Heterotetramerization of plant PIP channels involves different stoichiometries

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

Sierra de la Ventana

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

Sociedad Argenina de Biofísica

As other multimeric membrane channels, aquaporins oligomers composition could be homooligomeric or heterooligomeric. Although physical and functional interaction among different PIPs has been proved, it is not elucidated how the different monomers are organized in a functional oligomer. First, we confirmed the existence of PIP oligomers as heterotetramers by studying some structural elements involved in the intermolecular interactions between PIP monomers (1). Now, we investigate the functional properties of heterotetramers comprising different PIP1-PIP2 stoichiometry ratios. Our experimental approaches include: i) performing homo and heterodimeric constructs made of either PIP1 or PIP2, as well as both subunits; ii) measuring water transport in control and inhibited (medium acidification) conditions in Xenopus oocytes; iii) localizing PIPs heterotetramers by confocal fluorescence microscopy; iv) detecting PIP assemblies by in gel fluorescence technique. Results indicate that PIP heterotetramers with stoichiometries PIP1-PIP2 2:2, 3:1 and 1:3 can exist in the plasma membrane since they are able to assemble by coexpression of PIP1-PIP2 dimers, and by co-expression of dimers with PIP1 or PIP2 monomers. Moreover, heterotetramer stoichiometry present biological relevance since it affects water transport activity and proton-dependent gating.