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A structure-function study of ligand recognition by CD22beta.
S M van Rossenberg1, L A Sliedregt, R Autar
1Leiden/Amsterdam Center for Drug Research, Division of Biopharmaceutics, Sylvius Laboratories, Leiden University, 2300 RA Leiden, The Netherlands. rossenbe@lacdr.leidenuniv.nl
The Journal of Biological Chemistry
|January 21, 2001
Summary
Researchers developed potent CD22 antagonists by modifying carbohydrate ligands. The most effective compound, a trivalent cluster, showed a 300-fold affinity increase, offering potential for targeted drug delivery in B-cell related diseases.
Area of Science:
- Biochemistry
- Immunology
- Medicinal Chemistry
Background:
- CD22 is a B-cell-specific adhesion molecule that binds sialic acid-containing glycans.
- CD22 engagement by endogenous ligands promotes B-cell activation and proliferation.
- High-affinity CD22 ligands could serve as inhibitors for B-cell mediated inflammatory diseases.
Purpose of the Study:
- To investigate the structural requirements for CD22 ligand binding.
- To synthesize and screen novel CD22 ligands with enhanced affinity.
- To evaluate the potential of potent CD22 ligands as targeted therapeutic agents.
Main Methods:
- Synthesis of a library of 20 mono-, di-, and trisaccharide analogs of Neu5Ac(alpha2,6)Lac.
- Screening of synthesized analogs for binding affinity to CD22beta.
- Generation of multivalent ligands using glutamate or Tris cluster cores.
- Affinity assessment of monovalent and multivalent ligands using fluorescence-activated cell sorting (FACS).
Main Results:
- CD22 ligand recognition showed tolerance to modifications on the anomeric sugar.
- A nitro aromatic group at C-2 enhanced ligand affinity.
- Multivalent ligands exhibited at least a 10-fold increase in affinity compared to monovalent forms.
- A trivalent Tris-based cluster of Neu5Ac-4-nitrobenzoyl-Glc demonstrated a 300-fold higher affinity, representing the most potent CD22 antagonist to date.
- Efficient cellular uptake of a CD22 substrate was confirmed via in vitro FACS studies.
Conclusions:
- Structural modifications, particularly the addition of a nitro aromatic group, can significantly enhance CD22 ligand affinity.
- Multivalency, especially bivalency, effectively increases ligand affinity for CD22.
- The synthesized potent CD22 antagonist holds promise for targeted delivery of immunomodulatory drugs and cytostatics.