Plasma Membrane Abundance of Human Aquaporin 5 Is Dynamically Regulated by Multiple Pathways

Philip Kitchen; Fredrik Öberg; Jennie Sjöhamn; Kristina Hedfalk; Roslyn M Bill; Alex C Conner; Matthew T Conner; Susanna Törnroth-Horsefield

doi:10.1371/journal.pone.0143027

Plasma Membrane Abundance of Human Aquaporin 5 Is Dynamically Regulated by Multiple Pathways

PLoS One. 2015 Nov 16;10(11):e0143027. doi: 10.1371/journal.pone.0143027. eCollection 2015.

Authors

Philip Kitchen¹, Fredrik Öberg², Jennie Sjöhamn², Kristina Hedfalk², Roslyn M Bill³, Alex C Conner⁴, Matthew T Conner⁵, Susanna Törnroth-Horsefield⁶

Affiliations

¹ Molecular Organization and Assembly in Cells Doctoral Training Centre, University of Warwick, Coventry, United Kingdom.
² Department of Chemistry, University of Gothenburg, Gothenburg, Sweden.
³ School of Life and Health Sciences, Aston University, Birmingham, United Kingdom.
⁴ Clinical and Experimental Medicine, The Medical School, University of Birmingham, Birmingham, United Kingdom.
⁵ Biomedical Research Centre, Sheffield Hallam University, Sheffield, United Kingdom.
⁶ Department of Biochemistry and Structural Biology, Centre for Molecular Protein Science, Lund University, Lund, Sweden.

Abstract

Aquaporin membrane protein channels mediate cellular water flow. Human aquaporin 5 (AQP5) is highly expressed in the respiratory system and secretory glands where it facilitates the osmotically-driven generation of pulmonary secretions, saliva, sweat and tears. Dysfunctional trafficking of AQP5 has been implicated in several human disease states, including Sjögren's syndrome, bronchitis and cystic fibrosis. In order to investigate how the plasma membrane expression levels of AQP5 are regulated, we studied real-time translocation of GFP-tagged AQP5 in HEK293 cells. We show that AQP5 plasma membrane abundance in transfected HEK293 cells is rapidly and reversibly regulated by at least three independent mechanisms involving phosphorylation at Ser156, protein kinase A activity and extracellular tonicity. The crystal structure of a Ser156 phosphomimetic mutant indicates that its involvement in regulating AQP5 membrane abundance is not mediated by a conformational change of the carboxy-terminus. We suggest that together these pathways regulate cellular water flow.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Aquaporin 5 / chemistry
Aquaporin 5 / metabolism*
Cell Membrane / drug effects
Cell Membrane / metabolism*
Crystallography, X-Ray
Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
Cyclic AMP-Dependent Protein Kinases / metabolism
HEK293 Cells
Humans
Hypotonic Solutions / pharmacology
Models, Molecular
Mutant Proteins / chemistry
Mutant Proteins / metabolism
Mutation / genetics
Phosphorylation / drug effects
Protein Kinase Inhibitors / pharmacology
Protein Structure, Secondary
Protein Transport / drug effects
Serine / genetics
Signal Transduction* / drug effects

Substances

Aquaporin 5
Hypotonic Solutions
Mutant Proteins
Protein Kinase Inhibitors
Serine
Cyclic AMP-Dependent Protein Kinases

Grants and funding

This work was supported by the Swedish Research Council (www.vr.se) grants 2009-360 and 2010-5208 (to STH), European Commission Framework Programme 7 (http://ec.europa.eu/research/fp7/index_en.cfm) Grant 201924 EDICT (to RMB) and by the Engineering and Physical Sciences Research Council (https://www.epsrc.ac.uk) through the Molecular Organisation and Assembly in Cells Doctoral Training Centre, University of Warwick, grant number EP/F500378/1 (PK). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.