Interleukin-6 signalling: more than Jaks and STATs.

The hallmark of signalling by many cytokines is the activation of the Janus kinase (Jak)/signal transducer and activator of transcription (STAT) pathway. However, cytokines additionally activate other pathways. In past years we realised that these pathways significantly contribute to the physiological functions of IL-6 and pathophysiological functions in the context of many inflammatory and proliferative diseases. Whereas other articles in this issue of the European Journal of Cell Biology focus on STAT activation and its regulation we here aim to summarise our knowledge and some remaining questions on interleukin-6 (IL-6)-induced STAT-independent pathways as well as the cross-talk with the Jak/STAT pathway. In the early stages of studying cytokine signalling we were used to analysing individual signalling pathways. These days we know about the importance of both, the crosstalk between pathways initiated by combinations of cytokines as well as the crosstalk between individual pathways initiated by a single cytokine. Whereas the inter-cytokine crosstalk can be studied relatively easily, more sophisticated experimental approaches are required to elucidate the intra-cytokine crosstalk.