Search

The HIV-1 accessory protein Nef hijacks clathrin adaptors to degrade or mislocalize host proteins involved in antiviral defenses. Here, using quantitative live-cell microscopy in genome-edited Jurkat cells, we investigate the impact of Nef on clathrin-mediated endocytosis (CME), a major pathway for membrane protein internalization in mammalian cells. Nef is recruited to CME sites on the plasma membrane, and this recruitment is associated with an increase in the recruitment and lifetime of the CME coat protein AP-2 and the late-arriving CME protein dynamin2. Furthermore, we find that CME sites that recruit Nef are more likely to recruit dynamin2 and transferrin, suggesting that Nef recruitment to CME sites promotes site maturation to ensure high efficiency in host protein downregulation. Implications of these observations for HIV-1 infection are discussed.

The adaptor protein (AP) complexes not only form the inner layer of clathrin coats but also have clathrin-independent roles in membrane traffic whose mechanisms are unknown. HIV-1 Nef hijacks AP-1 to sequester major histocompatibility complex class I (MHC-I), evading immune detection. We found that AP-1:Arf1:Nef:MHC-I forms a coat on tubulated membranes without clathrin and determined its structure. The coat assembles via Arf1 dimer interfaces. AP-1-positive tubules are enriched in cells upon clathrin knockdown. Nef localizes preferentially to AP-1 tubules in cells, explaining how Nef sequesters MHC-I. Coat contact residues are conserved across Arf isoforms and the Arf-dependent AP complexes AP-1, AP-3, and AP-4. Thus, AP complexes can self-assemble with Arf1 into tubular coats without clathrin or other scaffolding factors. The AP-1:Arf1 coat defines the structural basis of a broader class of tubulovesicular membrane coats as an intermediate in clathrin vesicle formation from internal membranes and as an MHC-I sequestration mechanism in HIV-1 infection.

The accessory protein Nef of human immunodeficiency virus (HIV) is a primary determinant of viral pathogenesis. Nef is abundantly expressed during infection and reroutes a variety of cell surface proteins to disrupt host immunity and promote the viral replication cycle. Nef counteracts host defenses by sequestering and/or degrading its targets via the endocytic and secretory pathways. Nef does this by physically engaging a number of host trafficking proteins. Substantial progress has been achieved in identifying the targets of Nef, and a structural and mechanistic understanding of Nef's ability to command the protein trafficking machinery has recently started to coalesce. Comparative analysis of HIV and simian immunodeficiency virus (SIV) Nef proteins in the context of recent structural advances sheds further light on both viral evolution and the mechanisms whereby trafficking is hijacked. This review describes how advances in cell and structural biology are uncovering in growing detail how Nef subverts the host immune system, facilitates virus release, and enhances viral infectivity.

Aim: Recently, the development of the oral glucagon‐like peptide‐1 receptor agonist semaglutide has drawn a great deal of attention. This study aimed to compare the effectiveness of oral glucagon‐like peptide‐1 receptor agonist semaglutide and dipeptidyl peptidase‐4 (DPP‐4) inhibitors on glycaemic control and several metabolic parameters in patients with type 2 diabetes mellitus over a 6‐month period. Methods: Fifty‐nine participants were included, and we compared various clinical parameters between before and after switching from DPP‐4 inhibitors to oral semaglutide in 'study 1' (pre‐post comparison) and set the control group using the propensity score matching method in 'study 2'. Results: In 'study 1', 6 months after the switching, the glycated haemoglobin value was significantly reduced from 7.5% to 7.0%, and the body mass index was also decreased from 29.7 kg/m2 to 28.8 kg/m2. Such effects were more clearly observed in participants whose glycaemic control was poor. In 'study 2', after 1:1 propensity score matching, 51 participants from each group were matched, and glycaemic control as well as body weight management were improved in the switching group compared with the DPP‐4 inhibitor continuation group over the 6‐month observation period. Conclusion: In this study, including obese participants with poor glycaemic control, switching DPP‐4 inhibitors to oral semaglutide showed more beneficial effects on both glycaemic and weight control, irrespective of age, body weight and diabetes duration. Therefore, we should bear in mind that it would be better to start using an oral semaglutide in clinical practice, particularly in obese participants with poor glycaemic control with DPP‐4 inhibitors. [ABSTRACT FROM AUTHOR]

Aim Materials and Methods Results Conclusion Tirzepatide, a dual agonist of glucagon‐like peptide receptor and glucose‐dependent insulinotropic polypeptide receptor, is expected to exhibit high clinical efficacy in obese type 2 diabetic patients. We evaluated the effects of tirzepatide on pancreatic β‐cells and the liver, an insulin‐target organ, in a mouse model of obese type 2 diabetes mellitus.Obese type 2 diabetic db/db mice (BKS.Cg−/+ Leprdb/+ Leprdb/Jcl*) were used in this study. Starting at 7 weeks of age, mice were treated with tirzepatide (30 nmol/kg, subcutaneous injection twice a week) or semaglutide (200 nmol/kg, subcutaneous injection twice a week). The control group received phosphate‐buffered saline (40–50 μL/subcutaneous injection twice a week). After 4 weeks of drug administration, pancreatic β‐cells and the liver were removed and examined.Compared to the control group, blood glucose and body weight were significantly reduced in the group that received either tirzepatide or semaglutide (p < 0.001 and p < 0.05, respectively). Fasting insulin was significantly higher in the semaglutide and tirzepatide groups compared to the control group (p < 0.001). β‐Cell mass and quality of insulin granules in β‐cells similarly increased in the semaglutide and tirzepatide groups compared to the control group (p < 0.05 and p < 0.001, respectively). The fat staining area in the liver in oil red O staining and the liver–spleen ratio in computed tomography showed improvement only in the tirzepatide group (p < 0.001 and p < 0.005, respectively). Liver macrophage M1/M2 ratio similarly improved with semaglutide and tirzepatide (p < 0.05).Tirzepatide and semaglutide exhibited similar potent glucose‐lowering effects. At concentrations used in the present experiments, tirzepatide exhibited more beneficial effects on β‐cell‐related gene expression, insulin granule count and glucose‐stimulated insulin secretion compared to semaglutide. In addition, tirzepatide exhibited a stronger favourable effect on hepatic fat deposition and improved inflammation in the liver. This is the first report showing that tirzepatide, a novel diabetes drug, exhibits a superior effect on pancreatic β‐cells and the liver of obese type 2 diabetic mice. [ABSTRACT FROM AUTHOR]

