title: Locally excitable Cdc42 signals steer cells during chemotaxis.
abstract: Neutrophils and other amoeboid cells chemotax by steering their front ends towards chemoattractant. Although Ras, Rac, Cdc42 and RhoA small GTPases all regulate chemotaxis, it has been unclear how they spatiotemporally control polarization and steering. Using fluorescence biosensors in neutrophil-like PLB-985 cells and photorelease of chemoattractant, we show that local Cdc42 signals, but not those of Rac, RhoA or Ras, precede cell turning during chemotaxis. Furthermore, pre-existing local Cdc42 signals in morphologically unpolarized cells predict the future direction of movement on uniform stimulation. Moreover, inhibition of actin polymerization uncovers recurring local Cdc42 activity pulses, suggesting that Cdc42 has the excitable characteristic of the compass activity proposed in models of chemotaxis. Globally, Cdc42 antagonizes RhoA, and maintains a steep spatial activity gradient during migration, whereas Ras and Rac form shallow gradients. Thus, chemotactic steering and de novo polarization are both directed by locally excitable Cdc42 signals.
authors.affiliation: Department of Chemical & Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Hee Won
authors.initials: HW
authors.lastname: Yang
authors.affiliation: Department of Chemical & Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Sean R
authors.initials: SR
authors.lastname: Collins
authors.affiliation: Department of Chemical & Systems Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Tobias
authors.initials: T
authors.lastname: Meyer
mesh_terms: D000199:Actins / Q000378:metabolism; D015374:Biosensing Techniques; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D002634:Chemotaxis, Leukocyte / Q000187:drug effects; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D008856:Microscopy, Fluorescence; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000031:analogs & derivatives / Q000494:pharmacology; D020556:Neutrophil Infiltration / Q000187:drug effects; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D058105:Polymerization; D034741:RNA, Small Interfering; D012815:Signal Processing, Computer-Assisted; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D034741:RNA, Small Interfering; C066737:RHOA protein, human; D009240:N-Formylmethionine Leucyl-Phenylalanine; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D018631:ras Proteins; D020742:rhoA GTP-Binding Protein