A defined aquaporin stoichiometry in order to understand water permeabilitiy and pH sensitivity

AGUSTIN YANEFF; LORENA SIGAUT; MERCEDES MARQUEZ; KARINA ALLEVA; LIA PIETRASANTA; GABRIELA AMODEO

Mendoza

Congreso; XLVIII Reunión Anual de la Sociedad de Investigación en Bioquímica y Biología molecular; 2012

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

bjectives Plant plasma membrane aquaporins are classified in PIP1 and PIP2 subgroups, all showing the ability to block water permeation after cytosolic acidification. While PIP2 prevails as an homotetrameric structure, most of the PIP1 request coexpression with a PIP2 to reach the plasma membrane and thus enhancing the osmotic water permeability (Pf). Our working hypothesis is that FaPIP1;1, interacts with FaPIP2;1 in a defined stoichiometry providing heterotetrameric units able to modify both Pf and pH sensitivity. Methods Water transport and PIPs pH regulation were studied in Xenopus oocyte heterologous system employing also a N228D FaPIP2;1 mutant. All EYFP tagged PIPs were localized by confocal microscopy. Results FaPIP1;1 cannot reach the PM unless it is coexpressed with FaPIP2;1 or N228D. Also, N228D can only achieve PM if it is coexpressed with FaPIP1;1. The pH sensitivity remains constant when different ratios of FaPIP1;1 and FaPIP2;1 or N228D are expressed, but differ from the pH sensitivity of FaPIP2;1 expressed alone. The maximum Pf achieved is constant when different ratios of FaPIP1;1 and FaPIP2;1 RNAc are injected but its variable when injected N228D RNAc is replaced by FaPIP2;1. Conclusion Results establish a possible stoichiometry for PIP1-PIP2 interaction and its influence on defining the pH sensitivity of the membrane water transport.