Ilyassov, O. | Search bioRxiv

bioRxiv2026

Hepatocyte growth factor activator inhibitor-2 rapidly inactivates airway-expressed human Type II Transmembrane Serine Proteases

Human Type II Transmembrane Serine Proteases (TTSPs) are essential entry factors for various influenza A and coronaviruses, and drive cancer metastasis when they are overexpressed by tumor cells. However, the natural inhibition mechanisms that regulate these proteases are not well understood. One natural transmembrane protease inhibitor, hepatocyte growth factor activator inhibitor-2 (HAI-2), has been shown to block TMPRSS2 activity and can prevent SARS-CoV-2 infection and reduce TMPRSS2-driven prostate cancer metastasis when overexpressed. In this study, we present biochemical and biophysical evidence showing that HAI-2 effectively inactivates TMPRSS2 and other TTSPs only after they have undergone zymogen activation. Through mutagenesis and ligand binding assays, we demonstrate that Kunitz Domain 1 (KD1) and KD2 can form stable ternary complexes with TMPRSS2 and other TTSPs, but do not employ the typical Laskowski inhibitor mechanism found for other macromolecular serine protease inhibitors. We also show that HAI-2 proteins do not inhibit the coagulation protease thrombin and that multivalent human IgG-tagged HAI-2 proteins are highly potent TMPRSS2 inhibitors. Our findings provide a mechanistic understanding of how TTSP activity is regulated in human airway cells and offer a foundation for developing engineered soluble HAI-2 proteins as anti-TTSP antivirals and anti-cancer therapeutics.

biochemistry↗

bioRxiv2024

Structural basis of TMPRSS11D specificity and autocleavage activation

Transmembrane Protease, Serine-2 (TMPRSS2) and TMPRSS11D are human proteases that enable SARS-CoV-2 and Influenza A/B virus infections, but their biochemical mechanisms for facilitating viral cell entry remain unclear. We demonstrate these proteases can spontaneously and efficiently cleave their own zymogen activation motifs, thereby activating their wider protease activity on other cellular substrates. We determined TMPRSS11D co-crystal structures in complexes with a native TMPRSS11D zymogen activation motif and with an engineered activation motif, providing insights into TMPRSS11D autocleavage activation and revealing unique regions of its substrate binding cleft. We further show that a protease inhibitor that underwent clinical trials for TMPRSS2-targeted COVID-19 therapy, nafamostat mesylate, was rapidly cleaved by TMPRSS11D and converted to low activity derivatives. These insights into human protease viral tropism and into liabilities with existing human serine protease inhibition strategies will guide future drug discovery campaigns for these targets.

biochemistry↗