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What is cAMP in Hormones?

Published in Hormone Signaling 2 mins read

Cyclic AMP (cAMP) acts as a crucial intracellular second messenger for many hormones and neurotransmitters, mediating their effects inside cells.

Here's a more detailed explanation:

  • Second Messenger Role: Hormones, acting as first messengers, often cannot directly enter cells. Instead, they bind to receptors on the cell surface. This binding triggers a cascade of events that lead to the production of cAMP inside the cell. cAMP then relays the hormone's message to the cell's interior, initiating various cellular responses.

  • How it Works:

    1. Hormone Binding: A hormone binds to its specific receptor on the cell membrane.
    2. G Protein Activation: The receptor activates a G protein.
    3. Adenylate Cyclase Activation: The activated G protein stimulates the enzyme adenylate cyclase.
    4. cAMP Production: Adenylate cyclase converts ATP (adenosine triphosphate) into cAMP.
    5. Protein Kinase A (PKA) Activation: cAMP activates protein kinase A (PKA).
    6. Phosphorylation: PKA phosphorylates specific target proteins within the cell, leading to changes in their activity and ultimately altering cell function.

  • Examples of Hormone Actions Mediated by cAMP:

    • Epinephrine and Glucagon: These hormones, involved in regulating blood sugar levels, use cAMP to stimulate the breakdown of glycogen into glucose in the liver and muscles.
    • Antidiuretic Hormone (ADH): ADH uses cAMP in the kidneys to increase water reabsorption.
    • Thyroid-Stimulating Hormone (TSH): TSH uses cAMP in the thyroid gland to stimulate the synthesis and release of thyroid hormones.

  • Termination of cAMP Signaling: The effects of cAMP are transient. The enzyme phosphodiesterase (PDE) breaks down cAMP, inactivating PKA and stopping the cellular response.

  • cAMP in T Cells: Importantly, as noted in the reference information, elevated cAMP levels can also inhibit certain cellular processes. For example, in T cells, cAMP can antagonize T cell activation by inhibiting T cell proliferation and suppressing the production of cytokines like IL-2 and IFN-γ.

In summary, cAMP is a key signaling molecule, relaying hormonal messages within cells to control a wide range of physiological processes.

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