title: Eisosomes Regulate Phosphatidylinositol 4,5-Bisphosphate (PI(4,5)P2) Cortical Clusters and Mitogen-activated Protein (MAP) Kinase Signaling upon Osmotic Stress.
abstract: Eisosomes are multiprotein structures that generate linear invaginations at the plasma membrane of yeast cells. The core component of eisosomes, the BAR domain protein Pil1, generates these invaginations through direct binding to lipids including phosphoinositides. Eisosomes promote hydrolysis of phosphatidylinositol 4,5 bisphosphate (PI(4,5)P2) by functioning with synaptojanin, but the cellular processes regulated by this pathway have been unknown. Here, we found that PI(4,5)P2 regulation by eisosomes inhibits the cell integrity pathway, a conserved MAPK signal transduction cascade. This pathway is activated by multiple environmental conditions including osmotic stress in the fission yeast Schizosaccharomyces pombe. Activation of the MAPK Pmk1 was impaired by mutations in the phosphatidylinositol (PI) 5-kinase Its3, but this defect was suppressed by removal of eisosomes. Using fluorescent biosensors, we found that osmotic stress induced the formation of PI(4,5)P2 clusters that were spatially organized by eisosomes in both fission yeast and budding yeast cells. These cortical clusters contained the PI 5-kinase Its3 and did not assemble in the its3-1 mutant. The GTPase Rho2, an upstream activator of Pmk1, also co-localized with PI(4,5)P2 clusters under osmotic stress, providing a molecular link between these novel clusters and MAPK activation. Our findings have revealed that eisosomes regulate activation of MAPK signal transduction through the organization of cortical lipid-based microdomains.
authors.affiliation: From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and.
authors.forename: Ruth
authors.initials: R
authors.lastname: Kabeche
authors.affiliation: Yeast Physiology Group, Department of Genetics and Microbiology, Facultad de Biología, Universidad de Murcia, 30071, Murcia, Spain.
authors.forename: Marisa
authors.initials: M
authors.lastname: Madrid
authors.affiliation: Yeast Physiology Group, Department of Genetics and Microbiology, Facultad de Biología, Universidad de Murcia, 30071, Murcia, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Cansado
authors.affiliation: From the Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755 and james.b.moseley@dartmouth.edu.
authors.forename: James B
authors.initials: JB
authors.lastname: Moseley
mesh_terms: D020935:MAP Kinase Signaling System / Q000502:physiology*; D015388:Organelles / Q000502:physiology*; D009997:Osmotic Pressure; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000201:enzymology / Q000378:metabolism*
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate
keywords: Rho (Rho GTPase); Schizosaccharomyces pombe; TORC2; cell biology; eisosome; lipid signaling; plasma membrane; stress response