Name: visualizing protein kinase a activity in head-fixed behaving mice using in vivo two-photon fluorescence lifetime imaging microscopy
Uploaded: 2019-06-07T14:00:00
Description: Watch this Scientific Journal Video about Visualizing Protein Kinase A Activity In Head-fixed Behaving Mice Using In Vivo Two-photon Fluorescence Lifetime Imaging Microscopy at JoVE.com

We thank Ms. Tess J. Lameyer, Ms. Ruth Frank, and Dr. Michael A. Muniak for edits and comments, and Dr. Ryohei Yasuda at Max Planck Florida for 2pFLIM acquisition software. This work was supported by two BRAIN Initiative awards U01NS094247 (H.Z. and T.M.) and R01NS104944 (H.Z. and T.M.), an R01 grant R01NS081071 (T.M.), and an R21 grant R21NS097856 (H.Z.). All awards are from the National Institute of Neurological Disorders and Stroke, United States.

All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Oregon Health and Science University.
1. 2pFLIM Microscope Setup
<ol>
	<li>Install a photon timing counting module (PTCM, Table of Materials) and connect to the computer (Figure 1) according to the manufacturer&#8217;s manual. 
	NOTE: The PTCM is typically a computer board that receives a &#8220;sync&#8221; input for ...

<ol>
	<li>Greengard, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Neurobiology+of+Slow+Synaptic+Transmission.">The Neurobiology of Slow Synaptic Transmission.</a> Science. 294 (5544), 1024-1030 (2001).</li><li>Petersen, S. E., Posner, M. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+attention+system+of+the+human+brain:+20+years+after.">The attention system of the human brain: 20 years after.</a> Annual Review of Neuroscience. 35 (2), 73-89 (2012).</li><li>Sun, Y., Hunt, S., Sah, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Norepinephrine+and+Corticotropin-Releasing+Hormone:+Partners+in+the+Neural+Circuits+that+Underpin+Stress+and+Anxiety.">Norepinephrine and Corticotropin-Releasing Hormone: Partners in the Neural Circuits that Underpin Stress and Anxiety.</a> Neuron. 87 (3), 468-470 (2015).</li><li>Berke, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=What+does+dopamine+mean?.">What does dopamine mean?.</a> Nature Neuroscience. 21 (6), 787-793 (2018).</li><li>Chen, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endogenous+G&#945;q-Coupled+Neuromodulator+Receptors+Activate+Protein+Kinase+A.">Endogenous G&#945;q-Coupled Neuromodulator Receptors Activate Protein Kinase A.</a> Neuron. 96 (5), 1070-1083 (2017).</li><li>Madison, D. V., Nicoll, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclic+adenosine+3&#8217;,5&#8217;-monophosphate+mediates+beta-receptor+actions+of+noradrenaline+in+rat+hippocampal+pyramidal+cells.">Cyclic adenosine 3&#8217;,5&#8217;-monophosphate mediates beta-receptor actions of noradrenaline in rat hippocampal pyramidal cells.</a> The Journal of Physiology. 372 (1), 245-259 (1986).</li><li>Yasuda, H., Barth, A. L., Stellwagen, D., Malenka, R. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+developmental+switch+in+the+signaling+cascades+for+LTP+induction.">A developmental switch in the signaling cascades for LTP induction.</a> Nature Neuroscience. 6 (1), 15-16 (2003).</li><li>Pedarzani, P., Storm, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PKA+mediates+the+effects+of+monoamine+transmitters+on+the+K++current+underlying+the+slow+spike+frequency+adaptation+in+hippocampal+neurons.">PKA mediates the effects of monoamine transmitters on the K+ current underlying the slow spike frequency adaptation in hippocampal neurons.</a> Neuron. 11 (6), 1023-1035 (1993).</li><li>Brandon, E. P., Idzerda, R. L., McKnight, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PKA+isoforms,+neural+pathways,+and+behaviour:+making+the+connection.">PKA isoforms, neural pathways, and behaviour: making the connection.</a> Current Opinion in Neurobiology. 7 (3), 397-403 (1997).</li><li>Radnikow, G., Feldmeyer, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Layer-+and+Cell+Type-Specific+Modulation+of+Excitatory+Neuronal+Activity+in+the+Neocortex.">Layer- and Cell Type-Specific Modulation of Excitatory Neuronal Activity in the Neocortex.