The cysteine protease papain was shown to induce production of IL-4 and other cytokines in murine basophils, a critical event for initiating and promoting type 2 immune responses. However, the papain ‘sensor(s)’ and the intracellular signaling pathway for IL-4 production triggered by the protease remained unknown. Here we show that basophils lacking FcRγ or expressing dominant negative Syk failed to produce IL-4 in response to papain, indicating the involvement of the FcRγ-Syk pathway that was essential also for IL-3-induced IL-4 production. While IL-3, IgE cross-linkage and papain induced production of IL-4, IFN-β production was induced only by papain, indicating that papain sensor(s) or its downstream signaling pathways for production of IL-4 seemed to be distinct from those for IFN-β production. We further showed using the artificial papain sensor CD8-FcRγ fusion protein that IL-3 potentiated, independently of FcRγ, basophil response to FcRγ-dependent papain signals. Thus, our current study showed that papain sensing and/or downstream signaling are unique for cytokines to be induced and regulated through cross-talk with other signals such as IL-3 signals.