***********************ANSWER ALL PARTS WITH DETAILED EXPLANATION***************

Question

***********************ANSWER ALL PARTS WITH DETAILED EXPLANATION***************************************

these are the only graphs and info provided

Analyze the Data 11-2: Using siRNA to study Aquaporin Function

In order to determine the function of aquaporin 7 (see Kondo et al., 2002, Eur. J. Biochem. 269:1814–1826 and Maeda et al., 2004, Proc. Nat’l. Acad. Sci. 101:17801–17806), a member of the aquaporin family expressed in adipocytes, expression is disrupted in isolated adipocytes by RNA interference (see Chapter 6 of the text).   In vivo, adipocytes hydrolyze triglycerides to free fatty acids and glycerol and release these products into the blood plasma. Similarly, in vitro, upon stimulation with adrenalin, adipocytes hydrolyze triglycerides and release free fatty acids and glycerol into the media. The graphs below show glycerol and fatty acid release into the media from control adipocytes (C), adipocytes in which expression of aquaporin 1 is inhibited (1-siRNA), and adipocytes in which expression of aquaporin 7 is inhibited (7-siRNA).

What do these experiments suggest about aquaporin 1 and aquaporin 7 function?

Injection of mRNA encoding aquaporin 1 into Xenopus oocytes has been shown to cause the oocytes to swell under certain conditions. mRNA encoding either wild-type aquaporin 7 (wt) or a mutation of aquaporin 7 found in a human subject in which glycine at residue 264 is replaced with valine (G264V) is injected into Xenopus oocytes. Two days after injection, the oocytes are shifted from a 200-mOsm (milliosmolarity) buffer to a 20 mOsm buffer and cell volume is measured. The results are shown below. Glycine 264 is located within a transmembrane loop of aquaporin 7.

What additional information do these data provide about aquaporin 7 function relative to aquaporin 1 function?

The blood plasma adrenalin and glycerol levels are measured for control human subjects (solid line in the graph below) and human subjects who are homozygous for the G264V substitution in aquaporin 7 (dashed line) prior to and during exercise.  

What do these data and those provided in the figure in part (b) suggest about transport through aquaporin 7?

***********************ANSWER ALL PARTS WITH DETAILED EXPLANATION***************************************

Explanation / Answer

Adipocytes with knocked down aquaporin 7 releases less glycerol into the media as compared to control cells and cells knocked down for aquaporin 1 after treatment with adrenaline. This suggests that aquaporin 7 is involved in transport of glycerol out from the cell. Also there is no change in fatty acid release in aquaprin 1 & 7 knock down cells relative to control cells, suggesting that neither of these aquaporins is involved in fatty acid transport.

placing the oocytes in solution of less osmolarity (hypotonic solution) leads to movement of water inside the cells, and hence increase in their cellular volume. oocytes expressing aquaporin 7 swells when placed in hypotonic solution suggesting its role in transport of water molecules, also G264V mutated aquaporin 7 fails to transport water molecules inside the cell as suggested by less marked increase in cell volume.

Although there is no change in levels of adrenaline in control subjects and subjects with G264V substitution, but there are significant reduced levels of glycerol in G264V individual suggesting that glycine264 plays an important role in transport of glycerol and water molecules through aquaporin 7. Mutation of this amiono acid residue leads to marked reduction in activity of aquaporin 7.

Related Questions

Navigate

• Browse (All)
• Browse #
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.