Study of the mechanical gating of the aquaporin FaPIP2;1 from strawberry

ACUÑA, CYNTHIA FLORENCIA; PANDOLFO, MICAELA; JEREZ FERREIRA, GUILLERMO; SUTKA, MOIRA; OZU, MARCELO

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias; 2017

Recently, we published the first works that experimentally demonstrate the direct regulation of both plant and animal aquaporins by membrane tension (s) changes. Our recent work with BvTIP1;2 and BvPIP2;1 from red beet show that the first one is mechanosentivewhile the second one is not. This different behavior could be related to the differential distribution of GxxxG sequences (suggested to be responsible for mechanosensitivity in ion channels) observed by homology modeling. Previously we demonstrated that hAQP1 isa mechanosensitive channel. Both the water permeability (Pf) and the elastic volumetric coefficient (E) are negatively correlated in experiments with hAQP1 and BvTIP1;2 (R2>0.98), indicating that these aquaporins close with s increments. Phylogenetics analysisindicate that AQP1 and PIPs share a common ancestor and that divergence of the AQP1-PIP and TIPs groups occurred earlier in evolution. Therefore, three hypotheses arise for mechanosensitivity: 1) it would had been present in the ancestor of AQP1-PIPs and TIPs and was lost in PIPs; 2) it appeared in AQP1-PIPs and TIPs by separately; 3) BvPIP2;1 is a mechanosensitive channel but less sensitive than hAQP1 and BvTIP1;2. Now, we are studying the mechanosensitive properties of FaPIP2;1 from strawberry. The homologymodel of FaPIP2;1 shows differences with BvPIP2;1 and similarities with BvTIP1;2, suggesting that FaPIP2;1 could behave as a mechanosensitive aquaporin. By means of simultaneous V and P measurements in Xenopus oocytes expressing FaPIP2;1 wedetermine Pf and E under osmotic gradients. Our previous results with osmotic gradients up to 200 mOmol.KgH2O-1 (E=0.5-0.8 KPa) showed that BvPIP2;1 is not regulated by membrane tension changes. Preliminary results with FaPIP2;1 show that this aquaporin doesnot behave as a mechanosenstive channel, at least up to changes induced with 200 mOmol.KgH2O-1.