Exploring Alpha 7 positive allosteric modulators from a single-channel perspective

ANDERSEN, NATALIA; CORRADI, JEREMIAS; TOLOSA, MA. FERNANDA; GASPARINI, NAHUEL; ARIAS, HUGO; BOUZAT, CECILIA

Sierra de la Ventana

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

Through the enhancement of endogenous ACh responses, positive allosteric modulators (PAMs) of the nicotinic α7 receptor represent a promising therapeutic approach for the treatment of several neurological disorders. We combine single-channel and macroscopic current recordings to explore the molecular basis underlying potentiation of human α7 by three amide derivatives compounds named as Compound 2 (3-furan-2-yl-N-p-tolyl-acrylamide), 3 and 4 (5-100 μM). In contrast to the brief and isolated openings typical of α7, in the presence of Compounds 2, 3 or 4 opening events show significantly increased durations (~7-fold) and appear grouped in bursts of about 10-20 ms. This activity pattern is similar to that observed in the presence of 5-hydroxyindole (5-HI), a type I PAM, which leads to openings of ~2 ms and bursts of ~5 ms. PNU-120596, a type II PAM, produces a more profound increase in open duration, and opening events appear in long clusters that last for several seconds. 5-HT3A and α7-5HT3A receptors as well as an α7 quintuple mutant receptor that is insensitive to PNU are not potentiated by Compound 2. At the macroscopic level, Compound 2 and 5-HI increase the net charge (~5-fold and 8-fold at 50 μM and 2 mM, respectively). However, such increase is mainly due to the decrease in the decay rate for Compound 2, which resembles the effect of a type II PAM, and to the increase of the maximal peak currents for 5-HI. Our results demonstrate that these novel compounds may bind to the same intrasubunit transmembrane cavity as PNU, decrease desensitization as type II PAMs, and modify single-channel activity similarly as type I PAMs. They also contribute to elucidating the foundations of α7 modulation.