Identification of isoform-specific dynamics in phosphorylation-dependent STAT5 dimerization by quantitative mass spectrometry and mathematical modeling.

摘要: STAT5A and STAT5B are important transcription factors that dimerize transduce activation signals of cytokine receptors directly to the nucleus. A typical mediates STAT5 is erythropoietin (Epo). Differential functions have been reported. However, extent which phosphorylated (pSTAT5A, pSTAT5B) form homo- or heterodimers not understood, nor how this might influence signal transmission To study this, we designed a concept investigate isoform-specific dimerization behavior pSTAT5A pSTAT5B comprises immunoprecipitation (IP), measurement degree phosphorylation, isoform ratio determination between STAT5B. For main analytical method, employed quantitative label-free -based mass spectrometry. cellular model system, used Epo receptor (EpoR)-expressing BaF3 cells (BaF3-EpoR) stimulated with Epo. Three hypotheses dimer formation were explain results by static mathematical model: (i) homodimers only, (ii) (iii) random heterodimers. The best agreement experimental data simulations was found for last case. Dynamics cytoplasmic could be explained distinct nuclear import rates individual retention STAT5.