BvPIP2;1 is an atypical PIP2 aquaporin

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

Salta, Argentina

Congreso; 3rd Latin American Protein Society Meeting; 2010

Protein Society and Sociedad Argentina de Biofisica

Aquaporins are important modulators of transcellular 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 types1. 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 osmotic permeability coefficient (Pf) of oocyte 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 analyzed the aminoacid sequence of the protein in comparison with the other members of its family and a N-glyscosylation motif, absent in other PIP2s and located in the loop A of the protein, was found. With the aim of investigate if this motif has relevant influence in BvPIP2;1 activity we tested two mutants with a modified loop A. 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-glyscosylation motif could be involved in PIP1-PIP2 interaction.