Changes in Corticotrope Gene Expression Upon Increased Expression of Peptidylglycine α-Amidating Monooxygenase.

Throughout evolution, secretion has played an essential role in the ability of organisms and single cells to survive in the face of a changing environment. Peptidylglycine α-amidating monooxygenase (PAM) is an integral membrane monooxygenase, first identified for its role in the biosynthesis of neuroendocrine peptides released by the regulated secretory pathway. PAM was subsequently identified in Chlamydomonas reinhardtii, a unicellular green alga, where it plays an essential role in constitutive secretion and in ciliogenesis. Reduced expression of C. reinhardtii PAM resulted in significant changes in secretion and ciliogenesis. Hence, a screen was performed for transcripts and proteins whose expression responded to changes in PAM levels in a mammalian corticotrope tumor cell line. The goal was to identify genes not previously known to play a role in secretion. The screen identified transcription factors, peptidyl prolyl isomerases, endosomal/lysosomal proteins, and proteins involved in tissue-specific responses to glucose and amino acid availability that had not previously been recognized as relevant to the secretory pathway. Perhaps reflecting the dependence of PAM on molecular oxygen, many PAM-responsive genes are known to be hypoxia responsive. The data highlight the extent to which the performance of the secretory pathway may be integrated into a wide diversity of signaling pathways.