Induction of plasminogen activator inhibitor type 2 expression during differentiation of human K562 cells towards a macrophage phenotype
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A Rehemtulla1, A Arndt, D A Hart
1Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Centre, Alta., Canada.
Abstract:
Human K562 cells, a multipotential cell line of hematopoietic origin, were found to differentiate towards a macrophage-like cell when incubated in the presence of phorbol myristate acetate (PMA). Differentiation was accompanied by the expression and secretion of a plasminogen activator inhibitor (PAI). Incubation of the cells in the presence of other agents (dimethyl sulfoxide, retinoic acid, vitamin D3) capable of inducing differentiation towards other phenotypes did not lead to the induction of PAI expression. The inhibitor induced by PMA was partially purified and it exhibited biochemical characteristics similar to PAI-2. The molecule is a glycoprotein with a pI of 5.8. Northern blot analysis of mRNA isolated from control and PMA-treated cells revealed the presence of an approximately 2-kilobase mRNA from treated cells that hybridized to a PAI-2-specific synthetic oligonucleotide. This mRNA did not hybridize with a PAI-I-specific oligonucleotide and was absent from control cells. These observations are consistent with the literature regarding PAI-2 expression by cells of the monocyte-macrophage lineage. Therefore, commitment of this multipotential cell line towards the macrophage lineage results in specific activation of the PAI-2 gene. Further analysis of the regulatory elements of the PAI-2 gene may provide additional insight into the relationship between this gene and the macrophage phenotype.
Insights
Phorbol myristate acetate (PMA) induces human K562 cells to differentiate into macrophage-like cells, activating the plasminogen activator inhibitor-2 (PAI-2) gene. This specific gene activation highlights the link between macrophage lineage commitment and PAI-2 expression.
Area of Science:
- Hematopoiesis
- Cell differentiation
- Molecular biology
Background:
- Human K562 cells are multipotential hematopoietic cells.
- Phorbol myristate acetate (PMA) is known to induce differentiation in various cell types.
- Plasminogen activator inhibitors (PAIs) play roles in cellular processes.
Purpose of the Study:
- To investigate the effect of PMA on K562 cell differentiation.
- To determine if PAI expression is induced during PMA-mediated differentiation.
- To characterize the specific PAI involved and its gene activation.
Main Methods:
- Incubation of K562 cells with PMA and other differentiating agents.
- Partial purification and biochemical characterization of induced inhibitor.
- Northern blot analysis of mRNA using PAI-specific oligonucleotides.
Main Results:
- PMA induced K562 cells to differentiate into macrophage-like cells.
- Differentiation was accompanied by PAI expression and secretion.
- The induced PAI exhibited characteristics of PAI-2, with specific mRNA induction.
- Other differentiating agents did not induce PAI expression.
Conclusions:
- Macrophage lineage commitment of K562 cells specifically activates the PAI-2 gene.
- PAI-2 expression is associated with the macrophage phenotype.
- Further study of PAI-2 gene regulation may elucidate its role in macrophage biology.