Abstract
In the filamentous fungus Sordaria macrospora (Sm), the STRIPAK complex is required for vegetative growth, fruiting-body development and hyphal fusion. The SmSTRIPAK core consists of the striatin homolog PRO11, the scaffolding subunit of phosphatase PP2A, SmPP2AA, and its catalytic subunit SmPP2Ac1. Among other STRIPAK proteins, the recently identified coiled-coil protein SCI1 was demonstrated to co-localize around the nucleus. Pulldown experiments with SCI identified the transmembrane nucleoporin (TM Nup) SmPOM33 as a potential nuclear-anchor of SmSTRIPAK. Localization studies revealed that SmPOM33 partially localizes to the nuclear envelope (NE), but mainly to the endoplasmic reticulum (ER). We succeeded to generate a Δpom33 deletion mutant by homologous recombination in a new S. macrospora Δku80 recipient strain, which is defective in non-homologous end joining. Deletion of Smpom33 did neither impair vegetative growth nor sexual development. In pulldown experiments of SmPOM33 followed by LC/MS analysis, ER-membrane proteins involved in ER morphology, protein translocation, glycosylation, sterol biosynthesis and Ca2+-transport were significantly enriched. Data are available via ProteomeXchange with identifier PXD026253. Although no SmSTRIPAK components were identified as putative interaction partners, it cannot be excluded that SmPOM33 is involved in temporarily anchoring the SmSTRIPAK to the NE or other sites in the cell.
Highlights
The striatin-interacting phosphatase and kinase (STRIPAK) complex is a conserved multiprotein complex involved in diverse cell-signaling pathways like cell growth and -fusion, vesicular traffic, endocytosis and even apoptosis in animals and fungi [1,2]
In pulldown experiments of SmPOM33 followed by Liquid Chromatography—Mass Spectrometry (LC/MS) analysis, endoplasmic reticulum (ER)-membrane proteins involved in ER morphology, protein translocation, glycosylation, sterol biosynthesis and Ca2+-transport were significantly enriched
S. macrospora POM33 Belongs to the Pom33/ TMEM33 Protein Family In LC/MS analysis with S. macrospora STRIPAK complex protein SCI1 as bait, a protein encoded by SMAC_00774 had previously been identified as putative interaction partner and predicted to be a POM33 homolog via BLASTP analysis [14]
Summary
The striatin-interacting phosphatase and kinase (STRIPAK) complex is a conserved multiprotein complex involved in diverse cell-signaling pathways like cell growth and -fusion, vesicular traffic, endocytosis and even apoptosis in animals and fungi [1,2]. The main components of STRIPAK complexes are striatin scaffolding proteins [3]. The major scaffold protein of the SmSTRIPAK complex is the human striatin homolog PRO11 [6,7,8]. The SmSTRIPAK complex consists of the STRIP1/2 homolog PRO22, SmMOB3, the scaffolding subunit of phosphatase PP2A, SmPP2AA, and its catalytic subunit SmPP2Ac1 as well as recruited GCKIII kinases SmKIN24 and SmKIN3 [6,9,10,11,12,13]. The SLMAP homolog PRO45 and the coiled-coil protein SCI1 were identified as key subunits of the SmSTRIPAK [9,14]. The STRIPAK components SLMAP homolog PRO45 and SmMOB3 were localized to the nuclear envelope (NE), endoplasmic reticulum (ER), and mitochondria [9]
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