Evolutionary well-conserved region in the signal peptide of parathyroid hormone-related protein is critical for its dual localization through the regulation of ER translocation

J Biochem. 2016 Apr;159(4):393-406. doi: 10.1093/jb/mvv111. Epub 2015 Nov 3.

Abstract

Parathyroid hormone-related protein (PTHrP) has two different targeting signals: an N-terminal signal peptide for the endoplasmic reticulum (ER) targeting and an internal nuclear localization signal. The protein not only functions as a secretory protein, but is also found in the nucleus and/or nucleolus under certain conditions. PTHrP signal peptide is less hydrophobic than most signal peptides mainly due to its evolutionarily well-conserved region (QQWS). The substitution of four tandem leucine residues for this conserved region resulted in a significant inhibition of the signal peptide cleavage. At the same time, proportion of nuclear and/or nucleolar localization decreased, probably due to tethering of the protein to the ER membrane by the uncleaved mutant signal peptide. Almost complete cleavage of the signal peptide accompanied by a lack of nuclear/nucleolar localization was achieved by combining the hydrophobic h-region and an optimized sequence of the cleavage site. In addition, mutational modifications of the distribution of charged residues in and around the signal peptide affect its cleavage and/or nuclear/nucleolar localization of the protein. These results indicate that the well-conserved region in the signal peptide plays an essential role in the dual localization of PTHrP through ER targeting and/or the membrane translocation.

Keywords: endoplasmic reticulum; nuclear localization signal; parathyroid hormone-related protein; protein conducting channel; signal peptide.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Cell Nucleolus / metabolism*
  • Chlorocebus aethiops
  • Conserved Sequence
  • Endoplasmic Reticulum / metabolism*
  • Evolution, Molecular*
  • Molecular Sequence Data
  • Mutation
  • Nuclear Localization Signals / metabolism*
  • Parathyroid Hormone-Related Protein / chemistry
  • Parathyroid Hormone-Related Protein / genetics
  • Parathyroid Hormone-Related Protein / metabolism*
  • Protein Transport
  • Rats
  • Signal Transduction
  • Structure-Activity Relationship

Substances

  • Nuclear Localization Signals
  • Parathyroid Hormone-Related Protein