Bad (Ser-26), Phosphospecific Antibody

Bad is a member of the BCL-2 family of regulators involved in programmed cell death. This protein positively regulates cell apoptosis by forming heterodimers with BCL-xL and BCL-2, and reversing their death repressor activity. Proapoptotic activity of this protein is regulated through its phosphorylation. Protein kinases AKT IKK, and MAP kinases, as well as protein phosphatase calcineurin are found to be involved in the regulation of this Bad activity. Phosphorylation of Bad occurs on one or more of Ser-26, Ser-112, Ser-136, and Ser-155 in response to survival stimuli, which blocks its pro-apoptotic activity. Phosphorylation on Ser-136 or Ser-112 promotes heterodimerization with 14-3-3 proteins. This interaction then facilitates the phosphorylation at Ser-155, a site within the BH3 motif, leading to the release of Bcl-xL and the promotion of cell survival. Ser-26 is phosphorylated by IKK leading to phosphorylation of C-terminal serine sites and disruption of binding to Bcl-xL. This inactivation of Bad inhibits TNFα-induced apoptosis independent of NF-κB activity.

The antibody detects a 23 kDa* doublet corresponding to the apparent molecular mass of phosphorylated Bad on SDS-PAGE immunoblots of mouse J774A.1 treated with calyculin A. This reactivity is not observed after lambda phosphatase treatment. This peptide sequence is highly conserved in rat Bad, but is not found in human Bad.