Table 1. Role of viruses/viral proteins on Ca²⁺ homeostasis.

Virus	Protein	Cytobiological consequences on Ca2+ signaling	Refs.
HIV-1	Nef	Activates T cell Receptors via NFAT activation.Enhances viral infectivity.	(Simmons et al., 2001) (Chami et al., 2006)
	Vpr	Interacts with cellular Ca2+ regulators.Induces mitochondrial Ca2+ leakage through membrane permeabilization.	(Jacotot et al., 2001, 2000)
	Tat	Induces Ca2+ dependent apoptosis	(Kruman et al., 1998)
	gp120	Increases [Ca2+]cyt that leads to increased ROS accumulation	(Haughey and Mattson, 2002)
	Env	Mediates Ca2+ dependent viral fusion	(Zaitseva et al., 2017)
HTLV-1	pI2I	Increases Ca2+ outflow from ER via binding to calreticulin and calnexin.Enhances viral infection through Ca2+ dependent activation of transcriptional co-activator p300.	(Ding et al., 2001) (Nair et al., 2006)
	pI3II	Affects mitochondrial Ca2+ permeability across IMMIncreases the sensitivity of cells to apoptosis.	(D’Agostino et al., 2002)(D’Agostino et al., 2005)
HCV	Core	Decreases [Ca2+]er, induces apoptosis via Bax-mediated mitochondrial membrane depolarization.Stimulates ER Ca2+ efflux to mitochondria through MCU activation.	(Benali-Furet et al., 2005; John et al., 1998)(Ivanov et al., 2015; Li et al., 2007)
	NS5A	Increases [Ca2+]mt and ROS production and affects transmembrane potential.	(Gong et al., 2001)
		Activates Ca2+ -dependent degradation of NFκB inhibitory subunit Iκβα.	(Waris et al., 2003)
	p7	Allows Ca2+ -flow from ER by forming ion channels in the cellular membrane	(Griffin et al., 2003)
Poliovirus	Viral particle	Accumulates Ca+2 in mitochondria that leads to mitochondrial dysfunction and apoptosis.	(Brisac et al., 2010)
Coxsackie virus B3	2B	Increases [Ca2+]cyt by rigorous Ca2+ outflow from ER.	(Peischard et al., 2019)
	3C	Promotes mitochondrial Ca2+mediated apoptosis through cleavage of procaspase 8.	(Peischard et al., 2019)
	2A	Along with 3C, it destabilizes cellular homeostasis by increased expression of Bax, p53 and decreased expression of Bcl2 leading to cell death	(Peischard et al., 2019)
	Viral particle	Disturbs mitochondrial homeostasis. Activates the AMPK/MEK/ERK and Ras/Raf/MEK/ERK signaling pathways to induce autophagy in host cells.	(Xin et al., 2015)
Rabies virus	Viral particle	Hampers Ca2+ homeostasis and GABAergic neurotransmission by loss of host proteins calbindin-D-28 k and elevation of m-calpin respectively.	(Schwaller et al., 2002; Torres-Fernández et al., 2005; Ubol et al., 2005)
Influenza virus	Viral particle	Targets Cav1.2 channel for binding and entry into host cells.	(Fujioka et al., 2018)
	M2	Regulates ROS dependent Mitochondrial Antiviral Signaling (MAVS)	(Wang et al., 2019)
Ebola virus	Viralparticle	Affects TPCs to control the movement of endosome-containing virus particles.STIM1/ORAI1-mediated Ca2+ signal critical for their budding from host cells	(Han et al., 2015; Kintzer and Stroud, 2016; Sakurai et al., 2015)
Rotavirus	NSP4	Decreases [Ca2+]er and increases [Ca2+]cyt through PLC activation and IP3 production.	(Dong et al., 1997; Tian et al., 1995)
Chandipura virus	Viral particle	Affects intracellular Ca2+ signaling mediated by angiotensin II.Causes neuronal apoptosis through FasL-FADD pathway.	(Verma et al., 2018)
HBV	HBx	Activates mitochondrial PTP opening to release mitochondrial Ca2+ to cytoplasm and activates Ca2+ ATPase to accumulate Ca2+ in ER that ultimately releases through IP3R, thus, results in increased [Ca2+]cyt. Enhances viral replication through activation of proline-rich tyrosine kinase 2 (Pyk2) and Focal Adhesion Kinase (FAK).	(Xia et al., 2006)(Bouchard et al., 2006)
HHV-8	K1	Increases prolonged intracellular Ca2+ concentration through a phosphorylation cascade of downstream elements.	(Lee et al., 2005)
	K7	Elevates [Ca2+]cyt by interacting with CAML protein of ER and activation of CCE pathway.	(Feng et al., 2002)
HSV		Increased [Ca2+]cyt results in FAK phosphorylation required for actin cytoskeleton reorganization and nuclear trafficking of the internalized virus. Enhances proinflammatory response through activation of NFkB.Targets T-type Ca2+ channels, downregulates VGCC and alters sensory neurons to transmit pain information.	(Chami et al., 2006; Chen et al., 2019b; Cheshenko et al., 2003; Mogensen et al., 2003; Zhang et al., 2019a, 2017)
Epstein-Barr virus	LMP1	Reactivates EBV in a calcium-dependent manner inducing a Ca2+/calmodulin dependent protein kinase type IV/Gr (CaMKIV/Gr).	(Chatila et al., 1997; Mosialos et al., 1994)
	LMP2A	Binds cellular phospho-tyrosine kinases (PTKs), prevent calcium mobilization and acts as a negative regulator of calcium-signaling.	(Fruehling and Longnecker, 1997; Miller et al., 1994, 1993)
HPV	E6	Interacts with E6BP, a Ca2+ binding protein of ER.	(Chen et al., 1995; Weis et al., 1994)
	E7	Allows virus-induced oncogenic activity.	(Tugizov et al., 2005)
HCMV	UL37X1	Activates STIM1/ORAI1 mediated calcium influx.	(Chen et al., 2019b)
Dengue virus	Viral particle	Activates SOC channels altering cellular Ca2+ homeostasis via STIM1/ORAI1 interaction.	(Cheshenko et al., 2007; Dionicio et al., 2018)