FaPIP2-FaPIP1 heterotretamers and FaPIP2 homotetramers show different sensitivity to mechanicals regulation

GUSTAFERRI, FLORENCIA; GALIZIA, LUCIANO; GOLDMAN, RAMIRO P.; SUTKA, M; OZU, M

San Luis

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Biofísica; 2019

FaPIP2;1 is a high Pf strawberry water channel that forms heterotetramers with FaPIP1;1,and can be regulated by pH, by means of a cooperative mechanism. In our previous workwe studied the transport properties of FaPIP2;1 and found that this water channelresponds just like a mechanosensitive aquaporin. It is hypothesized that this mechanismwould also be cooperative involving the four monomers. The study of pH sensitivity withFaPIP2;1-FaPIP1;1 heterotetramers demonstrated that the interactions between differentsubunits modify the cooperativity among monomers. We consider FaPIP2;1-FaPIP1;1heterotetramers would be a good model to study the cooperativity in mechanicalregulation of aquaporins. Our hypothesis is that FaPIP2;1-FaPIP1;1 heterotetramers showdifferent sensitivity to mechanical regulation than FaPIP2;1 homotetramers. By means ofthe same methods followed in previous works, we determined the water flux (Jw) andosmotic permeability coefficient (Pf) of xenopus oocytes injected with a mix of cRNA ofFaPIP2;1 and FaPIP1;1 (1:3). Each oocyte was injected with 5 ng of cRNA and subjected todifferent osmotic gradients (Δosm) created with mannitol. On our most recent results theJw (nl.s-1) measured in oocytes subjected to 40, 90 and 140 mOmol.Kgw -1 was 0.30 ±0.10 (n=6), 0.59 ± 0.10 (n=8) and 1.13 ± 0.07 (n=8), respectively. These results show alinear Jw-Δosm relationship (R2>0.98), and the same Pf value, of about 2.0x10-2 cm.s-1, inall tested conditions. In comparison, FaPIP2;1 homotetramers show deviations fromlinearity for said relationships, a typical behavior of mechanosensitive aquaporins. Thatbeing so, it can be said that FaPIP2;1-FaPIP1;1 heterotetramers appear to be at least lesssensitive to membrane tension changes than FaPIP2;1 homotetramers.