Mechanisms of HCMV-induced monocyte-to-macrophage differentiation.

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Human cytomegalovirus (HCMV) infection is generally asymptomatic in immunocompetent individuals, although HCMV is a primary viral candidate in the etiology of several chronic inflammatory diseases including atherosclerosis and inflammatory bowel disease. In immunocompromised individuals, such as neonates, AIDS patients, and transplant recipients, HCMV infection can lead to acute multi-organ inflammation resulting in significant morbidity and mortality. Inflammatory organ diseases associated with a HCMV infection is a direct consequence of the systemic viral spread to and infection of multiple organ sites that occur during either asymptomatic or symptomatic infections. Monocytes are responsible for delivering the virus into tissue and play a central role in the inflammatory state of infected organs. However, because anti-apoptotic viral proteins are not expressed during the early stages of infection, it remains unclear how HCMV promotes the survival and differentiation of these short-lived cells. We found that viral glycoproteins induced an atypical activation of Akt, a critical cell fate determinant of monocyte survival, during HCMV entry, which led to the upregulation of a specific subset of Akt-dependent pro-survival proteins required for the early anti-apoptotic state within infected monocytes. We found HCMV infection aberrantly regulated the phosphoinositide (principal investigator) signaling network, which is responsible for modulating Akt activity. Thus, we hypothesize that HCMV glycoproteins stimulate a unique activation of Akt leading to the expression of select cellular anti-apoptotic proteins specifically required for the survival of infected monocytes. Aim 1 will delineate the role of viral glycoproteins in modulating the principal investigator signaling necessary for the HCMV-specific activation of Akt. We will characterize the components of the glycoprotein-initiated principal investigator signaling receptor complex(es). Additionally, the functional role of each component within the HCMV-induced principal investigator signaling complex(es) will be confirmed using a combination of soluble glycoproteins, neutralizing antibodies, small-molecule inhibitors, and siRNAs. Aim 2 will determine the mechanism by which the HCMV-initiated principal investigator signaling network aberrantly regulates Akt activity. We will map the glycoprotein-driven cellular signaling network used to induce the atypical activation of Akt using siRNAs and small-molecule inhibitors. In conjunction, we will determine how coordinated signaling from glycoproteins alters the substrate specificity of Akt using glycoprotein-neutralized HCMV and soluble glycoproteins. Aim 3 will elucidate the unique HCMV-induced monocyte pro-survival translational landscape generated by the aberrant activation of Akt. We will examine the role of HCMV-activated Akt in stimulating the synthesis of select survival proteins by altering the HCMV-specific principal investigator signaling network. The function of newly identified virus-induced survival proteins will be confirmed by small-molecule inhibitors and genetic approaches. These studies will increase our understanding about the mechanisms of HCMV pathogenesis and dissemination.