New Roles of Aquaporins in the Activation of Processes Involving Changes in Cell Volume

FLAMENCO MP; RIVAROLA V; GALIZIA L; FORD P; CAPURRO C

Bahia, Brasil

Congreso; 7th International Congress of Comparative Physiology and Biochemestry; 2007

South American Society of Comparative Physiology and Biochemistry

The discovery of aquaporins (AQPs), opened a new frontier in the comprehension of many physiological processes. Although it is accepted that the major role of AQPs is to increase the water permeability of plasma membranes (Pf), the use of models that express, or not, specific AQPs, provided new insights in previously unrecognized roles. The aim of this work was to evaluate the role of AQP2 in the activation of cell volume regulation mechanisms as well as its participation in processes which involve changes in cell volume such us apoptosis. The mammalian collecting duct cells are a good model for these studies since they express AQP2 and they are exposed to sudden variations in extracellular osmolality, inducing changes in cell volume, which in limit situations may lead to cell death. We demonstrated that AQP2 expression is critical for a rapid activation of regulatory volume decrease mechanisms, which would be linked to CFTR and to barium-sensitive K+ channels. Even more, our results suggest that in cells exposed to apoptotic stimulus, the rate of apoptosis (RA) is 30 % increased in the presence of AQP2 and Pf is significantly decreased. The increased RA suggests that the initial high Pf in AQP2 cells is necessary for a cell to undergo the apoptotic volume decrease, earliest event in apoptosis. However, a secondary decrease in Pf may be due to AQP2 inactivation, critical to allow intracellular K+ to be reduced to levels necessary to activate the apoptotic enzymatic cascade. We conclude that AQP2 modulation plays a critical role in processes that require transient changes in cell volume and in the activation of ion transporters/channels