FIGURE 5.

Transforming properties of JAK2-V617F are not activated by expression of IL12RB1. A, a schematic diagram comparing IL27Ra and IL12RB1 is shown. The white regions of the extracellular region of the receptors represent cytokine receptor homology domains, whereas the gray regions represent fibronectin-like domains. The transmembrane (tm) domain of each receptor is indicated. Within the cytoplasmic tail of each receptor the Box 1 motif for IL27Ra and the Box 1 and 2 motifs of IL12RB1 are indicated. B, BaF3 cells co-expressing wild type JAK2 (JAK2 WT, left) or JAK2-V617F (right) with a control empty vector (filled circles), IL27Ra (filled squares), or IL12RB1 (open triangles) were washed and plated in the absence of cytokine on day 0. Total viable cells were determined by trypan blue exclusion over time. C, BaF3 cells co-expressing empty vector (lanes 1 and 2), IL27Ra (lanes 3 and 4), or IL12RB1 (lanes 5 and 6) with wild type JAK2 (WT) (lanes 1, 3, and 5), or JAK2-V617F (VF) (lanes 2, 4, and 6) were starved of cytokine for 3 h. Cells were then lysed and an equal amount of lysate protein was analyzed by immunoblotting for pJAK2 (Tyr¹⁰⁰⁷/Tyr¹⁰⁰⁸), JAK2, pSTAT5 (Tyr⁶⁹⁴), STAT5, pERK (Thr²⁰²/Tyr²⁰⁴), ERK, IL27Ra, and IL12RB1, as indicated.