Clathrin-mediated endocytosis (CME) is a critical trafficking process that begins when an elaborate endocytic protein network is established at the plasma membrane. Interaction of early endocytic proteins with anionic phospholipids and/or cargo has been suggested to trigger CME initiation. However, the exact mechanism by which CME sites are initiated has not been fully elucidated. In the budding yeast Saccharomyces cerevisiae, higher levels of anionic phospholipids and cargo molecules exist in the newly formed daughter cell compared to the levels in the mother cell during polarized growth. Taking advantage of this asymmetry, we quantitatively compared CME proteins in S. cerevisiae mother versus daughter cells, observing differences in the dynamics and composition of key endocytic proteins. Our results show that CME site initiation occurs preferentially on regions of the plasma membrane with a relatively higher density of endocytic cargo and/or acidic phospholipids. Furthermore, our combined live cell-imaging and yeast genetics analysis provided evidence for a molecular mechanism in which CME sites are initiated when Yap1801 and Yap1802 (yeast CALM/AP180) and Syp1 (yeast FCHo1/2) coordinate with anionic phospholipids and cargo molecules to trigger Ede1 (yeast Eps15)-centric CME initiation complex assembly at the plasma membrane. Clathrin-mediated endocytosis (CME) is one of the main trafficking processes, but the mechanism that initiates CME sites remain unclear. These authors show that yeast CALM/AP180 and FCHo1/2 adaptor proteins interact with Eps15 to promote CME initiation. [ABSTRACT FROM AUTHOR]

Aims: To evaluate the correlation between C‐peptide index (CPI) at 2 h post‐meal and endogenous insulin secretory capacity and to develop clinical models to predict the possibility of withdrawal from insulin therapy in patients with type 2 diabetes. Method: This was a single‐centre retrospective study of patients with type 2 diabetes admitted to our hospital. Patients were divided into a withdrawal group (n = 72) and a non‐withdrawal group (n = 75) based on whether they were able to withdraw from insulin therapy at discharge, and the correlation between CPI at 2 h after meal and diabetes‐related parameters was evaluated. In addition, we created two clinical models to predict the possibility of withdrawal from insulin therapy using machine learning. Results: The glycated haemoglobin values of the study participants were 87.8 ± 22.6 mmol/mo. The CPI at 2 h post‐meal was 1.93 ± 1.28 in the non‐withdrawal group and 2.97 ± 2.07 in the withdrawal group (p < 0.001). CPI at 2 h post‐meal was an independent predictor of withdrawal from insulin therapy. In addition, CPI at 2 h post‐meal was a better predictor than fasting CPI. Six factors associated with insulin therapy withdrawal (age, duration of diabetes, creatinine, alanine aminotransferase, insulin therapy until hospitalization, and CPI at 2 h post‐meal) were used to generate two clinical models by machine learning. The accuracy of the generated clinical models ranged from 78.3% to 82.6%. Conclusion: The CPI at 2 h post‐meal is a clinically useful measure of endogenous insulin secretory capacity under non‐fasting conditions. [ABSTRACT FROM AUTHOR]

Aim: To compare the clinical usefulness of once‐weekly glucagon‐like peptide‐1 receptor agonists dulaglutide and semaglutide at the doses approved for use in Japanese patients with type 2 diabetes. Methods: In total, 120 patients with glycated haemoglobin (HbA1c) ≥7% were randomly assigned to dulaglutide (n = 59) or semaglutide group (n = 61), and 107 participants (dulaglutide/semaglutide = 53/54) completed the 24‐week trial. The primary endpoint was the difference of HbA1c level between the two groups at 24 weeks. Results: HbA1c level at 24 weeks was significantly lower in the semaglutide group (7.9 ± 0.5%‐6.7 ± 0.5%) compared with the dulaglutide group (8.1 ± 0.6%‐7.4 ± 0.8%) (p <.0001). Reduction in body mass index and visceral fat area were also more significant in the semaglutide group (p <.05, respectively). The achievement rate of HbA1c <7% was higher in the semaglutide group (p <.0001). The parameters such as low‐density lipoprotein cholesterol, alanine aminotransferase and γ‐glutamyl transpeptidase were decreased in the semaglutide group. Surprisingly, only semaglutide group significantly improved the apolipoprotein B/A1 ratio, which is considered a useful myocardial infarction risk index. Using computed tomography, the liver to spleen ratio was significantly elevated only in the semaglutide group. In contrast, gastrointestinal symptoms were observed in 13.2% of dulaglutide and 46.3% of semaglutide group (p <.01). The Diabetes Treatment‐Related Quality of Life scores related to pain and gastrointestinal symptoms were also superior in the dulaglutide group. Conclusions: This prospective trial showed that semaglutide has more pronounced glucose‐ and body mass index‐lowering effects and reduces liver fat percentage and visceral fat area and that dulaglutide has less gastrointestinal symptoms and superior Diabetes Treatment‐Related Quality of Life scores related to pain and gastrointestinal symptoms. [ABSTRACT FROM AUTHOR]