Impact of μ-opioid receptor (MOR) splice variant interactions with the chemokine receptor CCR5 in the context of morphine and HIV-1 entry inhibitor therapy

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 DESCRIPTION (provided by applicant): Growing evidence suggests that opioid abuse exacerbates neuroAIDS and these effects are mainly mediated through the μ-opioid receptor (MOR). There is also evidence to suggest that MOR-1 may have a direct role in HIV type-1 (HIV-1) replication and pathogenesis. MOR is not a single entity, but instead exists as multiple isoforms that differs in function. Despite significant fundamental differences, most studies examining MOR have focused on the canonical MOR-1, and this is particularly true in studies of opioid drug-HIV interactions. Although MOR-1- HIV-1interactions have been studied extensively, the role of MOR splice variant regulation by HIV and, conversely, MOR variant regulation of HIV cellular binding and entry is an unexplored area. Therefore, given that MOR-1 is thought to interact with HIV co-receptors such as CCR5 via heterodimerization and/or downstream signaling, the goal of this grant is to address the variation of MOR in relation to CCR5 mediation of HIV-associated processes in the CNS in the context of morphine and the HIV-1 entry inhibitor maraviroc. Preliminary studies found that: (i) MOR-1 may not be the predominate form of MOR on all CNS cell types, (ii) the N-terminal variant MOR-1K differs functionally in cellular signaling compared to MOR-1 (iii) although both astrocytes and microglia harbors multiple MOR variants, astrocytes harbors the most (iv) MOR-CCR5 interaction occurs in both microglia and astrocytes, although more so in astrocytes and (iv) morphine the predominant agonist of MOR was able to abolish the antiviral effect of the CCR5-mediated viral entry inhibitor maraviroc in a MOR-dependent manner in both astrocytes and microglia. The present proposal is designed to 1. (i) identify the MOR splice variants that interact with the chemokine and HIV (co-) receptor CCR5 in glia (astroglia and microglia) and (ii) determine how these interactions affect viral entry in opioid using individuals in the context of the clinically relevant viral entry inhibitor maraviroc which targets CCR5-mediated entry. The findings from this project could further define the mechanisms in the progression of HIV-related complications in opioid abusers by targeting specific MOR variants and whether a particular cell type is modulating the vulnerability to these complications in the CNS. These findings may also extend to further develop HIV entry inhibitors targeting this interaction.