Functional and structural characterization of an aquaporin 5 from Pomacea canaliculata

Aquaporins (AQPs) are crucial biomolecules involved in the transport of water and few solutes across the cell membranes of various organisms. In this study, we isolated and characterized PcAQP5 from Pomacea canaliculata to elucidate its contribution to development and stress tolerance. The PcAQP5 gene encodes a protein of 36.6 kDa with an isoelectric point of 5.90. Transmembrane topology analysis revealed that PcAQP5 comprised six transmembrane domains, along with the asparagine-proline-alanine/asparagine-threonine-alanine (NPA/NTA) motifs and the aromatic/arginine (ar/R) constriction region. The investigation of functional expression in Xenopus laevis oocytes revealed that PcAQP5 preferentially transports water (0.0025 cm/s) and Zn²⁺ (2.714e^-6 cm/s), showing a higher capacity than for other small molecules like glycerol and urea. Mass spectrometry analysis confirms both the accurate translation and transmembrane topology of PcAQP5. Additionally, expression analyses in various tissues of P. canaliculata indicated that the PcAQP5 gene is most highly expressed in the siphon, with minimal expression in the foot muscle. Notably, PcAQP5 gene expression was significantly up-regulated following 2 h of exposure to both heat and cold stress, as well as in response to water stress in P. canaliculata eggs. These findings suggest that PcAQP5 may enhance environmental stress tolerance, thus indicating its potential involvement in adaptive physiological functions of P. canaliculata.