</a> Frontiers in Neuroanatomy. 12 (January), (2018).</li><li>Kennedy, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Emerging+trends+in+in+vivo+neurochemical+monitoring+by+microdialysis.">Emerging trends in in vivo neurochemical monitoring by microdialysis.</a> Current Opinion in Chemical Biology. 17 (5), 860-867 (2013).</li><li>Rodeberg, N. T., Sandberg, S. G., Johnson, J. A., Phillips, P. E. M., Wightman, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hitchhiker&#8217;s+Guide+to+Voltammetry:+Acute+and+Chronic+Electrodes+for+In+Vivo+Fast-Scan+Cyclic+Voltammetry.">Hitchhiker&#8217;s Guide to Voltammetry: Acute and Chronic Electrodes for In Vivo Fast-Scan Cyclic Voltammetry.</a> ACS Chemical Neuroscience. 8 (2), 221-234 (2017).</li><li>Hamel, E. J. O., Grewe, B. F., Parker, J. G., Schnitzer, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+level+brain+imaging+in+behaving+mammals:+An+engineering+approach.">Cellular level brain imaging in behaving mammals: An engineering approach.</a> Neuron. 86 (1), 140-159 (2015).</li><li>Allen, M. D., Zhang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Subcellular+dynamics+of+protein+kinase+A+activity+visualized+by+FRET-based+reporters.">Subcellular dynamics of protein kinase A activity visualized by FRET-based reporters.</a> Biochemical and Biophysical Research Communications. 348 (2), 716-721 (2006).</li><li>Zhang, J., Ma, Y., Taylor, S. S., Tsien, R. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetically+encoded+reporters+of+protein+kinase+A+activity+reveal+impact+of+substrate+tethering.">Genetically encoded reporters of protein kinase A activity reveal impact of substrate tethering.</a> Proceedings of the National Academy of Sciences of the United States of America. 98 (26), 14997-15002 (2001).</li><li>Chen, Y., Saulnier, J. L., Yellen, G., Sabatini, B. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+PKA+activity+sensor+for+quantitative+analysis+of+endogenous+GPCR+signaling+via+2-photon+FRET-FLIM+imaging.">A PKA activity sensor for quantitative analysis of endogenous GPCR signaling via 2-photon FRET-FLIM imaging.</a> Frontiers in Pharmacology. 5 (April), 1-12 (2014).</li><li>Ma, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Highly+Sensitive+A-Kinase+Activity+Reporter+for+Imaging+Neuromodulatory+Events+in+Awake+Mice.">A Highly Sensitive A-Kinase Activity Reporter for Imaging Neuromodulatory Events in Awake Mice.</a> Neuron. 99 (4), 665-679 (2018).</li><li>Yellen, G., Mongeon, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+two-photon+imaging+of+fluorescent+biosensors.">Quantitative two-photon imaging of fluorescent biosensors.</a> Current Opinion in Chemical Biology. 27, 24-30 (2015).</li><li>Tang, S., Yasuda, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+ERK+and+PKA+Activation+in+Single+Dendritic+Spines+during+Structural+Plasticity.">Imaging ERK and PKA Activation in Single Dendritic Spines during Structural Plasticity.</a> Neuron. 93 (6), 1315-1324 (2017).</li><li>Tillo, S. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liberated+PKA+Catalytic+Subunits+Associate+with+the+Membrane+via+Myristoylation+to+Preferentially+Phosphorylate+Membrane+Substrates.">Liberated PKA Catalytic Subunits Associate with the Membrane via Myristoylation to Preferentially Phosphorylate Membrane Substrates.</a> Cell Reports. 19 (3), 617-629 (2017).</li><li>Yasuda, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+spatiotemporal+dynamics+of+neuronal+signaling+using+fluorescence+resonance+energy+transfer+and+fluorescence+lifetime+imaging+microscopy.">Imaging spatiotemporal dynamics of neuronal signaling using fluorescence resonance energy transfer and fluorescence lifetime imaging microscopy.</a> Current Opinion in Neurobiology. 16 (5), 551-561 (2006).</li><li>Theurkauf, W. E., Vallee, R. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+characterization+of+the+cAMP-dependent+protein+kinase+bound+to+microtubule-associated+protein+2.">Molecular characterization of the cAMP-dependent protein kinase bound to microtubule-associated protein 2.