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Processing of proopiomelanocortin (POMC) approached by immunoelectron microscopy pre-embedding method
1Department of Pathology, Tokai University School of Medicine, Boseidai Isehara-city, Japan.
Abstract:
Immunoelectron microscopy pre-embedding method was applied to study the processing of proopiomelanocortin (POMC). Premature pituitary cells and cancer cells showed POMC derived peptides in perinuclear spaces (PNS), rough endoplasmic reticula (RER) and in a few secretory granules (SG). These cells demonstrated immature processing of POMC and suggested constitutive pathway. Cultured mouse fibroblasts transfected with human POMC gene was a good model for this system. Mature pituitary cells and pituitary adenomas showed POMC derived peptides predominantly in SG which correlated with authentic processing of POMC. Cultured mouse AtT 20 cells transfected with human POMC gene showed similar secretory pathway and processing. These results emphasized that SG is mandatory for proper processing of POMC. SG is probably essential for the regulated system of secretion.
Insights
Secretory granules (SG) are essential for proper processing of pro-opiomelanocortin (POMC) peptides. This study highlights the role of SG in the regulated secretion pathway for POMC.
Area of Science:
- Cell Biology
- Endocrinology
- Molecular Biology
Background:
- Pro-opiomelanocortin (POMC) is a precursor protein processed into various bioactive peptides.
- Understanding POMC processing is crucial for studying endocrine disorders and cancer.
- The role of different cellular compartments in POMC processing requires further elucidation.
Purpose of the Study:
- To investigate the intracellular processing pathway of POMC.
- To determine the role of secretory granules (SG) in POMC maturation and secretion.
- To compare POMC processing in different cell types and experimental models.
Main Methods:
- Immunoelectron microscopy (pre-embedding method) was utilized.
- Study involved premature and mature pituitary cells, pituitary adenomas, cultured mouse fibroblasts transfected with human POMC, and cultured mouse AtT 20 cells.
Main Results:
- Premature pituitary and cancer cells showed immature POMC processing with peptides in perinuclear spaces (PNS), rough endoplasmic reticulum (RER), and few SG, suggesting a constitutive pathway.
- Mature pituitary cells and pituitary adenomas exhibited POMC peptides predominantly in SG, indicating authentic processing.
- Transfected mouse fibroblasts and AtT 20 cells demonstrated similar processing pathways to mature pituitary cells.
Conclusions:
- Secretory granules (SG) are mandatory for the proper processing of POMC.
- SG are likely essential for the regulated system of POMC secretion.
- The findings provide insights into the molecular mechanisms underlying POMC processing and secretion.