Aquaporin-11 containing a divergent NPA motif has normal water channel activity
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
Authors: Yakata, Kaya; Hiroaki, Yoko; Ishibashi, Kenichi; Sohara, Eisei; Sasaki, Sei; Mitsuoka, Kaoru; Fujiyoshi, Yoshinori
Abstract
Recently, two novel mammalian aquaporins (AQPs), AQPs 11 and 12, have been identified and classified as members of a new AQP subfamily, the "subcellular AQPs". in members of this subfamily one of the two asparagine-proline-alanine (NPA) motifs, which play a crucial role in selective water conduction, are not completely conserved. Mouse AQP 11 (mAQP11) was expressed in Sf9 cells and purified using the detergent Fos-choline 10. The protein was reconstituted into liposomes, which were used for water conduction studies with a stopped-flow device. Single water permeability (pk) of AQP11 was measured to be 1.72 +/- 0.03 x 10(-13) cm(3)/S, suggesting that other members of the subfamily with incompletely conserved NPA motifs may also function as water channels. (c) 2606 Elsevier B.V. All rights reserved.
Human Aquaporin-11 Is a Water and Glycerol Channel and Localizes in the Vicinity of Lipid Droplets in Human Adipocytes
OBESITY
Authors: Madeira, Ana; Fernandez-Veledo, Sonia; Camps, Marta; Zorzano, Antonio; Moura, Teresa F.; Ceperuelo-Mallafre, Victoria; Vendrell, Joan; Soveral, Graca
Abstract
Objective: For a long time Aquaporin-7 has been the only aquaporin associated with the adipose tissue, and its dysregulation has been linked to the underlying mechanisms of obesity. However, the presence of alternative glycerol channels within the adipose tissue has been postulated, which has prompted us to the search of alternate glycerol transport routes in adipocytes. In view of this, it is hypothesized that Aquaporin-11 (AQP11) would have a role in adipocyte cell biology. Methods: The expression, the localization and the function of human AQP11 (hAQP11) in cultured differentiated adipocytes were investigated. Results: Gene expression analysis revealed the presence of AQP11 in both subcutaneous and visceral human mature adipocytes. It is found that hAQP11 is primarily located intracellularly in human adipocytes and partially colocalizes with perilipin, pointing towards AQP11 preferential location in the vicinity of lipid droplets. Overexpression of hAQP11 in 3T3-L1 adipocytes enabled to validate its function as a water channel and reveal its glycerol permeation activity. Conclusions: hAQP11 permeates both water and glycerol, localizing in the vicinity of lipid droplets in human adipocytes.
COA
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