SummarySexual development in fungi is a complex process involving the generation of new cell types and tissues -an essential step for all eukaryotic life. The characterization of sterile mutants in the ascomycete Sordaria macrospora has led to a number of proteins involved in sexual development, but a link between these proteins is still missing. Using a combined tandem-affinity purification/mass spectrometry approach, we showed in vivo association of developmental protein PRO22 with PRO11, homologue of mammalian striatin, and SmPP2AA, scaffolding subunit of protein phosphatase 2A. Further experiments extended the protein network to the putative kinase activator SmMOB3, known to be involved in sexual development. Extensive yeast two-hybrid studies allowed us to pinpoint functional domains involved in protein-protein interaction. We show for the first time that a number of already known factors together with new components associate in vivo to form a highly conserved multi-subunit complex. Strikingly, a similar complex has been described in humans, but the function of this so-called striatin interacting phosphatase and kinase (STRIPAK) complex is largely unknown. In S. macrospora, truncation of PRO11 and PRO22 leads to distinct defects in sexual development and cell fusion, indicating a role for the fungal STRIPAK complex in both processes.
Members of the striatin family and their highly conserved interacting protein phocein/Mob3 are key components in the regulation of cell differentiation in multicellular eukaryotes. The striatin homologue PRO11 of the filamentous ascomycete Sordaria macrospora has a crucial role in fruiting body development. Here, we functionally characterized the phocein/Mob3 orthologue SmMOB3 of S. macrospora. We isolated the gene and showed that both, pro11 and Smmob3 are expressed during early and late developmental stages. Deletion of Smmob3 resulted in a sexually sterile strain, similar to the previously characterized pro11 mutant. Fusion assays revealed that ∆Smmob3 was unable to undergo self-fusion and fusion with the pro11 strain. The essential function of the SmMOB3 N-terminus containing the conserved mob domain was demonstrated by complementation analysis of the sterile S. macrospora ∆Smmob3 strain. Downregulation of either pro11 in ∆Smmob3, or Smmob3 in pro11 mutants by means of RNA interference (RNAi) resulted in synthetic sexual defects, demonstrating for the first time the importance of a putative PRO11/SmMOB3 complex in fruiting body development.Electronic supplementary materialThe online version of this article (doi:10.1007/s00294-010-0333-z) contains supplementary material, which is available to authorized users.
Die Familie der Striatin-Proteine aus Eukaryoten 2.1 Die vielfältigen Funktionen von Striatin-Proteinen 2.2 Interaktionspartner von Striatin-Proteinen und die Signalwege in denen sie wirken 2.2.1 Phocein/Mob3 -ein Protein aus der Mob-Familie 2.2.2 Die Protein-Phosphatase 2A (PP2A) 2.2.3 ER -Östrogen-vermittelte nicht-genomische und genomische Signalwege 2.2.4 Die Rolle von Striatin-Proteinen bei der Zell-Adhäsion 2.2.5 Die Rolle von Striatin-Proteinen bei der Virus-Assemblierung Das S. macrospora Protein Sm9375 -Beteiligung eines GPI-geankerten Proteins am SmMOB3/PRO11-Komplex 4 Reguliert der PRO11/SmMOB3-Komplex während Hyphenfusion und Fruchtkörperentwicklung die Endocytose und den Vesikel-Transport? 5 Zusammenfassung der vielfältigen Funktionen von S. macrospora PRO11-Proteinkomplexen bei zellulären Differenzierungsprozessen V ZUSAMMENFASSUNG
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