The SARS-CoV-2 Virus and the Cholinergic System: Spike Protein Interaction with Human Nicotinic Acetylcholine Receptors and the Nicotinic Agonist Varenicline

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is responsible for the worldwide coronavirus disease 2019 (COVID-19) pandemic. Although the pathophysiology of SARS-CoV-2 infection is still being elucidated, the nicotinic cholinergic system may play a role. To evaluate the interaction of the SARS-CoV-2 virus with human nicotinic acetylcholine receptors (nAChRs), we assessed the in vitro interaction of the spike protein of the SARS-CoV-2 virus with various subunits of nAChRs. Electrophysiology recordings were conducted at α4β2, α3β4, α3α5β4, α4α6β2, and α7 neuronal nAChRs expressed in oocytes. In cells expressing the α4β2 or α4α6β2 nAChRs, exposure to the 1 µg/mL Spike-RBD protein caused a marked reduction of the current amplitude; effects at the α3α5β4 receptor were equivocal and effects at the α3β4 and α7 receptors were absent. Overall, the spike protein of the SARS-CoV-2 virus can interact with select nAChRs, namely the α4β2 and/or α4α6β2 subtypes, likely at an allosteric binding site. The nAChR agonist varenicline has the potential to interact with Spike-RBD and form a complex that may interfere with spike function, although this effect appears to have been lost with the omicron mutation. These results help understand nAChR's involvement with acute and long-term sequelae associated with COVID-19, especially within the central nervous system.