</a> Journal of Biological Chemistry. 257 (6), 3284-3290 (1982).</li><li>Zhong, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Subcellular+dynamics+of+type+II+PKA+in+neurons.">Subcellular dynamics of type II PKA in neurons.</a> Neuron. 62 (3), 363-374 (2009).</li><li>Borrell, V., Yoshimura, Y., Callaway, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+gene+delivery+to+telencephalic+inhibitory+neurons+by+directional+in+utero+electroporation.">Targeted gene delivery to telencephalic inhibitory neurons by directional in utero electroporation.</a> Journal of Neuroscience Methods. 143 (2), 151-158 (2005).</li><li>Baumgart, J., Baumgart, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cortex-,+Hippocampus-,+Thalamus-,+Hypothalamus-,+Lateral+Septal+Nucleus-+and+Striatum-specific+In+utero+Electroporation+in+the+C57BL/6+Mouse.">Cortex-, Hippocampus-, Thalamus-, Hypothalamus-, Lateral Septal Nucleus- and Striatum-specific In utero Electroporation in the C57BL/6 Mouse.</a> Journal of Visualized Experiments. (107), e53303 (2016).</li><li>Lowery, R. L., Majewska, A. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracranial+Injection+of+Adeno-associated+Viral+Vectors.">Intracranial Injection of Adeno-associated Viral Vectors.</a> Journal of Visualized Experiments. (45), 1-4 (2010).</li><li>Mostany, R., Portera-Cailliau, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Craniotomy+Surgery+Procedure+for+Chronic+Brain+Imaging.">A Craniotomy Surgery Procedure for Chronic Brain Imaging.</a> Journal of Visualized Experiments. (12), 18-19 (2008).</li><li>Holtmaat, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term,+high-resolution+imaging+in+the+mouse+neocortex+through+a+chronic+cranial+window.">Long-term, high-resolution imaging in the mouse neocortex through a chronic cranial window.</a> Nature Protocols. 4 (8), 1128-1144 (2009).</li><li>Murakoshi, H., Lee, S. J., Yasuda, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Highly+sensitive+and+quantitative+FRET-FLIM+imaging+in+single+dendritic+spines+using+improved+non-radiative+YFP.">Highly sensitive and quantitative FRET-FLIM imaging in single dendritic spines using improved non-radiative YFP.</a> Brain Cell Biology. 36 (1-4), 31-42 (2008).</li><li>Murakoshi, H., Shibata, A. C. E., Nakahata, Y., Nabekura, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+dark+green+fluorescent+protein+as+an+acceptor+for+measurement+of+F&#246;rster+resonance+energy+transfer.">A dark green fluorescent protein as an acceptor for measurement of F&#246;rster resonance energy transfer.</a> Scientific Reports. 5, 1-11 (2015).</li><li>Guo, Z. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Procedures+for+behavioral+experiments+in+head-fixed+mice.">Procedures for behavioral experiments in head-fixed mice.</a> PLoS ONE. 9 (2), (2014).</li><li>Yu, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+central+amygdala+controls+learning+in+the+lateral+amygdala.">The central amygdala controls learning in the lateral amygdala.</a> Nature Neuroscience. 20 (12), 1680-1685 (2017).</li><li>Harvey, C. D., Collman, F., Dombeck, D. A., Tank, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracellular+dynamics+of+hippocampal+place+cells+during+virtual+navigation.">Intracellular dynamics of hippocampal place cells during virtual navigation.</a> Nature. 461 (7266), 941-946 (2009).</li><li>Yasuda, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+intracellular+signaling+using+two-photon+fluorescent+lifetime+imaging+microscopy.">Imaging intracellular signaling using two-photon fluorescent lifetime imaging microscopy.</a> Cold Spring Harbor Protocols. 7 (11), 1121-1128 (2012).</li><li>Mehta, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-fluorophore+biosensors+for+sensitive+and+multiplexed+detection+of+signalling+activities.">Single-fluorophore biosensors for sensitive and multiplexed detection of signalling activities.</a> Nature Cell Biology. 20 (10), 1215-1225 (2018).</li></ol>

