Disease relevance of Chemoreceptors

• Although chemoreceptor methylation in Salmonella typhimurium and Escherichia coli has been shown to be at the core of the chemotactic phenomenon, mutants in the gene (cheR) that codes for the methylating enzyme still respond and adapt to repellent stimuli [1].
• The identification of an oxygen-sensing mechanism (namely the presence of an O2-sensitive potassium channel coupled to an O2 sensor protein) in the cells of pulmonary neuroepithelial bodies indicates that they are transducers of the hypoxia stimulus and hence may function as airway chemoreceptors in the regulation of respiration [2].
• The chemoreceptors of enteric bacteria mediate attractant responses by interrupting a phosphotransfer circuit initiated at receptor complexes with the protein kinase CheA [3].
• Metoclopramide may improve symptoms of diabetic gastric stasis through two mechanisms: its peripheral effect on gastric smooth muscle, which increases gastric emptying; and its central effects on the chemoreceptor vomiting zone, which decrease nausea [4].
• Cloning and characterization of the Salmonella typhimurium-specific chemoreceptor Tcp for taxis to citrate and from phenol [5].

Psychiatry related information on Chemoreceptors

• The combination of reduction of sensitivity to CO2 and lower tissue PCO2 during REM sleep makes it likely that the output of the central chemoreceptors during this state is less than that during SWS and wakefulness [6].
• Feeding behavior in hydra is initiated by the association of glutathione (GSH) with a putative external chemoreceptor [7].
• Response time and sensitivity of the ventilatory response to CO2 in unanesthetized intact dogs: central vs. peripheral chemoreceptors [8].

High impact information on Chemoreceptors

• This amplification requires a full complement of chemoreceptors; deletion of the aspartate (Tar) or dipeptide (Tap) receptors diminishes the amplification of the serine response [9].
• Synthetic multivalent ligands that interact through the low-abundance, galactose-sensing receptor Trg stabilize large clusters of chemoreceptors and markedly enhance signal output from these enforced clusters [9].
• A quaternary complex formed which consisted of the response regulator CheY, the histidine protein kinase CheA, a coupling protein CheW and a membrane-bound chemoreceptor Tar. Using various experimental conditions and mutant proteins, we have shown that the complex dissociates under conditions that favour phosphorylation of CheY [10].
• This protein represents the first example of a periplasmic chemoreceptor that does not have a sugar substrate [11].
• Tsr and Tar act directly as chemoreceptors for the amino acid attractants and signal changes in their degree of occupancy to the flagellar apparatus [12].

Chemical compound and disease context of Chemoreceptors

• Dopamine may inhibit chemoreceptor afferents and hence decrease chemoreflex sensitivity to hypoxia [13].
• Functional and developmental studies of the peripheral arterial chemoreceptors in rat: effects of nicotine and possible relation to sudden infant death syndrome [14].
• To test the degree of conservation of signaling properties, a chimeric receptor containing the ligand-binding extracellular domain of the Escherichia coli aspartate chemoreceptor and the cytosolic portion of the human insulin receptor was constructed [15].
• The Tar protein of Escherichia coli is unique among known bacterial chemoreceptors in that it generates additive responses to two very disparate ligands, aspartate and maltose [16].
• Identification of a methyl-accepting chemotaxis protein for the ribose and galactose chemoreceptors of Escherichia coli [17].

Biological context of Chemoreceptors

• This glucose analogue seems to elicit feeding in intact rats due to its inhibition of glycolysis in cerebral chemoreceptor cells [18].
• Because the function of this methyl-accepting chemotaxis protein involves two of the best-characterized chemoreceptors, the discovery of this protein represents a promising base for further study of the linkage between chemoreceptors and flagella in bacteria [17].
• The deduced amino acid sequence of Tcp, consisting of 547-amino acid residues, is homologous with that of the aspartate chemoreceptor of S. typhimurium [5].
• With heart rate held constant by electrical stimulation, and with respiration controlled or allowed to vary spontaneously, carotid chemoreceptor reflex activation (induced by intracarotid nicotine) elicited a striking biphasic coronary vascular response characterized by an early dilation (previously described) and a late constriction [19].
• The str family of genes encoding seven-transmembrane G-protein-coupled or serpentine receptors related to the ODR-10 diacetyl chemoreceptor is very large, with at least 197 members in the Caenorhabditis elegans genome [20].

