Cross-Presentation and Activation of CD8+ T Cells: The Role of Pannexin-1 in Dendritic Cells

Cross-presentation of exogenous antigens by dendritic cells (DCs) relies on the cytosolic pathway, enabling proteasomal processing and subsequent loading of antigenic peptides onto major histocompatibility complex class I (MHC-I) molecules. Although this pathway is central to CD8+ T-cell activation, the molecular mechanisms that regulate intracellular antigen processing and redistribution during cross-presentation remain incompletely defined. In this study, we investigated the contribution of the large-pore channel Pannexin-1 (Panx1) to antigen handling during cross-presentation. Using confocal microscopy and quantitative image analysis in granulocyte–macrophage colony-stimulating factor/interleukin-4 (GM-CSF/IL-4)-derived inflammatory bone marrow-derived dendritic cell (BMDC)-like cellsexposed to ovalbumin (OVA)–Alexa Fluor 488, we observed time-dependent changes in intracellular antigen distribution that were altered upon pharmacological inhibition of Panx1 with the blocking peptide 10Panx1. In parallel, functional assays revealed that Panx1 inhibition significantly reduced SIINFEKL peptide-dependentactivation of B3Z CD8+ T-cell hybridomas following pulsing with full-length OVA. Similar effects were observed in the cross-presentation-competent MUTU1940 dendritic cell line. Importantly, Panx1 inhibition did not significantly affect dendritic-cell viability or LPS-induced activation under the experimental conditions tested. In contrast, pharmacological inhibition or genetic deficiency of P2X7 receptor (P2X7) did not produce comparable reductions in cross-presentation, and combined inhibition did not result in additive effects under the experimental conditions tested. Together, these findings provide functional evidence supporting a role for Panx1 in regulating intracellular antigen redistribution associated with cross-presentation. While not establishing direct genetic causality, our data identify Panx1 as a modulatory component influencing antigen-processing events that culminate in CD8+ T-cell activation, thereby expanding the current framework of intracellular antigen-processing mechanisms involved in dendritic-cell-mediated cross-presentation.