title: Ssp1 promotes actin depolymerization and is involved in stress response and new end take-off control in fission yeast.
abstract: The ssp1 gene encodes a protein kinase involved in alteration of cell polarity in Schizosaccharomyces pombe. ssp1 deletion causes stress sensitivity, reminiscent of defects in the stress-activated MAP kinase, Spc1; however, the two protein kinases do not act through the same pathway. Ssp1 is localized mainly in the cytoplasm, but after a rise in external osmolarity it is rapidly recruited to the plasma membrane, preferentially to active growth zones and septa. Loss of Ssp1 function inhibits actin relocalization during osmotic stress, in cdc3 and cdc8 mutant backgrounds, and in the presence of latrunculin A, implicating Ssp1 in promotion of actin depolymerization. We propose a model in which Ssp1 can be activated independently of Spc1 and can partially compensate for its loss. The ssp1 deletion mutant exhibited monopolar actin distribution, but new end take-off (NETO) could be induced in these cells by exposure to KCl or to latrunculin A pulse treatment. This treatment induced NETO in cdc10 cells arrested in G1 but not in tea1 cells. This suggests that cells that contain intact cell end markers are competent to undergo NETO throughout interphase, and Ssp1 is involved in generating the NETO stimulus by enlarging the actin monomer pool.
authors.affiliation: Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada.
authors.forename: I
authors.initials: I
authors.lastname: Rupes
authors.forename: Z
authors.initials: Z
authors.lastname: Jia
authors.forename: P G
authors.initials: PG
authors.lastname: Young
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000222:Adaptation, Physiological; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins; D020928:Mitogen-Activated Protein Kinases; D009154:Mutation; D018384:Oxidative Stress / Q000502:physiology*; D010641:Phenotype; D011494:Protein Kinases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000187:drug effects / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; C111935:PSS1 protein, S pombe; D012097:Repressor Proteins; D029702:Schizosaccharomyces pombe Proteins; D013844:Thiazoles; D053778:Thiazolidines; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C095409:sty1 protein, S pombe; C037067:latrunculin A