title: Fungal communication requires the MAK-2 pathway elements STE-20 and RAS-2, the NRC-1 adapter STE-50 and the MAP kinase scaffold HAM-5.
abstract: Intercellular communication is critical for the survival of unicellular organisms as well as for the development and function of multicellular tissues. Cell-to-cell signaling is also required to develop the interconnected mycelial network characteristic of filamentous fungi and is a prerequisite for symbiotic and pathogenic host colonization achieved by molds. Somatic cell-cell communication and subsequent cell fusion is governed by the MAK-2 mitogen activated protein kinase (MAPK) cascade in the filamentous ascomycete model Neurospora crassa, yet the composition and mode of regulation of the MAK-2 pathway are currently unclear. In order to identify additional components involved in MAK-2 signaling we performed affinity purification experiments coupled to mass spectrometry with strains expressing functional GFP-fusion proteins of the MAPK cascade. This approach identified STE-50 as a regulatory subunit of the Ste11p homolog NRC-1 and HAM-5 as cell-communication-specific scaffold protein of the MAPK cascade. Moreover, we defined a network of proteins consisting of two Ste20-related kinases, the small GTPase RAS-2 and the adenylate cyclase capping protein CAP-1 that function upstream of the MAK-2 pathway and whose signals converge on the NRC-1/STE-50 MAP3K complex and the HAM-5 scaffold. Finally, our data suggest an involvement of the striatin interacting phosphatase and kinase (STRIPAK) complex, the casein kinase 2 heterodimer, the phospholipid flippase modulators YPK-1 and NRC-2 and motor protein-dependent vesicle trafficking in the regulation of MAK-2 pathway activity and function. Taken together, these data will have significant implications for our mechanistic understanding of MAPK signaling and for homotypic cell-cell communication in fungi and higher eukaryotes.
authors.affiliation: Institute for Biology II - Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Freiburg, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Dettmann
authors.affiliation: Institute for Biology II - Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Freiburg, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Heilig
authors.affiliation: Institute for Microbiology and Genetics, University of Goettingen, Goettingen, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Valerius
authors.affiliation: Institute for Biology II - Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Freiburg, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Ludwig
authors.affiliation: Institute for Biology II - Molecular Plant Physiology, Albert-Ludwigs University Freiburg, Freiburg, Germany; Freiburg Institute for Advanced Studies (FRIAS), Albert-Ludwigs University Freiburg, Freiburg, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Seiler
mesh_terms: D002450:Cell Communication / Q000235:genetics; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D000071677:Histidine Kinase; D020935:MAP Kinase Signaling System / Q000235:genetics; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics* / Q000378:metabolism; D009492:Neurospora crassa / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D018631:ras Proteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D000071677:Histidine Kinase; D018631:ras Proteins