title: The small GTPase HRas shapes local PI3K signals through positive feedback and regulates persistent membrane extension in migrating fibroblasts.
abstract: Self-amplification of phosphoinositide 3-kinase (PI3K) signaling is believed to regulate asymmetric membrane extension and cell migration, but the molecular organization of the underlying feedback circuit is elusive. Here we use an inducible approach to synthetically activate PI3K and interrogate the feedback circuitry governing self-enhancement of 3'-phosphoinositide (3-PI) signals in NIH3T3 fibroblasts. Synthetic activation of PI3K initially leads to uniform production of 3-PIs at the plasma membrane, followed by the appearance of asymmetric and highly amplified 3-PI signals. A detailed spatiotemporal analysis shows that local self-amplifying 3-PI signals drive rapid membrane extension with remarkable directional persistence and initiate a robust migratory response. This positive feedback loop is critically dependent on the small GTPase HRas. Silencing of HRas abrogates local amplification of 3-PI signals upon synthetic PI3K activation and results in short-lived protrusion events that do not support cell migration. Finally, our data indicate that this feedback circuit is likely to operate during platelet-derived growth factor-induced random cell migration. We conclude that positive feedback between PI3K and HRas is essential for fibroblasts to spontaneously self-organize and generate a productive migratory response in the absence of spatial cues.
authors.affiliation: Program in Neuroscience and Neurobehavioral Disorders, Duke-NUS Graduate Medical School, Singapore 169857.
authors.forename: Jervis Vermal
authors.initials: JV
authors.lastname: Thevathasan
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Tan
authors.forename: Hui
authors.initials: H
authors.lastname: Zheng
authors.forename: Yu-Chun
authors.initials: YC
authors.lastname: Lin
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.forename: Takanari
authors.initials: T
authors.lastname: Inoue
authors.forename: Marc
authors.initials: M
authors.lastname: Fivaz
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D002465:Cell Movement / Q000187:drug effects; D025461:Feedback, Physiological; D005786:Gene Expression Regulation; D051379:Mice; D041681:NIH 3T3 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D016283:Proto-Oncogene Proteins p21(ras) / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D059008:Time-Lapse Imaging
chemical_list: D019869:Phosphatidylinositol 3-Kinases; D010716:Phosphatidylinositols; D010982:Platelet-Derived Growth Factor; D016283:Proto-Oncogene Proteins p21(ras); D034741:RNA, Small Interfering; C495971:Hras protein, mouse