Alfy, a novel FYVE-domain-containing protein associated with protein granules and autophagic membranes.
Phosphatidylinositol-3-phosphate [PtdIns(3)P] regulates endocytic and autophagic membrane traffic. In order to understand the downstream effects of PtdIns(3)P in these processes, it is important to identify PtdIns(3)P-binding proteins, many of which contain FYVE zinc-finger domains. Here, we describe a novel giant FYVE-domain-containing protein, named autophagy-linked FYVE protein (Alfy). Alfy is ubiquitously expressed, shares sequence similarity with the Chediak-Higashi-syndrome protein and has putative homologues in flies, nematodes and fission yeast. Alfy binds PtdIns(3)P in vitro and partially colocalizes with PtdIns(3)P in vivo. Unlike most other FYVE-domain proteins, Alfy is not found on endosomes but instead localizes mainly to the nuclear envelope. When HeLa cells are starved or treated with a proteasome inhibitor, Alfy relocalizes to characteristic filamentous cytoplasmic structures located close to autophagic membranes and ubiquitin-containing protein aggregates. By electron microscopy, similar structures can be found within autophagosomes. We propose that Alfy might target cytosolic protein aggregates for autophagic degradation.
Simonsen
Anne
A
Department of Biochemistry, The Norwegian Radium Hospital, Montebello, Oslo 0310, Norway.
Birkeland
Hanne C G
HC
Gillooly
David J
DJ
Mizushima
Noboru
N
Kuma
Akiko
A
Yoshimori
Tamotsu
T
Slagsvold
Thomas
T
Brech
Andreas
A
Stenmark
Harald
H
D048868:Adaptor Proteins, Signal Transducing; D001343:Autophagy / Q000502:physiology*; D000071183:Autophagy-Related Proteins; D002894:Chromosomes, Human, Pair 4; D017124:Conserved Sequence; D003594:Cytoplasmic Granules / Q000378:metabolism; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism / Q000648:ultrastructure; D046911:Macromolecular Substances / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000378:metabolism / Q000648:ultrastructure; D010588:Phagosomes / Q000378:metabolism* / Q000648:ultrastructure; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D016335:Zinc Fingers / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; D000071183:Autophagy-Related Proteins; D018076:DNA, Complementary; D046911:Macromolecular Substances; D008565:Membrane Proteins; D014157:Transcription Factors; D025801:Ubiquitin; C499825:WDFY3 protein, human; D010744:Phosphoric Monoester Hydrolases; C061816:phosphatidylinositol-3-phosphatase; D046988:Proteasome Endopeptidase Complex