Signaling at the neuromuscular synapse requires C(losed-channel)?O(pen-channel) 'gating'of acetylcholine receptors (AChRs). The thermodynamic foundation of this allosteric transition is well understood: transmitter molecules released from the nerve terminal bind to AChRs with higher affinity to O vs. C to increase the probability that the channel is Open. The microscopic events within C?O are less certain. We will use single-channel kinetics and phi-value analysis to probe the interior of AChR gating and illuminate the ultra-fast protein rearrangements within this reaction. So far, results show that AChRs change from C-to-O in 4 steps. The first amino acids to move are not at the transmitter binding sites but in a distant membrane domain linker that joins the M2 and M3 helices of the subunit. Further, the unlocking of a double-gate in M2 (all subunits) occurs in the final 2 gating activation steps. Most side chain gating movements are 'resettling'events that have only local energetic consequences. We will investigate two new hypotheses for AChR gating: 1) communication between the binding sites and the gate is not by a structural-mechanical process but, rather, by the vibrational entropy of the entire backbone, and 2) allosteric communication commences with low-affinity binding of the agonist to the resting receptor.
Chemical synaptic transmission requires the activation of membrane receptors by neurotransmitters. We will use the nerve-muscle synaptic receptor as a model system for understanding the mechanism of this activation. What we will learn increases our basic knowledge of molecular neuroscience, especially with regard to receptor physiology, pharmacology and diseases.
|Gupta, Shaweta; Chakraborty, Srirupa; Vij, Ridhima et al. (2017) A mechanism for acetylcholine receptor gating based on structure, coupling, phi, and flip. J Gen Physiol 149:85-103|
|Purohit, Prasad; Chakraborty, Srirupa; Auerbach, Anthony (2015) Function of the M1 ?-helix in endplate receptor activation and desensitization. J Physiol 593:2851-66|
|Auerbach, Anthony (2015) Agonist activation of a nicotinic acetylcholine receptor. Neuropharmacology 96:150-6|
|Purohit, Prasad; Bruhova, Iva; Gupta, Shaweta et al. (2014) Catch-and-hold activation of muscle acetylcholine receptors having transmitter binding site mutations. Biophys J 107:88-99|
|Nayak, Tapan K; Bruhova, Iva; Chakraborty, Srirupa et al. (2014) Functional differences between neurotransmitter binding sites of muscle acetylcholine receptors. Proc Natl Acad Sci U S A 111:17660-5|
|Purohit, Prasad; Gupta, Shaweta; Jadey, Snehal et al. (2013) Functional anatomy of an allosteric protein. Nat Commun 4:2984|
|Gupta, Shaweta; Purohit, Prasad; Auerbach, Anthony (2013) Function of interfacial prolines at the transmitter-binding sites of the neuromuscular acetylcholine receptor. J Biol Chem 288:12667-79|
|Auerbach, Anthony (2013) The energy and work of a ligand-gated ion channel. J Mol Biol 425:1461-75|
|Jha, Archana; Gupta, Shaweta; Zucker, Shoshanna N et al. (2012) The energetic consequences of loop 9 gating motions in acetylcholine receptor-channels. J Physiol 590:119-29|
|Auerbach, Anthony (2012) Thinking in cycles: MWC is a good model for acetylcholine receptor-channels. J Physiol 590:93-8|
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