Further Characterization of Anuran‐Like Aquaporins in the Urinary Bladder of Urodeles, Notopthalmus viridescens and Cynops pyrrhogaster

Abstract

Recent Bayesian analysis of tetrapod aquaporin gene clusters by Finn et al (PLOS1, November 26, 2014) suggests anuran‐specific aquaporins that mediate water transport across the ventral skin (AQPa2S) and urinary bladder (AQPa2U) are more closely related to AQP6 found in mammals and reptiles. Furthermore, AQP6/a2 aquaporins are syntenic with AQP5. We used RT‐PCR to show both AQP6/a2U and AQP5 homologs are expressed in the urinary bladder of the newts, Notophthalmus viridescens (nv) and Cynops pyrrhogaster (cp). Full length amino acid sequences showed 72% and 71% identity between AQP6/a2U of nv and anuran species Hyla japonica and Xenopus tropicalis (xt). Amino acid identity of AQP5 between nv and cp was 95% while identity between both urodeles and xt was 69%–70%.Consensus phosphorylation sites for PKA were identified for AQP6/a2U and AQP5 for both nv and cp. AQP5 could be immunolocalized in the apical membrane of bladder epithelial cells in rehydrating newts. These results indicate an absorptive role for AQP5 in the urodele urinary bladder and suggest that this role may originate in the ancestor of urodeles and anurans.Support or Funding InformationSupported by a Grant‐in‐Aid for Scientific Research (26440165) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.