Proteolytic Release of Human Angiotensin-Converting Enzyme Expressed in Chinese Hamster Ovary Cells Is Enhanced by Phorbol Ester

• Published in: Biochemical and biophysical research communications 1995-01, Vol.206 (2), p.541-547
• Main Authors: Ehlers, M.R.W., Scholle, R.R., Riordan, J.F.
• Format: Article
• Language: English
• Subjects: Alkaloids - pharmacology; Animals; Cell Membrane - enzymology; CHO Cells; Cricetinae; Endopeptidases - metabolism; Humans; Kinetics; Peptidyl-Dipeptidase A - biosynthesis; Peptidyl-Dipeptidase A - metabolism; Phorbol 12,13-Dibutyrate - pharmacology; Protease Inhibitors - pharmacology; Protein Kinase C - antagonists & inhibitors; Protein Processing, Post-Translational - drug effects; Recombinant Proteins - biosynthesis; Recombinant Proteins - metabolism; Staurosporine; Transfection
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1995.1077

Membrane-bound angiotensin-converting enzyme (ACE) expressed in Chinese hamster ovary (CHO) cells is proteolytically released in soluble form into the medium. We find that this release is stimulated up to 50-fold by phorbol-12, 13-dibutyrate and also by the addition of fresh, serum-containing media. Concomitant with the enhanced release is a marked decrease in levels of membrane-bound ACE, down to 7% of resting levels in the case of phorbol eater stimulation. Staurosporine, a protein kinase C (PKC) inhibitor, abolishes the phorbol ester effect. Kinetic analysis of the stimulated release rate indicates that it is first order, likely due to substrate depletion; calculated half times, t12, are 174 ± 12 min and 40 ± 6 min for the media-change and phorbol eater stimulated rates, respectively. Thus, release of membrane-bound ACE in CHO cells is regulated, in part, by a PKC-dependent mechanism.