Acute inhibition of carboxypeptidase E expression in AtT-20 cells does not affect regulated secretion of ACTH

Regul Pept. 2010 Dec 10;165(2-3):174-9. doi: 10.1016/j.regpep.2010.07.162. Epub 2010 Jul 22.


Carboxypeptidase E (CPE) is an exopeptidase that removes C-terminal basic amino acids from a variety of bioactive peptides. In addition to this role, data obtained in recent years has supported a potential function for CPE as a sorting receptor, helping direct peptides destined for regulated secretion from the trans-Golgi to granules in preparation for release. This possible sorting function was assessed using mouse AtT-20 cells, a well-established corticotroph cell line that synthesizes and releases POMC/ACTH in regulated fashion. Cells that were treated with siRNA to Cpe effectively suppressed CPE expression. ACTH was released in a regulated fashion from CPE-depleted cells in response to two secretagogues, 8-bromo-cyclic AMP and corticotrophin-releasing hormone. POMC/ACTH content of CPE-depleted cells was higher than that of control cells, but both released a similar percentage of ACTH content in response to secretagogue addition. Cells depleted of CPE generally secreted more high-molecular weight forms of POMC/ACTH under basal conditions than control cells; however, the CPE-depleted cells responded to a secretagogue by releasing newly synthesized ACTH 1-39 in a manner similar to controls. These results, whereby RNAi was used to acutely suppress CPE, do not support a role for this protein as necessary for or central to sorting of POMC/ACTH to the regulated secretory pathway in AtT-20 cells.

MeSH terms

  • Adrenocorticotropic Hormone / metabolism*
  • Animals
  • Blotting, Western
  • Carboxypeptidase H / genetics
  • Carboxypeptidase H / metabolism*
  • Cell Line
  • Corticotrophs / enzymology*
  • Corticotrophs / metabolism*
  • Mice
  • Polymerase Chain Reaction
  • RNA, Small Interfering


  • RNA, Small Interfering
  • Adrenocorticotropic Hormone
  • Carboxypeptidase H