Grant: Discovery Grants Program - Individual

***Cell-to-cell communication is vital for homeostasis and proper development of all cells and tissues in mammals. This communication can take place by direct contact between cells, as in the case of gap junctions, or by release of signals to neighboring cells from single membrane channels formed at the cell surface. These channels are made of protein subunits, and are tightly regulated to open and close to release small molecules and metabolites that can act on neighbouring cells to convey the messages. The channel-forming pannexins are a novel family of three proteins (Panx1, 2 and 3) that were discovered in 2000 and cloned based on their homology to the invertebrate gap junction proteins (innexins). Pannexins were thought to form a new family of gap junctions similar to connexins, but instead, we have discovered that their primary function is to form large-pore membrane channels for the passage of ions and metabolites involved in paracrine signaling. All three pannexins are able to form functional channels. Panx1 and Panx3 have been more extensively studied and we know that they are conduits of physiologically important molecules such as ATP, and intracellular Ca++, while Panx2 channel function remains unknown.***Panx2 has been implicated in neuronal lineage commitment and differentiation, as well as neuronal cell death. Panx2 proteins are expressed in neuronal stem cells and the channels formed play a role in early stages of development, but need to be regulated in the adult to avoid deleterious effects from pannexin channel opening. Panx2 can also influence the function of Panx1 channels by potential intermixing of the proteins to form hybrid channels with different properties when co-expressed in the same cell. In the present study, I will characterize these novel channel proteins and the regulation of their large-pore channels. Panx2 can be localized predominantly in intracellular organelles and its specific function is presently unknown. I propose that the cellular localization of these Panx2 channels as well as their function in neurons is regulated by post-translational modifications. These modification alter the protein by the addition of sugars (glycosylation), phosphate groups (phosphorylation) or protein cleavage done by caspase enzymes that can affect the channel opening and/or their localization to either the cell surface or intracellular compartments for potentially different purposes. These studies will be among the first to establish the basic biology and regulation of Panx2 channels in neuronal differentiation and function, and will provide new insights into the intricate control of neuronal cell development and death in the central nervous system.**