Biased allosteric modulation of agonist-induced beta-arrestin recruitment by M2 muscarinic receptor autoantibodies from Chagas disease patients with cardiac dysautonomia

CARRERA PÁEZ LC; BELTRAME, S; CARPINTERO POLANCO, YM; AUGER, SR; SABRA, AH.; BILDER, CR.; WALDNER, CI.; GOIN, JC

Congreso; XXXVII Congreso Anual de la Sociedad Argentina de Investigación en Neurociencias; 2022

Serum levels of IgG autoantibodies against M2 muscarinic receptors (M2R AAb) correlate with the degree of cardiac vagal impairment in chronic Chagas disease (CCD). Recent data showed that the exposure of cardiac M2R to M2R AAb could attenuate agonist-induced Gi protein activation and arrestin-2 (Arr-2) recruitment in heterologous mammalian cells. In this study, we used Bioluminescent Resonance Energy Transfer to investigate the ability of M2R AAb from CCD patients with dysautonomia to modulate agonist-induced β-arrestin recruitment through an allosteric mechanism. Carbachol treatment of HEK 293T cells expressing M2R fused to Renilla luciferase (RM2-RLuc) and Arr-2 (or Arr-3) fused to yellow fluorescent protein (Arr-2-YFP or Arr-3-YFP) (BRET pair) stimulated the interaction between M2R and Arr-2 (or Arr-3) in the presence of GRK2. However, treatment of cells with serum IgG fractions from seropositive patients for M2R AAb (IgG Ch+) or IgG from uninfected individuals (control IgG) failed to promote Arr-2 or Arr-3 translocation, suggesting that these AAb are unable to desensitize M2R. Preincubation of cells coexpressing the BRET pair and GRK2 with IgG Ch+, followed by the addition of carbachol, resulted in a noncompetitive inhibition of Arr-2 recruitment (but not Arr-3), whereas control IgG was unable to modulate the translocation either β-arrestin. This study suggests that M2R AAb act as Arr-2-biased allosteric modulators of agonist efficacy.