Activity of neutral endopeptidase and aminopeptidase N in mouse thymic stromal cells which bind double-positive thymocytes.
The activity of two peptidases was determined in immortalized lines of thymic stromal cells. A line of total stromal cells (T-TG-St) was grown from transgenic mouse expressing temperature-sensitive SV40 T antigen under the control of the regulatory elements of the mouse major histocompatibility complex class I gene. From these cells we isolated a subset (DP-TG-St) that binds thymocytes which are mainly CD4+8+. We also assayed a clone of fetal thymic epithelial cells (BA/10) that binds CD4+8+ thymocytes. Both lines of double -positive cell-binding stroma exhibited strong activity of two peptidases, neutral endopeptidase (NEP; EC 3.4.24.11) and aminopeptidase N (APN; EC 3.4.11.2). In contrast, the activity of both enzymes was very low in the total thymic stromal line. Use of the specific inhibitors confirmed that these two enzymes were responsible for the activity observed but also suggested the presence of additional unidentified aminopeptidase(s) in the same stromal cells. The high activity of the two peptidases on stromal cells that bind thymocytes at the double-positive stage raises the possibility that they might contribute to the microenvironment of the developing thymocytes.
Small
M
M
Department of Cell Biology and Histology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel.
Kaiser
M
M
Tse
W
W
Heimfeld
S
S
Blumberg
S
S
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D018826:CD13 Antigens / Q000378:metabolism*; D015704:CD4 Antigens / Q000032:analysis; D016827:CD8 Antigens / Q000032:analysis; D002454:Cell Differentiation; D002461:Cell Line, Transformed; D003238:Connective Tissue / Q000201:enzymology* / Q000378:metabolism; D005434:Flow Cytometry; D016130:Immunophenotyping; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010455:Peptides; D011480:Protease Inhibitors / Q000494:pharmacology; D016176:T-Lymphocyte Subsets / Q000276:immunology / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology
D000900:Anti-Bacterial Agents; D015704:CD4 Antigens; D016827:CD8 Antigens; D010455:Peptides; D011480:Protease Inhibitors; C016977:amastatin; D018826:CD13 Antigens; D015260:Neprilysin; D007930:Leucine; C012211:ubenimex