Interleukin-4 receptor subunit alpha
The functional IL4 receptor is not formed until initial binding of IL-4. The immune cell membrane complex has subsequent recruitment of the common gamma chain, to create a type I receptor while, in non-immune cells, subsequent recruitment of interleukin-13 receptor subunit alpha-1 forms a type II receptor. IL-4RA can also interact with the IL-13/[interleukin-13 receptor subunit alpha-1]] complex to form a similar type II receptor.
It couples to the JAK1/2/3-STAT6 pathway. The IL-4 response is involved in promoting Th2 differentiation. The IL-4 and IL-13 responses are involved in regulating IgE production and, chemokine and mucus production at sites of allergic inflammation such as in atopic dermatitis. In some cell types it can signal through activation of insulin receptors. On IL-4 binding it is phosphorylated on C-terminal tyrosine residues. Phosphorylation on any one of tyrosine residues, Tyr-575, Tyr-603 or Tyr-631, is required for STAT6-induced gene induction The soluble form formed by cleavage (soluble interleukin-4 receptor subunit alpha, soluble IL-4 receptor subunit alpha, soluble IL-4R-alpha,sIL4R alpha, IL-4-binding protein, IL4-BP, sIL4R) inhibits IL-4-mediated cell proliferation and IL-5 up-regulation by T-cells.