Laura M. Bohn, Ph.D.

Associate Professor
Departments of Pharmacology and Psychiatry
OSU Program in Pharmacogenomics
798 Biomedical Research Tower - Box 7
460 W. 12th Avenue
Columbus, OH 43210
Phone: (614) 292-1303
Fax: (614) 292-7544
Email: Laura.Bohn@osumc.edu

Curriculum Vitae

Research Synopsis

Research Summary Statement:
Our laboratory is committed to understanding how the molecular regulation of G protein coupled receptors (GPCR) can translate to overall drug responsiveness in vivo. We focus on the regulation of the mu opioid receptor and this can determine behavioral and physiological responses to the opiate narcotic drugs, such as morphine.

Morphine, and the related opiates fentanyl, methadone, and oxycodone are potent pain relievers and mediate their analgesic effects primarily by activation of the mu opioid receptor. However, these drugs produce many unwanted drug effects as well, including constipation and respiratory suppression. Long-term use of opiates can produce drug tolerance, physical dependence and, in some cases, drug addiction.

Our focus has been to determine how GPCR regulatory mechanisms could play a role in determining the variety of biological responses a single drug can elicit. For example, we have asked: If morphine activates the mu opioid receptor, are the signal transduction pathways that determine opiate-induced pain relief the same as those that determine opiate-induced constipation? Our second question is: If the signaling if different for these two distinct biological responses could the variation be delineated a the point of receptor regulation?

To address these questions we have employed an extensive array of physiological and behavioral measurements in genetically modified mouse models. Our mouse models lack certain regulatory components that are involved in GPCR desensitization and GPCR signaling. A model of GPCR regulation is shown in Figure 1. Upon activation, the receptor signals by coupling to a G protein and this activates a downstream signaling cascade which ultimately results in the biological response. The receptor can then be turned off by GPCR kinase (GRK)-mediated phosphorylation followed by the subsequent binding of Beta-arrestin (ßarrestin) proteins. This process is a fundamentally conserved process for desensitizing most GPCRs; however, some GPCRs can signal via other pathways upon binding ßarrestin, independently of the G protein interaction.

We want to know how the GRK and the ßarrestin interactions with the receptor can determine the degree of biological response mediated by the drug actions at the receptor. We use mice that have genetic deletions of GRKs (GRK3, GRK4, GRK5, and GRK6; heterozygotes for GRK2) and ßarrestin-2. In earlier work performed at Duke University under the training of Dr. Marc Caron and in collaboration with Dr Robert Lefkowitz, we found that mice lacking ßarrestin2 have greater analgesic responses to morphine with very little opiate-tolerance. We have expanded these studies and have recently found that while the morphine-induced pain relief is greater; these mice experience less morphine-induced constipation and very little respiratory suppression.

We are currently trying to understand the role of ßarrestin2 in mediating morphine-induced constipation and respiratory suppression. One of our major goals is to exploit the GPCR regulatory components for the development of novel therapeutics that may provide greater pain relief with limited narcotic side effects.

Current Laboratory Projects
There are FOUR major areas in which we are concentrating our efforts:

Molecular biology of opioid receptor regulation- NIDA R01 DA 18860-
This research focuses on the molecular components of the mu opioid receptor signaling complex that dictate the receptor's responsiveness. We study the organization of this complex in the absence of certain key regulatory protein components (GRKs and arrestins) in both cellular culture systems and in animal tissues. The goal is to learn the consequence of receptor regulation as it pertains to drug responsiveness in vivo.

Opioid-induced gastrointestinal constipation and respiratory suppression. NIDA K01 DA14600, NIDA R01 DA 18860
Opioid receptor activation mediates morphine-induced constipation and respiratory suppression and we are studying how receptor regulation can determine the extent of these effects. This line of work benefits greatly by collaborations with Dr. Jack Wood in the Department of Physiology and Cell Biology.

Drug development- Novel approaches for developing opiate ligands based on receptor regulation.
We have been working with Dr. Tom Prisinzano, a medicinal chemist from the University of Iowa, to study novel plant products that activate the opioid receptors. It is hopeful that our studies will allow us to take advantage of differences in receptor regulation produced by certain agonists to fine-tune opioid-directed pharmacology to enhance analgesia and limit side effects.

