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[Motilin and motilin receptor]
Abstract:
Motilin, a 22 amino acid polypeptide, is known to play an important role in the initiation of phase III activity of the interdigestive migrating contractions (IMC) in the dog and man. The precursor of human motilin consists of 115 amino acids including a 25 amino acid signal peptide in direct linkage with the 22 amino acid motilin sequence and a 66 amino acid carboxy-terminal motilin-associated peptide (MAP). Northern blot analysis revealed that motilin mRNA is abundant in the duodenum. In vitro studies suggested that motilin acts directly on motilin receptors located on gastrointestinal smooth muscle cells in the rabbit, cat and man. On the contrary, in vivo studies suggested that motilin receptors are likely to be present in the nervous system. The cloning of motilin receptors is needed to clarify the detailed mechanism(s) of motilin's action.
Insights
Motilin initiates digestive muscle contractions. Further research is needed to clone motilin receptors and clarify its precise action mechanism in the nervous system.
Area of Science:
- Gastroenterology
- Molecular Biology
- Neuroscience
Context:
- Motilin is a polypeptide hormone regulating gastrointestinal motility.
- Interdigestive migrating contractions (IMC) are crucial for gut cleansing.
- Human motilin precursor contains signal peptide and motilin-associated peptide (MAP).
Purpose:
- To review the role of motilin in initiating phase III IMC.
- To discuss the cellular localization of motilin action.
- To highlight the need for motilin receptor cloning.
Summary:
- Motilin (22 amino acids) initiates phase III IMC in dogs and humans.
- Motilin mRNA is abundant in the duodenum.
- In vitro studies suggest direct action on gastrointestinal smooth muscle receptors, while in vivo studies indicate neuronal receptors.
Impact:
- Clarifies motilin's role in digestive physiology.
- Identifies potential targets for motility disorders.
- Emphasizes the necessity of motilin receptor cloning for mechanistic understanding.