title: RGS proteins and septins cooperate to promote chemotropism by regulating polar cap mobility.
abstract: BACKGROUND
  Septins are well known to form a boundary between mother and daughter cells in mitosis, but their role in other morphogenic states is poorly understood.
  
  
  RESULTS
  Using microfluidics and live-cell microscopy, coupled with new computational methods for image analysis, we investigated septin function during pheromone-dependent chemotropic growth in yeast. We show that septins colocalize with the regulator of G protein signaling (RGS) Sst2, a GTPase-activating protein that dampens pheromone receptor signaling. We show further that the septin structure surrounds the polar cap, ensuring that cell growth is directed toward the source of pheromone. When RGS activity is abrogated, septins are partially disorganized. Under these circumstances, the polar cap travels toward septin structures and away from sites of exocytosis, resulting in a loss of gradient tracking.
  
  
  CONCLUSIONS
  Septin organization is dependent on RGS protein activity. When assembled correctly, septins promote turning of the polar cap and proper tracking of a pheromone gradient.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 3046 Genetic Medicine Building, Campus Box 7260, Chapel Hill, NC 27599, USA; Department of Pharmacology, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 4009 Genetic Medicine Building, Campus Box 7365, Chapel Hill, NC 27599, USA.
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Kelley
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 3046 Genetic Medicine Building, Campus Box 7260, Chapel Hill, NC 27599, USA.
authors.forename: Gauri
authors.initials: G
authors.lastname: Dixit
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 3046 Genetic Medicine Building, Campus Box 7260, Chapel Hill, NC 27599, USA.
authors.forename: Joshua B
authors.initials: JB
authors.lastname: Sheetz
authors.affiliation: Department of Pharmacology, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 4009 Genetic Medicine Building, Campus Box 7365, Chapel Hill, NC 27599, USA; Curriculum in Bioinformatics and Computational Biology, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 4092 Genetic Medicine Building, Campus Box 7365, Chapel Hill, NC 27599, USA.
authors.forename: Sai Phanindra
authors.initials: SP
authors.lastname: Venkatapurapu
authors.affiliation: Department of Pharmacology, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 4009 Genetic Medicine Building, Campus Box 7365, Chapel Hill, NC 27599, USA. Electronic address: timothy_elston@med.unc.edu.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Elston
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 3046 Genetic Medicine Building, Campus Box 7260, Chapel Hill, NC 27599, USA; Department of Pharmacology, University of North Carolina at Chapel Hill, 120 Mason Farm Road, 4009 Genetic Medicine Building, Campus Box 7365, Chapel Hill, NC 27599, USA. Electronic address: henrik_dohlman@med.unc.edu.
authors.forename: Henrik G
authors.initials: HG
authors.lastname: Dohlman
mesh_terms: D016764:Cell Polarity / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D046210:Microfluidic Analytical Techniques; D008954:Models, Biological; D020710:RGS Proteins / Q000378:metabolism*; D043563:Receptors, Pheromone / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D058112:Septins / Q000378:metabolism*; D059010:Single-Cell Analysis; D018523:Tropism / Q000502:physiology*
chemical_list: D020690:GTPase-Activating Proteins; D020710:RGS Proteins; D043563:Receptors, Pheromone; C094301:SST2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D058112:Septins