Loss of Function Due to Heteromerization of wild-type P2X7 Receptor with the mood disorder-associated Gln460Arg variant

FERNANDO APRILE-GARCIA; SANDRA WALSER; NINA DEDIC; MARCELO PAEZ PEREDA; ANA C LIBERMAN; SERGIO SENIN; JUAN GEREZ; ESTEBAN HOIJMAN; DAMIAN REFOJO; MISO MITKOVSKI; WALTER STUHMER; FLORIAN HOLSBOER; JAN M DEUSSING; EDUARDO ARZT

Simposio; Second South American Spring Symposium in Signal Transduction and Molecular Medicine (SISTAM); 2012

The P2X7 receptor is a member of the P2X family of ligand-gated ion channels. In the central nervous system, P2X7R has an important role in the regulation of diverse neuronal functions including neurotransmitter release, synaptic transmission and aspects of behavior. The single-nucleotide polymorphism Gln460Arg in this gene has been consistently associated with bipolar disorder and major depression, but the P2X7R-Gln460Arg variant itself is not compromised in its activity. Calcium imaging, patch clamp analysis and ERK 1/2 activation, indicate that the P2X7R-Gln460Arg variant shows no functional differences compared to P2X7R-WT when either forms are expressed alone in the cell. The co-expression of both the normal and the mutant variants significantly diminishes P2X7R normal function. Moreover, co immunoprecipitation and FRET studies show that the P2X7R-Gln460Arg protein physically interacts with the P2X7R-WT subunit. When co-expressed, specific silencing of either the normal or mutated variant rescues the heterozygous loss of function phenotype and restores normal function. To investigate its functional significance in vivo we generated mice expressing human wild-type P2X7R or hP2X7R-Gln460Arg, respectively. Interestingly, only the mice heterozygous for both variants showed changes in the sleep electroencephalogram equivalent to those of human depression and an altered response to chronic social stress. The described loss of function due to heteromerization explains the mechanism by which the P2X7RGln460Arg variant acts providing an explanation for the observed susceptibility to mood disorders.