PIP2;1 is an atypical PIP2 aquaporin

ALLEVA KARINA; JOZEFKOWICZ CINTIA; BELLATI JORGE; VITALI VICTORIA; SOTO GABRIELA; AMODEO GABRIELA

Salta

Congreso; 3rd Latin American Protein Society Meeting.; 2010

Latin American Protein Society

Aquaporins are important modulators of transcelular water movement. The Beta vulgaris plasma membrane expresses two different types of aquaporins, PIP1 and PIP2, characterized by the ability to modulate whole membrane water permeability by co-expression of both types. Three aquaporins from Beta vulgaris root have been cloned: BvPIP1;1 and BvPIP2;2, which present expected functional characteristics as members of PIP1 and PIP2 subfamilies respectively, and BvPIP2;1 which present some atypical aspects. First, at the cRNA level, only when BvPIP2;1 cRNA was specially protected with polyA tailing the channel was efficiently translated and the permeability osmotic coefficient (Pf ) of oocytes plasma membrane was compatible with water transport through active aquaporins; second, BvPIP2;1 did not interact cooperatively when co-expressed with BvPIP1;1 as most PIP2 aquaporins do. We analysed the aminoacid sequence of the protein in comparison with the other members of its family and a N-glyscosilation motive, absent in other PIP2s and located in loop A was found. With the aim of investigate if this motive has relevant influence in BvPIP2;1 activity we tested two mutants where loop A was modified. Functional studies of the mutants show that both are able to transport water and, interestingly, preliminary results indicates these two mutated channels will be able to affect Pf when co-expressed with BvPIP1;1 in oocytes, suggesting that the N-glyscosilation motive could be involved in PIP1-PIP2 interaction.