Ciliary signaling cascades in photoreceptors

Abstract

For being a polarized neuron and having a sensory cilium, photoreceptors attract remarkable attention. This is due their highly polarized structure and active visual signal transduction cascades and for the enrichment of complex networks of proteins in the cilium. Structural and functional maintenance of the photoreceptor sensory cilium, also called outer segment, ensures that light signal is received and relayed appropriately to the brain. Any perturbations in the protein content of the outer segment result in photoreceptor dysfunction, degeneration and eventually, blindness. This review focuses on the importance of photoreceptor sensory cilium to carry out signal transduction cascade for vision.

GCY-8, PDE-2, and NCS-1 are critical elements of the cGMP-dependent thermotransduction cascade in the AFD neurons responsible for C. elegans thermotaxis

“…Many sensory transduction cascades, including those responsible for vertebrate vision and olfaction, regulate the concentration of cyclic nucleotides inside sensory endings and result in electrical signals by regulating the activity of CNG ion channels localized to specialized sensory cilia (Kleene, 2008;Fain et al, 2010;Kaupp, 2010;Yildiz and Khanna, 2012). From the present experiments, we draw two main conclusions about AFD thermotransduction: PDE activity helps to set both the threshold, T *, and the lifetime of ThRCs, and, of two PDE genes expressed in AFD, only PDE-2 is required for responses to temperature.…”

Loss of retinitis pigmentosa 2 (RP2) protein affects cone photoreceptor sensory cilium elongation in mice

“…Cilia are microtubule-based extensions of the plasma membrane, which originate from the mother centriole (also called basal body) [Satir, 2008;Satir and Christensen 2008]. Cilia maintain a unique composition of their membrane by retaining specific signaling receptor moieties, which sense the extrinsic cues to regulate intracellular signaling cascades, such as sonic hedgehog signaling, olfaction, and photoreception [Yildiz and Khanna, 2012]. The function and the composition of the cilia are regulated by an elaborate and conserved protein trafficking mechanism called intraflagellar transport (IFT).…”

The role of primary cilia in the development and disease of the retina

“…These cells perform essential roles in phototransduction, and ciliary signaling is a crucial component of this activity that, when disrupted, can lead to retinal disease. The role of ciliary signaling in retinal disease has been reviewed recently 15 and the present review will instead focus on photoreceptor assembly, organization and maintenance.…”