calcitonin receptor activity

Definition

Target type: molecularfunction

Combining with calcitonin and transmitting the signal across the membrane by activating an associated G-protein; promotes the exchange of GDP for GTP on the alpha subunit of a heterotrimeric G-protein complex. [GOC:mah, GOC:signaling, PMID:21649645]

Calcitonin receptor activity involves the binding of calcitonin, a hormone produced by the thyroid gland, to its cognate receptor, a G protein-coupled receptor (GPCR) located on the surface of cells, primarily osteoblasts and chondrocytes. This binding initiates a signaling cascade that ultimately leads to a reduction in blood calcium levels. The process can be summarized as follows:

1. **Ligand binding:** Calcitonin binds to the extracellular domain of the calcitonin receptor, triggering a conformational change in the receptor protein.

2. **G protein activation:** The conformational change activates a heterotrimeric G protein, specifically the Gsα subunit, which is associated with the receptor's intracellular domain.

3. **Adenylate cyclase stimulation:** The activated Gsα subunit binds to and stimulates the enzyme adenylate cyclase, leading to the production of cyclic adenosine monophosphate (cAMP) from adenosine triphosphate (ATP).

4. **Protein kinase A activation:** Increased intracellular cAMP levels activate protein kinase A (PKA), a key enzyme in signal transduction pathways.

5. **Target protein phosphorylation:** PKA phosphorylates specific target proteins, including various transcription factors and other signaling molecules.

6. **Downstream effects:** The phosphorylation of target proteins ultimately leads to the following physiological responses:
- Inhibition of osteoclast activity, which are cells responsible for bone resorption.
- Stimulation of osteoblast activity, which are cells responsible for bone formation.
- Reduced calcium release from bone.
- Increased renal calcium excretion.

These combined effects result in a decrease in blood calcium levels, a critical homeostatic mechanism for maintaining skeletal integrity and calcium balance in the body.

Calcitonin receptor activity is essential for regulating bone metabolism and calcium homeostasis. Its dysregulation can contribute to various disorders, including osteoporosis, hypercalcemia, and Paget's disease.'
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Proteins (2)

Compounds (8)