Proopiomelanocortin

Overview

Diagram of thyroid hormones, which are influenced by POMC-derived peptides.

Proopiomelanocortin (POMC) is a large precursor polypeptide that is synthesized in the anterior pituitary gland, as well as in other tissues such as the hypothalamus, skin, and placenta. POMC is cleaved into several important peptide hormones, each with distinct physiological roles.

Structure and Synthesis

POMC is a 241-amino acid polypeptide that undergoes extensive post-translational processing. The gene encoding POMC is located on chromosome 2 in humans. The synthesis of POMC is regulated by various factors, including corticotropin-releasing hormone (CRH) and dopamine.

Peptide Hormones Derived from POMC

POMC is cleaved by specific prohormone convertases to produce several biologically active peptides:

• Adrenocorticotropic hormone (ACTH): This peptide stimulates the production of cortisol from the adrenal cortex.
• Melanocyte-stimulating hormones (MSH): These peptides influence skin pigmentation and have roles in energy homeostasis.
• Beta-endorphin: An endogenous opioid peptide with roles in pain modulation and immune response.
• Lipotropin: Involved in lipid metabolism.

Physiological Roles

POMC-derived peptides have diverse roles in the body:

• Stress Response: ACTH is crucial for the stress response by stimulating cortisol release.
• Pigmentation: MSH peptides influence the production of melanin in the skin.
• Energy Balance: POMC neurons in the arcuate nucleus of the hypothalamus are involved in regulating appetite and energy expenditure.
• Pain and Immune Function: Beta-endorphin modulates pain perception and has immunomodulatory effects.

Clinical Significance

Mutations in the POMC gene can lead to disorders such as congenital adrenal hyperplasia and obesity. POMC deficiency is characterized by adrenal insufficiency, red hair, and early-onset obesity.

Related Pages

• Anterior pituitary gland
• Corticotropin-releasing hormone
• Adrenal cortex
• Melanocyte-stimulating hormones
• Beta-endorphin