Emerging functions of pannexin 1 in the eye

Pannexin 1 (Panxl) is a high-conductance, voltage-gated channel protein found in vertebrates. Panxl is widely expressed in many organs and tissues, including sensory systems. In the eye, Panxl is expressed in major divisions including the retina, lens and cornea. Panxl is found in different neuronal and non neuronal cell types. The channel is mechanosensitive and responds to changes in extracellular ATP intracellular calcium, pH, or ROS/nitric oxide. Since Panxl channels operate at the crossroad of major signaling pathways, physiological functions in important autocrine and paracrine feedback signaling mechanisms were hypothesized. This review starts with describing in depth the initial Panxl expression and localization studies fostering functional studies that uncovered distinct roles in processing visual information in subsets of neurons in the rodent and fish retina. Panxl is expressed along the entire anatomical axis from optical nerve to retina and cornea in glia, epithelial and endothelial cells as well as in neurons. The expression and diverse localizations throughout the eye points towards versatile functions of Panxl in neuronal and non-neuronal cells, implicating Ranx1 in the crosstalk between immune and neural cells, pressure related pathological conditions like glaucoma, wound repair or neuronal cell death caused by ischemia. Summarizing the literature on Panxl in the eye highlights the diversity of emerging Panxl channel functions in health and disease.