ER network formation requires a balance of the dynamin-like GTPase Sey1p and the Lunapark family member Lnp1p.
Although studies on endoplasmic reticulum (ER) structure and dynamics have focused on the ER tubule-forming proteins (reticulons and DP1/Yop1p) and the tubule fusion protein atlastin, nothing is known about the proteins and processes that act to counterbalance this machinery. Here we show that Lnp1p, a member of the conserved Lunapark family, plays a role in ER network formation. Lnp1p binds to the reticulons and Yop1p and resides at ER tubule junctions in both yeast and mammalian cells. In the yeast Saccharomyces cerevisiae, the interaction of Lnp1p with the reticulon protein, Rtn1p, and the localization of Lnp1p to ER junctions are regulated by Sey1p, the yeast orthologue of atlastin. We propose that Lnp1p and Sey1p act antagonistically to balance polygonal network formation. In support of this proposal, we show that the collapsed, densely reticulated ER network in lnp1 Δ cells is partially restored when the GTPase activity of Sey1p is abrogated.
Department of Cellular and Molecular Medicine, George Palade Labs, University of California at San Diego, La Jolla, California 92093-0668, USA.
Shuliang
S
Chen
Peter
P
Novick
Susan
S
Ferro-Novick
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D054730:Protein Interaction Domains and Motifs; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D000069816:SEC Translocation Channels; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
D018398:Homeodomain Proteins; C474231:LNPK protein, human; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; C505725:Rtn1 protein, S cerevisiae; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; C472231:SEY1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins