title: The AP-2 complex has a specialized clathrin-independent role in apical endocytosis and polar growth in fungi.
abstract: Filamentous fungi provide excellent systems for investigating the role of the AP-2 complex in polar growth. UsingAspergillus nidulans,we show that AP-2 has a clathrin-independent essential role in polarity maintenance and growth. This is in line with a sequence analysis showing that the AP-2 β subunit (β2) of higher fungi lacks a clathrin-binding domain, and experiments showing that AP-2 does not co-localize with clathrin. We provide genetic and cellular evidence that AP-2 interacts with endocytic markers SlaBEnd4and SagAEnd3and the lipid flippases DnfA and DnfB in the sub-apical collar region of hyphae. The role of AP-2 in the maintenance of proper apical membrane lipid and cell wall composition is further supported by its functional interaction with BasA (sphingolipid biosynthesis) and StoA (apical sterol-rich membrane domains), and its essentiality in polar deposition of chitin. Our findings support that the AP-2 complex of dikarya has acquired, in the course of evolution, a specialized clathrin-independent function necessary for fungal polar growth.
authors.affiliation: Department of Biology, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Olga
authors.initials: O
authors.lastname: Martzoukou
authors.affiliation: Department of Biology, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Sotiris
authors.initials: S
authors.lastname: Amillis
authors.affiliation: Department of Biology, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Amalia
authors.initials: A
authors.lastname: Zervakou
authors.affiliation: Institute of Molecular Biology and Biotechnology-Biomedical Research, Foundation for Research and Technology, Ioannina, Greece.|Laboratory of Biological Chemistry, Department of Medicine, School of Health Sciences, University of Ioannina, Ioannina, Greece.
authors.forename: Savvas
authors.initials: S
authors.lastname: Christoforidis
authors.affiliation: Department of Biology, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: George
authors.identifier: 0000-0002-3426-726X
authors.initials: G
authors.lastname: Diallinas
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000378:metabolism*; D001233:Aspergillus nidulans / Q000254:growth & development* / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D002686:Chitin / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism*; D004705:Endocytosis
chemical_list: D033962:Adaptor Protein Complex 2; D002966:Clathrin; D002686:Chitin
keywords: Aspergillus nidulans; cell biology; endocytosis; flippase; polarity maintenance; transporters