cell regulation by the intrinsically disordered region of Src – FUZZY-SRC

Most eukaryotic proteins have intrinsically disordered regions (IDRs) that challenge the classical structure-function paradigm. IDRs are very frequent in transcription and signaling proteins implicated in human diseases. The Src kinase, a master regulator of cell growth and adhesion, is a prototype of IDR-containing signaling kinases. IDRs adopt multiple conformations that are sensitive to the environment and, through multiple weak interactions in a fuzzy complex, may direct the activity of folded domains of signaling proteins towards different pathways. Consistent with this, our molecular studies suggest that Src-IDR makes an intramolecular fuzzy complex that modulates Src membrane anchoring and kinase signaling, and our main objective is to decipher this phospho-signaling mechanism. For this, both NMR-characterized mutations and a synthetic library of Src-IDR mutants will be functionally screened after transduction in Src-dependent cell lines to detect changes in Src activity. Then, changes in Src compaction, intramolecular interactions and membrane anchoring in selected mutants will be analyzed by NMR/biophysical and imaging methods. Finally, their effect on Src signaling and adhesive activity will be evaluated by extensive proteomics and optogenetics in cells. Overall, this multidisciplinary project will address how unstructured regions regulate activity of folded domains to ensure protein signaling specificity.