Transduction and Adaptation Mechanisms in the Cilium or Microvilli of Photoreceptors and Olfactory Receptors From Insects to Humans

Sensing changes in the environment is crucial for survival. Animals from invertebrates to vertebrates use both visual and olfactory stimuli to direct survival behaviors including identification of food sources, finding mates, and predator avoidance. In primary sensory neurons there are signal transduction mechanisms that convert chemical or light signals into an electrical response through ligand binding or photoactivation of a receptor, that can be propagated to the olfactory and visual centers of the brain to create a perception of the odor and visual landscapes surrounding us. The fundamental principles of olfactory and phototransduction pathways within vertebrates are somewhat analogous. Signal transduction in both systems takes place in the ciliary sub-compartments of the sensory cells and relies upon the activation of G protein-coupled receptors (GPCRs) to close cyclic nucleotide-gated (CNG) cation channels in photoreceptors to produce a hyperpolarization of the cell, or in olfactory sensory neurons open CNG channels to produce a depolarization. However, while invertebrate phototransduction also involves GPCRs, invertebrate photoreceptors can be either ciliary and/or microvillar with hyperpolarizing and depolarizing responses to light, respectively. Moreover, olfactory transduction in invertebrates may be a mixture of metabotropic G protein and ionotropic signaling pathways. This review will highlight differences of the visual and olfactory transduction mechanisms between vertebrates and invertebrates, focusing on the implications to the gain of the transduction processes, and how they are modulated to allow detection of small changes in odor concentration and light intensity over a wide range of background stimulus levels.

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Signal transduction and TGF-β superfamily receptors

Biochemistry and Cell Biology ◽

10.1139/o96-033 ◽

1996 ◽

Vol 74 (3) ◽

pp. 299-314 ◽

Cited By ~ 22

Author(s):

Steven M. Kolodziejczyk ◽

Brian K. Hall

Keyword(s):

Signal Transduction ◽

G Protein ◽

Intracellular Signaling ◽

Specific Cell ◽

Type I ◽

Type Ii ◽

Type Iii ◽

Wide Range ◽

Transduction Mechanisms ◽

Kinase Cascade

The TGF-β superfamily includes a large number of related growth and differentiation factors expressed in virtually all phyla. Superfamily members bind to specific cell surface receptors that activate signal transduction mechanisms to elicit their effects. Candidate receptors fall into two primary groups, termed type I and type II receptors. Both types are serine/threonine kinases. Upon activation by the appropriate ligand, type I and type II receptors physically interact to form hetero-oligomers and subsequently activate intracellular signaling cascades, ultimately regulating gene transcription and expression. In addition, TGF-β binds to a third receptor class, type III, a membrane-anchored proteoglycan lacking the kinase activity typical of signal transducing molecules. Type III receptors appear to regulate ligand availability to type I and type II receptors. Although a number of transduction mechanisms may be available to TGF-β superfamily members, evidence gathered through the use of specific kinase and G-protein inhibitors and through assays measuring activation and levels of signaling intermediates suggests that at least one signaling pathway interacts with Ras and Raf proteins via a G-protein intermediate. Raf begins the cytoplasmic kinase cascade that leads to gene regulation. The myriad responses regulated by TGF-β superfamily members makes the understanding of signal transduction mechanisms utilized by these proteins of great interest to a wide range of biological disciplines.Key words: TGF-β superfamily, serine/threonine kinase receptors, G-proteins, Ras, cytoplasmic kinase cascade.

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The mutational landscape of human olfactory G protein-coupled receptors

BMC Biology ◽

10.1186/s12915-021-00962-0 ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Ramón Cierco Jimenez ◽

Nil Casajuana-Martin ◽

Adrián García-Recio ◽

Lidia Alcántara ◽

Leonardo Pardo ◽

...

