Hormone receptor

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== Hormone Receptor ==

A hormone receptor is a protein molecule that receives and responds to a hormone signal. Hormone receptors are found either on the surface of the cell membrane or within the cell, and they play a crucial role in the regulation of various physiological processes.

Types of Hormone Receptors

Hormone receptors can be broadly classified into two main types:

Cell Surface Receptors

Cell surface receptors, also known as membrane receptors, are embedded in the cell membrane. They interact with peptide hormones and catecholamines that cannot cross the cell membrane. These receptors typically activate second messenger systems to relay the hormone's signal into the cell.

Examples of cell surface receptors include:

• G protein-coupled receptors (GPCRs)
• Receptor tyrosine kinases (RTKs)

Intracellular Receptors

Intracellular receptors are located within the cell, either in the cytoplasm or the nucleus. These receptors bind to steroid hormones and thyroid hormones, which can pass through the cell membrane. Upon binding to their respective hormones, these receptors often act as transcription factors to regulate the expression of specific genes.

Examples of intracellular receptors include:

• Glucocorticoid receptor
• Estrogen receptor
• Thyroid hormone receptor

Mechanism of Action

The mechanism of action of hormone receptors involves several steps:

1. **Hormone Binding**: The hormone binds to its specific receptor. 2. **Receptor Activation**: The binding induces a conformational change in the receptor, activating it. 3. **Signal Transduction**: For cell surface receptors, this involves the activation of intracellular signaling pathways. For intracellular receptors, this often involves the receptor-hormone complex translocating to the nucleus. 4. **Gene Expression**: Intracellular receptors typically bind to specific DNA sequences, regulating the transcription of target genes. 5. **Physiological Response**: The changes in gene expression lead to a physiological response appropriate to the hormone signal.

Clinical Significance

Hormone receptors are critical in the diagnosis and treatment of various diseases. For example, the presence of estrogen receptors and progesterone receptors in breast cancer cells can influence treatment decisions and prognosis. Similarly, androgen receptors play a role in prostate cancer.

See Also

• Endocrine system
• Signal transduction
• Receptor (biochemistry)
• Transcription factor
• Second messenger system