Regulation of cathepsin D dependent on the phenotype of colon carcinoma cells.
We have studied the intracellular trafficking of cathepsin D in different colon carcinoma cell populations: the HT-29 cell line, composed of >95% undifferentiated cells; 2 subpopulations derived from this cell line, containing cells committed to differentiation into mucin-secreting cells (HT-29 MTX) or enterocyte-like cells (HT-29 G-) after confluence; and the Caco-2 cell line, which spontaneously differentiates into enterocyte-like cells after confluence. Post-confluent undifferentiated HT-29 cells and differentiated enterocyte-like HT-29 G- and Caco-2 cells secrete significant levels of cathepsin D in culture medium, in contrast to post-confluent differentiated mucin-secreting HT-29 MTX cells, which secrete this enzyme at a very low level. The intracellular content and the mRNA level of cathepsin D increase after confluence in the different cell types, particularly in Caco-2 cells, which intensify the secretion of cathepsin D along with the differentiation process post-confluence. Membrane-associated mature cathepsin D was detected in HT-29 cells but not in Caco-2 cells. In the different types of cell, pro-cathepsin D associates with the membrane concomitantly to its binding to an Mr 72,000 protein. Membrane association persists after dissociation of the complex in HT-29 cells but not in Caco-2 cells. In the mucin-secreting HT-29 MTX cells, cathepsin D was immunolocalised to the membrane of mucin vacuoles localised under the brush border. Our results show that cathepsin D can be regulated differently in colon carcinoma cells, and this finding might have specific functional implications for each cell type.
Hennebicq Reig
S
S
Laboratoire de Biochemie, Hôpital Claude Huriez, Lille, France.
Kim
I
I
Janin
A
A
Grard
G
G
Hémon
B
B
Moreau
O
O
Porchet
N
N
Aubert
J P
JP
Degand
P
P
Huet
G
G
D002402:Cathepsin D / Q000235:genetics / Q000378:metabolism*; D003110:Colonic Neoplasms / Q000201:enzymology* / Q000473:pathology; D019073:HT29 Cells; D006801:Humans; D016253:Microscopy, Immunoelectron; D010641:Phenotype; D012333:RNA, Messenger / Q000032:analysis
D012333:RNA, Messenger; D002402:Cathepsin D