MRI biosensor for protein kinase A encoded by a single synthetic gene

Raag D. Airan, Amnon Bar-Shir, Guanshu Liu, Galit Pelled, Michael T. McMahon, Peter C.M. Van Zijl, Jeff W.M. Bulte, Assaf A. Gilad

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


Purpose: Protein kinases including protein kinase A (PKA) underlie myriad important signaling pathways. The ability to monitor kinase activity in vivo and in real-time with high spatial resolution in genetically specified cellular populations is a yet unmet need, crucial for understanding complex biological systems as well as for preclinical development and screening of novel therapeutics. Methods: Using the hypothesis that the natural recognition sequences of protein kinases may be detected using chemical exchange saturation transfer magnetic resonance imaging, we designed a genetically encoded biosensor composed of eight tandem repeats of the peptide LRRASLG, a natural target of PKA. Results: This sensor displays a measurable change in chemical exchange saturation transfer signal following phosphorylation by PKA. The natural PKA substrate LRRASLG exhibits a chemical exchange saturation transfer-magnetic resonance imaging contrast at +1.8 and +3.6 ppm, with a >50% change after phosphorylation with minutes-scale temporal resolution. Expression of a synthetic gene encoding eight monomers of LRRASLG yielded two peaks at these chemical exchange saturation transfer frequencies. Conclusion: Taken together, these results suggest that this gene may be used to assay PKA levels in a biologically relevant system. Importantly, the design strategy used for this specific sensor may be adapted for a host of clinically interesting protein kinases.

Original languageEnglish (US)
Pages (from-to)1919-1923
Number of pages5
JournalMagnetic resonance in medicine
Issue number6
StatePublished - Dec 2012


  • biosensor
  • chemical exchange saturation transfer
  • protein kinase A
  • reporter gene

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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