Raag D. Airan1, 2, Amnon Bar-Shir1, 2, Guanshu Liu1, 3, Michael T. McMahon1, 3, Galit Pelled1, 3, Peter C.M. van Zijl1, 3, Jeff W.M. Bulte1, 2, Assaf A. Gilad1, 2
1Department of Radiology and Radiological Sciences, Johns Hopkins Medical Institutions, Baltimore, MD, United States; 2Cellular Imaging Section, Institute for Cell Engineering, Johns Hopkins Medical Institutions, Baltimore, MD, United States; 3F.M. Kirby Research Center for Functional Imaging, Kennedy Krieger Institute, Baltimore, MD, United States
Protein kinases, such as Protein Kinase A (PKA), underlie myriad clinically important signaling pathways. We developed a genetically encoded molecular MRI biosensor for detecting real-time PKA activity dynamics. This biosensor uses chemical exchange saturation transfer (CEST) MRI and its advantages over traditional molecular imaging techniques for detecting organic metabolite activity dynamics. We find that PKA phosphorylation of the biosensor resulted in a >50% modulation of its baseline CEST contrast, with near 250 M discrimination sensitivity and minutes temporal resolution In Vitro. CEST contrast change with phosphorylation likely results from coordination of CEST-contrast generating residues by the negatively-charged phosphate group.
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