Figure 4

Termination of BMP signaling by dephosphorylation and/or degradation of phospho-Mad.

(a) 9 hour time course assay showing stabilization of linker phosphorylated Mad using the proteasomal inhibitor MG2132 (MG132 was resuspended in DMSO). (b) Treatment of S2R+ cells with DMSO alone over 9 hours shows it has no effect on Mad linker phosphorylation levels. (c) Mad phosphorylations were stabilized by Dullard knockdown or proteasomal inhibition (MG132). Strongest stabilization is found when both Dullard and the proteasome were inhibited. Note Mad C-terminal phosphorylation is not detectable in the absence of an activated-Tkv receptor, however, C-terminal phosphorylation becomes evident either by knocking down the phosphatase Dullard or inhibiting the proteasome by MG132. (d) Activated-Tkv induced C-terminal and linker phosphorylated Mad was strongly stabilized by Dullard knockdown and/or proteasomal inhibition compared to control untreated or DMSO treated cells.