Noncanonical NF-kappaB activation requires coordinated assembly of a regulatory complex of the adaptors cIAP1, cIAP2, TRAF2 and TRAF3 and the kinase NIK

Targeting protein kinases for the development of anti-inflammatory drugs

In recent years, protein kinases have become the pharmaceutical industry's most studied class of drug target, and some 10 protein kinase inhibitors have so far been approved for the treatment of cancer. However, whether safe drugs that modulate protein kinase activities can also be developed for the treatment of chronic diseases, where they may need to be taken for decades, is an issue that is still unresolved. A number of compounds that inhibit the p38alpha MAPK have entered clinical trials for the treatment of rheumatoid arthritis and psoriasis, but side effects have prevented their progression to Phase III clinical trials. Here I briefly review the potential problems in targeting p38 MAPK and discuss other protein kinases that regulate the innate immune system, such as Tpl2, MAPKAP-K2/3, MSK1/2 and IRAK4, which may be better targets for the treatment of chronic inflammatory diseases, and NIK, which is an attractive target for the treatment of multiple myeloma, a late stage B-cell malignancy.

Dectin-1 directs T helper cell differentiation by controlling noncanonical NF-kappaB activation through Raf-1 and Syk

The C-type lectin dectin-1 activates the transcription factor NF-kappaB through a Syk kinase-dependent signaling pathway to induce antifungal immunity. Here we show that dectin-1 expressed on human dendritic cells activates not only the Syk-dependent canonical NF-kappaB subunits p65 and c-Rel, but also the noncanonical NF-kappaB subunit RelB. Dectin-1, when stimulated by the beta-glucan curdlan or by Candida albicans, induced a second signaling pathway mediated by the serine-threonine kinase Raf-1, which integrated with the Syk pathway at the point of NF-kappaB activation. Raf-1 antagonized Syk-induced RelB activation by promoting sequestration of RelB into inactive p65-RelB dimers, thereby altering T helper cell differentiation. Thus, dectin-1 activates two independent signaling pathways, one through Syk and one through Raf-1, to induce immune responses.