Activation of human meprin-alpha in a cell culture model of colorectal cancer is triggered by the plasminogen-activating system.
The activation of latent proenzymes is an important mechanism for the regulation of localized proteolytic activity. Human meprin-alpha, an astacin-like zinc metalloprotease expressed in normal colon epithelial cells, is secreted as a zymogen into the intestinal lumen. Here, meprin is activated after propeptide cleavage by trypsin. In contrast, colorectal cancer cells secrete meprin-alpha in a non-polarized way, leading to accumulation and increased activity of meprin-alpha in the tumor stroma. We have analyzed the activation mechanism of promeprin-alpha in colorectal cancer using a co-culture model of the intestinal mucosa composed of colorectal adenocarcinoma cells (Caco-2) cultivated on filter supports and intestinal fibroblasts grown in the companion dish. We provide evidence that meprin-alpha is activated by plasmin and show that the presence of plasminogen in the basolateral compartment of the co-cultures is sufficient for promeprin-alpha activation. Analysis of the plasminogen-activating system in the co-cultures revealed that plasminogen activators produced and secreted by fibroblasts converted plasminogen to active plasmin, which in turn generated active meprin-alpha. This activation mechanism offers an explanation for the observed meprin-alpha activity in the tumor stroma, a prerequisite for a potential role of this protease in colorectal cancer.
Institute of Biochemistry and Molecular Biology, Department of Pediatrics, University of Berne, Bühlstrasse 28, CH-3012 Berne, Switzerland.
Sandra
S
Rösmann
Dagmar
D
Hahn
Daniel
D
Lottaz
Markus-N
MN
Kruse
Walter
W
Stöcker
Erwin E
EE
Sterchi
D000818:Animals; D001483:Base Sequence; D018938:Caco-2 Cells; D018920:Coculture Techniques; D015179:Colorectal Neoplasms / Q000378:metabolism* / Q000473:pathology; D017931:DNA Primers; D004285:Dogs; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology; D008666:Metalloendopeptidases / Q000378:metabolism*; D008954:Models, Biological; D010958:Plasminogen / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
D017931:DNA Primers; D010958:Plasminogen; D014568:Urokinase-Type Plasminogen Activator; D008666:Metalloendopeptidases; C053833:meprin A