Manganese for COVID-19

 Manganese has been reported as potentially beneficial for COVID-19 in the following studies.
COVID-19 involves the interplay of 350+ viral and host proteins and factors providing many therapeutic targets. Scientists have proposed 10,000+ potential treatments. c19early.org analyzes 210+ treatments. We have not reviewed manganese in detail.
Loucera et al., Drug repurposing for COVID-19 using machine learning and mechanistic models of signal transduction circuits related to SARS-CoV-2 infection, Signal Transduction and Targeted Therapy, doi:10.1038/s41392-020-00417-y
Shetler et al., Therapeutic potential of metal ions for COVID-19: insights from the papain-like protease of SARS-CoV-2, Biochemical Journal, doi:10.1042/BCJ20220380
Coronaviruses have been responsible for multiple challenging global pandemics, including coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Papain-like protease (PLpro), one of two cysteine proteases responsible for the maturation and infectivity of SARS-CoV-2, processes and liberates functional proteins from the viral polyproteins and cleaves ubiquitin and ISG15 modifications to inhibit innate immune sensing. Consequently, PLpro is an attractive target for developing COVID-19 therapies. PLpro contains a zinc-finger domain important for substrate binding and structural stability. However, the impact of metal ions on the activity and biophysical properties of SARS-CoV-2 PLpro has not been comprehensively studied. Here, we assessed the impacts of metal ions on the catalytic activity of PLpro. Zinc had the largest inhibitory effect on PLpro, followed by manganese. Calcium, magnesium, and iron had smaller or no effects on PLpro activity. EDTA at a concentration of 0.5 mM was essential for PLpro activity, likely by chelating trace metals that inhibit PLpro. IC50 values for ZnCl2, ZnSO4, and MnCl2 of 0.42 ± 0.02 mM, 0.35 ± 0.01 mM, and 2.6 ± 0.3 mM were obtained in the presence of 0.5 mM EDTA; in the absence of EDTA, the estimated IC50 of ZnCl2 was 14 µM. Tryptophan intrinsic fluorescence analysis confirmed the binding of zinc and manganese to PLpro, and differential scanning calorimetry revealed that zinc but not manganese reduced ΔHcal of PLpro. The results of this study provide a reference for further work targeting PLpro to prevent and treat COVID-19.