Signal transduction by the atopy-associated human thymic stromal lymphopoietin (TSLP) receptor depends on Janus kinase function

Thymic stromal lymphopoietin ( TSLP) is an interleukin-(IL)-7-like cytokine with emerging pathological importance for the development of atopic diseases such as allergic asthma bronchiale. The TSLP receptor ( TSLPR), a heterodimeric type I cytokine receptor, shares the IL-7R alpha-subunit with the IL-7 receptor system. The specific TSLPR alpha-chain shows similarities with the gamma c receptor chain, but has some unusual features within the receptor family in both its ligand-binding and cytoplasmic domain. The murine TSLPR signals via the signal transducers and activators of transcription STAT5 and STAT3, but is unique among cytokine receptors in that it activates STATs without the involvement of Janus (JAK) tyrosine kinases, but instead utilizes the Src type kinase Tec. Here, we show by Western blotting and reporter gene experiments in combination with the application of a specific JAK inhibitor that the human TSLP receptor, in contrast, requires the function of JAK1 and JAK2 for STAT activation. Moreover, we demonstrate that the human TSLPR mediates gene regulation not only through STAT5 and STAT3 but has also the potential to mediate transcription via STAT1. Our work should help to understand more thoroughly how TSLP triggers inflammatory responses in the course of atopic diseases.