This protocol demonstrates the use of FRET-FLIM sensor tAKAR&#945; to visualize neuromodulation-triggered PKA activity in head-fixed behaving mice. This application is based on extensive testing and characterizations of tAKAR&#945; in vitro and in vivo to demonstrate that the FLIM signal obtained is relevant to physiological neuromodulatory events17. Here, one in vivo application, locomotion-induced PKA activity in the motor cortex, is used to describe the procedures for delivering the sensor to t...

Neuromodulation, also known as slow synaptic transmission, imposes strong control over brain function during different behavioral states, such as stress, arousal, attention, and locomotion1,2,3,4. Despite its importance, the study of when and where neuromodulatory events take place is still in its infancy. Neuromodulators, including acetylcholine, dopamine, noradrenaline, serotonin, and many neuropeptides, activate G protein-coupled receptors (GPCRs), which in turn trigger intracellular second messenger pathways with a wide window of timescales ranging from seconds to hours. While each neuromodulator triggers a distinct set of signaling events, the cAMP/protein kinase A (PKA) pathway is a common downstream pathway for many neuromodulators1,5. The cAMP/PKA pathway regulates neuronal excitability, synaptic transmission, and plasticity6,7,8,9, and therefore, tunes the neuronal network dynamics. Because different neurons or neuronal types express different types or levels of neuromodulator receptors10, the intracellular effects of the same extracellular neuromodulator may be heterogeneous across different neurons, and thus, have to be studied with cellular resolution. To date, it remains challenging to monitor neuromodulatory events in individual neurons in vivo during behavior.
To study the spatiotemporal dynamics of neuromodulation, a suitable recording modality is required. Microdialysis and fast-scan cyclic voltammetry are frequently used to study release of neuromodulators, but they lack the spatial resolution to monitor cellular events11,12. Analogous to calcium dynamics being used as a proxy for neuronal electrical activity in population imaging13, PKA imaging may be used to read out neuromodulatory events across a neuronal population at cellular resolution. The present protocol describes the use of an improved A-kinase activity reporter (AKAR) to monitor PKA activities in vivo during animal behavior. The method described here allows for simultaneous imaging of neuronal populations at subcellular resolution with a temporal resolution that tracks physiological neuromodulatory events.
AKARs are composed of a donor and an acceptor fluorescent proteins linked by a PKA phosphorylation substrate peptide and a forkhead-associated (FHA) domain that binds to the phosphorylated serine or threonine of the substrate14,15. Upon activation of the PKA pathway, the substrate peptide of AKAR is phosphorylated. As a result, the FHA domain binds to the phosphorylated substrate peptide, thereby bringing the two fluorophores into close proximity, referred to as the closed state of AKAR. The closed state of a phosphorylated AKAR results in increased F&#246;rster resonance energy transfer (FRET) between the donor and acceptor fluorophores. Since the proportion of phosphorylated AKARs is related to the level of PKA activity16, the amount of FRET in a biological sample can be used to quantify the level of PKA activity16,17,18,19,20.
Early versions of AKARs were primarily designed for two-color ratiometric imaging14. When imaging deeper into brain tissue, the ratiometric method suffers from signal distortion due to wavelength-dependent light scattering17,18,21. As discussed below, fluorescence lifetime imaging microscopy (FLIM) eliminates this problem because FLIM only measures photons emitted by the donor fluorophore18,21. As a result, FLIM quantification of FRET is not affected by the tissue-depth17. In addition, a &#8220;dark&#8221; (i.e., low quantum yield [QY]) variant of the acceptor fluorophore can be used. This frees a color channel to facilitate multiplexed measurement of orthogonal neuronal properties via simultaneous imaging of a second sensor or a morphological marker17,19,20.
FLIM imaging quantifies the time that a fluorophore spends in the excited state, i.e., the fluorescence lifetime18. The return of a fluorophore to the ground state, thus the end of the excited state, often concomitates with the emission of a photon. Although the emission of a photon for an individual excited molecule is stochastic, in a population the mean fluorescence lifetime is a characteristic of that particular fluorophore. When a pure population of fluorophores are excited simultaneously, the resulting fluorescence will follow a single exponential decay. The time constant of this exponential decay corresponds to the mean fluorescence lifetime, which typically ranges from one to four nanoseconds for fluorescent proteins. The return of an excited donor fluorophore to the ground state can also occur by FRET. In the presence of FRET, the fluorescence lifetime of the donor fluorophore is reduced. The unphosphorylated AKARs exhibit a relatively longer donor fluorescence lifetime. Upon phosphorylation by PKA, the sensor exhibits a shorter lifetime because the donor and acceptor fluorophores are brought near each other and FRET is increased. The quantification of the fluorescence lifetime in a population of AKARs therefore represents the level of PKA activity.
Early versions of AKARs have not been successfully used for in vivo imaging at single-cell resolution. This is mainly due to the low signal amplitude of the AKAR sensors to physiological activations17. Recently, by systematically comparing available AKAR sensors for two-photon fluorescence lifetime imaging microscopy (2pFLIM), a sensor called FLIM-AKAR was found to outperform alternative sensors. Furthermore, a series of FLIM-AKAR variants called targeted AKARs (tAKARs) were developed to visualize PKA activity at specific subcellular locations: microtubules (tAKAR&#945;), cytosol (tAKAR&#946;), actin (tAKAR&#948;), filamentous actin (tAKAR&#949;), membrane (tAKAR&#947;), and postsynaptic density (tAKAR&#950;). Among tAKARs, tAKAR&#945; increased the signal amplitude elicited by norepinephrine by 2.7-fold. This is consistent with the knowledge that the majority of PKA in neurons are anchored to microtubules at the resting state22,23. tAKAR&#945; was the best performer among existing AKARs for 2pFLIM. Furthermore, tAKAR&#945; detected physiologically-relevant PKA activity elicited by multiple neuromodulators, and the expression of tAKAR&#945; did not alter neuronal functions17.
Recently, tAKAR&#945; was successfully used to visualize PKA activities in head-fixed behaving mice17. It was shown that enforced locomotion triggered PKA activity in the soma of superficial layer neurons (layer 1 through 3, up to a depth of ~300 &#956;m from pia) in the motor, barrel, and visual cortices. The locomotion-triggered PKA activity was in part dependent on signaling via &#946;-adrenergic receptors and D1 dopamine receptors, but was not affected by a D2 dopamine receptor antagonist. This work illustrates the ability of tAKARs to track neuromodulation events in vivo using 2pFLIM.
In the current protocol, the entire method for PKA activity imaging in head-fixed awake mice during an enforced locomotion paradigm is described in six steps. First, the addition of 2pFLIM capabilities to a conventional two-photon microscope (Figure 1). Second, the construction of a motorized treadmill (Figure 2). Third, the expression of the tAKAR&#945; sensor in the mouse cortex by in utero electroporation (IUE) of DNA plasmids, or stereotaxic injection of adeno-associated virus (AAV). Excellent protocols for surgeries for IUE24,25 and stereotaxic injection of viral particles26 have been previously published. The key parameters we used are described below. Forth, the installation of a cranial window. Excellent protocols have been previously published for cranial window surgery27,28. Several steps that have been modified from the standard protocols are described. Fifth, performing in vivo 2pFLIM. Sixth, the analyses of 2pFLIM images (Figure 3 and Figure 4). This approach should be readily applicable to many other head-fixed behavioral paradigms and brain areas.

