Two of the major rat mast cell proteases, rat mast cell protease 1 (RMCP-1) and RMCP-2, have for many years served as important phenotypic markers for studies of various aspects of mast cell (MC) biology. However, except for these proteases only fragmentary information has been available on the structure and complexity of proteases expressed by different subpopulations of rat MCs. To address these questions, cDNA libraries were constructed from freshly isolated rat peritoneal MCs and from the rat mucosal MC line RBL-1. cDNA clones for 10 different serine proteases (RMCP-1-10), and the MC carboxypeptidase A were isolated and characterized. Six of these proteases have not been isolated previously. Based on their protease content, three separate subpopulations of MCs were identified. Connective tissue MCs (CTMCs) from the ear and peritoneum express the chymases RMCP-1 and -5, the tryptases RMCP-6, and -7 and the carboxypeptidase A. However, based on a large difference in the level of expression of RMCP-7, CTMCs of these two organs may be regarded as two separate subpopulations. RMCP-2 and the three closely related proteases of the RMCP-8 subfamily were identified as the major mucosal MC proteases in rat. In contrast to what has been reported for human MCs, no expression of cathepsin G or cathepsin G–like proteases was detected in any of the rat MC populations. To determine mRNA frequencies for the various proteases expressed by normal tissue MCs, an unamplified peritoneal MC cDNA library was screened with a panel of monospecific cDNA probes. These results showed that peritoneal MCs are highly specialized effector cells with mRNA frequencies for the major proteases in the range of several percent of the total mRNA pool.
Secretory Granule Proteases in Rat Mast Cells. Cloning of 10 Different Serine Proteases and a Carboxypeptidase A from Various Rat Mast Cell Populations
Address correspondence to Dr. Lars Hellman, Department of Medical Immunology and Microbiology, University of Uppsala, Biomedical Center, Box 582, S-751 23 Uppsala, Sweden.
1 Abbreviations used in this paper:3H-DFP, (3H)diisopropyl fluorophosphate; aa, amino acid; BMMC, bone marrow-derived mast cell; CPA, carboxypeptidase A; CTMC, connective tissue mast cell; DFP, diisopropyl fluorophosphate; IgERI, the IgE high-affinity receptor; MC, mast cell; MMC, mucosal mast cell; MMCP, mouse mast cell protease; MTC, mastocytoma tumor cell; nt, nucleotide(s); pos., position; RMCP, rat mast cell protease.
Claudia Lützelschwab, Gunnar Pejler, Maria Aveskogh, Lars Hellman; Secretory Granule Proteases in Rat Mast Cells. Cloning of 10 Different Serine Proteases and a Carboxypeptidase A from Various Rat Mast Cell Populations. J Exp Med 6 January 1997; 185 (1): 13–30. doi: https://doi.org/10.1084/jem.185.1.13
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