PIP aquaporins heterotetramerization

CINTIA JOZEFKOWICZ; FLORENCIA SCOCHERA; AGUSTINA CANESSA FORTUNA; GABRIELA AMODEO; NICOLAS AYUB; GABRIELA SOTO; F. LUIS GONZÁLEZ FLECHA; KARINA ALLEVA

Salto

Congreso; Latin American Crosstalk in Biophysics and Physiology; 2015

Sociedad Argentina de Biofísica y Seccional Biofísica de la Sociedad Uruguaya de Biociencias

Protein multimerization play diverse roles in biology and particularly maydiversify biological activity. In the last years, the study of PIP (plasmamembrane intrinsic proteins) channels allowed a deeper understanding ofthe oligomerization phenomenon in aquaporins.It is well known that in the particular case of PIP aquaporins, PIP1 and PIP2paralogs can ensamble both as homotetramers or heterotetramers1,2,3.However the structural elements involved in heterotetramerization and thestoichiometry of the ensamble were recently described. Our results showthat loop A is involved in monomer-monomer interaction2 and that PIP2-PIP1 heterotetramers with variable stoichiometries can all be formed.Interestingly, all stoichiometric PIP1-PIP2 ensambles present equivalentbiological activity in terms of water transport (Pf), pH regulation andcooperative response.According to these results, it can be suggested that the flexiblestoichiometry of these tetrameric water channels can fine-tune the cellplasma membrane permeability from low to high Pf values depending onthe relative expression of PIP1 and PIP2. The expression of only PIP2monomers promotes medium water transport values and maximal Pf is onlyachieved when equal quantities of PIP1 and PIP2 monomers are expressedor when singular heterotetramers with 2:2 stoichiometry are present in theplasma membrane