Anisomycin is a phenylpyrolidine derivative shown to strongly activate the stress-induced MAP kinases JNK and p38. This activity results in the induction of the immediate-early genes: c-Fos, c-Jun, Fos B, Jun B and Jun D, and enhanced phosphorylation of p54/nrb, ATF-2, ERK, Caldesmon, IRS-1 and IRS-2. This compound behaves as a true signaling agonist, and has been implicated to play an important role in hyperosmolarity and UV-stimulated responses. Anisomycin has also been shown to increase the phosphorylation of p70 S6 kinase α.