Signal Transduction In The Retina

In the twenty-first century, we are just beginning to understand more clearly the enormous diversity and complexity of signaling processes in the retina. Integrating advances in the biochemistry, cell biology, physiology, and physics of phototransduction, Signal Transduction in the Retina presents the methodologies and experimental approache

The main purpose of this volume is to provide a focused analysis of the function of the G protein-coupled signaling pathways that operate in the interconnected network of retinal neurons as they detect and encode the information carried by light. The organization of this volume will generally follow the path of signal flow in the retina. First we will describe recent advances in understanding the phototransduction cascade of rod and cone photoreceptors, which use signaling cascade based on the GPCR rhodopsin to transduce incident light into neural activity. Chapters will be devoted to unique specializations of the two major types of photosensitive cells that comprise the predominant input for our spatial and color vision. Subsequently, the mechanisms of synaptic information encoding by retinal ON bipolar cells will be described, where the GPCR mGluR6 plays a fundamental role. Chapters in this section will examine macromolecular organization of the mGluR6 signaling pathway as well as current understanding of its function. The functional characteristics of this signaling mechanism will be explored in detail. Additionally, this section will cover the role of dopamine receptors in modulating signal transmission between photoreceptors and ON-bipolar cells. Finally, chapters will be focused on the output neurons of the inner retina, ganglion cells, where the components of the emerging GPCR melanopsin cascade in intrinsically photosensitive ganglion cells will be detailed. Collectively these mechanisms allow the retina to represent visual space over a wide range of light intensities.

This book deals with the mechanism of signal transduction in vertebrate and invertebrate photoreceptors. It contains contributions on the structure and function of rhodopsin or other G-coupled receptors, on the regulation of second messengers by enzyme cascade, the role of Ca2+ in light adaptation, control of ionic channels in photoreceptor cells.

This book reveals not only how the eye evolved into an organ of vision, but also describes how molecular mechanisms of key molecules operate in the phototransduction cascade. In this groundbreaking text, experts also explain mechanisms for sensing radiation outside of the visible wavelengths. Comprehensive and penetrating, the book brings together the mechanisms of the visual transduction cascade and is an invaluable text for everyone conducting research in the visual system.

This book offers comprehensive coverage of the most important areas in photoreceptors and light signalling. Photoreceptors enable most species to sense not only the presence of light but also the information, such as irradiance, colour or spectral distribution, direction and polarization of light. They are vital, therefore, in providing organisms with energy and information about their surroundings, such as day and night cycles. This book covers the range of photoreceptors that have been discovered to date and the broad range of methods used when researching how they operate, including: action spectroscopy; methods for protein purification; the whole range of molecular biological and genetic methods; and numerous spectroscopic methods, from absorption and fluorescence spectroscopy to X-ray diffraction, used for solving the structure of photoreceptors. Written by leading experts in the field, Photoreceptors and Light Signalling provides the reader with the most recent results and research. This book will be valued by a wide-range of readers, including students of photochemistry, photobiology, biology, chemistry and physics and other professionals in academia.

Brings together key new results of interdisciplinary collaborations among various research fields on rhodopsin including the photoreceptive mechanism of rhodopsins, the molecular mechanism of the visual transduction process, visual processes in the retina and other transduction processes in the retina and brain. The structures of the rhodopsin molecule are studied in the fields of protein chemistry, molecular biology, organic chemistry and structural biology; the ultra fast reactions of the retinal protein are studied in physics, biophysics, physical chemistry, organic chemistry and photobiology; the phototransduction in retinal proteins and visual cells are studied in biophysics, biochemistry, biophysical chemistry and photobiology; and the localization in the tissues is studied in anatomy and histochemistry. The diversity of visual systems in various animals is studied in zoology and comparative biochemistry.

Molecular mechanisms in visual transduction is presently one of the most intensely studied areas in the field of signal transduction research in biological cells. Because the sense of vision plays a primary role in animal biology, and thus has been subject to long evolutionary development, the molecular and cellular mechanisms underlying vision have a high degree of sensitivity and versatility. The aims of visual transduction research are firstto determine which molecules participate, and then to understand how they act in concert to produce the exquisite electrical responses of the photoreceptor cells.Since the 1940s [1] we have known that rod vision begins with the capture of a quantum of energy, a photon, by a visual pigment molecule, rhodopsin. As the function of photon absorption is to convert the visual pigment molecule into a G-protein activating state, the structural details of the visual pigments must beexplained from the perspective of their role in activating their specific G-proteins. Thus, Chapters 1-3 of this Handbook extensively cover the physico-chemical molecular characteristics of the vertebrate rhodopsins. Following photoconversion and G-protein activation, the phototransduction cascade leads to modifications of the population of closed and open ion channels in the photoreceptor plasma membrane, and thereby to the electrical response. The nature of the channels of vertebrate photoreceptors is examined in Chapter 4, and Chapter 5 integrates the present body of knowledge of the activation steps in the cascade into a quantitative framework. Once the phototransduction cascade is activated, it must be subsequently silenced. The various molecular mechanisms participating in inactivation aretreated in Chapters 1-4 and especially Chapter 5. Molecular biology is now an indispensable tool in signal transduction studies. Numerous vertebrate (Chapter 6) and invertebrate (Chapter 7) visual pigments have been characterized and cloned. The genetics and evolutionary aspects of this great subfamily of G-protein activating receptors are intriguing as they present a natural probe for the intimate relationship between structure and function of the visual pigments. Understanding the spectral characteristics from the molecular composition can be expected to