TIP1 but not PIP2 form Beta vulgaris is regulated by cell mechanics

RAMIRO GOLDMAN; CINTIA JOZEFKOWICZ; MOIRA SUTKA; KARINA ALLEVA; MARCELO OZU

Tucumán

Congreso; III Latin American Federation of Biophysical Societies (LAFeBS) ? IX IberoAmerican Congress of Biophysics ? XLV Reunion Anual SAB; 2016

Latin American Federation of Biophysical Societies (LAFeBS) ? Sociedad Argentina de Biofisica

Different regulatory mechanisms are known in aquaporins (AQPs). It was demonstrated in the last years that animal and plant aquaporins are regulated by cell membrane mechanics (Ozu et al., 2013; Leitao et al., 2014). However, this mechanism has not been studied in deep. No direct measurements of membrane mechanics and aquaporins function have been reported yet. Moreover, important topics in the study of mechano-sensitivity in aquaporins are not known. For example, it is not clear if this is a general feature shared by all aquaporins or not, and it is not known which is the sensitivity of this regulation. To characterize the biophysical properties of mechanical regulation in aquaporins, we stud- ied the osmotic response of Xenopus oocytes expressing the water chan- nels TIP1 or PIP2 from the beet root Beta bulgaris by simultaneously measuring the internal pressure and volume under different osmotic and initial pressure conditions. Our results indicate that PIP2 would not be a mechanosensitive member of the aquaporin family whereas TIP1 would be since the osmotic permeability coefficient (Pf) measured in oocytes expressing TIP1 follows an exponential decay function with the volu- metric elastic modulus (E). Filogenetic analysis classifies human AQP1 and PIPs from plants into the same group, whereas TIPs are classified within another group (Soto et al, 2012). In this context, mechanosensi- tivity seems to be a feature not shared by all aquaporins, and its appear- ance along evolution will not be easy to determine.