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Frida Henningsson, Johan Ledin, Carolina Lunderius, Maria Wilén, Lars Hellman, Gunnar Pejler
Altered Storage of Proteases in Mast Cells from Mice Lacking Heparin: A Possible Role for Heparin Carboxypeptidase A Processing
Heparindeficient mice, generated by gene targeting of Ndeacetylase/Nsulfotransferase-2 (NDST-2), display severe mast cell defects, including an absence of stored mast cell proteases. However, the mechanism behind these observations is not clear. Here we show that NDST-2+/+ bone marrowderived mast cells cultured in the presence of IL-3 synthesise, in addition to highly sulphated chondroitin sulphate (CS), small amounts of equally highly sulphated heparinlike polysaccharide. The corresponding NDST-2/ cells produced highly sulphated CS only. Carboxypeptidase A (CPA) activity was detected in NDST+/+ cells but was almost absent in the NDST/ cells, whereas tryptase (mouse mast cell protease 6; mMCP-6) activity and antigen was detected in both cell types. Antigen for the chymase mMCP-5 was detected in NDST-2+/+ cells but not in the heparindeficient cells. Northern blot analysis revealed mRNA expression of CPA, mMCP-5 and mMCP-6 in both wildtype and NDST-2/ cells. A ~36 kDa CPA band, corresponding to proteolytically processed active CPA, as well as a ~50 kDa proCPA band was present in NDST-2+/+ cells. The NDST-2/ mast cells contained similar levels of proCPA as the wildtype mast cells, but the ~36 kDa band was totally absent. This indicates that the processing of proCPA to its active form may require the presence of heparin and provides the first insight into a mechanism by which the absence of heparin may cause disturbed secretory granule organisation in mast cells.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 383, 05/2002
Pages: 793 - 801