Conservation of inner nuclear membrane targeting sequences in mammalian Pom121 and yeast Heh2 membrane proteins

Mol Biol Cell. 2015 Sep 15;26(18):3301-12. doi: 10.1091/mbc.E15-03-0184. Epub 2015 Jul 15.

Abstract

Endoplasmic reticulum-synthesized membrane proteins traffic through the nuclear pore complex (NPC) en route to the inner nuclear membrane (INM). Although many membrane proteins pass the NPC by simple diffusion, two yeast proteins, ScSrc1/ScHeh1 and ScHeh2, are actively imported. In these proteins, a nuclear localization signal (NLS) and an intrinsically disordered linker encode the sorting signal for recruiting the transport factors for FG-Nup and RanGTP-dependent transport through the NPC. Here we address whether a similar import mechanism applies in metazoans. We show that the (putative) NLSs of metazoan HsSun2, MmLem2, HsLBR, and HsLap2β are not sufficient to drive nuclear accumulation of a membrane protein in yeast, but the NLS from RnPom121 is. This NLS of Pom121 adapts a similar fold as the NLS of Heh2 when transport factor bound and rescues the subcellular localization and synthetic sickness of Heh2ΔNLS mutants. Consistent with the conservation of these NLSs, the NLS and linker of Heh2 support INM localization in HEK293T cells. The conserved features of the NLSs of ScHeh1, ScHeh2, and RnPom121 and the effective sorting of Heh2-derived reporters in human cells suggest that active import is conserved but confined to a small subset of INM proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Amino Acid Sequence
  • Animals
  • Cells, Cultured
  • Endoplasmic Reticulum / metabolism
  • HEK293 Cells
  • Humans
  • Membrane Glycoproteins / metabolism*
  • Membrane Proteins / metabolism*
  • Mice
  • Nuclear Envelope / metabolism*
  • Nuclear Localization Signals / metabolism*
  • Nuclear Pore / metabolism
  • Nuclear Proteins / metabolism*
  • Protein Structure, Tertiary

Substances

  • Heh2 protein, S cerevisiae
  • Membrane Glycoproteins
  • Membrane Proteins
  • Nuclear Localization Signals
  • Nuclear Proteins
  • POM121 protein, human

Associated data

  • PDB/4YI0