title: Intracellular gene transcription factor protein-guided MRI by DNA aptamers in vivo.
abstract: The mechanisms by which transcription factor (TF) protein AP-1 modulates amphetamine's effects on gene transcription in living brains are unclear. We describe here the first part of our studies to investigate these mechanisms, specifically, our efforts to develop and validate aptamers containing the binding sequence of TF AP-1 (5ECdsAP1), in order to elucidate its mechanism of action in living brains. This AP-1-targeting aptamer, as well as a random sequence aptamer with no target (5ECdsRan) as a control, was partially phosphorothioate modified and tagged with superparamagnetic iron oxide nanoparticles (SPIONs), gold, or fluorescein isothiothianate contrast agent for imaging. Optical and transmission electron microscopy studies revealed that 5ECdsAP1 is taken up by endocytosis and is localized in the neuronal endoplasmic reticulum. The results of magnetic resonance imaging (MRI) with SPION-5ECdsAP1 revealed that neuronal AP-1 TF protein levels were elevated in neurons of live male C57black6 mice after amphetamine exposure; however, pretreatment with SCH23390, a dopaminergic receptor antagonist, suppressed this elevation. As studies in transgenic mice with neuronal dominant-negative A-FOS mutant protein, which has no binding affinity for the AP-1 sequence, showed a completely null MRI signal in the striatum, we can conclude that the MR signal reflects specific binding between the 5ECdsAP1 aptamer and endogenous AP-1 protein. Together, these data lend support to the application of 5ECdsAP1 aptamer for intracellular protein-guided imaging and modulation of gene transcription, which will thus allow investigation of the mechanisms of signal transduction in living brains.
authors.affiliation: 3Massachusetts General Hospital, CNY149 (2301) Thirteenth St., Charlestown, MA 02129, USA. philipl@nmr.mgh.harvard.edu.
authors.forename: Christina H
authors.initials: CH
authors.lastname: Liu
authors.forename: Jiaqian
authors.initials: J
authors.lastname: Ren
authors.forename: Charng-Ming
authors.initials: CM
authors.lastname: Liu
authors.forename: Philip K
authors.initials: PK
authors.lastname: Liu
mesh_terms: D000818:Animals; D052157:Aptamers, Nucleotide / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008995:Monoamine Oxidase / Q000378:metabolism
chemical_list: D052157:Aptamers, Nucleotide; D008995:Monoamine Oxidase
keywords: AP1 knockout; attention; monoamine oxidase A; stress; transgenic mice