Fig 9.

Enzymatic activity of SOS1 is dispensable for BCR-induced p38 activation. (A) Flow cytometric assay of phospho-p38 induced by BCR cross-linking in wild-type DT40 cells. (B) hSOS1 expression profile of transiently transfected SOS1/2 DT40 cells. Two gates show hSOS1-positive (hSOS+) and -negative (hSOS−) populations. (C and E) BCR-induced ERK and p38 activation in transiently transfected SOS1/2 DT40 cells. The hSOS1− subset (open histogram) of each transfection is compared with the hSOS1+ subset (gray histogram) as gated in panel B. (C) Two arbitrarily chosen reference lines in the histogram plot represent basal (left) and maximal (right) pERK intensities of wild-type hSOS1 transfection. (E) Reference line represents basal pP38 intensity. (D and F) Graphical representation of pERK and phospho-p38 mean fluorescence intensities (MFI) shown in panels C and E. “SOS1 negative” represents the average phospho-p38 MFI value of the hSOS− subset in three samples. Data are representative of two experiments.