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Module 10 Worksheet

Terms in this set (50)

Receptors can be desensitized by phosphorylation of the receptor itself. The phosphorylated receptor can bind the ligand but cannot activate adenylyl cyclase. Therefore, it cannot cause an increase in cAMP, and thus no activation of protein kinase A or target proteins. Thus, the receptor pathway is desensitized to the effect of ligand binding.

Phosphorylated receptors are reset to the original sensitized state when phosphatase enzymes remove phosphate from the receptor.

3. Describe the various molecular mechanisms for receptor desensitization. How can a receptor be reset to its original sensitized state?

Homologous desensitization of a receptor occurs when a receptor is under constant influence of an agonist. After so long, the receptor will lighten the response of the cascade events it triggers (basically decreasing the signal) when the agonist is at a high concentration.
Heterologous desensitization is similar in which it no longer can react to an agonist. After so many bindings of an agonist, the receptor no longer will activate a pathway.
There are more specific mechanisms to talk about such as receptor uncoupling and endocytosis. Receptor uncoupling uses beta androgenic receptor kinases to add a phosphate to the receptor. Beta arrestin has an increased affinity for receptors that are phosphorylated and active. The receptor is uncoupled resulting in a desensitized receptor. GCPR endocytosis can be similarly phosphorylated, but will be taken into the cytoplasm and degraded by lysosomes or put back in the plasma membrane later.