CONICET | Buscador de Institutos y Recursos Humanos

In previous reports we showed that the M2 muscarinic acetylcholine receptor (M2R) forms constitutive homodimers in live cells. In this work we tested the ability of serum IgG antibodies against M2R from chronic Chagas´ disease patients (ChD-IgG) to modulate M2 receptor-receptor interaction by bioluminescence resonance energy transfer (BRET). HEK 293 cells cotransfected with fusion proteins M2R-RLuc and M2R-YFP were exposed to ChD-IgG or the IgG fraction from normal subjects (N-IgG) during 60 min at 25°C, and the BRET between M2-RLuc and M2R-YFP was assessed by luminometry. ChD-IgG promoted a concentration-dependent increase in the BRET signal reaching a maximum at 50 µM (23.4 ± 6.6 mBRET, n=7), which was significantly higher than the effect induced by N-IgG (10.1 ± 2.9 mBRET, n=5) (p<0.002). Pretreatment of cotransfected cells with 1µ M atropine failed to inhibit the increased energy transfer induced by ChD-IgG, suggesting that the observed effect is not a consequence of receptor activation. BRET signals obtained by treating cells coexpressing M2R-RLuc and M3R-YFP or M3R-RLuc and M2R-YFP or M3R-RLuc and M3R-YFP with ChD-IgG were not different from that induced by N-IgG, indicating that the effect of ChD-IgG is strictly subtype-specific. Our data show that serum IgG antibodies from ChD patients can enhance M2 receptor-receptor interaction in live cells, defining a new differential pharmacological property for these anti-M2R antibodies as compared with conventional muscarinic ligands.