Molecular glue is a small molecule that induces or stabilizes interactions between proteins or between proteins and other biomolecules (e.g., DNA, RNA) that would not normally bind or would bind only weakly. These molecules “glue” two or more biomolecules together, often enhancing or disrupting biological functions.

Key Features of Molecular Glues:
1. Small Molecules – Typically <500 Da in size, making them drug-like.
2. Induce or Stabilize Protein-Protein Interactions (PPIs) – They can bring two proteins together or strengthen existing weak interactions.
3. Can Be Natural or Synthetic – Some are naturally occurring (e.g., cyclosporine, rapamycin), while others are designed in labs.
4. Used in Drug Development – They can modulate biological pathways by stabilizing or disrupting protein complexes.

Mechanisms of Action:
– Stabilizing Weak Interactions – Some molecular glues strengthen naturally occurring but transient interactions.
– Inducing Neo-Interactions – They can force two proteins to bind that normally wouldn’t.
– Targeted Protein Degradation – Some (like thalidomide analogs) recruit E3 ubiquitin ligases to mark proteins for degradation (e.g., CRBN-based molecular glues in PROTACs).

Examples of Molecular Glues:
– Immunosuppressants:
– Cyclosporine A – Glues cyclophilin to calcineurin, inhibiting T-cell activation.
– Rapamycin (Sirolimus) – Binds FKBP12 and mTOR, blocking cell growth signals.
– Cancer & Degradation Inducers:
– Lenalidomide & Pomalidomide – Recruit CRBN E3 ligase to degrade transcription factors like IKZF1/3 in multiple myeloma.
– Auxin (plant hormone) – Acts as a natural molecular glue in plants to degrade transcriptional repressors.

Applications:
– Drug Discovery – Especially in targeted protein degradation (e.g., PROTACs).
– Chemical Biology – Used to study protein interactions and pathways.
– Therapeutics – Treating cancer, autoimmune diseases, and neurodegenerative disorders.

Difference Between Molecular Glues & PROTACs:
– Molecular glues are usually smaller and work by directly stabilizing interactions.
– PROTACs (Proteolysis-Targeting Chimeras) are bifunctional molecules that actively recruit E3 ligases to degrade target proteins.

Molecular glues represent a promising area in drug development due to their ability to modulate “undruggable” targets by manipulating protein interactions.

Answer generated by DeepSeek.