title: Phosphorylation-dependent inhibition of Cdc42 GEF Gef1 by 14-3-3 protein Rad24 spatially regulates Cdc42 GTPase activity and oscillatory dynamics during cell morphogenesis.
abstract: Active Cdc42 GTPase, a key regulator of cell polarity, displays oscillatory dynamics that are anticorrelated at the two cell tips in fission yeast. Anticorrelation suggests competition for active Cdc42 or for its effectors. Here we show how 14-3-3 protein Rad24 associates with Cdc42 guanine exchange factor (GEF) Gef1, limiting Gef1 availability to promote Cdc42 activation. Phosphorylation of Gef1 by conserved NDR kinase Orb6 promotes Gef1 binding to Rad24. Loss of Rad24-Gef1 interaction increases Gef1 protein localization and Cdc42 activation at the cell tips and reduces the anticorrelation of active Cdc42 oscillations. Increased Cdc42 activation promotes precocious bipolar growth activation, bypassing the normal requirement for an intact microtubule cytoskeleton and for microtubule-dependent polarity landmark Tea4-PP1. Further, increased Cdc42 activation by Gef1 widens cell diameter and alters tip curvature, countering the effects of Cdc42 GTPase-activating protein Rga4. The respective levels of Gef1 and Rga4 proteins at the membrane define dynamically the growing area at each cell tip. Our findings show how the 14-3-3 protein Rad24 modulates the availability of Cdc42 GEF Gef1, a homologue of mammalian Cdc42 GEF DNMBP/TUBA, to spatially control Cdc42 GTPase activity and promote cell polarization and cell shape emergence.
authors.affiliation: Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101.
authors.forename: Maitreyi
authors.initials: M
authors.lastname: Das
authors.affiliation: Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101.
authors.forename: Illyce
authors.initials: I
authors.lastname: Nuñez
authors.affiliation: Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101.
authors.forename: Marbelys
authors.initials: M
authors.lastname: Rodriguez
authors.affiliation: Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101.
authors.forename: David J
authors.initials: DJ
authors.lastname: Wiley
authors.affiliation: Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101.
authors.forename: Juan
authors.initials: J
authors.lastname: Rodriguez
authors.affiliation: Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101.
authors.forename: Ali
authors.initials: A
authors.lastname: Sarkeshik
authors.affiliation: Department of Chemical Physiology, Scripps Research Institute, La Jolla, CA 92037.
authors.forename: John R
authors.initials: JR
authors.lastname: Yates
authors.affiliation: Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101.
authors.forename: Peter
authors.initials: P
authors.lastname: Buchwald
authors.affiliation: Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101 Marine Biological Laboratory, Woods Hole, MA 02543. fverde@med.miami.edu).
authors.forename: Fulvia
authors.initials: F
authors.lastname: Verde
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology; D048430:Cell Shape / Q000502:physiology; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000254:growth & development / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D018118:Chloride Channels; C089713:GEF1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; C088385:RAD24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C113424:Orb6 protein, S pombe; D017346:Protein Serine-Threonine Kinases; D020558:GTP Phosphohydrolases; D020764:cdc42 GTP-Binding Protein; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae