Constitutive lysosomal targeting and degradation of bovine endothelin-converting enzyme-1a mediated by novel signals in its alternatively spliced cytoplasmic tail.
Endothelin-converting enzyme-1 (ECE-1) is a type II membrane protein that catalyzes the proteolytic activation of big endothelin-1 to endothelin-1 (ET-1). The subcellular distribution of ECE-1, and hence the exact site of physiological activation of big ET-1, remains controversial. Here, we demonstrate with several complementary methods that the two alternatively spliced bovine ECE-1 isoforms, ECE-1a and ECE-1b, differing only in the first 30 amino acids of their N-terminal cytoplasmic tails, exhibit strikingly distinct intracellular sorting patterns. Bovine ECE-1a, which is responsible for the intracellular cleavage of big ET-1 in endothelial cells, is constitutively recruited into the lysosome, where it is rapidly degraded. In contrast, bovine ECE-1b, the isoform found in cultured smooth muscle cells, is transported to the plasma membrane by a default pathway and functions as an ectoenzyme. Mutational analyses reveal that the N-terminal tip of the cytoplasmic domain of bovine ECE-1a contains novel proline-containing signals that mediate constitutive lysosomal targeting. Analyses of chimeric ECE-1/transferrin receptors demonstrate that the cytoplasmic tail of bovine ECE-1a is sufficient for the lysosomal delivery and rapid degradation. Our results suggest that the distinct intracellular targeting of bovine ECE-1 isoforms may provide new insights into functional aspect of the endothelin system and that the cell permeability of ECE inhibitor compounds should be carefully considered during their pharmacological development.
Emoto
N
N
Division of Genetics, International Center for Medical Research, Kobe University School of Medicine, Kobe, 6500017 Japan. emoto@med.kobe-u.ac.jp
Nurhantari
Y
Y
Alimsardjono
H
H
Xie
J
J
Yamada
T
T
Yanagisawa
M
M
Matsuo
M
M
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000235:genetics* / Q000378:metabolism*; D016466:CHO Cells; D002417:Cattle; D006224:Cricetinae; D003593:Cytoplasm / Q000378:metabolism; D004252:DNA Mutational Analysis; D019332:Endothelin-1 / Q000378:metabolism; D000072396:Endothelin-Converting Enzymes; D008247:Lysosomes / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism*; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000378:metabolism; D021382:Protein Sorting Signals / Q000235:genetics* / Q000378:metabolism*; D014162:Transfection
D019332:Endothelin-1; D021382:Protein Sorting Signals; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D000072396:Endothelin-Converting Enzymes