Figure 2. Identification of CaSR autoantibody working as a biased allosteric modulator to CaSR.

(A) Effects of our AHH patient autoantibody (1:5) on CaSR-dependent PI turnover (left) and ERK1/2 phosphorylation (right) in HEK293 cells stably expressing CaSR stimulated by different concentrations of calcium ions. EC₅₀ of calcium concentration ± SEM in the presence of control IgG or the patient IgG was 2.48 ± 0.01 vs. 1.89 ± 0.04 mM (**P < 0.01) (left) and 2.61 ± 0.03 vs. 3.75 ± 0.20 mM (**P < 0.01) (right). Statistical analysis was performed using Student’s t test. Values represent mean ± SEM of triplicate determinations. Each set of results is representative of at least 2 additional experiments. (B) Effects of cinacalcet on these AHH patient autoantibody effects. Statistical analysis was performed using 2-way ANOVA with Tukey’s multiple comparison test. Values represent mean ± SEM of triplicate determinations. Each set of results is representative of at least 2 additional experiments. Scale bar: 50 μm (inset). (C) Effects of the AHH patient sera (1:20 dilution) (left) and pertussis toxin (PTX) (right) on PTH secretion from parathyroid adenoma cells. Statistical analysis was performed using Student’s t test. Values represent mean ± SEM of triplicate determinations. Each set of results is representative of at least 2 additional experiments. **P < 0.01; ***P < 0.0001.