Impairment of starvation-induced and constitutive autophagy in Atg7-deficient mice

Autophagy is a membrane-trafficking mechanism that delivers cytoplasmic constituents into the lysosome/vacuole for bulk protein degradation. This mechanism is involved in the preservation of nutrients under starvation condition as well as the normal turnover of cytoplasmic component. Aberrant autophagy has been reported in several neurodegenerative disorders, hepatitis, and myopathies. Here, we generated conditional knockout mice of Atg7, an essential gene for autophagy in yeast. Atg7 was essential for ATG conjugation systems and autophagosome formation, amino acid supply in neonates, and starvation-induced bulk degradation of proteins and organelles in mice. Furthermore, Atg7 deficiency led to multiple cellular abnormalities, such as appearance of concentric membranous structure and deformed mitochondria, and accumulation of ubiquitin-positive aggregates. Our results indicate the important role of autophagy in starvation response and the quality control of proteins and organelles in quiescent cells

COVID-19 severity and thrombo-inflammatory response linked to ethnicity

Although there is strong evidence that SARS-CoV-2 infection is associated with adverse outcomes in certain ethnic groups, the association of disease severity and risk factors such as comorbidities and biomarkers with racial disparities remains undefined. This retrospective study between March 2020 and February 2021 explores COVID-19 risk factors as predictors for patients’ disease progression through country comparison. Disease severity predictors in Germany and Japan were cardiovascular-associated comorbidities, dementia, and age. We adjusted age, sex, body mass index, and history of cardiovascular disease comorbidity in the country cohorts using a propensity score matching (PSM) technique to reduce the influence of differences in sample size and the surprisingly young, lean Japanese cohort. Analysis of the 170 PSM pairs confirmed that 65.29% of German and 85.29% of Japanese patients were in the uncomplicated phase. More German than Japanese patients were admitted in the complicated and critical phase. Ethnic differences were identified in patients without cardiovascular comorbidities. Japanese patients in the uncomplicated phase presented a suppressed inflammatory response and coagulopathy with hypocoagulation. In contrast, German patients exhibited a hyperactive inflammatory response and coagulopathy with hypercoagulation. These differences were less pronounced in patients in the complicated phase or with cardiovascular diseases. Coagulation/fibrinolysis-associated biomarkers rather than inflammatory-related biomarkers predicted disease severity in patients with cardiovascular comorbidities: platelet counts were associated with severe illness in German patients. In contrast, high D-dimer and fibrinogen levels predicted disease severity in Japanese patients. Our comparative study indicates that ethnicity influences COVID-19-associated biomarker expression linked to the inflammatory and coagulation (thrombo-inflammatory) response. Future studies will be necessary to determine whether these differences contributed to the less severe disease progression observed in Japanese COVID-19 patients compared with those in Germany

Autophagy pathway intersects with HIV-1 biosynthesis and regulates viral yields in macrophages

Autophagy is a cytoplasmic degradative pathway that can participate in biosynthetic processes, as in the yeast Cvt pathway, but is more commonly known for its functions in removing damaged or surplus organelles and macromolecular complexes. Here, we find that autophagy intersects with human immunodeficiency virus (HIV) biogenesis, mirroring the above dichotomy. Early, nondegradative stages of autophagy promoted HIV yields. HIV Gag-derived proteins colocalized and interacted with the autophagy factor LC3, and autophagy promoted productive Gag processing. Nevertheless, when autophagy progressed through maturation stages, HIV was degraded. This, however, does not occur, as the HIV protein Nef acts as an antiautophagic maturation factor through interactions with the autophagy regulatory factor Beclin 1, thus protecting HIV from degradation. The dual interaction of HIV with the autophagy pathway enhances viral yields by using the early stages while inhibiting the late stages of autophagy. The role of Nef in the latter process enhances yields of infectious HIV and may be of significance for progression to clinical AIDS

Multi-step processing of procathepsin L in vitro

AbstractThe proteolytic processes involved in the conversion of procathepsin L to cathepsin L on a negatively charged surface, dextran sulfate, were studied. Upon incubation for 30 min at 37°C, pH 5.5 with dextran-sulfate and dithiothreitol, purified procathepsin L showed maximal activation and, correspondingly, the complete conversion to the 30 kDa, single chain mature form of enzyme was observed. In contrast, incubation under the same conditions on ice rather than at 37°C for 30 or 60 min resulted in partial proteolysis to produce a 31 kDa form without a significant increase in activity. Amino terminal amino acid sequence analyses showed that the 30 kDa form obtained by incubation at 37°C corresponds to the purified form of mature cathepsin L with a 2 amino acid extension at the amino terminal, and that the 31 kDa form generated by incubation on ice possesses a 6 amino acid amino terminal extension, suggesting that the activation and processing of procathepsin L are different processes, and that 4 amino acid residues (Glu-Pro-Leu-Met) at the carboxyterminal in the propeptide function to prevent the activation of processed cathepsin L