Keyword(s):

G Protein ◽

Olfactory Receptors ◽

Activation Mechanism ◽

Gene Repertoire ◽

Structural Level ◽

Ongoing Research ◽

Wide Range ◽

Natural Variants ◽

The Impact ◽

G Protein Coupled

Abstract Background Olfactory receptors (ORs) constitute a large family of sensory proteins that enable us to recognize a wide range of chemical volatiles in the environment. By contrast to the extensive information about human olfactory thresholds for thousands of odorants, studies of the genetic influence on olfaction are limited to a few examples. To annotate on a broad scale the impact of mutations at the structural level, here we analyzed a compendium of 119,069 natural variants in human ORs collected from the public domain. Results OR mutations were categorized depending on their genomic and protein contexts, as well as their frequency of occurrence in several human populations. Functional interpretation of the natural changes was estimated from the increasing knowledge of the structure and function of the G protein-coupled receptor (GPCR) family, to which ORs belong. Our analysis reveals an extraordinary diversity of natural variations in the olfactory gene repertoire between individuals and populations, with a significant number of changes occurring at the structurally conserved regions. A particular attention is paid to mutations in positions linked to the conserved GPCR activation mechanism that could imply phenotypic variation in the olfactory perception. An interactive web application (hORMdb, Human Olfactory Receptor Mutation Database) was developed for the management and visualization of this mutational dataset. Conclusion We performed topological annotations and population analysis of natural variants of human olfactory receptors and provide an interactive application to explore human OR mutation data. We envisage that the utility of this information will increase as the amount of available pharmacological data for these receptors grow. This effort, together with ongoing research in the study of genetic changes in other sensory receptors could shape an emerging sensegenomics field of knowledge, which should be considered by food and cosmetic consumer product manufacturers for the benefit of the general population.

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Review: Signal transduction mechanisms of the angiotensin II type AT1-receptor: looking beyond the heterotrimeric G protein paradigm

Journal of the Renin-Angiotensin-Aldosterone System ◽

10.3317/jraas.2001.007 ◽

2001 ◽

Vol 2 (1) ◽

pp. 4-10 ◽

Cited By ~ 17

Author(s):

Peter P Sayeski ◽

Kenneth E Bernstein

Keyword(s):

Signal Transduction ◽

Angiotensin Ii ◽

G Protein ◽

At1 Receptor ◽

Heterotrimeric G Protein ◽

Transduction Mechanisms

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Review: Molecular response of plant cells to UV-B stress

Functional Plant Biology ◽

10.1071/fp02062 ◽

2002 ◽

Vol 29 (8) ◽

pp. 909 ◽

Cited By ~ 112

Author(s):

Brian R. Jordan

Keyword(s):

Gene Expression ◽

Signal Transduction ◽

Plant Cells ◽

Environmental Parameters ◽

Induced Response ◽

Molecular Response ◽

Wide Range ◽

Transduction Mechanisms ◽

Gene Expression Studies ◽

Induced Signal

UV-B radiation (UV-B: 280-320 nm) can cause a wide range of responses in plant cells. These responses depend on the perception of the UV-B radiation, signal transduction mechanisms, and modification of gene expression. Studies over the last ten years have revealed a complex molecular response of plant cells to UV-B radiation. A number of signal transduction pathways are established and specific changes in gene activity take place. In addition, other environmental parameters strongly influence the UV-B-induced response. Although molecular studies have advanced our knowledge, our understanding of UV-B-induced cellular changes remains limited compared with other areas of plant photobiology / molecular biology. This review will focus on UV-B-induced signal transduction, gene expression and defence mechanisms. Comparisons will be made with other light-regulated systems to provide an insight into UV-B responses. This review will also attempt to identify present limitations to our understanding of molecular responses of plant cells to UV-B radiation.

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Cytosensor techniques for examining signal transduction of neurohormones

Biochemistry and Cell Biology ◽

10.1139/o00-019 ◽

2000 ◽

Vol 78 (3) ◽

pp. 281-288 ◽

Cited By ~ 15

Author(s):

D Smart ◽

M D Wood

Keyword(s):

Signal Transduction ◽

G Protein ◽

Cross Talk ◽

Neuropeptide Receptors ◽

Transduction Mechanisms ◽

G Protein Coupled

This review describes the principles of microphysiometry and how they can be applied, using the Cytosensor, to the investigation of the signal transduction mechanisms activated by both G-protein and non-G-protein coupled hormone and neuropeptide receptors. The use of the Cytosensor to study desensitisation and cross-talk is also discussed, as are the benefits and limitations of this technique.Key words: Cytosensor, microphysiometry, signal transduction, neuropeptides, hormones.

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