title: Calcineurin regulates the yeast synaptojanin Inp53/Sjl3 during membrane stress.
abstract: During hyperosmotic shock, Saccharomyces cerevisiae adjusts to physiological challenges, including large plasma membrane invaginations generated by rapid cell shrinkage. Calcineurin, the Ca(2+)/calmodulin-dependent phosphatase, is normally cytosolic but concentrates in puncta and at sites of polarized growth during intense osmotic stress; inhibition of calcineurin-activated gene expression suggests that restricting its access to substrates tunes calcineurin signaling specificity. Hyperosmotic shock promotes calcineurin binding to and dephosphorylation of the PI(4,5)P2 phosphatase synaptojanin/Inp53/Sjl3 and causes dramatic calcineurin-dependent reorganization of PI(4,5)P2-enriched membrane domains. Inp53 normally promotes sorting at the trans-Golgi network but localizes to cortical actin patches in osmotically stressed cells. By activating Inp53, calcineurin repolarizes the actin cytoskeleton and maintains normal plasma membrane morphology in synaptojanin-limited cells. In response to hyperosmotic shock and calcineurin-dependent regulation, Inp53 shifts from associating predominantly with clathrin to interacting with endocytic proteins Sla1, Bzz1, and Bsp1, suggesting that Inp53 mediates stress-specific endocytic events. This response has physiological and molecular similarities to calcineurin-regulated activity-dependent bulk endocytosis in neurons, which retrieves a bolus of plasma membrane deposited by synaptic vesicle fusion. We propose that activation of Ca(2+)/calcineurin and PI(4,5)P2 signaling to regulate endocytosis is a fundamental and conserved response to excess membrane in eukaryotic cells.
authors.affiliation: Department of Biology, Stanford University, Stanford, CA 94305.
authors.forename: Evan L
authors.initials: EL
authors.lastname: Guiney
authors.affiliation: Department of Biology, Stanford University, Stanford, CA 94305.
authors.forename: Aaron R
authors.initials: AR
authors.lastname: Goldman
authors.affiliation: Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305.
authors.forename: Joshua E
authors.initials: JE
authors.lastname: Elias
authors.affiliation: Department of Biology, Stanford University, Stanford, CA 94305 mcyert@stanford.edu.
authors.forename: Martha S
authors.initials: MS
authors.lastname: Cyert
mesh_terms: D000199:Actins; D019703:Calcineurin / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002966:Clathrin; D004705:Endocytosis; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009997:Osmotic Pressure; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D021601:trans-Golgi Network
chemical_list: D000199:Actins; D002966:Clathrin; D009419:Nerve Tissue Proteins; D029701:Saccharomyces cerevisiae Proteins; C110553:INP53 protein, S cerevisiae; C097702:synaptojanin; D019703:Calcineurin; D010744:Phosphoric Monoester Hydrolases