Molecular characterization and expression of the gene encoding human erythroid-potentiating activity

Abstract

Erythropoietin is the primary physiological regulator of erythropoiesis; however, in vitro studies have identified another class of mediators which appear to be important in stimulating erythroid progenitors. These factors have generally been referred to as burst-promoting activities (BPA), because they stimulate the growth of early erythroid progenitors referred to as burst-forming units-erythroid (BFU-E) which give rise to colonies of up to thousands of haemoglobinized cells. We recently reported purification of a burst-promoting activity from medium conditioned by the Mo T-lymphoblast cell line infected with human T-cell lymphotropic virus type II (HTLV-II). This purified glycoprotein of relative molecular mass (Mr) 28,000 also stimulates colony formation by more mature erythroid precursors (CFU-E) and is therefore referred to as erythroid-potentiating activity (EPA). Purified EPA specifically stimulates human and murine cells of the erythroid lineage, unlike murine interleukin-3 (IL-3) which stimulates precursor cells from all haematopoietic lineages. We report here the isolation of a complementary DNA molecular clone encoding EPA and its use in producing EPA in COS (monkey) cells and CHO (Chinese hamster ovary) cells. We also define the organization of the EPA gene in human DNA.

Differential expression and localization of TIMP-1 and TIMP-4 in human gliomas

“…Alternatively, since TIMP-1 preferentially binds the pro-enzyme form of MMP-9, upregulation of this inhibitor in GBM may reflect a specific regulatory mechanism that links these two functions, and could be seen as an attempt by the host to neutralize increased MMP-9 activity and thus slow invasion or angiogenesis. It is also possible that TIMP-1 may stimulate glioma proliferation directly in vivo since TIMP-1 has erythroid potentiating activity (EPA), and stimulates proliferation of numerous cell types (Gasson et al, 1985;Bertaux et al, 1991;Hayakawa et al, 1992Hayakawa et al, , 1994. Moreover, TIMP-1, but not TIMP-2 or the synthetic hydroxamate inhibitor BB-94, has been shown to confer resistance to apoptosis in Burkitt's lymphoma cells (Guedez et al, 1998).…”

“…For example, TIMP-1 stimulates the proliferation of erythroid precursors (Gasson et al, 1985), and both TIMP-1 and TIMP-2 can positively influence the proliferation of numerous cell types (Hayakawa et al 1992(Hayakawa et al , 1994Wingfield et al, 1999). Additionally, TIMP-2 inhibits in vitro proliferation of human microvascular endothelial cells stimulated with bFGF (Murphy et al, 1993), and TIMP-3 promotes apoptosis (Ahonen et al, 1998;Baker et al, 1998), possibly through stabilization of TNF alpha receptors (Smith et al, 1997).…”

Tissue inhibitor of metalloproteinase‐2 (TIMP‐2) has erythroid‐potentiating activity

“…We identified an erythroid-potentiating activity (EPA) in the supernatant of the HTLV-II-transformed human T-lymphblast cell line (Me), and purified the 28 000 Da glycoprotein molecule to homogeneity [5,16]. Subsequent eDNA cloning demonstrated that EPA was identical to tissue inhibitor of metalloproteinases (TIMP, TIMP-1) [17,18], which can be isolated from a variety of human tissues and body fluids and which has been shown to inhibit the eollagenase family of enzymes [19][20][21]. The purified natural EPA and, subsequently, the recombinant EPA were shown to augment colony formation by human CFU-E, BFU-E and K-562 cells [16,17,22,23].…”

“…Subsequent eDNA cloning demonstrated that EPA was identical to tissue inhibitor of metalloproteinases (TIMP, TIMP-1) [17,18], which can be isolated from a variety of human tissues and body fluids and which has been shown to inhibit the eollagenase family of enzymes [19][20][21]. The purified natural EPA and, subsequently, the recombinant EPA were shown to augment colony formation by human CFU-E, BFU-E and K-562 cells [16,17,22,23]. We were also able to demonstrate specific binding of radioiodinated recombinant EPA to the K-562 erythroleukemia cells [23].…”

“…This inhibitor, which we refer to as TIMP-2, was initially isolated as a complex with the 72 000 Da type IV collagenase/gelatinase proenzyme from the conditioned media of haman melanoma cells [17]. This complex has also been isolated from endothelial cells [26].…”