title: HAM-2 and HAM-3 are central for the assembly of the Neurospora STRIPAK complex at the nuclear envelope and regulate nuclear accumulation of the MAP kinase MAK-1 in a MAK-2-dependent manner.
abstract: Intercellular communication and somatic cell fusion are important for fungal colony establishment, multicellular differentiation and have been associated with host colonization and virulence of pathogenic species. By a combination of genetic, biochemical and live cell imaging techniques, we characterized the Neurospora crassa STRIPAK complex that is essential for self-signalling and consists of the six proteins HAM-2/STRIP, HAM-3/striatin, HAM-4/SLMAP, MOB-3/phocein, PPG-1/PP2A-C and PP2A-A. We describe that the core STRIPAK components HAM-2 and HAM-3 are central for the assembly of the complex at the nuclear envelope, while the phosphatase PPG-1 only transiently associates with this central subcomplex. Our data connect the STRIPAK complex with two MAP kinase pathways: (i) nuclear accumulation of the cell wall integrity MAP kinase MAK-1 depends on the functional integrity of the STRIPAK complex at the nuclear envelope, and (ii) phosphorylation of MOB-3 by the MAP kinase MAK-2 impacts the nuclear accumulation of MAK-1. In summary, these data support a model, in which MAK-2-dependent phosphorylation of MOB-3 is part of a MAK-1 import mechanism. Although self-communication remained intact in the absence of nuclear MAK-1 accumulation, supporting the presence of multiple mechanisms that co-ordinate robust intercellular communication, proper fruiting body morphology was dependent on the MAK-2-phosphorylated N-terminus of MOB-3.
authors.affiliation: Institute for Biology II - Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Schänzlestr. 1, 79104, Freiburg, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Dettmann
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Heilig
authors.forename: Sarah
authors.initials: S
authors.lastname: Ludwig
authors.forename: Kerstin
authors.initials: K
authors.lastname: Schmitt
authors.forename: Julia
authors.initials: J
authors.lastname: Illgen
authors.forename: Andre
authors.initials: A
authors.lastname: Fleißner
authors.forename: Oliver
authors.initials: O
authors.lastname: Valerius
authors.forename: Stephan
authors.initials: S
authors.lastname: Seiler
mesh_terms: D021581:Active Transport, Cell Nucleus; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D020935:MAP Kinase Signaling System; D008565:Membrane Proteins / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D016296:Mutagenesis; D009492:Neurospora crassa / Q000235:genetics / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation
chemical_list: D005656:Fungal Proteins; D008565:Membrane Proteins; C492210:ham-2 protein, Neurospora crassa; D020928:Mitogen-Activated Protein Kinases