Modulation of metabotropic and ionotropic functions of the nicotinic alpha7 receptor by the intracellular domain

KÖLHER, I.; ESANDI, M.C.; BRUZZONE, A.; CHRESTIA, F.; BOUZAT, C.

Mar del Plata

Congreso; Reunión Anual de Sociedades de Biociencia 2019; 2019

The α7 receptor is a nicotinic receptor present in the nervous system and also in non-neuronal cells. It has been demonstrated that α7 not only mediates fast synaptic transmission in neurons, but also regulates inflammatory responses in immune cell, neurite growth and neuronal protection, as well as cancer cell proliferation. The concept of α7 as a dual metabotropic/ionotropic receptor is attracting increasing attention. A key role in this dual nature corresponds to the receptor ICD domain, which contains sites for modulation and intracellular signaling. Here, we explored the reciprocal crosstalk between phosphorylation-dependent signaling and receptor function by combining mammalian cell expression, electrophysiological recordings and western blot. By using patch clamp recording, we determined a significant increase of burst duration and in the frequency of channel opening in HEK cells expressing a7 and exposed to PP2, an inhibitor of Src family kinases. Prolonged burst duration was also described in receptors mutated at potential phosphorylated tyrosine residues of the ICD domain (Y386F and Y442F). Kinetics of α7 activation by a specific agonist PNU-282987 demonstrated an increase of ERK1/2 phosphorylation in transfected cells, measured by Western blot. However, a tyrosine kinase inhibitor abolished PNU-induced ERK phosphorylation. PNU was not able to trigger ERK phosphorylation neither when the double mutant was transfected nor when α7 and the ICD domain were co-transfected. Finally, in cells co-expressing α7 and 2 adrenergic receptors nicotine, an α7 agonist, decreased the phosphorylation of CREB, a known activated β2-pathway. This study indicates that the phosphorylated states of α7-ICD domain play a key role in the dual metabotropic/ionotropic receptor nature. It also suggests future studies of the possible role of the ICD as a modulator of the crosstalk with other metabotropic receptors.