Modulation of SARS-CoV-2 Spike-induced Unfolded Protein Response (UPR) in HEK293T cells by selected small chemical molecules

Coronaviruses (CoV) exploits the endoplasmic reticulum (ER) of the host cells for replication and in doing so, increases ER stress. evokes Unfolded Protein Response (UPR) and possibly autophagy, which could all attribute to the pathophysiology of the viral infections. To date, little is known about the roles of ER stress, UPR, and autophagy in SARS-CoV-2 infection. Here we over-expressed the viral Spike (S) protein in cultured HEK293T cells, as it has been shown that such protein is largely responsible for UPR activation in other CoV-infected cells. We noticed, in the transfected cells, heightened ER stress, activation of the PERK-eIF2α arm of the UPR, induction of autophagy and cell death. When we treated the transfected cells with Tauroursodeoxycholic acid (TUDCA), 4-phenyl butyric acid (PBA), Salubrinal, Trazadone hydrochloride, and Dibenzoylmethane (DBM), we saw reduced the BiP/GRP78 levels, but only PBA and TUDCA could significantly diminish the levels of peIF2α and autophagy expression.