Positive regulation of TNFR1 signaling via SH3 recognition motif

TNF is a pleiotropic cytokine and shows its biological function by binding to its receptors called TNFR1 and TNFR2. While TNFR1 induces apoptosis by activation of caspase-8 via the death domain, it also activates IKK alpha/ss, MKK3/6, MKK4/7 by activation of TAK1. Although the TNFR1 signaling pathway is known by in large, it is not known how AKT and MAPKs p38, ERK1/2, and JNK1/2 are activated. The presence of a proline-rich PPAP region, (P(448)PAP(451), a binding site for the SH3 domain-containing proteins) very close to the C-terminus promoted us to determine whether this region has any role in the TNFR1 signal transduction. To test this, the codons of P 448 and P 451 were changed to that of Alanin, GCG, via site-directed mutagenesis, and this plasmid was named as TNFR1-SH3-P/A. Subsequently, ectopically expressed the wild type TNFR1 and TNFR1-SH3-P/A in 293T cells and determined the levels of TNF-alpha-mediated phosphorylations of ERK, p38, JNK and AKT, NF-kB, and caspase-8 activation. While ectopic expression of our mutant diminished TNF alpha-mediated phosphorylations of p38, JNK, ERK and AKT, it increased NF-kB, and caspase-8 activations. In conclusion, TNF alpha-mediated ERK, AKT, JNK, p38 activations are affected by TNFR1 SH3 domain modifications.

Automated summary

The study revealed that mutations in the SH3 domain of TNFR1 affect the activation of ERK, AKT, JNK, and p38 mediated by TNF alpha, providing further insight into the TNFR1 signaling pathway.