Expression of Bomapin, a Novel Human Serpin, in Normal/Malignant Hematopoiesis and in the Monocytic Cell Lines THP-1 and AML-193

Abstract

Our group recently cloned the cDNA-encoding bomapin, a member of the serine protease inhibitor (serpin) superfamily, from a human bone marrow cDNA library (J Biol Chem 270:2675, 1995). To understand its expression within the hematopoietic compartment, RNA extracted from bone marrow or peripheral blood from normal donors and patients with leukemia was reverse transcribed and analyzed by polymerase chain reaction (PCR). Bomapin PCR products were readily detected in normal bone marrow, which was designated as a medium mRNA level. In peripheral blood, bomapin expression was low or undetectable in normal donors (n = 6) and patients with chronic lymphocytic leukemia (n = 6). Blood from patients with chronic myeloid leukemia (n = 6), chronic myelomonocytic leukemia (n = 6), acute myeloid leukemia (n = 5), and acute lymphocytic leukemia (n = 5) exhibited low to medium levels of bomapin expression. Furthermore, a high level of bomapin expression was detected in one individual with acute monocytic leukemia. These data suggest that bomapin expression may be elevated in hematopoietic cells of monocytic lineage. Therefore, we analyzed the expression of bomapin within cell lines that exhibited characteristics of the monocytic lineage. Bomapin PCR products were detected in the monocytic THP-1 and AML-193 cell lines but not in CRL 7607, CRL 7541, KG-1, or K562 cells. Induction of bomapin transcripts was not detected in the latter series of cell lines following a 24-hour treatment with phorbol myristate acetate (PMA, 10−8mol/L) or tumor necrosis factor-α (TNF-α, 30 U/mL), whereas treatment of THP-1 or AML-193 cells with these agents reduced the intensity of the bomapin PCR products. Northern blotting confirmed these results and showed that the expression of bomapin in THP-1 cells was downregulated over a 4-day period by PMA and, to a lesser extent, TNF-α. Immunoblotting was used to show the presence of a 40-kD protein in THP-1 cytosol preparations. Bomapin antigen levels were correspondingly reduced after treatment with PMA. Because PMA and TNF-α induce monocytic differentiation in THP-1 and AML-193 cells, these data increase the possibility that bomapin may play a role in the regulation of protease activities specifically in early stages of cellular differentiation.

Stage specific gene expression of serpins and their cognate proteases during myeloid differentiation

“…However, FACS‐isolated CD61 + ,42a + cells (see below) also showed a strong signal for MNEI, suggesting that the gene is likely to be expressed in megakaryocytes. The intracellular serpin proteinase inhibitor‐10 (PI‐10, bomapin) was exclusively expressed in bone marrow in keeping with previous reports (Riewald et al , 1998). There was no evidence of significant plasminogen activator inhibitor‐2 (PAI‐2) expression in any of the cells examined.…”

The role of serpins in vertebrate immunity

“…However, mice lacking B2 do not have any defects in leukocyte differentiation or recruitment (34). B10 (bomapin) is a nuclear serpin found in bone marrow in the developing blood cells of the monocyte lineage (35, 36). Mitogen‐induced maturation of monocyte cell lines reduces or ablates bomapin expression, suggesting an involvement in monocyte development (36).…”

A genome-wide association study highlights a regulatory role forIFNG-AS1contributing to cutaneous leishmaniasis in Brazil

“…Two further genes, SERPINB10 and IFNG-AS1, are highlighted in relation to more central roles in determining immune responses. Serpin family B member 10 encoded by SERPINB10 is a peptidase inhibitor expressed in bone marrow [58] in haematopoietic cells of the monocytic lineage [59] and is known to inhibit TNF-induced apoptosis [60]. Epithelial SERPINB10 contributes to allergic eosinophilic inflammation [61], suggesting additional roles for this molecule in immunopathology.…”