Interference with JNK attenuates MRGPRX2 expression in the absence of IL-33. (a,b) Cells were deprived of growth factors overnight, and treated with the inhibitor SB203580 (p38) or SP600125 (JNK) for 24 h. (a) Cumulative data from 16 independent experiments are given as net mean fluorescence intensity (MFI), normalized to control (no Inh). (b) Representative histograms, red: Isotype, blue: MRGPRX2-specific antibody. (c,d) Cells were subjected to RNAi targeting JNK1 by the Accell® technology, a matching non-target siRNA served as control. (c) MRGPRX2 cell surface expression given as net mean fluorescence intensity, normalized to control (n = 5). (d) Representative histograms as above. * p < 0.05, *** p < 0.001. Inh = inhibitor.