Inhibiting the Deubiquitinase UCHL1 Reduces SARS-CoV-2 Viral Uptake by ACE2.

Coronavirus disease (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a significant public health burden with limited treatment options. Many ß-coronaviruses, including SARS-CoV-2, gain entry to host cells through the interaction of SARS-CoV-2 spike protein with membrane-bound ACE2 (angiotensin-converting enzyme 2). Given its necessity for SARS-CoV-2 infection, ACE2 represents a potential therapeutic target in COVID-19. However, early attempts focusing on ACE2 in COVID-19 have not validated it as a druggable target nor identified other ACE2-related novel proteins for therapeutic intervention. Here, we identify a mechanism for ACE2 protein modulation by the deubiquitinase (DUB) enzyme UCHL1 (ubiquitin carboxyl-terminal hydrolase isozyme L1). ACE2 is constitutively ubiquitinated and degraded by the proteasome in lung epithelia. SARS-CoV-2 spike protein cellular internalization increased ACE2 protein abundance by decreasing its degradation. Using an siRNA library targeting 96 human DUBs, we identified UCHL1 as a putative regulator of ACE2 function as a viral receptor. Overexpressed UCHL1 preserved ACE2 protein abundance, whereas silencing of the DUB in cells destabilized ACE2 through increased polyubiquitination. A commercially available small molecule inhibitor of UCHL1 DUB activity decreased ACE2 protein concentrations coupled with inhibition of SARS-CoV-2 infection in epithelial cells. These findings describe a unique pathway of ACE2 regulation uncovering UCHL1 as a potential therapeutic target to modulate COVID-19 viral entry as a platform for future small molecule design and testing.

Mice infected with Mycobacterium tuberculosis are resistant to acute disease caused by secondary infection with SARS-CoV-2.

Mycobacterium tuberculosis (Mtb) and SARS-CoV-2 (CoV2) are the leading causes of death due to infectious disease. Although Mtb and CoV2 both cause serious and sometimes fatal respiratory infections, the effect of Mtb infection and its associated immune response on secondary infection with CoV2 is unknown. To address this question we applied two mouse models of COVID19, using mice which were chronically infected with Mtb. In both model systems, Mtb-infected mice were resistant to the pathological consequences of secondary CoV2 infection, and CoV2 infection did not affect Mtb burdens. Single cell RNA sequencing of coinfected and monoinfected lungs demonstrated the resistance of Mtb-infected mice is associated with expansion of T and B cell subsets upon viral challenge. Collectively, these data demonstrate that Mtb infection conditions the lung environment in a manner that is not conducive to CoV2 survival.

Syrian hamsters as a model of lung injury with SARS-CoV-2 infection: Pathologic, physiologic, and detailed molecular profiling.

The acute respiratory distress syndrome (ARDS) is a common complication of severe COVID-19 (coronavirus disease 2019) caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection. Knowledge of molecular mechanisms driving host responses to SARS-CoV-2 is limited by the lack of reliable preclinical models of COVID-19 that recapitulate human illness. Further, existing COVID-19 animal models are not characterized as models of experimental acute lung injury (ALI) or ARDS. Acknowledging differences in experimental lung injury in animal models and human ARDS, here we systematically evaluate a model of experimental acute lung injury as a result of SARS-CoV-2 infection in Syrian golden hamsters. Following intranasal inoculation, hamsters demonstrate acute SARS-CoV-2 infection, viral pneumonia, and systemic illness but survive infection with clearance of virus. Hamsters exposed to SARS-CoV-2 exhibited key features of experimental ALI, including histologic evidence of lung injury, increased pulmonary permeability, acute inflammation, and hypoxemia. RNA sequencing of lungs indicated upregulation of inflammatory mediators that persisted after infection clearance. Lipidomic analysis demonstrated significant differences in hamster phospholipidome with SARS-CoV-2 infection. Lungs infected with SARS-CoV-2 showed increased apoptosis and ferroptosis. Thus, SARS-CoV-2 infected hamsters exhibit key features of experimental lung injury supporting their use as a preclinical model of COVID-19 ARDS.