Protein N-myristoylation plays a critical role in the endoplasmic reticulum morphological change induced by overexpression of protein Lunapark, an integral membrane protein of the endoplasmic reticulum

PLoS One. 2013 Nov 4;8(11):e78235. doi: 10.1371/journal.pone.0078235. eCollection 2013.

Abstract

N-myristoylation of eukaryotic cellular proteins has been recognized as a modification that occurs mainly on cytoplasmic proteins. In this study, we examined the membrane localization, membrane integration, and intracellular localization of four recently identified human N-myristoylated proteins with predicted transmembrane domains. As a result, it was found that protein Lunapark, the human ortholog of yeast protein Lnp1p that has recently been found to be involved in network formation of the endoplasmic reticulum (ER), is an N-myristoylated polytopic integral membrane protein. Analysis of tumor necrosis factor-fusion proteins with each of the two putative transmembrane domains and their flanking regions of protein Lunapark revealed that transmembrane domain 1 and 2 functioned as type II signal anchor sequence and stop transfer sequence, respectively, and together generated a double-spanning integral membrane protein with an N-/C-terminal cytoplasmic orientation. Immunofluorescence staining of HEK293T cells transfected with a cDNA encoding protein Lunapark tagged with FLAG-tag at its C-terminus revealed that overexpressed protein Lunapark localized mainly to the peripheral ER and induced the formation of large polygonal tubular structures. Morphological changes in the ER induced by overexpressed protein Lunapark were significantly inhibited by the inhibition of protein N-myristoylation by means of replacing Gly2 with Ala. These results indicated that protein N-myristoylation plays a critical role in the ER morphological change induced by overexpression of protein Lunapark.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • DNA, Complementary / genetics
  • DNA, Complementary / metabolism
  • Endoplasmic Reticulum / genetics
  • Endoplasmic Reticulum / metabolism*
  • Gene Expression Regulation
  • Genetic Vectors
  • HEK293 Cells
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Molecular Sequence Data
  • Myristic Acid / metabolism*
  • Protein Processing, Post-Translational*
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Transfection
  • Zinc Fingers / genetics

Substances

  • DNA, Complementary
  • Homeodomain Proteins
  • LNPK protein, human
  • Membrane Proteins
  • SERINC1 protein, human
  • Myristic Acid

Grant support

This work was supported in part by a Grant-in-Aid for Scientific Research (No. 23580136) from the Ministry of Education, Culture, Sports, Science and Technology of Japan (to TU). This work was also supported in part by a research grant (The YU “Pump-Priming Program” for Fostering Research Activities) from Yamaguchi University (to TU). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No additional external funding received for this study.