Dysregulation of host cell calcium signaling during viral infections: Emerging paradigm with high clinical relevance

Viral infections are one of the leading causes of human illness. Viruses take over host cell signaling cascades for their replication and infection. Calcium (Ca(2+)) is a versatile and ubiquitous second messenger that modulates plethora of cellular functions. In last two decades, a critical role of host cell Ca(2+) signaling in modulating viral infections has emerged. Furthermore, recent literature clearly implicates a vital role for the organellar Ca(2+) dynamics (influx and efflux across organelles) in regulating virus entry, replication and severity of the infection. Therefore, it is not surprising that a number of viral infections including current SARS-CoV-2 driven COVID-19 pandemic are associated with dysregulated Ca(2+) homeostasis. The focus of this review is to first discuss the role of host cell Ca(2+) signaling in viral entry, replication and egress. We further deliberate on emerging literature demonstrating hijacking of the host cell Ca(2+) dynamics by viruses. In particular, a variety of viruses including SARS-CoV-2 modulate lysosomal and cytosolic Ca(2+) signaling for host cell entry and replication. Moreover, we delve into the recent studies, which have demonstrated the potential of several FDA-approved drugs targeting Ca(2+) handling machinery in inhibiting viral infections. Importantly, we discuss the prospective of targeting intracellular Ca(2+) signaling for better management and treatment of viral pathogenesis including COVID-19. Finally, we highlight the key outstanding questions in the field that demand critical and timely attention.