membrane bound receptors Flashcards

Question

Cys-Loop receptors

Answer 1

Ligand gated ion channel pentamer (5 subunits) -named for the loop formed by disulfide bond between 2 cysteines near the N-terminus - Five types of subunits: α, β, γ, δ, ε * up to 5 but doesn't have to be all five ex. NAChR in muscle --> 2α, β, γ, δ, NAChR in CNS --> only α, β excitatory; nAChR, serotonin receptors, 5HT inhibitory; Glycine, GABAa

Answer 2

How Cys-Loop works; second transmembrane domain of α subunit usually obstructs the ion pore agonist binds to α subunit and changes the conformation, moving the obstruction and allowing flow through pore

Answer 3

Cys- loop receptors; nAChR; - Nicotine -Varenicline (Chantix) ;partial agonist --> help quit smoking GABAa receptors; - Ambiem - Alcohol - Barbiturates (phenobarbitals; dilantin, thiopental) - Benzodiazepines (diazepam; valium, lorazepam; valium) Inotropic Glutamate Receptors NMDA receptors; -Ketamine; noncompetitive antagonist (effect; sedation, amnesia) AMPA receptors; -Aniracetam; cognition/ memory enhancer by stimulating AMPAR

Answer 4

excitatory cys-loop ligand gated ion channel - located at NMJ and CNS; - NMJ nAChR contain a, β, δ, and γ subunits - Neuronal nAChRs contain only a and β subunits Receptor state; - closed - open - desensitized excitatory; pass Na+, K+ and Ca++ Cys- loop; Pentamer;5 subunits in the brain nAChR up regulates in response to chronic nicotine smokers have 2x more nAChR receptors than nonsmokers *this is why its hard to quite ;

Answer 5

- not open or closed - higher the affinity ligand for the receptor the more likely to desensitize * only thing that can relieve it is time

Answer 6

ligand gated ion channel - composed of 4 subunits (tetramer) - each subunit has 4 transmembrane domains - second transmembrane domain forms ion pore - each subunit has its own binding site - not all binding sites are for glutamate Types; - NMDA receptors - AMPA receptors - Kainate receptors * only excitatory; pass Na+, K+ and NMDAR pass Ca++

Answer 7

Ligand gated ion channel inotropic glutamte receptor - 2 binding sites for glutamate - 2 binding istes for glycine * all 4 binding sites with 2 of each enzyme must be filled for channel to open * at resting membrane potential NMDAR blocked by Mg * NMDARs "coincidence detectors"

Answer 8

Both NMDA receptors and AMPA receptors are located in the post synaptic terminal of a synapse -AMPA receptors are activated first/ faster and can be activated by a weak stimulations and can create a slight depolarization of a cell, at that same time when glutamate binds to NMDAR only a few ions flow through channel bc it is blocked by Mg++ - with frequent AP AMPAR can generate a larger enough depolarization will cause Mg++ to leave bc the cell will be more postive * depolarization relieves the block and allows NMDAR to open - NMDAR open and passes Ca++, which binds to calmodulin and activates CaMKinase (CaMKII) which leads to an upregulation of AMPARs on the synapse * more AMPARs = stronger synapse **NMDARs are coincidence detectors --> only activate when cell is activated or AP happens in quick succesiolns ^multiple AP needed to move Mg++ block

Answer 9

aka 7 transmembrane receptors - slower signaling than ligand gated ion channels (neurotransmitters use both) - rely on second messenger for signaling - 3% of our genome dedicated for GPCR coding - target for more than half of current pharmaceuticals -α, β, γ, subunits ^most drugs target α 3 main classes - class A; - adrenergic receptors - muscarinic AChR - class B; - parathyroid hormone (PTH) - class C; - metabotropic glutamate receptor - GABAb receptors

Answer 10

* Second messenger system - α subunit has GDP sitting on it - when agonist binds to receptor the α subunit moves over and attaches to it - GDP is kicked out and turned into GTP - α subunit ATP dissociates and is free to activate an effector - activation is terminated when the GTP molecule is hydrolyzed, which allows the α subunit to recombine with β, γ * single agonist-receptor complex can activate several G-protein molecules

Answer 11

Gαs; activates adenylyl cyclase and increases cAMP Gαi; inhibits adenylyl cyclase and decreases cAMP ``` Gαq; activates phospholipase, phosphoinositol hydrolysis; increases IP3 (inositol triphosphate) and DAG (diacylglycerol); which releasesCa++ from intracellular stores and activates protein kinase ```

Answer 12

βγ subunits of G i & G o proteins, appears to be a general mechanism for controlling K + and Ca 2+ channels.

Answer 13

- its internalized by the cell. - disrupts the conversion of GTP to GDP - increased levels of GTP lead to abnormally high cAMP levels - increased cAMP activate Cl ion pump and releases Cl into intestinal lumen - NA+, K+ and bicarb ions follow leading to more water being. held in intestinal lumen to balance osmolarity * diarrhea

Answer 14

- ligand is bound to G-protein coupling receptor for prolonged period of time - recruit another protein β-arrestin binds to the receptor - blocks the signal tagging it for cell to internalize * contributes to drug tolerance

Answer 15

- can act as a proton scaffold inside the cell | - can have it own signaling pathway independent of GPCR signaling inside cell

Answer 16

GABAa [[ligand gated ion channel; cys-loop; inhibitory receptor]] -increased GABAa affinity --> prolonged Cl- conductance [[hyperpolarize]] *vol anesthetics work on GABA and glycine

membrane bound receptors Flashcards

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