The effects of phosphoramidon on the expression of human endothelin-converting enzyme-1 (ECE-1) isoforms

Daiji Isaka, Noriaki Emoto, Sunu Budhi Raharjo, Mitsuhiro Yokoyama, Masafumi Matsuo

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Endothelin-1 (ET-1) is generated from big ET-1 by endothelin converting enzyme-1 (ECE-1). This process is inhibited by phosphoramidon through binding to the catalytic domain of ECE-1. There are four isoforms of human ECE-1 (ECE-1a, ECE-1b, ECE-1c and ECE-1d) which possess a conserved catalytic domain. Interestingly, a recent study has shown that in ECE-1b-transfected CHO cells phosphoramidon increases the expression and activity of ECE-1b. It is not known, however, whether phosphoramidon has similar effects on the expression of other ECE-1 isoforms. To address this point, we have established recombinant CHO cell lines that permanently express either human ECE-1a, ECE-1b or ECE-1c. Incubation of CHO/ECE-1a, -1b, and -1c with phosphoramidon (100 μM) for 16 hours markedly elevated the intracellular expression of ECE-1a and ECE-1b, but not ECE-1c protein, as indicated by Western blotting and immunocytochemistry. These increases appear to be due to inhibition of intracellular degradation of the protein because metabolic labeling followed by immunoprecipitation showed ECE-1a and ECE-1b proteins had prolonged half-lives in the phosphoramidon-treated cells. This is further supported by the finding that ECE-1 mRNA levels were unchanged following phosphoramidon treatment. Taken together, our results demonstrate that phosphoramidon differentially affects the expression of three human ECE-1 isoforms.

Original languageEnglish
Pages (from-to)136-141
Number of pages6
JournalJournal of Cardiovascular Pharmacology
Issue number1
Publication statusPublished - 1 Jul 2003


  • ECE-1 isoforms
  • Endothelin
  • Endothelin converting enzyme
  • Phosphoramidon
  • Protein expression


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