<table>
	<tbody>
		<tr>
			<td>0.2 &#956;m cellulose acetate syringe filter</td>
			<td>Nalgene</td>
			<td>190-2520</td>
			<td>Step 3.2.2.</td>
		</tr>
		<tr>
			<td>16x 0.8 NA water-immersion objective</td>
			<td>Nikon</td>
			<td>MRP07220</td>
			<td>Step 5.5.</td>
		</tr>
		<tr>
			<td>3-pin cable</td>
			<td>US digital</td>
			<td>CA-MIC3-SH-NC</td>
			<td>Step 2.5. To connect rotation sensor to the DAQ input of the microscope</td>
		</tr>
		<tr>
			<td>Aluminum bread board</td>
			<td>Thorlabs</td>
			<td>MB1012</td>
			<td>Step 2.5.</td>
		</tr>
		<tr>
			<td>AnimalTracker MATLAB software</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Step 2.5 and sections 5 - 6. Will be provided upon request to the lead author</td>
		</tr>
		<tr>
			<td>Band-pass barrier filter</td>
			<td>Chroma</td>
			<td>ET500-40m</td>
			<td>Step 1.4.</td>
		</tr>
		<tr>
			<td>Cage plate</td>
			<td>Thorlabs</td>
			<td>CP01</td>
			<td>Step 2.4. Used as mount for rotation sensor</td>
		</tr>
		<tr>
			<td>Carbon steel burrs for micro drill, 0.5 mm tip diameter</td>
			<td>FST</td>
			<td>19007-05</td>
			<td>Steps 3.2.3. and 4.4.</td>
		</tr>
		<tr>
			<td>Circular coverslip (5mm diameter)</td>
			<td>VWR</td>
			<td>101413-528</td>
			<td>Step 4.5.</td>
		</tr>
		<tr>
			<td>Custom-made injection needle holder</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Step 3.2.4. Technical details provided upon request to the lead author</td>
		</tr>
		<tr>
			<td>Dental acrylic</td>
			<td>Yates Motloid</td>
			<td>44114</td>
			<td>Steps 4.3. and 4.5.</td>
		</tr>
		<tr>
			<td>Dental drill; Microtorque ii</td>
			<td>Ram products</td>
			<td>66699</td>
			<td>Steps 3.2.3. and 4.4.</td>
		</tr>
		<tr>
			<td>Dowsil transparent polymer</td>
			<td>The Dow Chemical Company</td>
			<td>3-4680</td>
			<td>Step 4.5. Artificial dura</td>
		</tr>
		<tr>
			<td>Electroporation electrode</td>
			<td>Bex</td>
			<td>LF650P5</td>
			<td>Step 3.1.4.</td>
		</tr>
		<tr>
			<td>Electroporator</td>
			<td>Bex</td>
			<td>CUY21</td>
			<td>Step 3.1.4.</td>
		</tr>
		<tr>
			<td>Fast green FCF</td>
			<td>Sigma-aldrich</td>
			<td>F7258-25G</td>
			<td>Step 3.1.1.</td>
		</tr>
		<tr>
			<td>FLIMimage MATLAB software</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Section 5. Kindly provided by Dr. Ryohei Yasuda, Max Planck Florida</td>
		</tr>
		<tr>
			<td>FLIMview MATLAB software</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Sections 5. and 6. Will be provided upon request to the lead author</td>
		</tr>
		<tr>
			<td>Foam-compatible glue (Gorilla White Glue)</td>
			<td>Gorilla</td>
			<td>5201204</td>
			<td>Step 2.3.</td>
		</tr>
		<tr>
			<td>Headplate</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Step 4.3. Technical details provided upon request to the lead author</td>
		</tr>
		<tr>
			<td>Headplate holder</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Step 2.6. Technical details provided upon request lead author, used in combination with mounting post bracket and right-angled bracket</td>
		</tr>
		<tr>
			<td>Hydraulic micromanipulator</td>
			<td>Narishige</td>
			<td>MO-10</td>
			<td>Step 3.2.4.</td>
		</tr>
		<tr>
			<td>Krazy glue</td>
			<td>Krazy glue</td>
			<td>KG82648R</td>
			<td>Step 4.3. Cyanoacrylate-based glue</td>
		</tr>
		<tr>
			<td>Low-noise fast photomultiplier tube</td>
			<td>Hamamatsu</td>
			<td>H7422PA-40 or H10769PA-40</td>
			<td>Step 1.3.</td>
		</tr>
		<tr>
			<td>MATLAB 2012b</td>
			<td>Mathworks</td>
			<td>N/A</td>
			<td>Steps 2.6, and sections 5, and 6. Used to run microscope acquisition and data analysis software</td>
		</tr>
		<tr>
			<td>Motor</td>
			<td>Zhengke</td>
			<td>ZGA37RG</td>
			<td>Step 2.4.</td>
		</tr>
		<tr>
			<td>Motor speed controller</td>
			<td>Elenker</td>
			<td>EK-G00015A1-1</td>
