Activation of the JAK/STAT pathway leads to proliferation of ST14A central nervous system progenitor cells.

We were interested in whether central nervous system progenitor cells possess the signal transduction machinery necessary to mediate cytokine functions and whether this machinery can become activated upon stable expression of a particular cytokine receptor. For this purpose we utilized a previously obtained conditionally immortalized striatum-derived nestin-positive cell line (ST14A). We found that ST14A cells express Jak2, but not Jak1 or Tyk2. An identical pattern of expression was found in embryonic striatal tissue. To evaluate the susceptibility of these cytokine specific cytoplasmic transducers to activation, ST14A cells were stably transfected with the alpha and beta (AIC2A) chains of the murine interleukin-3 receptor. Four independent lines expressing both the alpha and beta receptor subunits were obtained. We found that cells from each of these lines were induced to proliferate upon exposure to interleukin-3. Dose response curve, antibody blocking experiments and binding studies revealed that the response was mediated by the reconstituted high affinity interleukin-3 receptor. Immunoprecipitation studies on these cells showed that Jak2 and Stat5 were being phosphorylated after stimulation of the reconstituted receptor. These results indicate that members of the JAK/STAT family of proteins are expressed in central nervous system progenitor cells and are susceptible to activation through stimulation of an exogenously expressed cytokine receptor, ultimately leading to cell proliferation.