IQUIFIB   02644
INSTITUTO DE QUIMICA Y FISICOQUIMICA BIOLOGICAS "PROF. ALEJANDRO C. PALADINI"
Unidad Ejecutora - UE
artículos
Título:
Loop B serine of a plasma membrane aquaporin type PIP2 but not PIP1 plays a key role in pH sensing
Autor/es:
LORENA SIGAUT; KARINA ALLEVA; AGUSTÍN YANEFF; CECILIA ALIAGAFANDIÑO; GABRIELA AMODEO; NATALIA GÓMEZ; LÍA ISABEL PIETRASANTA
Revista:
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2016 vol. 1858 p. 2778 - 2787
ISSN:
0005-2736
Resumen:
In the plant kingdom, the plasma membrane intrinsic aquaporins (PIPs) constitute ahighly conserved group of water channels with the capacity of rapidly adjusting thewater permeability (Pf) of a cell by a gating response. Most evidence regarding thismechanism was obtained by different biophysical approaches including thecrystallization of a Spinaca olaracea PIP2 aquaporin (SoPIP2;1) in an open and closeconformation. A close state seems to prevail under certain stimuli such as cytosolic pHdecrease, intracellular Ca2+ concentration increase and dephosphorylation of specificSerines. In this work we decided to address whether the state of phosphorylation of aloop B Serine -highly conserved in all PIPs- combined with cytosolic acidification canjointly affect the gating response. To achieve this goal we generated loop B Serinemutants of two PIP types of Fragaria x ananassa (FaPIP2;1S121A andFaPIP1;1S131A) in order to simulate a dephosphorylated state and characterize theirbehavior in terms of Pf and pH sensitivity. The response was tested for different coexpressionsof PIPs (homo and heterotetramers combining wild-type and mutant PIPs)in Xenopus oocytes. Our results show that loop B Serine phosphorylation status affectspH gating of FaPIP2;1 but not of FaPIP1;1 by changing its sensitivity to more alkalinepHs. Therefore, we propose that a counterpoint of different regulatory mechanisms -heterotetramerization, serine phosphorylation status and pH sensitivity- affectaquaporin gating thus ruling the Pf of a membrane that expresses PIPs when fastresponses are mandatory.