			<td>Step 2.5.</td>
		</tr>
		<tr>
			<td>Motorized micromanipulator</td>
			<td>Sutter</td>
			<td>MP-285</td>
			<td>Step 3.2.4.</td>
		</tr>
		<tr>
			<td>Mounting base</td>
			<td>Thorlabs</td>
			<td>BA1S</td>
			<td>Step 2.5. Used for posts for motor and sensor in combination with PH4 and TR2</td>
		</tr>
		<tr>
			<td>Mounting post</td>
			<td>Thorlabs</td>
			<td>P14</td>
			<td>Step 2.6. Used for headplate holder post in combination with PB2</td>
		</tr>
		<tr>
			<td>Mounting post base</td>
			<td>Thorlabs</td>
			<td>PB2</td>
			<td>Step 2.6. Used for headplate holder post in combination with P14</td>
		</tr>
		<tr>
			<td>Mounting post bracket</td>
			<td>Thorlabs</td>
			<td>C1515</td>
			<td>Step 2.6. Used in combination with right-angle bracket and headplate holder</td>
		</tr>
		<tr>
			<td>Optical post</td>
			<td>Thorlabs</td>
			<td>TR2</td>
			<td>Step 2.5. Used for posts for motor and sensor in combination with BA1S and PH4</td>
		</tr>
		<tr>
			<td>Phosphate-buffered saline</td>
			<td>&#925;/&#913;</td>
			<td>&#925;/&#913;</td>
			<td>Step 3.2.2. Protocol: Cold Spring Harbor Protocols 2006, doi: 10.1101/pbd.rec8247</td>
		</tr>
		<tr>
			<td>Photodiode</td>
			<td>Thorlabs</td>
			<td>FDS010</td>
			<td>Step 1.2.</td>
		</tr>
		<tr>
			<td>Photon timing counting module</td>
			<td>Becker and Hickl</td>
			<td>SPC-150</td>
			<td>Step 1.1.</td>
		</tr>
		<tr>
			<td>Plasmid: tAKAR&#945; (CAG-tAKAR&#945;-WPRE)</td>
			<td>Addgene</td>
			<td>119913</td>
			<td>Step 3.1.3.</td>
		</tr>
		<tr>
			<td>Post holder</td>
			<td>Thorlabs</td>
			<td>PH4</td>
			<td>Step 2.5. Used for posts for motor and sensor in combination with BA1S and TR2</td>
		</tr>
		<tr>
			<td>Right-angle bracket</td>
			<td>Thorlabs</td>
			<td>AB90</td>
			<td>Step 2.6 Used in combination with mounting post bracket and headplate holder</td>
		</tr>
		<tr>
			<td>Rotation sensor</td>
			<td>US digital</td>
			<td>MA3-A10-250-N</td>
			<td>Step 2.4.</td>
		</tr>
		<tr>
			<td>Rubber mat</td>
			<td>Rubber-Cal</td>
			<td>B01DCR5LUG</td>
			<td>Step 2.1.</td>
		</tr>
		<tr>
			<td>Shaft coupling (1/4 inch x 1/4 inch)</td>
			<td>McMaster</td>
			<td>6208K433</td>
			<td>Steps 2.3. and 2.4.</td>
		</tr>
		<tr>
			<td>ScanImage 3.6</td>
			<td>Svoboda Lab/Vidrio Technology</td>
			<td>N/A</td>
			<td>Steps 5.9. and 6.1.</td>
		</tr>
		<tr>
			<td>Signal splitter</td>
			<td>Becker and Hickl</td>
			<td>HPM-CON-02</td>
			<td>Step 1.3.1.</td>
		</tr>
		<tr>
			<td>Stainless steel axle (diameter 1/4 inch, L = 12 inch)</td>
			<td>McMaster</td>
			<td>1327K66</td>
			<td>Step 2.3.</td>
		</tr>
		<tr>
			<td>Stereotaxic alignment systsem</td>
			<td>David kopf</td>
			<td>1900</td>
			<td>Steps 3.2. and 4.1. modified; Sutter micromanipulator, custom-made injection needle holder, hydraulic micromanipulator</td>
		</tr>
		<tr>
			<td>Two-photon microscope</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Section 5. Built based on Modular in vivo multiphoton microscopy system (MIMMS) from HHMI Janelia Research Campus (https://www.janelia.org/open-science/mimms)</td>
		</tr>
		<tr>
			<td>Vetbond tissue adhesive</td>
			<td>3M</td>
			<td>14006</td>
			<td>Step 3.2.6.</td>
		</tr>
		<tr>
			<td>Virus: tAKAR&#945; (AAV2/1 hSyn-tAKAR&#945;-WPRE)</td>
			<td>Addgene</td>
			<td>119921</td>
			<td>Step 3.2.2.</td>
		</tr>
		<tr>
			<td>White PE foam roller (8 x 12 inch)</td>
			<td>Fabrication enterprises INC.</td>
			<td>30-2261</td>
			<td>Step 2.1.1.</td>
		</tr>
		<tr>
			<td>White polystyrene fom ball halves</td>
			<td>GrahamSweet</td>
			<td>200mm diameter 2 hollow halves</td>
			<td>Step 2.1.1.</td>
		</tr>
		<tr>
			<td>Zipkicker</td>
			<td>PACER</td>
			<td>PT29</td>
			<td>Step 4.3. Hardening accelerator</td>
		</tr>
	</tbody>
</table>

