| Human cytomegalovirus (HCMV) is the leading viral cause of neurological birth defects, causing sensorineural hearing loss, epilepsy, and mental retardation. HCMV infections are highly ubiquitous, and due to its prevalence and ease of transmission, remains a significant burden on current health care systems, amounting to a cost of over ;HCMV expresses various anti-apoptotic products, and the immediate early pUL37x1 viral protein, also called viral mitochondria localized inhibitor of apoptosis, (vMIA), is one of the most well known HCMV proteins to provide an anti-apoptotic mechanism for the virus. This viral protein is sequentially trafficked from the endoplasmic reticulum (ER) to the mitochondria, where it displays its known anti-apoptotic function by inhibiting the pro-apoptotic cellular protein Bcl-2-associated protein X (Bax). One of the goals of this study was to examine whether pUL37x1 could regulate apoptosis induction at the mitochondria, as well as the ER. Furthermore, we sought to determine if aberrant trafficking of pUL37x1, or a partial block in the incorporation of pUL37x1 into ER lipid rafts would affect its ability to inhibit apoptosis. Towards that end, we used the transfection of pUL37x1 wt or mutant proteins, followed by stimulation of either ER or mitochondrial apoptosis to examine pUL37x1 apoptotic inhibition. We determined that pUL37x1 inhibits apoptosis induced by either the ER or the mitochondria, that a disruption in pUL37x1 trafficking to the mitochondria partially blocks pUL37x1 mediated anti-apoptotic activity, and finally, that the disruption in pUL37x1 ER lipid raft incorporation, when coupled with the mutation of a critical amino acid residue at position 23, would also partially block pUL37x1 anti-apoptotic function.;Although HCMV has customarily demonstrated anti-apoptotic activity, recent studies have suggested that HCMV infection could induce apoptosis within the cells of the developing nervous system. Due to the controversy surrounding these observations, and the presence of conflicting studies, another goal of this study was to determine whether HCMV infection induces apoptosis within human neural precursor cells (hNPC) cultured and infected under physiologically relevant low oxygen conditions. We demonstrated that, as measured by morphological changes and the induction of molecular markers of apoptosis, HCMV infection of hNPC in physiologically relevant oxygen conditions triggers apoptosis. Furthermore, we demonstrated that this phenotype of apoptosis induction is neither inhibited nor promoted by the presence of pUL37x1. |
