Análisis funcional de acuaporinas subtipo PIP y mutantes para investigar la actividad del canal como transportador de agua

摘要

The plant aquaporin PIP subfamily represents one of the main gateways for water exchange atthe level of the plasma membrane. Among them, a fraction of this subfamily -known as PIP1-does not reach the plasma membrane unless they are co-expressed with a PIP2 aquaporin.Although ubiquitous and abundantly expressed, the role and properties of PIP1 aquaporinshave therefore remained masked. Here we unravel how FaPIP1;1 -a fruit specific PIP1aquaporin from Fragaria x ananassa- contributes to modulate membrane water permeability (Pf)using a mathematical model approach applied to experimentally obtained Pf from different coexpression ratios of FaPIP1;1 and FaPIP2;1 or a FaPIP2;1 mutant. For the first time we dissect the individual contribution of each PIP when co-expressed in Xenopus oocytes, showing that i) PIP1 has also high water transport capacity when co-expressed with PIP2; ii) PIP2 water permeability is enhanced when it physically interacts with PIP1; iii) PIP1-PIP2 seem to form heterotetramers with a random stoichiometry arrangement. Also, we characterized FaPIP2;1 and FaPIP1;1 pH gating sensitivity and how the phosphorylation status of a specific Serine could influence in this response. A crosstalk between different regulatory mechanisms that would rule the Pf of a membrane that express PIPs is proposed.