visualizing protein kinase a activity in head-fixed behaving mice using in vivo two-photon fluorescence lifetime imaging microscopy

Neuromodulation exerts powerful control over brain function. Dysfunction of neuromodulatory systems results in neurological and psychiatric disorders. Despite their importance, technologies for tracking neuromodulatory events with cellular resolution are just beginning to emerge. Neuromodulators, such as dopamine, norepinephrine, acetylcholine, and serotonin, trigger intracellular signaling events via their respective G protein-coupled receptors to modulate neuronal excitability, synaptic communications, and other neuronal functions, thereby regulating information processing in the neuronal network. The above mentioned neuromodulators converge onto the cAMP/protein kinase A (PKA) pathway. Therefore, in vivo PKA imaging with single-cell resolution was developed as a readout for neuromodulatory events in a manner analogous to calcium imaging for neuronal electrical activities. Herein, a method is presented to visualize PKA activity at the level of individual neurons in the cortex of head-fixed behaving mice. To do so, an improved A-kinase activity reporter (AKAR), called tAKAR&#945;, is used, which is based on F&#246;rster resonance energy transfer (FRET). This genetically-encoded PKA sensor is introduced into the motor cortex via in utero electroporation (IUE) of DNA plasmids, or stereotaxic injection of adeno-associated virus (AAV). FRET changes are imaged using two-photon fluorescence lifetime imaging microscopy (2pFLIM), which offers advantages over ratiometric FRET measurements for quantifying FRET signal in light-scattering brain tissue. To study PKA activities during enforced locomotion, tAKAR&#945; is imaged through a chronic cranial window above the cortex of awake, head-fixed mice, which run or rest on a speed-controlled motorized treadmill. This imaging approach will be applicable to many other brain regions to study corresponding behavior-induced PKA activities and to other FLIM-based sensors for in vivo imaging.

