title: Tracking shallow chemical gradients by actin-driven wandering of the polarization site.
abstract: BACKGROUND
  Many cells are remarkably proficient at tracking very shallow chemical gradients, despite considerable noise from stochastic receptor-ligand interactions. Motile cells appear to undergo a biased random walk: spatial noise in receptor activity may determine the instantaneous direction, but because noise is spatially unbiased, it is filtered out by time averaging, resulting in net movement upgradient. How nonmotile cells might filter out noise is unknown.
  
  
  RESULTS
  Using yeast chemotropic mating as a model, we demonstrate that a polarized patch of polarity regulators "wanders" along the cortex during gradient tracking. Computational and experimental findings suggest that actin-directed membrane traffic contributes to wandering by diluting local polarity factors. The pheromone gradient appears to bias wandering via interactions between receptor-activated Gβγ and polarity regulators. Artificially blocking patch wandering impairs gradient tracking.
  
  
  CONCLUSIONS
  We suggest that the polarity patch undergoes an intracellular biased random walk that enables noise filtering by time averaging, allowing nonmotile cells to track shallow gradients.
authors.affiliation: Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Jayme M
authors.initials: JM
authors.lastname: Dyer
authors.forename: Natasha S
authors.initials: NS
authors.lastname: Savage
authors.forename: Meng
authors.initials: M
authors.lastname: Jin
authors.forename: Trevin R
authors.initials: TR
authors.lastname: Zyla
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Elston
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Lew
mesh_terms: D000199:Actins / Q000378:metabolism / Q000502:physiology; D016764:Cell Polarity; D002633:Chemotaxis; D010675:Pheromones / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology; D013997:Time Factors; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000032:analysis / Q000378:metabolism / Q000502:physiology
chemical_list: D000199:Actins; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae