PIP aquaporins heterotetramerization

CINTIA JOZEFKOWICZ; FLORENCIA SCOCHERA; AGUSTINA CANESSA FORTUNA; GABRIELA AMODEO; NICOLAS AYUB; GABRIELA SOTO; 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 (plasma membrane intrinsic proteins) channels allowed a deeper understanding of the oligomerization phenomenon in aquaporins. It is well known that in the particular case of PIP aquaporins, PIP1 and PIP2 paralogs can ensamble both as homotetramers or heterotetramers1,2,3. However the structural elements involved in heterotetramerization and the stoichiometry of the ensamble were recently described. Our results show that 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 equivalent biological activity in terms of water transport (Pf), pH regulation and cooperative response.According to these results, it can be suggested that the flexible stoichiometry of these tetrameric water channels can fine-tune the cell plasma membrane permeability from low to high Pf values depending on the relative expression of PIP1 and PIP2. The expression of only PIP2 monomers promotes medium water transport values and maximal Pf is only achieved when equal quantities of PIP1 and PIP2 monomers are expressed or when singular heterotetramers with 2:2 stoichiometry are present in the plasma membrane.