Cloning and Functional Expression of a New Aquaporin (AQP9) Abundantly Expressed in the Peripheral Leukocytes Permeable to Water and Urea, but Not to Glycerol

Selection of highly specific and sensitive mRNA biomarkers for the identification of blood

“…Blood was chosen for its easy availability, stability and the number of reported markers [6][7][8][9][10][13][14][16][17][19][20]. The following blood markers were included in the study: HBA and HBB are the alpha-and betasubunits of hemoglobin A [21,22]; aminolevulinate synthase 2 (ALAS2) is an erythroid-specific mitochondrial enzyme, that catalyzes the first step in the heme biosynthetic pathway [23]; CD3 gamma molecule (CD3G) is part of the T-cell receptor-CD3 complex, which plays an important role in coupling antigen recognition to several intracellular signal-transduction pathways [24]; ankyrin 1 (ANK1) is an erythrocyte membrane protein, which provides the primary linkage between the membrane skeleton and the plasma membrane [25]; the erythroid form of porphobilinogen deaminase (PBGD) is the third enzyme of the heme biosynthetic pathway [26]; β-spectrin (SPTB) is an erythrocyte membrane protein [27]; Aquaporin (AQP9) is a water channel protein expressed in peripheral leukocytes [28]. AQP9 was chosen as one representative out of nine, all of which were stated by the authors [13] to be co-expressed in vaginal secretion.…”

Structural basis of water-specific transport through the AQP1 water channel

“…Members of the water channel superfamily have been found in a range of cell types from bacteria to human. In mammals, there are currently 10 families of water channels, referred to as the aquaporins (AQP): AQP0 -AQP9, which can be divided into two major groups 3,4 ; AQP0, AQP1, AQP2, AQP4-AQP6 and AQP8, permeable to water but not to small organic and inorganic molecules 5 , and AQP3, AQP7 and AQP9, permeable to glycerol or urea as well as water 3,5 .…”

Cytoprotective effects of growth factors: BDNF more potent than GDNF in an organotypic culture model of Parkinson's disease

“…AQP9 shares sequence homology with the aquaglyceroporins AQP3 (48%), and AQP7 (45%) (10), and further shares similarities with AQP10 and bacterial GlpF (241) when clustered in a phylogenetic tree, indicating a common ancestral gene ( Figure 3). Its gene consists of six exons and five introns distributed over ~25 kb (12), with a negative insulin response element (IRE) in the promoter region (267).…”

“…AQP9 has been demonstrated to be selectively expressed in dopaminergic neurons in the SN (15)(16)(17). Further, this aquaglyceroporin has particularly wide substance permeability to structurally unrelated molecules, including toxins, such as arsenite (10)(11)(12)(13)(14).…”

“…Although not previously related to PD, several lines of evidence argue for a link between these. AQP9 is an aquaglyceroporin with particularly broad substance permeability, transporting water, glycerol, monocarboxylates and arsenite, among others (10)(11)(12)(13)(14). This water channel has recently been found to be selectively expressed in dopaminergic plasma membranes as well as mitochondrial inner membranes in the SN (15)(16)(17), indicating that it may serve as a toxin influx route into these cells, thereby accounting for an increased susceptibility to cell death.…”