The cytotoxic prodigiosin induces phosphorylation of p38-MAPK but not of SAPK/JNK.

Prodigiosin (PG) is a red pigment produced by Serratia marcescens, with cytotoxic and immunosuppressive activity. It induces apoptosis in several cancer cell lines, including Jurkat-T cells. Here we examine the role of two stress-stimulated kinase cascades in this induction. Time course experiments using polyclonal antibodies showed that p38-MAPK phosphorylation began at 15 min and lasted for 3 h, whereas JNK was not phosphorylated, although both proteins were present. SB203580, a selective inhibitor of p38-MAPK, blocked its phosphorylation in PG-treated cells. Taken together, these data suggest that the PG induces phosphorylation of p38-MAPK but not of SAPK/JNK and that it increases the expression of both c-jun and c-fos oncoproteins.