Glycerol channels

AQP7 is expressed in the proximal tubule of the kidney, testis, gastrointestinal tract, immature dendritic cells and ear. This glycerol channel is also highly expressed in adipocytes where it is thought to control the release of triglycerides. 

Wang, Y. Schulten, K. Tajkhorshid, E., What makes an aquaporin a glycerol channel A comparative study of AqpZ and GlpF, Structure 2005,13, 1107-1118. 

Nollert, P., Harries, W. E., Fu, D., Miercke, L. J. and Stroud, R. M. (2001). Atomic structure of a glycerol channel and implications for substrate permeation in aqua(glycero)porins, FEBS Lett., 504, 112-117. 

Lagree, V., Froger, A., Deschamps, S., Hubert,J. F., Delamarche, C., Bonnec, G., Thomas, D., Gouranton, J., and Pellerin, I. (1999). Switch from an aquaporin to a glycerol channel by two amino acids substitution./. Biol. Chem. 274, 6817-6819. 

K. Kishida, H. Kuriyama, and T. Funa-hashi, et ah, Aquaporin adipose, a putative glycerol channel in adipocytes, /. 

Figure 13. Survival (% unhemolyzed) vs. unfrozen water fraction of human red blood cells frozen very slowly at 0.6 °C/min (VSC) in solutions of glycerol-NaCI-H20 to temperatures producing the indicated concentrations of NaCI (m,) in the unfrozen channels. Warming and thawing were rapid (RW). (From Mazur et al., 1981.)...

Schulten and coworkers coupled SMD [23] simulations with the Jarzynski identity [102] to derive the free energy profile for glycerol conduction in the facilitator GlpF, a channel that allows the selective passage of water and small, linear alcohols,... 

Helliwell RM, Large WA 1997 Alphal-adrenoceptor activation of a non-selective cation current in rabbit portal vein by 1,2-diacyl-sn-glycerol. J Physiol 499 417-428 Hofmann F, Lacinova L, Klugbauer N 1999 Voltage-dependent calcium channels from structure to function. Rev Physiol Biochem Pharmacol 139 33—87 Hofmann T, Schaefer M, Schultz G, Gundermann T 2000 Transient receptor potential channels as molecular substrates of receptor-mediated cation entry. J Mol Med 78 14—25 Inoue R, Okada T, Onoue H et al 2001 The transient receptor potential protein homologue TRP6 is the essential component of vascular aj-adrenoceptor-activated Ca2+-permeable cation channel. Circ Res 88 325—332... 

L. lactis is the first Gram-positive bacterium in which a MIP channel has been functionally characterised. The lactococcal MIP protein is shown to be permeable to glycerol, like E. coli GlpF, and to water, like E. coli AQPZ. That was the first description of a microbial MIP that has a mixed function. This result provided important insights for reconstructing the evolutionary history of the MIP family and elucidating the molecular pathway of water and other solutes in these channels [86]. 

Thus, the apparent membrane permeability characteristics of hydrophilic compounds listed in Table 3.4 indicate that colonic epithelium is different from small intestinal epithelium in selectivity, or size or density distribution of the paracellular pathway. This is further complicated because of the possible involvement of unidentified carriers or channels for some compounds, as suggested for glycerol and D-xylose. However, the colon-to-SI ratios of the apparent membrane permeability are generally comparable with (or lower than) those calculated considering the morphological surface area, suggesting that such factors are not in favor for colonic absorption in most cases. Matching... 

Ma T, Kara M, Sougrat R, Verbavatz JM, Verkman AS (2002) Impaired stratum corneum hydration in mice lacking epidermal water channel aquaporin-3. J Biol Chem 277 17147-17153 Maeda N, Funahashi T, Hibuse T, Nagasawa A, Kishida K, Kuriyama H, Nakamura T, Kihara S, Shimomura I, Matsuzawa Y (2004) Adaptation to fasting by glycerol transport through aquaporin 7 in adipose tissue. Proc Natl Acad Sci USA 101 17801-17806... 

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