Ionotróp receptorok allosztérikus modulációja = Allosteric modulation of ionotropic receptors

A pentamer szerkezetű ionofór neurotranszmitter ?-aminovajsav, szerotonin és glicin receptorok (GABAAR, 5-HT3R, GlyR) szerkezetét és allosztérikus szabályozását vizsgáltuk meg. Az 5-HT3AR-ok pontmutációi és számítógépes modellezése antagonistáik kétféle kötődésmódját igazolták. Két fő neuroszteroidnak (allopregnanolon és THDOC) a GABAAR kötődésre és ionofór funkciója potencírozására kifejtett eltérő hatásai alapján a nanomoláris allopregnanolon az α6ßδ GABAAR-ok fiziológiás modulátora. Au allopregnanolon 17ß-származékát az első nanomólos affinitású, α6ßδ receptor- és sztereoszelektív neuroszteroid antagonistaként jellemeztük. Bifenil származékok gyulladásgátló és GABAAR-kötődési hatásainak szerkezeti kritériumait megkülönböztettük. 5-HT3 R antagonistákból kifejlesztettünk GlyR-okra és hiperekplexia mutánsukra szelektív potenciáló (nor)tropeineket. A heteroaromás tropein észterek heterogén GlyR-kötődésének nanomólos fázisát potenciáláshoz, a µmólost gátláshoz rendeltük. Az α1 GlyR pontmutációi és molekuladinamikai szimulációja alátámasztja az Arg-119 rotamerek és nortropeinek kötődésmódjai eltérő szerepét a GlyR-t gátló és potenciáló hatásokban. | The structures and allosteric modulation of pentameric ionotropic neurotransmitter receptors of ?-aminobutyric acid, serotonin and glycine (GABAAR, 5-HT3R, GlyR) were examined. Point mutations and computer modeling of 5-HT3ARs supported dual binding modes of antagonists. Based on different effects of two major neurosteroids, allopregnanolone and THDOC, on GABAAR binding and ionophore potentiation, nanomolar allopregnanolone is the physiologic modulator of α6ßδ GABAARs. Structural requirements of the anti-inflammatory and GABAAR-binding effects of biphenyl derivatives were distinguished. From 5-HT3 R antagonists (nor)tropeines were developed to selective potentiators of GlyRs and their hyperekplexia mutants. Nanomolar and micromolar phases of GlyR binding of heteroaromatic tropeine esters were attributed to potentiation and inhibition of GlyRs respectively. Point mutations of α1 GlyRs and molecular dynamic simulations supported the differential roles of Arg-119 rotamers and dual binding modes of nortropeines to block versus potentiate GlyRs

Hyperekplexia mutation R271L of alpha1 glycine receptors potentiates allosteric interactions of nortropeines, propofol and glycine with [3H]strychnine binding.

Human alpha1 and hyperekplexia mutant alpha1(R271L) glycine receptors (GlyRs) were transiently expressed in human embryonic kidney 293 cells for [3H]strychnine binding. Binding parameters were determined using a ternary allosteric model. The hyperekplexia mutation increased the positive cooperativity of 0.3 mM propofol and glycine binding by about six times: the cooperativity factor beta was 0.26 for alpha1 GlyRs and 0.04 for alpha1(R271L) GlyRs. Thus, propofol restored the potency of glycine impaired by the mutation. Five nortropeines, i.e. substituted benzoates of nortropine and a new compound, nortropisetron were prepared and also examined on [3H]strychnine binding. They showed nanomolar displacing potencies amplified by the hyperekplexia mutation. The affinity of nor-O-zatosetron (2.6 nM) is one of the highest reported for GlyRs. This binding test offers an in vitro method to evaluate agents against neurological disorders associated with inherited mutations of GlyRs

Synthesis of (nor)tropeine (di)esters and allosteric modulation of glycine receptor binding

(Hetero)aromatic mono- and diesters of tropine and nortropine were prepared. Modulation of [3H]strychnine binding to glycine receptors of rat spinal cord was examined with a ternary allosteric model. The esters displaced [3H]strychnine binding with nano- or micromolar potencies and strong negative cooperativity. Coplanarity and distance of the ester moieties of diesters affected the binding affinity being nanomolar for isophthaloyl-bistropane and nortropeines. Nortropisetron had the highest affinity (K(A) approximately 10 nM). Two esters displayed negative cooperativity with glycine in displacement, while three esters of low-affinity and nortropisetron exerted positive cooperativity with glycin

Hyperekplexia mutation R271L of alpha1 glycine receptors potentiates allosteric interactions of nortropeines, propofol and glycine with [3H]strychnine binding

Human alpha1 and hyperekplexia mutant alpha1(R271L) glycine receptors (GlyRs) were transiently expressed in human embryonic kidney 293 cells for [3H]strychnine binding. Binding parameters were determined using a ternary allosteric model. The hyperekplexia mutation increased the positive cooperativity of 0.3 mM propofol and glycine binding by about six times: the cooperativity factor beta was 0.26 for alpha1 GlyRs and 0.04 for alpha1(R271L) GlyRs. Thus, propofol restored the potency of glycine impaired by the mutation. Five nortropeines, i.e. substituted benzoates of nortropine and a new compound, nortropisetron were prepared and also examined on [3H]strychnine binding. They showed nanomolar displacing potencies amplified by the hyperekplexia mutation. The affinity of nor-O-zatosetron (2.6 nM) is one of the highest reported for GlyRs. This binding test offers an in vitro method to evaluate agents against neurological disorders associated with inherited mutations of GlyR