Oxidized low-density lipoproteins inhibit the uptake of glucose into cells… We w
ID: 487274 • Letter: O
Question
Oxidized low-density lipoproteins inhibit the uptake of glucose into cells…
We went over evidence that the GLUT4 receptor, the protein responsible for transporting glucose inside the cell, was synthesized in the correct amount, but was not properly located to the plasma membrane when oxidized LDL is present.
We also saw evidence that IRS-1 is phosphorylated at Serine residues when oxidized LDL is present and that the amount of IRS-1 decreased over time when cells were exposed to oxidized LDL
1. (6 pts) The hypothesis that was generated as we ended our discussion was:
Phosphorylation of the Ser residue on IRS-1 changed the topography of IRS-1, causing it to be degraded by a different signaling pathway. In eukaryotes, the protein machine that degrades proteins is called the proteasome. Given the fact that pharmacological molecules that are capable of inhibiting the proteasome are available to researchers, design a simple experiment to prove your hypothesis (3pts). Be sure to show me your predicted results (3 pts).
Explanation / Answer
There are pharmacological molecules that are capable of inhibiting proteasomes.
Exp: pretreatment with Aspirin inhibits growth hormone(GH)-induced insulin resistance.GH is observed to lead to serine phosphorylation of IRS-1 a phenomenon which is reversed by aspirin in liver and muscle in parallel with reduction in JNK activity.
Results:In liver IR tyrosine phosphorylation is observed to increase by 8.5 fold following insulin administration compared with 2.9 fold increase in liver of GH-pretreated rats and a 6.7 fold increase in liver of GH+aspirin pretreated rats.
In muscles there is a 9.9 fold increase in GH+aspirin pretreated rats compared to 4.2 fold increase in GH-pretreated rats and a 9.3 fold in control animals following inulin administration.
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