Journal of Membrane Biology

, Volume 234, Issue 3, pp 149–158

A Membrane-Proximal Region in the C-Terminal Tail of NHE7 Is Required for Its Distribution in the Trans-Golgi Network, Distinct from NHE6 Localization at Endosomes

  • Naomi Fukura
  • Ryuichi Ohgaki
  • Masafumi Matsushita
  • Norihiro Nakamura
  • Keiji Mitsui
  • Hiroshi Kanazawa
Article

DOI: 10.1007/s00232-010-9242-9

Cite this article as:
Fukura, N., Ohgaki, R., Matsushita, M. et al. J Membrane Biol (2010) 234: 149. doi:10.1007/s00232-010-9242-9

Abstract

Mammalian Na+/H+ exchanger (NHE) isoform NHE6 is localized in sorting/recycling endosomes, whereas NHE7 is localized in the trans-Golgi network (TGN) and mid-trans-Golgi stacks. The mechanism targeting each NHE to a specific organelle is largely unknown, although the targeting is thought to be important for pH control in the lumen of various organelles. NHE6 and NHE7 exhibit distinct localization despite conserved amino acid sequences. To specify the intramolecular region involved in the specific localization, we examined the intracellular localization of chimeric NHE6 and NHE7 constructs. NHEs are composed of an N-terminal transmembrane domain (TM) and a C-terminal hydrophilic tail domain (Ct). Exchange of the Ct between the isoforms suggested that the Ct is required for the specific localization. We further split the Ct into three regions, and chimeras with various combinations of these small regions indicated that the most membrane-proximal region among the three contributes to the specific localization. Mutant forms of NHE7 with sequential alanine substitutions in the most membrane-proximal region, between residues 530 and 589, showed that two regions (residues 553–559 and 563–568) are required for NHE7-like localization. However, NHE6 with alanine substitutions in the membrane-proximal region exhibited no apparent change in localization. These results suggest that two membrane proximal regions (residues 533–559 and 563–568) play an important role in targeting NHE7 to the TGN.

Keywords

NHE6 NHE7 Localization Endosome Trans-Golgi network Chimera NHE transporter 

Supplementary material

232_2010_9242_MOESM1_ESM.pdf (241 kb)
Supplemental Fig. 1Alignment of amino acid sequences of human NHE6 and NHE7. The boundary between the N-terminal transmembrane domain (TM) and the C-terminal hydrophilic domain (Ct) is denoted by a vertical line with arrows. Split regions (A, B and C) in Ct are indicated with boxes. The binding sites of RACK1 and SCAMP2 are also shown with light blue and purple lines, respectively. The YXXΦ-like sequence in NHE7 is shown with a red line (PDF 241 kb)

Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Naomi Fukura
    • 1
  • Ryuichi Ohgaki
    • 1
  • Masafumi Matsushita
    • 1
  • Norihiro Nakamura
    • 1
  • Keiji Mitsui
    • 1
  • Hiroshi Kanazawa
    • 1
  1. 1.Department of Biological ScienceGraduate School of Science, Osaka UniversityToyonaka CityJapan

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