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

• Published in: Magnetic resonance in medicine Vol. 68; no. 6; pp. 1919 - 1923
• Main Authors: Airan, Raag D., Bar-Shir, Amnon, Liu, Guanshu, Pelled, Galit, McMahon, Michael T., van Zijl, Peter C. M., Bulte, Jeff W. M., Gilad, Assaf A.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.12.2012; Wiley Subscription Services, Inc
• Subjects: Biosensing Techniques - methods; biosensor; chemical exchange saturation transfer; Cyclic AMP-Dependent Protein Kinases - analysis; Cyclic AMP-Dependent Protein Kinases - genetics; Genes, Synthetic - genetics; Magnetic Resonance Imaging - methods; Molecular Imaging - methods; protein kinase A; reporter gene; Reproducibility of Results; Sensitivity and Specificity
• ISSN: 0740-3194; 1522-2594
• DOI: 10.1002/mrm.24483

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. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.