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Receptors 1
Published in James E. Ferrell, Systems Biology of Cell Signaling, 2021
The largest class of receptors in humans is the G-protein-coupled receptors (GPCRs), a diverse family of proteins that are evolutionarily related to bacterial rhodopsin proteins and that share a common topology—they span the plasma membrane seven times, with the N-terminus of the protein outside the cell and the C-terminus inside. Probably the best-studied of the GPCRs are the adrenergic receptors, so-named because one of the hormones that activates them—epinephrine or adrenaline—is synthesized and released by cells in the medulla of the adrenal glands. Adrenergic receptors function in the central nervous system, the peripheral nervous system, and in organs such as the heart and the lung. In humans there are nine types of adrenergic receptors, which are divided into two groups (α and β) based on their pharmacology. Adrenergic receptors regulate blood pressure, cardiac contractility, pupil size, the smooth muscles in the bronchial tree, and intermediary metabolism. Studies of adrenergic signaling, from the late 19th century through the present day, have yielded and continue to yield enormous insights into physiology, disease, and the general principles of cellular regulation.
Mechanobiological Evidence for the Control of Neutrophil Activity by Fluid Shear Stress
Published in Jiro Nagatomi, Eno Essien Ebong, Mechanobiology Handbook, 2018
Hainsworth Y. Shin, Xiaoyan Zhang, Ayako Makino, Geert W. Schmid-Schönbein
Processes associated with remodeling of the F-actin cytoskeleton in leukocytes are controlled predominantly by cytosolic signaling pathways of the Ras superfamily of small guanine triphosphate (GTP)-binding proteins, particularly the small GTP-binding phosphatases (GTPases; i.e., Rac1, Rac2, cdc42, and members of the Rho family (e.g., RhoA) as reviewed in the literature, Cicchetti et al., 2002; Niggli, 2003; Tybulewicz and Henderson, 2009). These small GTPases mediate the actions of chemokines on the leukocyte cytoskeleton through the classical GPCR signaling pathway. Principally, ligand-GPCR binding leads to recruitment of G-proteins (typically bound in an inactive state to the cell membrane) to the cytosolic receptor domain. This event leads to phosphoinositide-3 kinase (PI3K)-dependent cellular signaling that ultimately increases the activity of downstream effectors of cytoskeletal reorganization, that is, the small GTPases. More importantly, each individual small GTPase is responsible for specific cytoskeletal responses. Typically, activation of cdc42 is responsible for actin polymerization associated with the formation of thin finger-like filipodia, but also, has been shown to activate Rac. Rac, on the other hand, plays a critical role in cytoskeletal events associated with the formation of lamellipodia and pseudopodia while RhoA plays a prominent regulatory role in uropod retraction at the trailing edge of the migrating cell.
Introduction to graph theory
Published in Karthik Raman, An Introduction to Computational Systems Biology, 2021
For instance, in a protein network, protein interactions can be represented by edges. An edge between proteins A and B indicates that A complexes with B. However, if a particular protein complex contains multiple sub-units, as in the case of haemoglobin, representing them in a simple graph is harder. G-protein coupled receptors, or GPCRs, interact with hetero-trimeric G proteins, comprising Gα, Gβ and Gγ sub-units4. Gβ, and Gγ bind to one another, and this complex binds to Gα. It is not possible to accurately represent this information in a simple graph—at best, we would have edges between all pairs of proteins, Gα, Gβ, and Gγ. On the other hand, the corresponding hypergraph will have V={Gα,Gβ,Gγ} and E={{Gα,Gβ,Gγ},{Gβ,Gγ}}. This clearly informs that there is no binary interaction (complexation) between Gα and Gβ or Gα and Gγ.
Plant pharmacology: Insights into in-planta kinetic and dynamic processes of xenobiotics
Published in Critical Reviews in Environmental Science and Technology, 2022
Tomer Malchi, Sara Eyal, Henryk Czosnek, Moshe Shenker, Benny Chefetz
There are numerous examples of analogies and homologies of receptors between animals and plants, and examples of such are transmembrane ion-channel receptors, transmembrane G-protein-coupled receptors and transmembrane receptors within cytosolic domains. Transmembrane ion-channel receptors such as voltage-gated ion channels regulate the ionic balance of the cell and cellular processes. Plant ion channel families exhibit homologies to animal proteins, and include hyperpolarization-and depolarization-activated Shaker-type potassium channels, chloride transporters/channels, cyclic nucleotide–gated channels, and ionotropic glutamate receptor homologs (Ward et al., 2009). Transmembrane G-protein-coupled receptors can activate a signal-transduction pathway that alters cellular processes through the activation of a second messenger system. Heterotrimeric G protein signaling regulates a wide range of growth and developmental processes in both animals and plants, but the two kingdoms are believed to have differences in protein structure, subunit composition and different G-protein-associated receptors (Stateczny et al., 2016; Trusov & Botella, 2016);
Guided dietary fibre intake as a means of directing short-chain fatty acid production by the gut microbiota
Published in Journal of the Royal Society of New Zealand, 2020
The metabolic products of the gut microbiota are probably instrumental in the maintenance of gut homeostasis, regulation of some aspects of host metabolism, and immune cell development and function (Roediger 1980; Arora et al. 2011; Cani 2014; Thorburn et al. 2014). Maintenance of epithelial integrity (barrier function) has been associated with butyrate, the main energy source for colonocytes (Dupaul-Chicoine et al. 2010). Colonocytes and immune cells associated with the gut mucosa have receptors that bind SCFAs (Table 3) (Thorburn et al. 2014). These G-protein-coupled receptors (GPCR) are associated with functions both in immunity and metabolism, but promoting the up-regulation of anti-inflammatory pathways and regulating appetite may be of most significance in reducing the prevalence of non-communicative diseases such as obesity, diabetes, cancer, and cardiovascular disease in Western countries.
Computerized screening of G-protein coupled receptors to identify and characterize olfactory receptors
Published in Journal of Toxicology and Environmental Health, Part A, 2020
Rui Zhang, Pu Wang, Shunbang Yu, Philip Hansbro, He Wang
G protein coupled receptors (GPCRs) are the largest family of cell-surface receptors which interact with signal molecules such as hormones, neurotransmitters, and local mediators, to activate internal signal transduction pathways, and ultimately induce cellular responses (Alberts et al. 2015). Despite the chemical and functional differences of the signal molecules that activate GPCRs, all of the GPCRs possess a similar structure with seven-transmembrane domains (Trzaskowski et al. 2012). GPCRs consist of six classes based upon sequence homology and functional similarity (Attwood and Findlay 1994; Kolakowski 1994). These include Class A (Rhodopsin-like), Class B (Secretin receptor family), Class C (Glutamate receptor/pheromone), Class D (Fungal mating pheromone receptors), Class E (Cyclic AMP receptors), Class F (Frizzled/Smoothened) and unclassified (Foord et al. 2005). Olfactory receptors (ORs) belong to the class A rhodopsin-like of GPCRs (Gaillard, Rouquier, and Giorgi 2004). Olfactory receptors (ORs) are predominantly located on the surface of olfactory receptors neurons (OSNs) in the olfactory mucosa (OM) of the nasal cavity, OSNs axons are directly connected with the olfactory bulb, which is a part of central nervous system (CNS).