title: Targeting of Tsc13p to nucleus-vacuole junctions: a role for very-long-chain fatty acids in the biogenesis of microautophagic vesicles.
abstract: TSC13 is required for the biosynthesis of very-long-chain fatty acids (VLCFAs) in yeast. Tsc13p is a polytopic endoplasmic reticulum (ER) membrane protein that accumulates at nucleus-vacuole (NV) junctions, which are formed through Velcro-like interactions between Nvj1p in the perinuclear ER and Vac8p on the vacuole membrane. NV junctions mediate piecemeal microautophagy of the nucleus (PMN), during which bleb-like portions of the nucleus are extruded into invaginations of the vacuole membrane and degraded in the vacuole lumen. We report that Tsc13p is sequestered into NV junctions from the peripheral ER through Vac8p-independent interactions with Nvj1p. During nutrient limitation, Tsc13p is incorporated into PMN vesicles in an Nvj1p-dependent manner. The lumenal diameters of PMN blebs and vesicles are significantly reduced in tsc13-1 and tsc13-1 elo3-Delta mutant cells. PMN structures are also smaller in cells treated with cerulenin, an inhibitor of de novo fatty acid synthesis and elongation. The targeting of Tsc13p-GFP into NV junctions is perturbed by cerulenin, suggesting that its binding to Nvj1p depends on the availability of fatty acid substrates. These results indicate that Nvj1p retains and compartmentalizes Tsc13p at NV junctions and that VLCFAs contribute to the normal biogenesis of trilaminar PMN structures in yeast.
authors.affiliation: Department of Biology, University of Rochester, Rochester, NY 14627, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Kvam
authors.forename: Kenneth
authors.initials: K
authors.lastname: Gable
authors.forename: Teresa M
authors.initials: TM
authors.lastname: Dunn
authors.forename: David S
authors.initials: DS
authors.lastname: Goldfarb
mesh_terms: D000215:Acylation; D000935:Antifungal Agents / Q000494:pharmacology; D001343:Autophagy / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism*; D002569:Cerulenin / Q000494:pharmacology; D022162:Cytoplasmic Vesicles / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis / Q000502:physiology*; D008074:Lipoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins
chemical_list: D000935:Antifungal Agents; D005227:Fatty Acids; D008074:Lipoproteins; D008565:Membrane Proteins; C499847:Nvj1 protein, S cerevisiae; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; C111373:VAC8 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D002569:Cerulenin; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C418219:TSC13 protein, S cerevisiae