Protein-linked oligosaccharide implicated in cell-cell adhesion in two Dictyostelium species

Area of Science:

• Cell Biology
• Developmental Biology
• Biochemistry

Background:

• Cell-cell adhesion is critical for multicellular organism development.
• Dictyostelium discoideum serves as a model organism for studying cell adhesion mechanisms.
• Monoclonal antibody d-41 has been identified as an inhibitor of cell adhesion.

Purpose of the Study:

• To investigate the role of monoclonal antibody d-41 in cell-cell adhesion across different Dictyostelium species.
• To identify the specific proteins targeted by antibody d-41 and their involvement in adhesion.
• To elucidate the molecular components of the d-41 epitope and their contribution to cell adhesion.

Main Methods:

• Utilized monoclonal antibody d-41 to assess cell-cell adhesion inhibition in Dictyostelium discoideum and Dictyostelium purpureum.
• Characterized d-41 reactive proteins using Western blotting and identified their molecular weights (approx. 80,000, 37,000, and 27,000).
• Determined the nature of the d-41 epitope through periodate oxidation and Pronase digestion experiments.
• Generated polyclonal antibodies against purified d-41 reactive glycoproteins and tested their adhesion-blocking activity.
• Investigated the effect of periodate oxidation on the adhesion-blocking capacity of polyclonal antibodies.

Main Results:

• Monoclonal antibody d-41 effectively blocked cell-cell adhesion in both Dictyostelium discoideum and Dictyostelium purpureum.
• Antibody d-41 recognized glycoproteins of approximately 80,000, 37,000, and 27,000 Mr in both species.
• The d-41 epitope was sensitive to periodate oxidation, indicating a carbohydrate component, but resistant to Pronase digestion.
• Polyclonal antibodies against purified glycoproteins potently inhibited D. discoideum adhesion.
• Adhesion-blocking activity of polyclonal antibodies was neutralized by the purified glycoproteins.
• Periodate oxidation of purified glycoproteins abolished the adhesion-blocking activity of the generated polyclonal antibodies, despite their continued binding to cell surface proteins.

Conclusions:

• The d-41 epitope, likely containing a specific oligosaccharide component, is crucial for cell-cell adhesion in Dictyostelium.
• The identified glycoproteins are involved in mediating cell adhesion in these organisms.
• Further investigation into the d-41 binding oligosaccharide may reveal novel insights into the molecular mechanisms of cell adhesion.