Processing of human cathepsin D is independent of its catalytic function and auto-activation: involvement of cathepsins L and B.
The current mechanism proposed for the processing and activation of the 52 kDa lysosomal aspartic protease cathepsin D (cath-D) is a combination of partial auto-activation generating a 51 kDa pseudo-cath-D, followed by enzyme-assisted maturation involving cysteine and/or aspartic proteases and yielding successively a 48 kDa intermediate and then 34 + 14 kDa cath-D mature species. Here we have investigated the in vivo processing of human cath-D in a cath-D-deficient fibroblast cell line in order to determine whether its maturation occurs through already active cath-D and/or other proteases. We demonstrate that cellular cath-D is processed in a manner independent of its catalytic function and that auto-activation is not a required step. Moreover, the cysteine protease inhibitor E-64 partially blocks processing, leading to accumulation of 52-48 kDa cath-D intermediates. Furthermore, two inhibitors, CLICK148 and CA-074Met, specific for the lysosomal cath-L and cath-B cysteine proteases induce accumulation of 48 kDa intermediate cath-D. Finally, maturation of endocytosed pro-cath-D is also independent of its catalytic function and requires cysteine proteases. We therefore conclude that the mechanism of cath-D maturation involves a fully-assisted processing similar to that of pro-renin.
Laurent-Matha
Valérie
V
Inserm, U540, Montpellier, F-34000 France.
Derocq
Danielle
D
Prébois
Christine
C
Katunuma
Nobuhiko
N
Liaudet-Coopman
Emmanuelle
E
D000818:Animals; D002384:Catalysis; D002401:Cathepsin B / Q000502:physiology*; D002402:Cathepsin D / Q000378:metabolism*; D056668:Cathepsin L; D002403:Cathepsins / Q000502:physiology*; D002461:Cell Line, Transformed; D003546:Cysteine Endopeptidases / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D006801:Humans; D051379:Mice; D011499:Protein Processing, Post-Translational / Q000502:physiology*
D002403:Cathepsins; D003546:Cysteine Endopeptidases; D002401:Cathepsin B; C534281:CTSL protein, human; D056668:Cathepsin L; C534278:Ctsl protein, mouse; D002402:Cathepsin D