Functional Gap Junctions Accumulate at the Immunological Synapse and Contribute to T Cell Activation

Abstract

Gap junction (GJ) mediate intercellular communication through linked hemichannels from each of two adjacent cells. Using human and mouse models we show that connexin 43 (Cx43), the main GJ protein in the immune system, was recruited to the immunological synapse during T cell priming as both GJs and stand-alone hemichannels. Cx43 accumulation at the synapse was antigen-specific and time-dependent, and required an intact actin cytoskeleton. Fluorescence recovery after photobleaching and Cx43-specific inhibitors were used to prove that intercellular communication between T cells and DCs is bidirectional and specifically mediated by Cx43. Moreover, this intercellular crosstalk contributed to T cell activation as silencing of Cx43 with an antisense or inhibition of GJ docking impaired intracellular Ca2+ responses and cytokine release by T cells. These findings identify Cx43 as an important functional component of the immunological synapse and reveal a crucial role for GJs and hemichannels as coordinators of the DC-T cell signaling machinery that regulates T cell activation.

Gap Junction Intercellular Communications Regulate NK Cell Activation and Modulate NK Cytotoxic Capacity

“…Recently, we showed that Cx43 accumulates at the immunological synapse (IS) during Ag-specific CD4 + T cell priming, mediating bidirectional crosstalk between DCs and T cells. We demonstrated that Cx43-GJIC between DCs and T cells regulates Ca 2+ signals and T cell activation (14), pointing to a role for Cx43 as an important functional component for intercellular signaling in the immune system.…”

“…Previously, we demonstrated that Cx43 accumulates in the IS during DC-mediated priming of CD4 + T cells, promoting lymphocyte activation through the formation of functional GJs and increased intracellular Ca 2+ signaling in T cells (14). Given that the reciprocal activation of DCs and NK cells is a cell contact-dependent process and shares some mechanisms with the DC-mediated T cell priming such as the formation of a functional IS (18), we aimed to examine whether Cx43-GJ channels may be involved in DC-NK intercellular communication.…”

“…GJ-mediated bidirectional communication between cells of the immune system has been previously described (7,14). The establishment of bidirectional GJIC between DCs and NK cells was monitored using a calcein transfer assay.…”

“…To investigate whether Cx43-mediated intercellular communication is involved in mDC-mediated activation of autologous rNK cells, CD69 and CD25 surface expression was evaluated in NK cells cocultured with mDCs in the presence of the Cx43-mimetic peptide 1848, which blocks docking between adjacent Cx43 Hchs (14). Induction of CD69 and CD25 on NK cells was strongly inhibited after treatment with the 1848 Cx43-mimetic peptide ( Fig.…”

Role of Connexin 43 in Helicobacter pylori VacA-Induced Cell Death

“…Therefore, connexins regulate many physiological processes. Cx43 is the most common connexin isoform and is expressed by many different cell types, including gastric and intestinal epithelial cells (49)(50)(51), ventricular myocytes, astrocytes, muscle cells, endothelial cells (52)(53)(54), and several types of immune cells (including T and B cells, neutrophils, mast cells, monocytes, and macrophages) (55)(56)(57)(58)(59)(60). We report that Cx43 is produced by AZ-521 cells but not by several other cell types that are commonly used for studies of VacA and provide evidence that variation among cell types in susceptibility to VacA-induced cell death is attributable at least in part to cell type-specific differences in Cx43 protein production.…”