Mechanosensitive characterization of a TIP1 aquaporin from Beta Vulgaris (beetroot)

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

Salto

Congreso; Latin American Crosstalk in Biophysics and Physiology; 2015

Sociedad Argentina de Biofísica y Seccional Biofísica de la Sociedad Uruguaya de Biociencias

Previously, we have shown that the aquaporins PIP2 and TIP1 from Betavulgaris have different responses to membrane tension changes. While PIP2seems not to be a mechanosensitive channel, osmotic experiments withTIP1 show a nonlinear relationship between water flux and the magnitudeof the osmotic gradient. In this work, we studied the mechanosensitiveproperties of TIP1 from Beta vulgaris (beetroot). We expressed the proteinin Xenopus oocyte membranes and measured volume and pressure changessimultaneously, applying different osmotic gradients by means of theemptied-out oocyte technique1. Preliminary results show that the incrementof the membrane elastance (E) is higher when the system is faced to ahigher osmotic gradient (100.74 ± 5.71 KPa/s with a 60 mM mannitolgradient and 134 ± 21.88 KPa/s with a 200 mM mannitol gradient). Theseresults also show that Pf and E are negatively correlated (r>0.88). Fitting toa linear function yields a slope equal to -0.0065 ± 0.0016 cm.s-1/MPa. Thisexperimental evidence suggests that the pore of TIP1 closes with increasingmembrane tensions. Similarly, this was previously proposed for humanAQP12. In conclusion, it is feasible to hypothesize that animal and plantaquaporins share a common mechanism of regulation mediated bymembrane-tension changes.