Lecture-15 GPCRs - Referring back to the last lecture, we...

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The second major type of neurotransmitter receptor Metabotropic – Neurotransmitter binding causes a conformational change in the receptor which leads to G protein binding and to the production of intracellular metabolites through enzymatic processes. These responses are of slow onset and long duration, compared to ionotropic receptors. These receptors are sometimes referred to as G-protein coupled receptors (GPCRs). Referring back to the last lecture, we learned that there were two major classes of neurotransmitter receptors, ionotropic receptors and. ..
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Some history. .. In the 1950’s Sutherland and Rall found that stimulation of cardiac cells with epinephrine resulted in increased concentrations of a water-soluble nucleotide called cyclic adenosine monophosphate (cAMP). They proposed that cAMP acted as a second messenger . Neurotransmitters, hormones and drugs that cannot cross the cell membrane ( first messengers ) exert their effects inside cells through molecules ( second messengers such as cyclic nucleotides, ions, phospholipids) that act intracellularly .
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Most hormones and many neurotransmitters act by regulating intracellular second messengers. In most cases, there are multiple receptors for single neurotransmitters that bind to GPCRs. This was predicted from classical binding studies. For example, there are 5 classes of muscarinic acetylcholine receptors and 6 classes of adrenergic receptors. In many cases, the complex pharmacological responses produced by a single ligand are due to its actions on a number of different receptors. The physiological roles of many of these receptors and why this diversity exists are poorly understood.
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Three components required for G-protein signaling 1. Receptor (on cell surface) 2. G protein (couples to receptor on intracellular side of cell membrane) 3. Effectors (usually enzymes) All three are either imbedded in the cell membrane or tightly associated with it.
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What does a G-protein coupled receptor look like? Huge family of related
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Lecture-15 GPCRs - Referring back to the last lecture, we...

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