Taxilin; a novel syntaxin-binding protein that is involved in Ca2+-dependent exocytosis in neuroendocrine cells.
The syntaxin family is a central coordinator and participates in multiple protein-protein interactions in the soluble N-ethyl maleimide-sensitive factor attachment protein receptor machinery, which is involved in intracellular vesicle traffic. However, the molecular mechanism by which the syntaxin family regulates intracellular vesicle transport is not well known.



We have identified and purified a novel binding partner of syntaxin-3 from rat lung, and isolated and sequenced the cDNA of its human homologue from a human brain cDNA library. The cDNA had an open reading frame encoding a protein of 546 amino acids with a calculated Mr of 61,890. We tentatively referred to this protein as taxilin. A structural analysis of taxilin revealed the existence of an extraordinarily long coiled-coil domain in its C-terminal half. Syntaxin-1a and -4, as well as syntaxin-3 interacted with taxilin, but syntaxin-7 or -8 did not. Northern blot analysis showed that taxilin was ubiquitously expressed. Over-expression of full-length taxilin inhibited Ca2+-dependent exocytosis in PC12 cells.



These results indicate that taxilin is a novel binding partner of several syntaxin family members and suggest that taxilin is involved in Ca2+-dependent exocytosis in neuroendocrine cells.
Nogami
Satoru
S
Division of Molecular and Cell Biology, Institute for Medical Science, Dokkyo University School of Medicine, Mibu-machi, Tochigi 321-0293, Japan.
Satoh
Sachie
S
Nakano
Michiko
M
Shimizu
Hiroaki
H
Fukushima
Hiromichi
H
Maruyama
Ayumi
A
Terano
Akira
A
Shirataki
Hiromichi
H
D000818:Animals; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008168:Lung; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D050765:Qa-SNARE Proteins; D051381:Rats; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology
D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050765:Qa-SNARE Proteins; C494212:STX1A protein, human; C494213:Stx1a protein, rat; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; C476840:taxilin protein, rat; D002118:Calcium