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Coexpression of the genes for platelet-derived growth factor B-chain receptor and macrophage colony-stimulating
P Pantazis1, S Kharbanda, A S Goustin
1Stehlin Foundation for Cancer Research, St. Joseph Hospital Cancer Research Laboratory, Houston, TX 77003.
Abstract:
Receptors for platelet-derived growth factor (PDGF) have not been identified previously to our knowledge in human myeloid cells that also produce PDGF. Here we report that phorbol ester-treated myeloid cells differentiated along the monocytic lineage express both a full-length 5.5-kilobase (kb) mRNA and a predominant, truncated 4.6-kb mRNA coding for the PDGF B-chain receptor (PDGF-BR). PDGF-BR was identified in phorbol ester-differentiated myeloid cells by indirect immunofluorescence with an antibody specific to PDGF-BR. This anti-PDGF-BR was also used in immunoprecipitation studies to demonstrate that lysates of phorbol ester-differentiated myeloid cells contain PDGF-BR molecules of 37 kDa to 130 kDa. The results also show that the tandemly linked genes for PDGF-BR and the macrophage colony-stimulating factor 1 receptor are coexpressed in the phorbol ester-differentiated myeloid cells. Expression of these two receptor genes has not been shown previously in any cell type to our knowledge.
Insights
Human myeloid cells that produce platelet-derived growth factor (PDGF) also express its receptor (PDGF-BR). This study identifies both full-length and truncated PDGF-BR mRNA and protein in differentiated myeloid cells.
Area of Science:
- Cell Biology
- Molecular Biology
- Hematology
Background:
- Human myeloid cells synthesize platelet-derived growth factor (PDGF).
- PDGF receptors (PDGF-BR) were previously unidentified in human myeloid cells.
- The role of autocrine PDGF signaling in myeloid cells remains unclear.
Purpose of the Study:
- To investigate the expression of PDGF receptors in human myeloid cells.
- To characterize the molecular forms of PDGF-BR in differentiated myeloid cells.
- To examine the coexpression of PDGF-BR and macrophage colony-stimulating factor 1 receptor (M-CSFR) genes.
Main Methods:
- Treatment of myeloid cells with phorbol ester to induce monocytic differentiation.
- Detection of PDGF-BR mRNA using Northern blot analysis.
- Immunofluorescence and immunoprecipitation assays to identify PDGF-BR protein.
- Analysis of gene coexpression using molecular techniques.
Main Results:
- Phorbol ester-differentiated myeloid cells express both 5.5-kb and 4.6-kb PDGF-BR mRNA.
- PDGF-BR protein was detected in differentiated myeloid cells via immunofluorescence and immunoprecipitation.
- PDGF-BR molecules of 37 kDa to 130 kDa were identified in cell lysates.
- Tandemly linked genes for PDGF-BR and M-CSFR are coexpressed in these cells.
Conclusions:
- Human myeloid cells differentiated along the monocytic lineage express PDGF-BR.
- This expression includes both full-length and truncated receptor forms.
- Coexpression of PDGF-BR and M-CSFR genes is demonstrated in these myeloid cells, suggesting novel autocrine/paracrine signaling pathways.