Splitting Function enables Dual Feedback Regulation to Control JAK2/STAT5 Signaling for a Wide Ligand Range

Cellular signal transduction is governed by multiple feedback mechanisms to elicit robust cellular decisions. We combined mathematical modeling and extensive time-resolved data sets in primary erythroid progenitor cells and dissected the roles of the two transcriptional feedback regulators of the SOCS family, CIS and SOCS3 in JAK2/STAT5 signaling. Our model revealed that both feedbacks are most effective at different ligand concentration ranges. To identify the relevant transcriptional feedback regulators that are involved in attenuation of Epo-induced JAK2-STAT5 signaling in addition to CIS, we performed a time-resolved genome-wide expression profiling of murine erythroid progenitor cells at the colony forming unit erythroid (CFU-E) stage up to 24 and 7 hours after EPO stimulation and in control, repectively. The analysis identified SOCS3 as the only further de novo regulated gene upon Epo-induced JAK2-STAT5 signaling. From subsequent mathematical modeling, we calculated the STAT5 response in previously unobserved Epo concentrations, which provided a quantitative link between cell survival and the integrated response of STAT5 in the nucleus. In conclusion, our combined modeling approach revealed novel insights into the orchestrated action of feedback control to regulate STAT5-mediated survival decisions over a broad range of ligand concentrations. Freshly sorted CFU-E cells were starved for 1 h in Panserin 401 supplemented with BSA and 50 µM β-Mercaptoethanol. Subsequently, cells were stimulated with 0.5 U/ml Epo or left untreated and RNA was extracted at different time points (0,1,2,3,4,5,6,7,8,14,19,24 hrs after Epo stimulation and at 0,1,2,3,4,5,6,7 hrs without Epo treatment) using the RNeasy Mini Plus Kit (Qiagen, Hilden, Germany).