COVID-19 and SARS-CoV-2 host cell entry mediators: Expression profiling of TMRSS4 in health and disease

Abstract Severe acute respiratory syndrome (SARS) coronavirus-2 (SARS-CoV-2), the causative viral agent for the ongoing COVID-19 pandemic, enters its host cells primarily via the binding of the SARS-CoV-2 spike (S) proteins to the angiotensin-converting enzyme 2 (ACE2). A number of other cell entry mediators have also been identified, including neuropilin-1 (NRP1) and transmembrane protease serine 2 (TMPRSS2). More recently, it has been demonstrated that transmembrane protease serine 4 (TMPRSS4) along with TMPRSS2 activate the SARS-CoV-2 S proteins, and enhance the