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Structural Constraint of Osteopontin Facilitates Efficient Binding to CD44.
Gulimirerouzi Fnu1, Palak Agrawal2, Gopal C Kundu2
1College of Pharmacy, University of Cincinnati Academic Health Center, Cincinnati, OH 45229, USA.
Biomolecules
|June 2, 2021
Summary
Osteopontin (OPN) binding to CD44 requires structural changes in OPN for strong interaction. Heparin binding to OPN, but not hyaluronate, enhances CD44 ligation, revealing key molecular requirements.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- The interaction between osteopontin (OPN) and CD44 is crucial in various physiological and pathological processes.
- Previous studies on OPN-CD44 binding have been complicated by posttranslational modifications and complex formation.
Purpose of the Study:
- To elucidate the molecular requirements for high-affinity binding between osteopontin (OPN) and CD44.
- To investigate the role of OPN structure and other binding partners in OPN-CD44 interactions.
Main Methods:
- Analysis of OPN-CD44 binding kinetics using titration experiments.
- Investigating the effect of OPN structural constraint (heparin, immobilization) on CD44 binding.
- Assessing the competitive or additive binding effects of integrins (α9β1, αVβ3) and hyaluronate.
Main Results:
- Unmodified OPN exhibits moderate binding to CD44, suggesting multiple binding sites or conformations.
- Structural constraint of OPN, induced by heparin or immobilization, is necessary for strong CD44 ligation.
- Integrin α9β1 competes with OPN-CD44 binding, while αVβ3 shows additive binding.
- Hyaluronate does not affect OPN-CD44 interaction.
Conclusions:
- Heparin-induced conformational changes in OPN are critical for high-affinity CD44 engagement.
- The CD44 binding site on OPN is distinct from the RGD motif but overlaps with the SVVYGLR domain.
- These findings clarify the molecular basis of OPN-CD44 interactions, impacting understanding of related biological processes.
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