Mitochondrial α7 nicotinic acetylcholine receptors are displaced from complexes with VDAC1 to form complexes with Bax upon apoptosis induction.

Nicotinic acetylcholine receptors (nAChRs) mediate fast synaptic transmission in muscles and autonomic ganglia and regulate cytokine and neurotransmitter release in the brain and non-excitable cells. The α7 nAChRs localized in the outer membrane of mitochondria regulate cytochrome c release stimulated by apoptosis-inducing agents. However, the mechanisms through which nAChRs influence mitochondrial permeability remain obscure. Here we put an aim to explore the interaction of nAChRs with voltage-dependent anion channels (VDAC1) and pro-apoptotic protein Bax in the course of apoptosis induction. By using molecular modeling in silico, it was shown that both Bax and VDAC1 can bind within the 4th transmembrane portion (M4) of nAChR subunits. Experimentally, α7 nAChR-Bax and α7 nAChR-VDAC1 complexes were identified by sandwich ELISA in mitochondria isolated from astrocytoma U373 cells. Stimulating apoptosis of U373 cells by HO disrupted α7-VDAC complexes and favored formation of α7-Bax complexes accompanied by cytochrome c release from mitochondria. α7-selective agonist PNU282987 or type 2 positive allosteric modulator PNU120596 disrupted α7-Bax and returned α7 nAChR to complex with VDAC1 resulting in attenuation of cytochrome c release. It is concluded that mitochondrial nAChRs regulate apoptosis-induced mitochondrial channel formation by modulating the interplay of apoptosis-related proteins in mitochondria outer membrane.