d. The effect of the siRNA -mediated B-arrestin depletion on cAMP accumulation b

Question

d. The effect of the siRNA -mediated B-arrestin depletion on cAMP accumulation by endogenously expressed ?-AR2 The cells were transfected with the indicated siRNA molecules and subsequently stimulated with isoproterenol (epinephrine). As a control the cells were not stimulated with Isoproterenol (NS). Data are expressed as percent of agonist-induced cAMP accumulation in control RNA-treated cells. What ? arrestin protein (1 or 2) participates in the desensitization of the ß-AR2? Justify your answer. 2 Isoproteren 100- 50 No RNA CTL SiRNA

Explanation / Answer

?-arrestin 2 is the one that is involved in densitization of ?-AR2 as cAMP levels go up significantly upon knocking down ?-arrestin 2 and upon agonistically activating with isoproteronol. If ?-arrestin 2 would have been there in the cells, the levels of cAMP in the cells would not have gone up as ?-arrestin would have densitized the ?-adrenergic receptor( eg). Thus, the desensitization process depends upon the cellular environment of the cells and particularly concentration of ?-arrestin 2 plays a fundamental role in desensitizing the receptor with the agonist.

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