Formation of functional innexin hemichannels, as well as gap junctional channels, in an insect cell line, NIAs-AeAl-2, derived from Asian tiger mosquito Aedes albopictus (Diptera: Culicidae): A partial but significant contribution of innexin 2.

In vertebrates, gap junctions and hemichannels consisting of connexins are important cell surface structures for communication with neighboring cells and for the regulation of various cell functions. To date, various gap-junction-related proteins have been found, including innexins in invertebrates and pannexins in vertebrates. Significant contributions of gap junctions by innexins and (hemi-)channels by pannexins to numerous functions have been reported. Verification of the presence and functional significance of innexin hemichannels, however, remains a gap in our knowledge in innexin physiology. In this study, we revealed the localization of an innexin protein (innexin 2) on the cell surface in mosquito tissues and cultured cells. Furthermore, we demonstrated the presence of functional hemichannels, as well as gap junctions, in mosquito cells using dye transfer assays. The inward uptake of fluorescent dye was inhibited by anti-innexin 2 antibody. These results suggest that innexin hemichannels are formed to function in cultured mosquito cells, in at least a partially innexin 2-dependent manner. Although only a few studies on insect hemichannels have been published, innexin-based hemichannels, as well as innexin gap junctions, could also significantly contribute to insect intercellular signal transduction.