Convergent NMDA receptor-Pannexin1 signaling pathways regulate the interaction of CaMKII with Connexin-36

Siu et al use FRET imaging in neuronal cell lines to explore the interplay between the gap junction channel protein Connexin-36 (Cx36) and NMDA receptor and Pannexin 1-mediated calcium signaling. They demonstrate that an increase in intracellular calcium promotes binding of CaMKII to Cx36, leading to increased gap junction opening, thus providing a pathway by which components of chemical and electrical synapses communicate. Ca2+/calmodulin-dependent protein kinase II (CaMKII) binding and phosphorylation of mammalian connexin-36 (Cx36) potentiate electrical coupling. To explain the molecular mechanism of how Cx36 modifies plasticity at gap junctions, we investigated the roles of ionotropic N-methyl-D-aspartate receptors and pannexin1 (Panx1) channels in regulating Cx36 binding to CaMKII. Pharmacological interference and site-directed mutagenesis of protein interaction sites shows that NMDA receptor activation opens Cx36 channels, causing the Cx36- CaMKII binding complex to adopt a compact conformation. Ectopic Panx1 expression in a Panx1 knock-down cell line is required to restore CaMKII mediated opening of Cx36. Furthermore, blocking of Src-family kinase activation of Panx1 is sufficient to prevent the opening of Cx36 channels. Our research demonstrates that the efficacy of Cx36 channels requires convergent calcium-dependent signaling processes in which activation of ionotropic N-methyl-D-aspartate receptor, Src-family kinase, and Pannexin1 open Cx36. Our results add to the best of our knowledge a new twist to mounting evidence for molecular communication between these core components of electrical and chemical synapses.

Automated summary

The study highlights the interplay between Connexin-36 (Cx36), NMDA receptor, and Pannexin 1 in calcium signaling in neuronal cells. It shows that CaMKII binding to Cx36 increases gap junction opening, with NMDA receptor and Pannexin 1 playing crucial roles. The research emphasizes the importance of calcium-dependent signaling in modulating the efficacy of Cx36 channels.