Molecular Biology of the Cell Call for Nominations: MBC Editor-in-Chief

Home Help [Feedback] [For Subscribers] [Archive] [Search] --
QUICK SEARCH:   [advanced]


     

MBC in Press, published online ahead of print May 21, 2008
Mol. Biol. Cell 10.1091/mbc.E08-03-0322

A more recent version of this article appeared on August 1, 2008
This Article
Right arrow Full Text (PDF)
Right arrow Supplemental Materials
Right arrow All Versions of this Article:
E08-03-0322v1
19/8/3369    most recent
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Crane, J. M.
Right arrow Articles by Verkman, A.S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Crane, J. M.
Right arrow Articles by Verkman, A.S.

Submitted on March 28, 2008
Revised on April 24, 2008
Accepted on May 9, 2008

Aquaporin-4 Dynamics in Orthogonal Arrays in Live Cells Visualized by Quantum Dot Single Particle Tracking

Jonathan M. Crane,* Alfred N. Van Hoek,{dagger} William R. Skach,{ddagger} and A.S. Verkman*

*Departments of Medicine and Physiology, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA, 94143-0521; {dagger}Center for Systems Biology, Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital, Boston, MA, 02114; {ddagger}Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR, 97239

Monitoring Editor: Jennifer Lippincott-Schwartz

Freeze-fracture electron microscopy (FFEM) indicates that aquaporin-4 (AQP4) water channels can assemble in cell plasma membranes in orthogonal arrays of particles (OAPs). We investigated the determinants and dynamics of AQP4 assembly in OAPs by tracking single AQP4 molecules labeled with quantum dots at an engineered external epitope. In several transfected cell types, including primary astrocyte cultures, the long N-terminus ’M1' form of AQP4 diffused freely with diffusion coefficient ~5 x 10-10 cm2/s, covering ~5 µm in 5 min. The short N-terminus ’M23' form of AQP4, which by FFEM was found to form OAPs, was relatively immobile, moving only ~0.4 µm in 5 min. Actin modulation by latrunculin or jasplakinolide did not affect AQP4-M23 diffusion, but deletion of its C-terminal PDZ-binding domain increased its range by ~twofold over minutes. Biophysical analysis of short-range AQP4-M23 diffusion within OAPs indicated a spring-like potential with a restoring force of ~6.5 pN/µm. These and additional experiments indicated that: (a) AQP4-M1 and AQP4-M23 isoforms do not coassociate in OAPs; (b) OAPs can be imaged directly by total internal reflection fluorescence microscopy; (c) OAPs are relatively fixed, noninterconvertible assemblies that do not require cytoskeletal or PDZ-mediated interactions for formation. Our measurements are the first to visualize OAPs in live cells.

Address correspondence to: A.S. Verkman (Alan.Verkman{at}ucsf.edu)






Home Help [Feedback] [For Subscribers] [Archive] [Search] --
Copyright © 2008 by The American Society for Cell Biology. Terms of copyright protection, warranties, and disclaimers.