VPS34-dependent control of apical membrane function of proximal tubule cells and nutrient recovery by the kidney.

The lipid kinase VPS34 orchestrates autophagy, endocytosis, and metabolism and is implicated in cancer and metabolic disease. The proximal tubule in the kidney is a key metabolic organ that controls reabsorption of nutrients such as fatty acids, amino acids, sugars, and proteins. Here, by combining metabolomics, proteomics, and phosphoproteomics analyses with functional and superresolution imaging assays of mice with an inducible deficiency in proximal tubular cells, we revealed that VPS34 controlled the metabolome of the proximal tubule. In addition to inhibiting pinocytosis and autophagy, VPS34 depletion induced membrane exocytosis and reduced the abundance of the retromer complex necessary for proper membrane recycling and lipid retention, leading to a loss of fuel and biomass. Integration of omics data into a kidney cell metabolomic model demonstrated that VPS34 deficiency increased ß-oxidation, reduced gluconeogenesis, and enhanced the use of glutamine for energy consumption. Furthermore, the omics datasets revealed that VPS34 depletion triggered an antiviral response that included a decrease in the abundance of apically localized virus receptors such as ACE2. VPS34 inhibition abrogated SARS-CoV-2 infection in human kidney organoids and cultured proximal tubule cells in a glutamine-dependent manner. Thus, our results demonstrate that VPS34 adjusts endocytosis, nutrient transport, autophagy, and antiviral responses in proximal tubule cells in the kidney.

Collateral Effects and Mortality of Kidney Transplant Recipients during the COVID-19 Pandemic.

Background: Collateral effects and consequences of the coronavirus disease 19 (COVID-19) pandemic on kidney transplant recipients remain widely unknown. Methods: This retrospective cohort study examined changes in admission rates, incidences of diseases leading to hospitalization, in-patient procedures, and maintenance medication in long-term kidney transplant recipients with functioning graft during the early COVID-19 pandemic in Germany. Data were derived from a nationwide health insurance database. Analysis was performed from March 15 to September 30 and compared the years 2019 and 2020. Effects on mortality and adverse allograft events were compared with COVID-19-attributed effects. Results: A total of 7725 patients were included in the final analysis. Admissions declined in 2020 by 17%, with the main dip during a 3-month lockdown (-31%) but without a subsequent rebound. Incidences for hospitalization did not increase for any investigated disease entities, whereas decreasing trends were noted for non-COVID-19 pulmonary and urogenital infections (incidence rate ratio 0.8, 95% CI, 0.62 to 1.03, and 0.82, 95% CI, 0.65 to 1.04, respectively). Non-COVID-19 hospital stays were 0.6 days shorter (P=0.03) and not complicated by increased dialysis, ventilation, or intensive care treatment rates. In-hospital and 90-day mortality remained stable. Incidences of severe COVID-19 requiring hospitalization was 0.09 per 1000 patient-days, and in-hospital mortality was 9%. A third (31%) of patients with calcineurin-inhibitor medication and without being hospitalized for COVID-19 reduced doses by at least 25%, which was associated with an increased allograft rejection risk (adjusted hazard ratio 1.29, 95% CI, 1.02 to 1.63). COVID-19 caused 17% of all deaths but had no significant association with allograft rejections. All-cause mortality remained stable (incidence rate ratio 1.15, 95% CI, 0.91 to 1.46), also when restricting analysis to patients with no or outpatient-treated COVID-19 (0.97, 95% CI, 0.76 to 1.25). Conclusion: Despite significant collateral effects, mortality remained unchanged during the early COVID-19 pandemic. Considerable temporary reductions in admissions are safe, whereas reducing immunosuppression results in increased allograft rejection risk.