Tyrosine-protein kinase JAK1 (JAK1) is phosphorylated after Interleukin-24 (IL24) ligand interaction with its receptor. There are two IL24 receptors. One consists of Interleukin-20 receptor subunit alpha (IL20RA), Tyrosine-protein kinase JAK1 (JAK1) and Interleukin-20 receptor subunit beta (IL20RB), the other uses nterleukin-22 receptor subunit alpha-1 (IL22RA1) instead of IL20RA (Dumoutier et al. 2001, Wang et al. 2002). IL24 can stimulate JAK1 phosphorylation in human colonic subepithelial myofibroblasts, where the components of both forms of the IL24 receptor are expresed (Andoh et al. 2009). It has been demonstrated that both forms of the IL24 receptor can activate STAT3 (Dumoutier et al. 2001, Wang et al. 2002). Based on the consensus understanding of JAK/STAT signaling, STAT3 activation is very likely to be preceded by JAK1 phosphorylation and it is therefore likely that JAK1 is phosphorylated in both forms of the IL24 receptor.
This is a black box event because it has not been established that both forms of the IL24 receptor are involved in JAK1 phosphorylation.