title: Mammalian ykt6 is a neuronal SNARE targeted to a specialized compartment by its profilin-like amino terminal domain.
abstract: SNAREs are required for specific membrane fusion throughout the endomembrane system. Here we report the characterization of rat ykt6, a prenylated SNARE selectively expressed in brain neurons. Immunofluorescence microscopy in neuronal and neuroendocrine cell lines revealed that membrane-associated ykt6 did not colocalize significantly with any conventional markers of endosomes, lysosomes, or the secretory pathway. However, ykt6-containing membranes displayed very minor overlaps with lysosomes and dense-core secretory granules and were similar to lysosomes in buoyant density. Thus, ykt6 appears to be specialized for the trafficking of a unique membrane compartment, perhaps related to lysosomes, involved in aspects of neuronal function. Targeting of this SNARE to the ykt6 compartment was mediated by its profilin-like amino-terminal domain, even in the absence of protein prenylation. Although several other R-SNAREs contain related amino-terminal domains, only the ykt6 version was able to confer the specialized localization. Rat ykt6, which contains an arginine in its SNARE motif zero-layer, was found to behave like other R-SNAREs in its SNARE assembly properties. Interestingly, cytosolic ykt6, constituting more than half of the total cellular pool, appeared to be conformationally inactive for SNARE complex assembly, perhaps indicative of a regulatory mechanism that prevents promiscuous and potentially deleterious SNARE interactions.
authors.affiliation: University of Michigan, Department of Molecular, Cellular, and Developmental Biology, Ann Arbor 48109-1048, USA.
authors.forename: Haruki
authors.initials: H
authors.lastname: Hasegawa
authors.forename: Sara
authors.initials: S
authors.lastname: Zinsser
authors.forename: Yeyoung
authors.initials: Y
authors.lastname: Rhee
authors.forename: Einar Osland
authors.initials: EO
authors.lastname: Vik-Mo
authors.forename: Svend
authors.initials: S
authors.lastname: Davanger
authors.forename: Jesse C
authors.initials: JC
authors.lastname: Hay
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D001120:Arginine / Q000737:chemistry; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens; D003285:Contractile Proteins; D003599:Cytoskeleton / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005982:Glutathione Transferase / Q000378:metabolism; D007150:Immunohistochemistry; D008247:Lysosomes / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology*; D008840:Microfilament Proteins / Q000737:chemistry*; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D016716:PC12 Cells; D010455:Peptides / Q000737:chemistry; D051304:Profilins; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D050683:R-SNARE Proteins; D051381:Rats; D050600:SNARE Proteins; D013347:Subcellular Fractions; D014018:Tissue Distribution; D033921:Vesicular Transport Proteins
chemical_list: D003285:Contractile Proteins; D018076:DNA, Complementary; D008565:Membrane Proteins; D008840:Microfilament Proteins; D010455:Peptides; C495740:Pfn1 protein, rat; D051304:Profilins; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; C491481:Ykt6 protein, rat; D001120:Arginine; D005982:Glutathione Transferase