Loop B Serine phosphorylation status differentially affects pH sensing of PIP aquaporins

AGUSTÍN YANEFF; LORENA SIGAUT; ANA CECILIA ALIAGA FANDIÑO ; KARINA ALLEVA; LÍA ISABEL PIETRASANTA; GABRIELA AMODEO

Sierra de la Ventana, Buenos Aires

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Biofísica; 2014

Sociedad Argentina de Biofísica

The crystallization of SoPIP2;1 in an open and close conformationas well as biophysical evidences have allowed to propose a gatingmechanism in PIP aquaporins. A close state seems to prevailunder different stimuli: cytosolic pH decrease2, intracellular Ca2+concentration increase and desphosphorylation of specificserines1. In previous work, we characterize FaPIP1;1 andFaPIP2;1 in terms of their Pf and pH inhibition response anddemonstrate that heterotetramerization affects pH gatingsensitivity2. In the light of these findings we decided to explore ifphosphorylation of specific residues is involved in this response.Several PIP2 mutants where Serine from the loop B was replacedto alanine showed less activity as water channels when expressedin Xenopus laevis oocytes3?5 or yeast6,7. However, for several plantspecies, loop B serine has shown to be non-phosphorylated invivo4,5,8. In this work, we generate loop B mutants (FaPIP2;1S121Aand FaPIP1;1S131A) in order to simulate desphosphorylated stateand characterize their behavior in terms of Pf and pH inhibitionresponse. Our results show that loop B serine phosphorylationstatus affects pH gating sensitivity for FaPIP2;1 but not forFaPIP1;1. Thus, we propose a crosstalk between differentregulatory mechanisms (heterotetramerization, serinephosphorylation status and pH sensitivity) that would rule the Pf ofa membrane that express PIPs