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Post‐Golgi Supramolecular Assembly of Aquaporin‐4 in Orthogonal Arrays
Author(s) -
Rossi Andrea,
Baumgart Florian,
van Hoek Alfred N.,
Verkman A. S.
Publication year - 2012
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2011.01299.x
Subject(s) - golgi apparatus , vesicle , aquaporin 4 , membrane , microbiology and biotechnology , endoplasmic reticulum , biology , biophysics , membrane curvature , biochemistry
The supramolecular assembly of aquaporin‐4 (AQP4) in orthogonal arrays of particles (OAPs) involves N‐terminus interactions of the M23‐AQP4 isoform. We found AQP4 OAPs in cell plasma membranes but not in endoplasmic reticulum (ER) or Golgi, as shown by: (i) native gel electrophoresis of brain and AQP4‐transfected cells, (ii) photobleaching recovery of green fluorescent protein‐AQP4 chimeras in live cells and (iii) freeze‐fracture electron microscopy (FFEM). We found that AQP4 OAP formation in plasma membranes, but not in the Golgi, was not related to AQP4 density, pH, membrane lipid composition, C‐terminal PDZ domain interactions or α‐syntrophin expression. Remarkably, however, fusion of AQP4‐containing Golgi vesicles with (AQP4‐free) plasma membrane vesicles produced OAPs, suggesting the involvement of plasma membrane factor(s) in AQP4 OAP formation. In investigating additional possible determinants of OAP assembly we discovered membrane curvature‐dependent OAP assembly, in which OAPs were disrupted by extrusion of plasma membrane vesicles to ∼110 nm diameter, but not to ∼220 nm diameter. We conclude that AQP4 supramolecular assembly in OAPs is a post‐Golgi phenomenon involving plasma membrane‐specific factor(s). Post‐Golgi and membrane curvature‐dependent OAP assembly may be important for vesicle transport of AQP4 in the secretory pathway and AQP4‐facilitated astrocyte migration, and suggests a novel therapeutic approach for neuromyelitis optica.