Hepatitis C virus core protein increases mitochondrial ROS production by stimulation of Ca²⁺uniporter activity

Abstract

Many viruses have evolved mechanisms to alter mitochondrial function. The hepatitis C virus (HCV) produces a viral core protein that targets to mitochondria and increases Ca2+-dependent ROS production. The aim of this study was to determine whether core's effects are mediated by changes in mitochondrial Ca2+ uptake. Core expression caused enhanced mitochondrial Ca2+ uptake in response to ER Ca2+ release induced by thapsigargin or ATP. It also increased mitochondrial superoxide production and mitochondrial permeability transition (MPT). Incubating mouse liver mitochondria with an HCV core (100 ng/mg) in vitro increased Ca2+ entry rate by approximately 2-fold. Entry was entirely inhibited by the mitochondrial Ca2+ uniporter inhibitor, Ru-360, but not influenced by an Na+/Ca2+ exchanger inhibitor or ROS scavengers. These results indicate that core directly increases mitochondrial Ca2+ uptake via a primary effect on the uniporter. This enhanced the ability of mitochondria to sequester Ca2+ in response to ER Ca2+ release, and increased mitochondrial ROS production and MPT. Thus, the mitochondrial Ca2+ uniporter is a newly identified target for viral modification of cell function.

Hepatitis C Virus-Linked Mitochondrial Dysfunction Promotes Hypoxia-Inducible Factor 1α-Mediated Glycolytic Adaptation

“…7B). HCV protein expression is linked to deregulation of the calcium fluxes between ER and mitochondrial stores (21,33). Increased mitochondrial calcium influx is known to activate a mitochondrial isoform of nitric oxide synthase and thereby to cause nitric oxide release (33), which has been reported to stabilize HIF-1 (5).…”

Chronic ethanol consumption enhances sensitivity to Ca2+-mediated opening of the mitochondrial permeability transition pore and increases cyclophilin D in liver

“…Ca 2ϩ is also a key regulator of internal mitochondrial functions and acts at several levels within the organelle to control ATP synthesis and ROS production (20). Dysregulation of mitochondrial Ca 2ϩ homeostasis is now recognized to play a key role in several pathologies, including liver disease (55). It is known that mitochondria have the ability to rapidly sequester large amounts of Ca 2ϩ in response to increased cytosolic Ca 2ϩ levels (30, 38); however, the ability to store and retain Ca 2ϩ may be impaired when mitochondrial function is negatively impacted during pathological states.…”

Role of free radicals in liver diseases

“…HCV core gene expression diminishes the intracellular GSH levels and the mitochondrial NADPH content that are associated with increased uptake of calcium and oxidative stress generation at complex I in mitochondria, providing an action mechanism for HCVinduced ROS production [42,91,92,96]. On the contrary, core protein modulates the production of cytokines and host enzymes, such as cyclooxygenase-2 and inducible nitric oxide synthase (iNOS), which can increase ROS and RNS [97][98][99][100][101][102][103].…”