NGF withdrawal induces apoptosis in CESS B cell line through p38 MAPK activation and Bcl-2 phosphorylation

The sIgG(+) lymphoblastoid B cell line CESS spontaneously produces a high a mount of NGF and expresses both high affinity (p140(Trk-A)) and low affinit y (p75(NTR)) NGF receptors. Blocking NGF signals with neutralizing antibodi es or specific Trk-A inhibitors induces a rapid phosphorylation of antiapop totic Bcl-2 protein, followed by caspase activation, and apoptotic death of CESS cells. Bcl-2 phosphorylation in several sites within a approximate to 60 aa "loop" domain of protein is known to regulate its antiapoptotic func tion. Accordingly, CESS cells expressing the loop deletional mutant cDNA co nstructs Bcl-2 Delta 40-91 were completely resistant to apoptosis induced b y NGF withdrawal, indicating that Bcl-2 phosphorylation is a critical event . NGF withdrawal induces p38 MAPK, but not JNK, activation in CESS cells, a nd SB203580, a specific inhibitor of p38 MAPK, is able to prevent both Bcl- 2 phosphorylation and apoptosis, indicating that p38 MAPK is the enzyme res ponsible for these events. (C) 2000 Academic Press.