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Human endothelin-converting enzyme (ECE-1): three isoforms with distinct subcellular localizations
A Schweizer1, O Valdenaire, P Nelböck
1F. Hoffmann-La Roche Ltd., Pharma Division, Preclinical Research, Grenzacherstrasse 124, CH-4070 Basel, Switzerland.
The Biochemical Journal
|February 7, 1998
Summary
Researchers discovered a third human endothelin-converting enzyme 1 (ECE-1) isoform, ECE-1c, bringing the total to three. This new isoform, along with ECE-1a and ECE-1b, exhibits distinct cellular locations and similar enzymatic activity in converting big endothelins.
Area of Science:
- Biochemistry
- Molecular Biology
- Enzymology
Background:
- Endothelin-converting enzyme 1 (ECE-1) is a key metalloprotease in endothelin synthesis.
- Previously, two human ECE-1 isoforms (ECE-1a and ECE-1b) were identified.
Purpose of the Study:
- To identify and characterize novel human ECE-1 isoforms.
- To investigate the differences and similarities among ECE-1 isoforms.
Main Methods:
- Cloning of the novel ECE-1c isoform.
- Ribonuclease protection assays to analyze mRNA expression.
- Immunofluorescence microscopy to determine subcellular localization.
- Enzymatic assays to assess kinetic properties.
Main Results:
- A third human ECE-1 isoform, ECE-1c, was identified, originating from a single gene via alternative promoters.
- ECE-1c mRNA is the predominant isoform in most human tissues.
- ECE-1a and ECE-1c localize to the cell surface, while ECE-1b is found in the trans-Golgi network.
- All three isoforms display similar kinetic parameters for big endothelin processing.
Conclusions:
- The existence of three distinct human ECE-1 isoforms (ECE-1a, ECE-1b, and ECE-1c) has been established.
- Isoform-specific subcellular localization suggests differential roles in endothelin regulation.
- Despite localization differences, the catalytic efficiency of the isoforms for big endothelin conversion is comparable.