title: Syntaxin 8 has two functionally distinct di-leucine-based motifs.
abstract: Syntaxin 8 has been shown to form the SNARE complex with syntaxin 7, vti1b and endobrevin. These have been shown to function as the machinery for the homotypic fusion of late endosomes. Recently, we showed that syntaxins 7 and 8 cycle through the plasma membrane, and that the di-leucine-based motifs in the cytoplasmic domain of syntaxins 7 and 8 respectively function in their endocytic and exocytic processes. However, we could not elucidate the mechanism by which syntaxin 8 cycles through the plasma membrane. In this study, we constructed several different syntaxin 8 molecules by mutating putative di-leucine-based motifs, and analyzed their intracellular localization and trafficking. We found a di-leucine-based motif in the cytoplasmic domain of syntaxin 8. It is similar to that of syntaxin 7, and functions in its endocytosis. These results suggest that in the cytoplasmic domain, syntaxin 8 has two functionally distinct di-leucine-based motifs that act independently in its endocytic and exocytic processes. This is the first report on two di-leucine-based motifs in the same molecule acting independently in distinct transport pathways.
authors.affiliation: Department of Cell Physiology, Kyorin University School of Medicine, Mitaka, Tokyo, 181-8611, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kasai
authors.forename: Kei
authors.initials: K
authors.lastname: Suga
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Izumi
authors.forename: Kimio
authors.initials: K
authors.lastname: Akagawa
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis / Q000235:genetics; D005089:Exocytosis / Q000235:genetics; D006801:Humans; D007930:Leucine / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary / Q000235:genetics; D050765:Qa-SNARE Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051381:Rats
chemical_list: D050765:Qa-SNARE Proteins; D007930:Leucine