Ca 2+-sensors and ROS-GC: Interlocked sensory transduction elements: A review

Abstract

From its initial discovery that ROS-GC membrane guanylate cyclase is a mono-modal Ca 2+- transduction system linked exclusively with the phototransduction machinery to the successive finding that it embodies a remarkable bimodal Ca 2+signaling device, its widened transduction role in the general signaling mechanisms of the sensory neuron cells was envisioned. A theoretical concept was proposed where Ca 2+-modulates ROS-GC through its generated cyclic GMP via a nearby cyclic nucleotide gated channel and creates a hyper- or depolarized sate in the neuron membrane (Ca 2+ Binding Proteins 1:1, 7-11, 2006). The generated electric potential then becomes a mode of transmission of the parent [Ca 2+]i signal. Ca 2+ and ROS-GC are interlocked messengers in multiple sensory transduction mechanisms. This comprehensive review discusses the developmental stages to the present status of this concept and demonstrates how neuronal Ca 2+-sensor proteins are the interconnected elements of this elegant ROS-GC transduction system. The focus is on the dynamism of the structural composition of this system, and how it accommodates selectivity and elasticity for the Ca 2+ signals to perform multiple tasks linked with the SENSES of vision, smell and possibly of taste and the pineal gland. An intriguing illustration is provided for the Ca 2+ sensor GCAP1 which displays its remarkable ability for its flexibility in function from being a photoreceptor sensor to an odorant receptor sensor. In doing so it reverses its function from an inhibitor of ROS-GC to the stimulator of ONE-GC membrane guanylate cyclase. © 2012 Sharma and Duda.