Reorientation of aquaporin-1 topology during maturation in the endoplasmic reticulum

Y. Lu, I. R. Turnbull, A. Bragin, K. Carveth, A. S. Verkman, William Skach

Research output: Contribution to journalArticle

90 Citations (Scopus)

Abstract

The topology of most eukaryotic polytopic membrane proteins is established cotranslationally in the endoplasmic reticulum (ER) through a series of coordinated translocation and membrane integration events. For the human aquaporin water channel AQP1, however, the initial four-segment-spanning topology at the ER membrane differs from the mature six-segment-spanning topology at the plasma membrane. Here we use epitope-tagged AQP1 constructs to follow the transmembrane (TM) orientation of key internal peptide loops in Xenopus oocyte and cell-free systems. This analysis revealed that AQP1 maturation in the ER involves a novel topological reorientation of three internal TM segments and two peptide loops. After the synthesis of TMs 4-6, TM3 underwent a 180-degree rotation in which TM3 C-terminal flanking residues were translocated from their initial cytosolic location into the ER lumen and N-terminal flanking residues underwent retrograde translocation from the ER lumen to the cytosol. These events convert TM3 from a type I to a type II topology and reposition TM2 and TM4 into transmembrane conformations consistent with the predicted six-segment-spanning AQP1 topology. AQP1 topological reorientation was also associated with maturation from a protease-sensitive conformation to a protease-resistant structure with water channel function. These studies demonstrate that initial protein topology established via cotranslational translocation events in the ER is dynamic and may be modified by subsequent steps of folding and/or maturation.

Original languageEnglish (US)
Pages (from-to)2973-2985
Number of pages13
JournalMolecular Biology of the Cell
Volume11
Issue number9
StatePublished - 2000

Fingerprint

Aquaporin 1
Endoplasmic Reticulum
Aquaporins
Peptide Hydrolases
Peptides
Membranes
Cell-Free System
Xenopus
Cytosol
Oocytes
Epitopes
Membrane Proteins
Cell Membrane

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cell Biology

Cite this

Lu, Y., Turnbull, I. R., Bragin, A., Carveth, K., Verkman, A. S., & Skach, W. (2000). Reorientation of aquaporin-1 topology during maturation in the endoplasmic reticulum. Molecular Biology of the Cell, 11(9), 2973-2985.

Reorientation of aquaporin-1 topology during maturation in the endoplasmic reticulum. / Lu, Y.; Turnbull, I. R.; Bragin, A.; Carveth, K.; Verkman, A. S.; Skach, William.

In: Molecular Biology of the Cell, Vol. 11, No. 9, 2000, p. 2973-2985.

Research output: Contribution to journalArticle

Lu, Y, Turnbull, IR, Bragin, A, Carveth, K, Verkman, AS & Skach, W 2000, 'Reorientation of aquaporin-1 topology during maturation in the endoplasmic reticulum', Molecular Biology of the Cell, vol. 11, no. 9, pp. 2973-2985.
Lu Y, Turnbull IR, Bragin A, Carveth K, Verkman AS, Skach W. Reorientation of aquaporin-1 topology during maturation in the endoplasmic reticulum. Molecular Biology of the Cell. 2000;11(9):2973-2985.
Lu, Y. ; Turnbull, I. R. ; Bragin, A. ; Carveth, K. ; Verkman, A. S. ; Skach, William. / Reorientation of aquaporin-1 topology during maturation in the endoplasmic reticulum. In: Molecular Biology of the Cell. 2000 ; Vol. 11, No. 9. pp. 2973-2985.
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