Heterotetramerization of plant PIP channels involves different stoichiometries

CINTIA JOZEFKOWICZ; LORENA SIGAUT; AGUSTINA CANESSA FORTUNA; FLORENCIA SCOCHERA; LUIS GONZÁLEZ FLECHA; LÍA ISABEL PIETRASANTA; GABRIELA AMODEO; KARINA ALLEVA

Sierra de la Ventana, Buenos Aires

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

Sociedad Argentina de Biofísica

As other multimeric membrane channels, aquaporins oligomerscomposition could be homooligomeric or heterooligomeric.Although physical and functional interaction among different PIPshas been proved, it is not elucidated how the different monomersare organized in a functional oligomer. First, we confirmed theexistence of PIP oligomers as heterotetramers by studying somestructural elements involved in the intermolecular interactionsbetween PIP monomers (1). Now, we investigate the functionalproperties of heterotetramers comprising different PIP1-PIP2stoichiometry ratios. Our experimental approaches include: i)performing homo and heterodimeric constructs made of eitherPIP1 or PIP2, as well as both subunits; ii) measuring watertransport in control and inhibited (medium acidification) conditionsin Xenopus oocytes; iii) localizing PIPs heterotetramers by confocalfluorescence microscopy; iv) detecting PIP assemblies by in gelfluorescence technique. Results indicate that PIP heterotetramerswith stoichiometries PIP1-PIP2 2:2, 3:1 and 1:3 can exist in theplasma membrane since they are able to assemble by coexpressionof PIP1-PIP2 dimers, and by co-expression of dimerswith PIP1 or PIP2 monomers. Moreover, heterotetramerstoichiometry present biological relevance since it affects watertransport activity and proton-dependent gating.Acknowledgements: PICT 2010-2042, UBACYT 2013 grants to K.A. and PICT11-2239, PIP12-14 CONICET grants to G.A.