title: Loss of Apm1, the micro1 subunit of the clathrin-associated adaptor-protein-1 complex, causes distinct phenotypes and synthetic lethality with calcineurin deletion in fission yeast.
abstract: Calcineurin is a highly conserved regulator of Ca(2+) signaling in eukaryotes. In fission yeast, calcineurin is not essential for viability but is required for cytokinesis and Cl(-) homeostasis. In a genetic screen for mutations that are synthetically lethal with calcineurin deletion, we isolated a mutant, cis1-1/apm1-1, an allele of the apm1(+) gene that encodes a homolog of the mammalian micro1A subunit of the clathrin-associated adaptor protein-1 (AP-1) complex. The cis1-1/apm1-1 mutant as well as the apm1-deleted (Deltaapm1) cells showed distinct phenotypes: temperature sensitivity; tacrolimus (FK506) sensitivity; and pleiotropic defects in cytokinesis, cell integrity, and vacuole fusion. Electron micrographs revealed that Deltaapm1 cells showed large vesicular structures associated with Golgi stacks and accumulated post-Golgi secretory vesicles. Deltaapm1 cells also showed the massive accumulation of the exocytic v-SNARE Syb1 in the Golgi/endosomes and a reduced secretion of acid phosphatase. These phenotypes observed in apm1 mutations were accentuated upon temperature up-shift and FK506 treatment. Notably, Apm1-GFP localized to the Golgi/endosomes, the spindle pole bodies, and the medial region. These findings suggest a role for Apm1 associated with the Golgi/endosome function, thereby affecting various cellular processes, including secretion, cytokinesis, vacuole fusion, and cell integrity and also suggest that calcineurin is involved in these events.
authors.affiliation: Division of Molecular Pharmacology and Pharmacogenomics, Department of Genome Sciences, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Kita
authors.forename: Reiko
authors.initials: R
authors.lastname: Sugiura
authors.forename: Hiromi
authors.initials: H
authors.lastname: Shoji
authors.forename: Yi
authors.initials: Y
authors.lastname: He
authors.forename: Lu
authors.initials: L
authors.lastname: Deng
authors.forename: Yabin
authors.initials: Y
authors.lastname: Lu
authors.forename: Susie O
authors.initials: SO
authors.lastname: Sio
authors.forename: Kaoru
authors.initials: K
authors.lastname: Takegawa
authors.forename: Motoyoshi
authors.initials: M
authors.lastname: Sakaue
authors.forename: Hisato
authors.initials: H
authors.lastname: Shuntoh
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Kuno
mesh_terms: D000135:Acid Phosphatase / Q000378:metabolism; D033961:Adaptor Protein Complex 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D033983:Adaptor Protein Complex mu Subunits / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D019703:Calcineurin / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000502:physiology; D048749:Cytokinesis; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D017353:Gene Deletion; D005800:Genes, Fungal / Q000235:genetics; D005804:Genes, Lethal / Q000235:genetics*; D006056:Golgi Apparatus / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009997:Osmotic Pressure; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D021122:Protein Subunits / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D050683:R-SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C438890:APM1 protein, S cerevisiae; D033961:Adaptor Protein Complex 1; D033983:Adaptor Protein Complex mu Subunits; D008565:Membrane Proteins; D021122:Protein Subunits; D050683:R-SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C075976:ypt3 protein, S pombe; D019703:Calcineurin; D000135:Acid Phosphatase; D020691:rab GTP-Binding Proteins