Secretory Carrier Membrane Protein 2 Regulates Cell-surface Targeting of Brain-enriched Na+/H+ Exchanger NHE5

J Biol Chem. 2009 May 15;284(20):13892-903. doi: 10.1074/jbc.M807055200. Epub 2009 Mar 10.

Abstract

NHE5 is a brain-enriched Na(+)/H(+) exchanger that dynamically shuttles between the plasma membrane and recycling endosomes, serving as a mechanism that acutely controls the local pH environment. In the current study we show that secretory carrier membrane proteins (SCAMPs), a group of tetraspanning integral membrane proteins that reside in multiple secretory and endocytic organelles, bind to NHE5 and co-localize predominantly in the recycling endosomes. In vitro protein-protein interaction assays revealed that NHE5 directly binds to the N- and C-terminal cytosolic extensions of SCAMP2. Heterologous expression of SCAMP2 but not SCAMP5 increased cell-surface abundance as well as transporter activity of NHE5 across the plasma membrane. Expression of a deletion mutant lacking the SCAMP2-specific N-terminal cytosolic domain, and a mini-gene encoding the N-terminal extension, reduced the transporter activity. Although both Arf6 and Rab11 positively regulate NHE5 cell-surface targeting and NHE5 activity across the plasma membrane, SCAMP2-mediated surface targeting of NHE5 was reversed by dominant-negative Arf6 but not by dominant-negative Rab11. Together, these results suggest that SCAMP2 regulates NHE5 transit through recycling endosomes and promotes its surface targeting in an Arf6-dependent manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADP-Ribosylation Factors / genetics
  • ADP-Ribosylation Factors / metabolism*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Line
  • Cell Membrane / genetics
  • Cell Membrane / metabolism*
  • Endosomes / genetics
  • Endosomes / metabolism*
  • Humans
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Protein Binding / physiology
  • Protein Structure, Tertiary / physiology
  • Protein Transport / physiology
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism*
  • rab GTP-Binding Proteins / genetics
  • rab GTP-Binding Proteins / metabolism*

Substances

  • Carrier Proteins
  • Membrane Proteins
  • SCAMP2 protein, human
  • Sodium-Hydrogen Exchangers
  • sodium-hydrogen exchanger 5
  • rab11 protein
  • ADP-Ribosylation Factors
  • ADP-ribosylation factor 6
  • rab GTP-Binding Proteins