title: Afi1p functions as an Arf3p polarization-specific docking factor for development of polarity.
abstract: ADP-ribosylation factors (Arfs) are highly conserved small GTPases and are critical components of vesicle trafficking. Yeast Arf3p, despite its similarity to mammalian Arf6, is not required for endocytosis but is involved in polarity development. In this study, we identified an Arf3p interacting protein 1 (Afi1p), which, through its N-terminal conserved region, specifically interacts with GTP-bound Arf3p. Afi1p is distributed asymmetrically at the plasma membrane and is required for polarized distribution of Arf3p but not of an Arf3p guanine nucleotide-exchange factor, Yel1p. However, Afi1p is not required for targeting of Arf3p or Yel1p to the plasma membrane. Like arf3 mutant yeast, afi1 mutant yeast exhibited an abnormal budding pattern and partially delayed actin patch polarization. An Afi1p, (38)KLGP4A-Afi1p, mutated at the Arf3p-binding region, loses its ability to interact with Arf3p and maintain the polarized distribution of Arf3p. Although (38)KLGP4A-Afi1p still possessed a proper polarized distribution, it lost its ability to rescue actin patch polarization in afi1 mutant cells. Our findings demonstrate that Afi1p functions as an Arf3p polarization-specific adapter and participates in development of polarity.
authors.affiliation: Institute of Molecular Medicine, School of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Pei-Chin
authors.initials: PC
authors.lastname: Tsai
authors.forename: Szu-Wei
authors.initials: SW
authors.lastname: Lee
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Liu
authors.forename: Chih-Wen
authors.initials: CW
authors.lastname: Chu
authors.forename: Kuan-Yu
authors.initials: KY
authors.lastname: Chen
authors.forename: Jui-Chih
authors.initials: JC
authors.lastname: Ho
authors.forename: Fang-Jen S
authors.initials: FJ
authors.lastname: Lee
mesh_terms: D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000199:Actins / Q000737:chemistry; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D010590:Phalloidine / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism* / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013347:Subcellular Fractions / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D000199:Actins; C530208:Afi1 protein, S cerevisiae; D002352:Carrier Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D010590:Phalloidine; C492128:ARF3 protein, S cerevisiae; D020727:ADP-Ribosylation Factors