7] Calcium-binding proteins and their assessment in ocular diseases

Abstract

Calcium-binding proteins play critical roles in the normal function and assorted pathologies of many cells including those of ocular origin. Interpretation of the vast array of calcium signals impinging on the cell depends on spatiotemporal information about the sources of the signals as well as the localization of specific target molecules. Often these cellular targets are calcium-binding proteins that alter their configuration on the chelation of calcium and in turn bind to and alter the activity of other biologically relevant molecules such as enzymes or ion channels. As the concentration of intracellular calcium diminishes on illumination, guanylate cyclase-activating protein 1 (GCAP1) stimulates guanylate cyclase to synthesize cyclic GMP, thus opening cation channels in the plasma membrane of the photoreceptor cell outer segment and reestablishing the dark resting potential of the cell. Aside from studies of phototransduction, these and other calcium-binding proteins are involved in ocular pathologies arising in humans. This chapter presents an assessment of these calcium-binding proteins and their role in ocular diseases.