SARS-CoV-2 ORF3a Interacts and Stabilizes HMOX1 Expression and Function



Jones, Naomi X

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This thesis describes the interaction between SARS-CoV-2 Open Reading Frame 3a (ORF3a) and the Heme Oxygenase 1 (HMOX1). SARS-CoV-2 is a novel coronavirus and the causative agent of COVID-19, the highly contagious infection behind the 2019 COVID-19 pandemic. SARS-CoV-2 ORF3a is a viroporin, a small virally encoded membrane protein that acts as an ion channel. Its expression causes cell apoptosis, necrosis, lysosomal damage, and disrupts host cell autophagy. It is also implicated in the egress of SARS-CoV-2 virions from infected cells. HMOX1 is an enzyme encoded by a human gene capable of modulating immune activity with an active role in suppressing viral infections and inflammatory pathways. In this thesis, we use confocal microscopy and a co-immunoprecipitation protocol to shed light on the interaction between SARS-CoV-2 ORF3a and HMOX1. Using this approach, we show that SARS-CoV-2 ORF3a and HMOX1 co-localize in the endoplasmic reticulum (ER). We also found that that ORF3a expression stabilizes HMOX1 protein levels within cells. These results suggest that ORF3a may affect TRC8, an important E3 ligase that help direct protein traffic through the ER and which is known to ubiquitinate HMOX1. These observations lay the foundation for additional studies aimed at studying the HMOX1/ORF3a interaction. They also suggest that SARS-CoV-2 targets TRC8 and potentially other E3 ligases to redirect ER trafficking.



SARS-CoV-2, ORF3a, HMOX1, Co-Immunoprecipitation