cAMP, or cyclic adenosine monophosphate, is not a hormone itself, but rather a crucial second messenger involved in many hormone signaling pathways. It plays a vital role in transmitting signals from various hormones to the inside of a cell, triggering specific cellular responses.
cAMP's Role as a Second Messenger
Hormones, such as those listed below, bind to receptors on the cell surface. This binding initiates a cascade of events within the cell. One common pathway involves the activation of adenylyl cyclase, an enzyme that converts ATP into cAMP. This newly formed cAMP then acts as a second messenger, activating protein kinase A (PKA), which in turn phosphorylates various proteins, leading to diverse cellular effects.
Several examples highlight cAMP's involvement in hormonal signaling:
- Follicle-stimulating hormone (FSH): FSH utilizes cAMP to regulate gene expression, notably the aromatase gene in the ovary, as shown in research on β-catenin's role in this process. https://pubmed.ncbi.nlm.nih.gov/16895991/ and https://www.pnas.org/doi/abs/10.1073/pnas.0603006103
- Glucagon-like peptide-1 (GLP-1): This incretin hormone, released after food intake, activates cAMP, influencing insulin secretion. https://pubmed.ncbi.nlm.nih.gov/21638053/
- Thyroid-stimulating hormone (TSH): TSH's action involves cAMP/PKA pathway activation, as evidenced by studies using inhibitors like H89 and SQ22536. https://www.nature.com/articles/srep13409
- Parathyroid hormone (PTH): PTH stimulates cAMP production through its interaction with PTH1R and PTH2R receptors. https://pmc.ncbi.nlm.nih.gov/articles/PMC3469678/
The cAMP pathway is involved in a wide range of physiological processes, impacting cellular metabolism, gene expression, and various other functions. cAMP itself isn't a hormone; it's the intermediary, relaying the hormonal message.
In summary: cAMP is a crucial second messenger activated by many hormones, not a hormone itself. It is involved in the intracellular signaling pathways triggered by hormone binding to receptors.