FRET-FLIM sensors allow for the visualization of many different signaling pathways, including the cAMP/PKA pathway involved in neuromodulation. The current protocol utilizes the recently-developed tAKAR&#945; sensor in combination with 2pFLIM to visualize PKA activities in head-fixed behaving mice. Most existing two-photon microscopes can be upgraded with 2pFLIM capabilities by adding three to four components, as illustrated in Figure 1 (see also section 1). ...

Watch this Scientific Journal Video about Visualizing Protein Kinase A Activity In Head-fixed Behaving Mice Using In Vivo Two-photon Fluorescence Lifetime Imaging Microscopy at JoVE.com

Visualizing Protein Kinase A Activity In Head-fixed Behaving Mice Using In Vivo Two-photon Fluorescence Lifetime Imaging Microscopy

A procedure is presented to visualize protein kinase A activities in head-fixed, behaving mice. An improved A-kinase activity reporter, tAKAR&#945;, is expressed in cortical neurons and made accessible for imaging through a cranial window. Two-photon fluorescence lifetime imaging microscopy is used to visualize PKA activities in vivo during enforced locomotion.

Neuromodulation exerts powerful control over brain function. Dysfunction of neuromodulatory systems results in neurological and psychiatric disorders. ...

Our method utilizes a novel protein kinase A sensor called target A kinase activity reporter alpha, or tAKAR

Research

JoVE Journal

Neuroscience

In vivo Imaging of the Mouse Spinal Cord Using Two-photon Microscopy

In vivo Imaging of the Mouse Spinal Cord Using Two-photon Microscopy

In vivo imaging using two-photon microscopy 1 in mice that have been genetically engineered to express fluorescent proteins in specific cell types 2-3 has ...

Functional Neuroimaging Using Ultrasonic Blood-brain Barrier Disruption and Manganese-enhanced MRI

Although mice are the dominant model system for studying the genetic and molecular underpinnings of neuroscience, functional neuroimaging in mice remains ...

In Vivo Two-photon Imaging Of Experience-dependent Molecular Changes In Cortical Neurons

In Vivo Two-photon Imaging Of Experience-dependent Molecular Changes In Cortical Neurons

The brain's ability to change in response to experience is essential for healthy brain function, and abnormalities in this process contribute to a variety ...

In Vivo Two-Photon Microscopy of Single Nerve Endings in Skin

In Vivo Two-Photon Microscopy of Single Nerve Endings in Skin

Nerve endings in skin are involved in physiological processes such as sensing1 as well as in pathological processes such as neuropathic pain2. Their ...

Two-Photon in vivo Imaging of Dendritic Spines in the Mouse Cortex Using a Thinned-skull Preparation

Two-Photon in vivo Imaging of Dendritic Spines in the Mouse Cortex Using a Thinned-skull Preparation

In the mammalian cortex, neurons form extremely complicated networks and exchange information at synapses. Changes in synaptic strength, as well as ...

In Vivo Two-photon Imaging of Cortical Neurons in Neonatal Mice

In Vivo Two-photon Imaging of Cortical Neurons in Neonatal Mice

Two-photon imaging is a powerful tool for the in vivo analysis of neuronal circuits in the mammalian brain. However, a limited number of in vivo imaging ...

In Vivo Three-Dimensional Two-Photon Microscopy to Study Conducted Vascular Responses by Local ATP Ejection Using a Glass Micro-Pipette

Maintenance of normal brain function requires a sufficient and efficient supply of oxygen and nutrition by a complex network of vessels. However, the ...

Transpupillary Two-Photon In Vivo Imaging of the Mouse Retina

The retina transforms light signals from the environment into electrical signals that are propagated to the brain. Diseases of the retina are prevalent ...