THE NEUROENDOCRINE CHAPERONE 7B2 CAN ENHANCE IN-VITRO POMC CLEAVAGE BY PROHORMONE CONVERTASE PC2

We previously showed that the neuroendocrine polypeptide 7B2 transient ly interacts with prohormone convertase PC2 in the secretory pathway o f neuroendocrine cells. Here we demonstrate that the processed, but no t the intact, form of 7B2 can enhance the in vitro cleavage of newly s ynthesized prohormone proopiomelanocortin (POMC) in lysates of Xenopus intermediate pituitary cells, PC2 is presumably the cleavage enzyme i nvolved since intact 7B2 abolishes the enhancing effect of processed 7 B2 and is known to act as a specific inhibitor of PC2. Furthermore, pr ocessed 7B2 stimulates in vitro POMC cleavage by immunopurified Xenopu s PC2, Our results indicate that 7B2 can display chaperone activity to wards PC2.