Plant aquaporins PIP2 and TIP2 show different responses to membrane deformation

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

Sierra de la Ventana

Congreso; SAB 2014: XLIII Reunión Anual de la Sociedad; 2014

Sociedad Argentina de Biofísica

In this work we studied the mechanosensitive properties of PIP2and TIP2, both aquaporins (AQPs) from Beta vulgaris (beetroot).We expressed the proteins in Xenopus oocyte membranes andtested their functionality applying different osmotic gradients bymeans of the emptied-out oocyte technique [1]. The resultsobtained with TIP2 show that the relationship between water flux(JW) and the osmotic gradient (DOsm) is similar to that observedwith human AQP1 [2]. However, this seems not to be the case forPIP2. These results would be reflecting differences between thesensibility of TIPs and PIPs to changes of membrane tension. Inthe case of TIP2, the osmotic permeability coefficient (Pf)decreases with increasing DOsm. This indicates that the closure ofthe water pore could be a cooperative phenomenon, occurring inTIPs in a similar way as in hAQP1 [2]. In conclusion, presentresults show that a closure mechanism gated by increasingmembrane tension is present in plant AQPs, as occur in animalmembers of the family.1. Ozu et al, J. Biochem. Biophys. Methods. 63(3). 2005. P187.2. Ozu et al, Biophys. J. 104(1). 2013. P 85.