A graduate student is trying to determine if soy bean extrac

A graduate student is trying to determine if soy bean extract can lessen the symptoms of diabetes. The student is working with a genetically manipulated mouse that mimics the effects of diabetes as follows. In each case, the mice have been given a small amount of insulin and then samples from the livers removed by biopsy. describe how/why (the molecular reason) the genetically manipulated mouse would show the phenotype of being diabetic make sure you start with the initial defect and follow it to the biological end point. Make sure you use all the data that you have. predict what the immunoblot would look like if an anti-phosphoglycogen synthase was used as a probe explain your blot

Solution

a) GLUT4 is the principal glucose transporter protein that mediates the uptake of glucose.It is in the family of solute carriers and is responsible for facilitating the transport glucose into the cells in response to insulin. Mutations in GLUT4 results in Diabetes which reduces the level of glucose uptake and hence there is high blood glucose level.

Insulin promotes dephosphorylation and activation of glycogen synthase (GS) by inactivating glycogen synthase kinase (GSK) 3 through phosphorylation. Therefore, when cell lysate probed with rabbit anti-phosphoGSK3, expression in normal cell is noticed, whereas in case of Diabetic, GSK3 is not phosphorylated which further inactivated the Glycogen synthase. Hence, there is a very low expression. Similarly, in immunoblot 3 when total cell lysate is probed with anti-GSK3, very high expression level is observed in both normal and Diabetic.

b) A reduced ability of insulin to activate glucose transport is a major defect leading to the development of impaired glucose tolerance and type 2 diabetes. Glycogen synthase kinase-3 (GSK-3) has an important roles in the regulation of glycogen synthesis. Overexpression and overactivity of GSK-3 of diabetic humans are associated with an impaired ability of insulin to activate glycogen synthase. When anti-phosphoglycogen synthase was used as probe,overexpression is seen in diabetic since, GSK3 is activated which in turn inhibits glycogen synthase by phosphorylation.