In Schizosaccharomyces pombe the exomer participates in trafficking through the Golgi, early endosomes and late endosomes under standard and stress conditions
| Autor: | Hoya, Marta, Moro, Sandra, Yanguas, Francisco, Curto, María Ángeles, Doncel, Cristina, Valdivieso, María Henar |
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| Přispěvatelé: | Junta de Castilla y León, Comisión Interministerial de Ciencia y Tecnología, CICYT (España), European Commission, Ministerio de Economía y Competitividad (España) |
| Rok vydání: | 2015 |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| Popis: | Resumen del trabajo presentado a la 10ª Reunión de la Red Española de Levaduras, celebrada en El Escorial (Madrid) del 16 al 18 de diciembre de 2015. Enzymes involved in cell wall construction must be delivered to the cell surface in order to exert their function. A great effort has been directed to study the regulation of chitin synthesis, leading to the characterization of several specific regulators. On the contrary, in the case of β-glucan synthases practically the only regulators under study are the Rho GTPases and their modulators. Our general objective is to study the regulation of β-glucan synthesis by the mechanisms of vesicle transport. The exomer is a hetero-pentameric complex required for the delivery of Fus1p and the chitin synthase Chs3p to the cell surface in Saccharomyces. The exomer is formed by the Chs5p scaffold and four ChAPs (Chs5-and-Arf1 binding-Protein). In S. pombe there are no Fus1p or Chs3p homologues, and the cell wall structural components are glucans; however, there are proteins similar to Chs5p and the ChAPs (termed Cfr1p and Bch1p, respectively). In order to understand whether the exomer is involved in the trafficking of β(1,3)glucan synthases in the fission yeast we are characterizing its function. Co-localization and subcellular fractioning analyses showed that Cfr1p localizes at the trans Golgi network (TGN)/early endosomes (EE) and at the prevacuolar compartment (PVC). Additionally, co-immunoprecipitation and genetic interaction experiments have shown that the exomer interacts with components of the AP1, AP2 and GGA clathrin adaptors. Thermosensitivity of single and double mutants is supressed by sorbitol, suggesting the participation of these protein complexes in cell wall synthesis. Surprisingly, all glucan synthases are transported to the plasma membrane in the exomer mutants. It has been described that in AP1-defective mutants Bgs1p delivery to the cell surface is inefficient. We have found the same result for Bgs3p and Bgs4p. In double cfr1/Δ apm1/Δ cells this defect is enhanced with respect to that of the single apm1/Δ mutant, showing collaboration between the exomer and the AP1 complex in trafficking through the EEs. A diagnostic test used to unveil defects in trafficking between the Golgi and LE is the detection of missorted carboxypeptidase Y to the cell surface by Western dot-blot. This phenotype has been detected in the S. pombe exomer mutants. Additionally, sucrose gradients show that in the cfr1/Δ strain a part of Bgs4 co-fractionates with LE/vacuole markers. All these results show that the function of the exomer is more pervasive than suspected. Finally, the exomer and the ggaΔ mutants exhibit sensitivity to different stress insults, which in some cases is accompanied by a defect in cytokinesis. The results obtained so far indicate that this sensitivity might be due to the alteration of various processes and that different pathways are involved in signalling the responses. Financial support: CICYT/EU FEDER program (grants BFU2010-15085 and BFU2013-48582-C2-2-P) and Junta de Castilla y León (grant SA073U14). |
| Databáze: | OpenAIRE |
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