Regulation of Plasma Membrane Nano-Domains of the Water Channel Aquaporin-3 Revealed by Fixed and Live Photoactivated Localization Microscopy

Several aquaporins (AQP) water channels are short-term regulated by the messenger cyclic adenosine monophosphate (cAMP), including AQP3. Bulk measurements show that cAMP can change diffusive properties of AQP3, however, it remains unknown how elevated cAMP affects AQP3 organization at the nanoscale. Here we analyzed AQP3 nano-organization following cAMP-stimulation using photoactivated localization microscopy (PALM) of fixed cells combined with pair correlation analysis. Moreover, we combined PALM acquisitions of single fluorophores combined with single-molecule tracking (spt-PALM). These analyses revealed that AQP3 tend to cluster and that the diffusive mobility is confined to nano-domains with radii of ~150 nm. This domain size increases by ~30 % upon elevation of cAMP, which, however, is not accompanied by a significant increase in the confined diffusion coefficient. This regulation of AQP3 organization at the nanoscale may be important for understanding the mechanisms of water AQP3-mediated water transport across plasma membranes.