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.
Department of Biochemistry, The Norwegian Radium Hospital, Montebello, Oslo 0310, Norway.
Anne
A
Simonsen
Hanne C G
HC
Birkeland
David J
DJ
Gillooly
Noboru
N
Mizushima
Akiko
A
Kuma
Tamotsu
T
Yoshimori
Thomas
T
Slagsvold
Andreas
A
Brech
Harald
H
Stenmark
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