Cell-type specific posttranslational processing of peptides by different pituitary cell lines.

Area of Science:

• Endocrinology
• Molecular Biology
• Cell Biology

Background:

• Prohormone processing is crucial for generating active peptide hormones.
• Pituitary cell types exhibit distinct secretory pathways and processing capabilities.
• Neuropeptide Y (NPY) is a key neuroendocrine peptide with diverse functions.

Purpose of the Study:

• To compare prohormone processing of preproneuropeptide Y (preproNPY) in somatomammotrope (GH3) and corticotrope (AtT-20) pituitary cell lines.
• To investigate the impact of different cleavage site sequences on NPY processing.
• To examine the influence of specific hormones on prohormone processing and storage.

Main Methods:

• Stable transfection of GH3 and AtT-20 cells with preproNPY vectors containing varied cleavage site sequences (wildtype/KR, RR, RK, KK).
• Analysis of prohormone cleavage products using biochemical methods.
• Treatment of cell lines with insulin, estradiol, and epidermal growth factor to assess hormonal effects on processing and storage.

Main Results:

• GH3 cells exhibited similar proNPY cleavage efficiency across all tested cleavage sites, producing NPY (1-36) and varying amounts of COOH-terminal peptides.
• AtT-20 cells displayed a distinct cleavage site preference (KR = RR > RK >> KK) and produced specific COOH-terminal peptides based on the cleavage sequence.
• Hormonal treatment of GH3 cells increased proNPY and NPY residence time without enhancing cleavage, while AtT-20 cells were unresponsive to these hormones.

Conclusions:

• Somatomammotropes and corticotropes demonstrate significant differences in post-translational processing and storage of peptide hormones like NPY.
• Cleavage site sequence profoundly influences prohormone processing in corticotropes but not somatomammotropes.
• Hormonal regulation of peptide hormone storage differs between pituitary cell types, impacting overall neuroendocrine function.