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Human peripheral blood monocytes secrete a unique form of PDGF
1Department of Medicine, Medical University of South Carolina, Charleston 29425.
Abstract:
PDGF isolated from platelets and forms of PDGF produced by cells transformed with the v-sis gene (PDGF B chain) or U-20S osteosarcoma cells which express the PDGF A chain gene are known to be processed as disulfide-linked dimers of approximately 30 kd. Western blot analysis with anti human PDGF antibody of the PDGF-like factor synthesized and secreted by human blood monocytes (MDGF) on SDS gels indicates that it lacks interchain disulfide bridges and behaves as a 16-kd monomer under nonreducing conditions. Additionally, MDGF exhibits different sensitivities to either formic acid or CNBr cleavage compared to PDGF A or B chain molecules indicating it may have a different primary structure. These data suggest that MDGF represents a unique form of PDGF which lacks interchain disulfide bridges and may represent a new member of the PDGF family of growth factors.
Insights
Human blood monocytes secrete a unique platelet-derived growth factor (PDGF)-like factor (MDGF) that lacks disulfide bridges, differing from typical PDGF dimers. This suggests MDGF may be a novel PDGF family member.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- Platelet-derived growth factor (PDGF) exists as disulfide-linked dimers (~30 kDa).
- PDGF A and B chains are produced by various cell types, including transformed cells and osteosarcoma cells.
Purpose of the Study:
- To characterize the structure and properties of a PDGF-like factor synthesized by human blood monocytes (MDGF).
- To determine if MDGF represents a novel member of the PDGF family.
Main Methods:
- Western blot analysis using anti-human PDGF antibody.
- SDS-PAGE under nonreducing conditions.
- Analysis of sensitivity to formic acid and CNBr cleavage.
Main Results:
- MDGF synthesized and secreted by human monocytes behaves as a 16-kDa monomer.
- MDGF lacks interchain disulfide bridges, unlike canonical PDGF dimers.
- MDGF shows distinct cleavage sensitivities compared to PDGF A or B chains, suggesting a different primary structure.
Conclusions:
- MDGF is a unique form of PDGF lacking interchain disulfide bridges.
- MDGF may represent a new member of the PDGF family of growth factors.