Molecular cloning, chromosomal localization, and expression of murine dipeptidyl peptidase I

Human cathepsins F and W: A new subgroup of cathepsins

Human cathepsin F is a recently described papain-like cysteine protease of unknown function. To investigate the evolutionary relatedness to other human cathepsins, we determined the genomic organization and the chromosomal localization of cathepsin F and isolated its putative promoter region. The gene of human cathepsin F (CTSF) is composed of twelve exons and eleven introns and was found to be similar to that of cathepsin W but different from the cathepsins K, S, L, O, B, and C. The splice sites of nine out of the eleven introns were identical to those determined in the cathepsin W gene (CTSW), whereas introns one and ten were unique for CTSF. The 4. 7 kb gene was mapped to the long arm of chromosome 11 at position q13.1-3, a locus shared with CTSW. Phylogenetic analysis of human cathepsin protein sequences demonstrated that (i) cathepsins F and W are evolutionarily separated from other human cathepsins, and (ii) cysteine proteases closely related to human cathepsin W and F are also expressed in parasites and mammals. Based on these phylogenetic findings, on the presence of a particular protein motif ("ERFNAQ") in the propeptides of cathepsins F and W as well as the genomic organization and chromosomal localization of their genes, we concluded that F and W form a novel subgroup of cathepsin proteases. We suggest the naming "cathepsin F-like" proteases distinct from the previously described cathepsins "L- and B-like" subgroups.

Regulated expression, processing, and secretion of dog mast cell dipeptidyl peptidase I

Dipeptidyl peptidase I (DPPI) is a cysteine protease found predominantly in myelomonocytic cells, cytotoxic T-cells, and mast cells. Recent studies identify an intracellular role for mast cell-DPPI (MC-DPPI) by activating prochymase and protryptase to their mature forms. To better define MC-DPPI and to explore the possibility of extracellular roles, we purified MC-DPPI from mastocytoma cells. We found the dog C2 mastocytoma cell line to be the richest source yet described for DPPI, purifying up to 200 microg of enzyme per g of cells. Dog MC-DPPI has an Mr of approximately 175,000 and consists of four subunits, each composed of a propeptide, light chain, and heavy chain. The heavy chain is N-glycosylated and is heterogeneously processed to three different forms. NH2-terminal sequences of the heavy chain and propeptide are identical to those predicted from a cDNA clone we sequenced from a mastocytoma cDNA library. The dog cDNA-derived sequence is 86% identical to that of human DPPI. Dog mastocytoma cells incubated with 12-O-tetradecanoylphorbol-13-acetate increase expression of MC-DPPI mRNA. MC-DPPI maintains its activity for dipeptide substrates at a neutral to alkaline pH. Cells stimulated with ionophore or substance P secrete MC-DPPI in parallel with the granule-associated mediators tryptase and histamine. Thus, dog mastocytoma cells secrete DPPI that is active at the pH of extracellular fluids, suggesting that MC-DPPI may act outside the cell.

Dipeptidyl Peptidase I and Granzyme A Are Coordinately Expressed During CD8+ T Cell Development and Differentiation

Dipeptidyl peptidase I (DPPI) is a granule protease that plays a requisite role in processing the proenzyme form of the CTL granule serine proteases (granzymes). This study assesses DPPI mRNA and enzyme expression during T lymphocyte ontogeny and CTL differentiation. The most immature CD3−CD4−CD8− thymocytes were found to express >40-fold higher levels of DPPI mRNA, although levels of DPPI enzymatic activity in CD3−CD4−CD8− thymocytes were only modestly higher than those seen for CD4+CD8+ or CD4+CD8− thymocytes. More mature CD8+CD4− thymocytes and CD8+ splenocytes expressed significantly higher levels of DPPI mRNA and enzymatic activity than CD4+CD8+ or CD4+CD8− thymocytes. Granzyme A mRNA expression was observed in DPPI expressing CD3−CD4−CD8− and CD8+CD4− thymocytes and was also observed in CD8+CD4− splenocytes; however, expression was not observed in CD4+CD8+ or CD4+CD8− thymocytes. Both DPPI mRNA and granzyme A mRNA expression in CD8+ T cells decreased to very low or undetectable levels during the first 48 h after allostimulation in MLCs. However, peak levels of both DPPI and granzyme A expression were observed later in the course of CD8+ T cell responses to alloantigen, with DPPI mRNA expression peaking on either day 3 or day 4 and granzyme A expression peaking at the end of a 5-day MLR. These data indicate that DPPI is expressed at all stages of T cell ontogeny and differentiation in which granzyme A mRNA is detected; consequently, DPPI appears to be available for the processing and activation of granzyme A during both CD8+ T cell development and differentiation.