HOMODIMERIZATION OF INTERLEUKIN-4 RECEPTOR-ALPHA CHAIN CAN INDUCE INTRACELLULAR SIGNALING

The possible role of homodimerization events in intracellular signal t ransduction triggered by the bipartite human interleukin-4 receptor wa s addressed, We generated cell lines functionally expressing derivativ es of the two receptor subunits alpha and gamma, which allow for a spe cific and background-free experimental induction of intracellular homo - and heterodimers, A heterodimer of alpha and gamma released an intra cellular signal, whereas a gamma-gamma homodimer did not, Unexpectedly , we found the intracellular domain of interleukin-4 receptor alpha ch ain to evoke cell proliferation and activation of tyrosine kinase Jak1 as well as of transcription factor State upon homodimerization. Both recruitment of the common gamma chain and activation of kinase Jak3 we re shown to be dispensible for these processes.