FIG. 9.
Jak1 is required for IL-2-induced phosphorylation of PI 3-K p85. (A) Transfection of Jak1 is required for IL-2-induced tyrosine phosphorylation of PI 3-K p85 in A49 cells. A49 cells were transfected with IL-2Rβ, γc, and Jak3, with or without wild-type (WT) Jak1 or DNJ1 (DNJak1). Cells were washed and starved overnight in DMEM–1% FBS and then not stimulated or stimulated for 10 min with 2 nM IL-2. The arrowhead points to a band that we believe to be Jak1. IP, immunoprecipitation; αPY, antiphosphotyrosine. (B) The lack of phosphorylation of p85 in lane 6 of panel A was not due to lack of association of DNJ1 with p85. Note that the decreased association of DNJ1 with p85 in the absence of IL-2 was not expected; however, the key point is that the degree of association in lane 6 was similar to that seen with wild-type Jak1 (lane 4). (C) Controls for expression of Jak1, Jak3, p85, IL-2Rβ, and γc in the transfected A49 cells.