients with AMI, who were divided into four groups according to the WHO BMI classification. Our results suggest that obese patients with AMI tended to be younger (p<0.001), be men (p=0.001) and have higher blood glucose and creatine kinase (p<0.001) compared with normal weight patients. In the adjusted model, compared with normal weight AMI patients, those who were overweight and obese had lower ICU risks of death HR=0.64 (95% CI 0.46 to 0.89) and 0.55 (0.38 to 0.78), respectively, inhospital risks of death (0.77 (0.56 to 1.09) and 0.61 (0.43 to 0.87)) and long-term risks of death (0.78 0.64 to 0.94) and 0.72 (0.59 to 0.89). On the other hand, underweight patients had higher risks of short-term(ICU or inhospital mortality) and long-term mortality compared with normal weight patients (HR=1.39 (95% CI 0.58 to 3.30), 1.46 (0.62 to 3.42) and 1.99 (1.15 to 3.44), respectively).

CONCLUSIONS

Overweight and obesity were protective factors for the short-term and long-term risks of death in patients with AMI.