Structural Basis of Covalent Inhibitory Mechanism of TMPRSS2-Related Serine Proteases by Camostat.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the viral pathogen causing the coronavirus disease 2019 (COVID-19) global pandemic. No effective treatment for COVID-19 has been established yet. The serine protease transmembrane protease serine 2 (TMPRSS2) is essential for viral spread and pathogenicity by facilitating the entry of SARS-CoV-2 into host cells. The protease inhibitor camostat, an anticoagulant used in the clinic, has potential anti-inflammatory and antiviral activities against COVID-19. However, the potential mechanisms of viral resistance and antiviral activity of camostat are unclear. Herein, we demonstrate high inhibitory potencies of camostat for a panel of serine proteases, indicating that camostat is a broad-spectrum inhibitor of serine proteases. In addition, we determined the crystal structure of camostat in complex with a serine protease (uPA [urokinase-type plasminogen activator]), which reveals that camostat is inserted in the S1 pocket of uPA but is hydrolyzed by uPA, and the cleaved camostat covalently binds to Ser195. We also generated a homology model of the structure of the TMPRSS2 serine protease domain. The model shows that camostat uses the same inhibitory mechanism to inhibit the activity of TMPRSS2, subsequently preventing SARS-CoV-2 spread. IMPORTANCE Serine proteases are a large family of enzymes critical for multiple physiological processes and proven diagnostic and therapeutic targets in several clinical indications. The serine protease transmembrane protease serine 2 (TMPRSS2) was recently found to mediate SARS-CoV-2 entry into the host. Camostat mesylate (FOY 305), a serine protease inhibitor active against TMPRSS2 and used for the treatment of oral squamous cell carcinoma and chronic pancreatitis, inhibits SARS-CoV-2 infection of human lung cells. However, the direct inhibition mechanism of camostat mesylate for TMPRSS2 is unclear. Herein, we demonstrate that camostat uses the same inhibitory mechanism to inhibit the activity of TMPRSS2 as uPA, subsequently preventing SARS-CoV-2 spread.

A Biocompatible Hydrogen-Bonded Organic Framework (HOF) as Sonosensitizer and Artificial Enzyme for In-Depth Treatment of Alzheimer's Disease.

Current phototherapeutic approaches for Alzheimer's disease (AD) exhibit restricted clinical outcomes due to the limited physical penetration and comprised brain microenvironment of noninvasive nanomedicine. Herein, a hydrogen-bonded organic framework (HOF) based sonosensitizer is designed and synthesized. Mn-TCPP, a planar molecule where Mn2+ ion is chelated in the core with a large p-conjugated system and 4 carboxylate acid groups, has been successfully used as building blocks to construct an ultrasound-sensitive HOF (USI-MHOF), which can go deep in the brain of AD animal models. The both in vitro and in vivo studies indicate that USI-MHOF can generate singlet oxygen (1O2) and oxidize ß-amyloid (Aß) to inhibit aggregation, consequently attenuating Aß neurotoxicity. More intriguingly, USI-MHOF exhibits catalase (CAT)- and superoxide dismutase (SOD)-like activities, mitigating neuron oxidative stress and reprograming the brain microenvironment. For better crossing the blood-brain barrier (BBB), the peptide KLVFFAED (KD8) has been covalently grafted to USI-MHOF for improving BBB permeability and Aß selectivity. Further, in vivo experiments demonstrate a significant reduction of the craniocerebral Aß plaques and improvement of the cognition deficits in triple-transgenic AD (3×Tg-AD) mice models following deep-penetration ultrasound treatment. The work provides the first example of an ultrasound-responsive biocompatible HOF as non-invasive nanomedicine for in-depth treatment of AD.