Anatomical context of Chemoreceptors

• O2-sensitive K+ currents in carotid body chemoreceptor cells from normoxic and chronically hypoxic rats and their roles in hypoxic chemotransduction [21].
• NADPH-oxidase and a hydrogen peroxide-sensitive K+ channel may function as an oxygen sensor complex in airway chemoreceptors and small cell lung carcinoma cell lines [22].
• Interestingly, whereas the C-terminal region of the TaxD1 polypeptide is similar to the signaling domain of enteric methyl-accepting chemoreceptor proteins, the N terminus has two domains resembling chromophore-binding domains of phytochrome, a photoreceptor in plants [23].
• Carotid chemoreceptors were activated with nicotine or hypoxic, hypercapnic blood; carotid baroreceptors were stimulated by changes in carotid pressure [24].
• In both the main and accessory olfactory systems, OCAM mRNA is expressed by sensory neurons in restricted chemoreceptor expression zones, and OCAM protein-expressing axons project to the glomeruli in the corresponding zones of the main and accessory bulbs [25].

Associations of Chemoreceptors with chemical compounds

• Thus, ionic conductances, and particularly the O2-sensitive potassium current, play a key role in the transduction mechanism of arterial chemoreceptors [26].
• Attractant signaling by an aspartate chemoreceptor dimer with a single cytoplasmic domain [3].
• Depression of ventilation by dopamine in man. Evidence for an effect on the chemoreceptor reflex [27].
• Like the surface chemoreceptors, folate- and cAMP-induced Ca2+ uptake responses were developmentally regulated; the former response was evident in vegetative but not aggregation-competent cells, whereas the latter response displayed the opposite pattern of expression [28].
• Ventilatory response to CO2 was similar in patients and controls (mean +/- SEM, 1.58 +/- 0.16 vs 1.58 +/- 0.14 L/min/mm Hg), suggesting that abnormal chemoreceptor sensitivity does not explain the behavioral sensitivity of panic patients to CO2 [29].

Gene context of Chemoreceptors

• Chemokine sequestration by viral chemoreceptors as a novel viral escape strategy: withdrawal of chemokines from the environment of cytomegalovirus-infected cells [30].
• Based on the observation that NEB cells have a candidate oxygen sensor enzyme complex (NADPH oxidase) and an oxygen-sensitive K+ current, it has been suggested that NEB may function as airway chemoreceptors [22].
• The modulation of hypoxic pattern of ventilation after i.v. injection of recombinant human Epo in WT mice and the dense EpoR immunosignal observed in carotid bodies showed that these chemoreceptors are sensitive to plasma levels of Epo [31].
• It may therefore be concluded that loss of NK1 receptors has little effect on chemoreceptor function in the mouse, and thus they play, at best, a minor role in the hypoxic chemoreception process [32].
• Chemoreceptor activity is normal in mice lacking the NK1 receptor [32].

Analytical, diagnostic and therapeutic context of Chemoreceptors

• 1. We have studied the release of noradrenaline and adrenaline from the adrenal glands of dogs and cats in response to the lowering of carotid sinus pressure (baroreceptor tests) and to the perfusion of the vascularly isolated carotid bifurcations with hypoxic blood (chemoreceptor tests) [33].
• 1. In four awake dogs we measured EMG activity of three inspiratory and four expiratory muscles during sustained central chemoreceptor stimulation (CO2 inhalation), and peripheral chemoreceptor stimulation (intravenous infusion of almitrine bismesylate (almitrine)) [34].
• No spontaneous chemoreceptor activity could be detected on the day of birth in twelve pentobarbitone anaesthetized lambs delivered vaginally or by Caesarean section at 135-146 days [35].
• 3. Intravenous injection of phenylbiguanide (PBG; a 5-HT3 receptor agonist; 8 microg) strongly stimulated the chemoreceptors and was followed by a period of chemodepression (3-21 s) [36].
• After denervation of the peripheral chemoreceptors, doxapram in doses as large as 6 mg/kg failed to stimulate ventilation [37].

References