Target Validation

  Drug Discovery

Aptamer applications in target validation:

• Validation on proteomic level (after RNAi)
  
• Targets: proteases, kinases, membrane proteins…
  
• In vitro and in vivo studies
  
• Intracellular applications
  
• Cell culture assays
  
• Serum

Aptamers are state of the art tools to obtain more information about a potential target on the protein level. They mimic the effect of a drug acting on the target protein. Unlike antibodies, aptamers can be transfected into or directly transcribed inside cells and applied with excellent biostability to extracellular targets when used in a stabilized form.

A specific aptamer (yellow) expressed in leukocytes inhibits a cytoskeletal regulatory factor (purple), and consequently, reorganization of the actin cytoskeleton. Control sequences have no effect on the morphology of the cell. (Mayer G. et al., Proc. Natl. Acad. Sci. USA 2001, 98, 4961-4965)

Aptamers as screening probes: 

• Binding proteins
  
• Enzymes lacking proper readout systems or substrate (specific esterases, oxidative / reductives enzymes…)
  
• Competitive inhibitors of validated or new binding sites
  
• Easily modified or labelled chemically to fit into most standard assay readouts
  
• Cost-effective alternative for expensive standard assays

Aptamers can be adapted to almost any kind of low or high-throughput assay format.
Aptamers are typically used as screening probes in
competitive assays, where their displacement by a
functionally equivalent small molecule generates a specific signal.

Example for aptamer selected on whole cells: The graph shows binding of a ³³P-labelled aptamer with low nanomolar affinity to the soluble receptor protein.