PT - JOURNAL ARTICLE AU - Seiya Fukushima AU - Satomi Matsuoka AU - Masahiro Ueda TI - Excitable dynamics of Ras triggers self-organized PIP3 signaling for spontaneous cell migration AID - 10.1101/356105 DP - 2018 Jan 01 TA - bioRxiv PG - 356105 4099 - http://biorxiv.org/content/early/2018/06/27/356105.short 4100 - http://biorxiv.org/content/early/2018/06/27/356105.full AB - Eukaryotic amoeboid cells generate an intracellular asymmetric signal through excitable dynamics of chemotactic signaling pathways, by which GTP-bound Ras (Ras-GTP) and PI(3,4,5)P3 phosphatidylinositol lipid (PIP3) accumulate in the anterior part of a migrating cell even in the absence of external asymmetric cues. In order to clarify key determinants in the signaling pathways for the spontaneous excitable dynamics, we have studied spatiotemporal dynamics of the major signaling components with genetic and pharmacological inhibition. Here we report that spontaneous excitability in the activation of Ras triggers symmetry breaking without the activation of downstream pathways. Quantitative live imaging of pairs of Ras-GTP and one of PIP3, PI(4,5)P2, PI3K or PTEN revealed that all these components followed the dynamics of Ras-GTP. Furthermore, the interaction between Ras-GTP and PI3K was essential for the asymmetric accumulation of downstream PIP3 on the membrane, which in turn enhanced Ras excitability via a positive feedback mechanism. Mathematical modeling of the excitable dynamics reconstituted the observations, illustrating that the Ras GTPase regulatory network is central for internal symmetry breaking. The results also suggest cellular decision-making mechanisms in response to external guidance cues.Author contributions:S.F. conducted the experiments; all authors analyzed the data and wrote the manuscript.AbbreviationsGAPGuanosine Triphosphate hydrolase activating proteinGEFGuanine nucleotide exchange factorGFPGreen fluorescent proteinPHDPleckstrin homology domainPI3KPhosphoinositide 3-kinasePIP2Phosphatidylinositol (4,5)-bisphosphatePIP3Phosphatidylinositol (3,4,5)-trisphosphatePKB&AktProtein kinase BPLCδ1Phospholipase C delta 1PTENPhosphatase and tensin homologRBDRas binding domainRFPRed fluorescent protein