Fibrinogen mitogenic effect on hemopoietic cell lines: control via receptor modulation

Area of Science:

• Cell biology
• Molecular biology
• Immunology

Background:

• Fibrinogen is a major plasma protein with known mitogenic effects.
• The mechanism behind fibrinogen's mitogenic activity, specifically the role of cell surface receptors, requires clarification.

Purpose of the Study:

• To investigate the presence and characteristics of specific membrane receptors mediating fibrinogen's mitogenic effect on hemopoietic cells.
• To determine if these receptors are distinct from known platelet fibrinogen receptors.

Main Methods:

• Specific binding analysis to detect and quantify fibrinogen receptors on hemopoietic cell lines.
• Competitive blocking assays using antibodies and peptides to characterize receptor specificity.
• Induction studies using cell-specific stimuli to modulate receptor expression and assess mitogenic response.

Main Results:

• Fibrinogen receptors are present exclusively on hemopoietic cell lines responsive to fibrinogen's mitogenic effects.
• These receptors differ from platelet fibrinogen receptors and are not blocked by Arg-Gly-Asp peptides.
• Receptor number varies between cell types (e.g., Raji vs. JM cells) and can be induced by lineage-specific stimuli, correlating with increased cell growth in the presence of fibrinogen.

Conclusions:

• Mitogenic fibrinogen effects are mediated by specific, distinct membrane receptors on hemopoietic cells.
• Fibrinogen receptor expression is inducible and directly linked to the mitogenic response, suggesting receptor modulation controls this effect.