Pharmacogenomics of opiate-induced constipation. Pilot studies.
We have a developing collaboration with Dr. Yun Xia in Anesthesiology and Dr. Sadee in the Pharmacogenomics group to search for a genetic marker of opiate induced constipation. We will be collecting patient blood from hip and knee replacement surgeries and screening blood samples for single nucleotide polymorphisms in genes implicated in gastrointestinal responses to opiates. We hope to find single nucleotide polymorphisms in certain genes that may provide a marker of which patients may be particularly sensitive to opioid-induced constipation. This approach may also shed light on the molecular mechanisms by which opioids affect gastrointestinal function


Publications

Schmid CL, Raehal KM, Bohn LM. (2008) Agonist-directed signaling of the serotonin 2A receptor depends on beta-arrestin-2 interactions in vivo.  Proc Natl Acad Sci USA 105:1079-1084 Appears with Commentary.

Tidgewell K, Groer CE, Harding WW, Lozama A, Schmidt M, Hiemstra J, Dersch CM, Rothman RB, Bohn LM, Prisinzano TE. (2008) Mu opioids derived from Salvinorin A with altered receptor regulation.  J Med Chem 51(8):2421-2431.

Gupta A, Rozenfeld R, Gomes I, Raehal K, Decaillot FM, Bohn LM, Devi LA. (2008) Post-activation mediated changes in opioid receptors detected by N-terminal antibodies.  J Biol Chem 283:10735-10744. 

Bohn LM. (2007) Constitutive trafficking - more than just running in circles? (Perspective) Mol Pharm 71:957-958.

Groer CE, Tidgewell K, Moyer RA, Harding WW, Rothman RB, Prisinzano TE, Bohn LM. (2007) An opioid agonist that does not induce mu opioid receptor - arrestin interactions or receptor internalization.  Mol Pharm 71:549-557.

Xu H, Partill JS, Wang X, Rutherford JM, Harding WW, Prisinzano TE, Bohn LM, Rothman RB.  (2007) A comparison of noninternalizing (herkinorin) and internalizing (DAMGO) mu-opioid agonists on cellular markers related to opioid tolerance and dependence.  Synapse 61:166-175.

Bohn LM, Raehal K. (2006) Opioid receptor signaling: Relevance for gastrointestinal therapy.  Curr Opin Pharmacol 6:559-563.

Sadee W, Bohn L. (2006) How specific are "Target-specific" drugs?  Celecoxib as a case in point.  Molec Interventions 6:196-198.

Raehal KM, Walker JKL, Bohn LM. (2005) Morphine side-effects in b-arrestin-2 knockout mice.  J Pharmacol Exp Ther 314:1195-1201.

Raehal KM, Bohn LM.  (2005) Mu opioid receptor regulation and opiate responsiveness.  AAPS Journal - special review issue: Drug Addiction from basic research to therapies AAPS Journal 07:E587-E591.

Wang D, Sun X, Bohn LM, Sadee W. (2005) Opioid receptor homo- and hetero-dimerization in living cells by quantitiative bioluminescence resonance energy transfer.  Mol Pharm 67:2173-2184.

Medvedev IO, Gainetidinov RR, Sotnikova TD, Bohn LM, Caron MG, Dykstra LA. (2005) Characterization of conditioned place preference to cocaine in congenic dopamine transporter knockout mice.  Psychopharmacology 180:408-413.

Bohn LM, Dykstra LA, Barak LS, Lefkowitz RJ, Caron MG. (2004) Relative opioid efficacy is determined by the complements of the G protein coupled receptor desensitization machinery.  Mol Pharm 66:106-112.

Gainetdinov RR, Premont RT, Bohn LM, Lefkowitz RJ, Caron MG. (2004) Desensitization of G protein-coupled receptors and neuronal functions.  Ann Reviews Neurosci 27:107-144.

Bohn LM, Gainetdinov RR, Caron MG. (2004) GRK/ barrestin systems and drugs of abuse: Psychostimulant and opiate studies in knockout mice.  (Invited Review) NeuroMolec Med 5:41-50.

Bohn, L.M., Gainetdinov, R.R., Sotnikova, T., Dykstra, L.A., Lefkowitz, R.J., and Caron, M.G. (2003) Enhanced Rewarding Properties of Morphine but not Cocaine in barrestin-2 Knockout Mice.  J. Neurosci 23(32): 10265-10273.

Gainetdinov, R.R., Bohn, L.M., Sotnikova, T.D., Cyr, M., Laakso A., Macrae, A.D, Torres, G.E., Kim, K.M, Lefkowitz, R.J., Caron, M.G. and Premont, R.T. (2003) Dopaminergic Supersensitivity in G Protein-Coupled Receptor Kinase 6 - Deficient Mice. Neuron 38:291-303.

Bohn, L.M., Lefkowitz, R.J. and Caron, M.G. (2002) Differential Mechanisms of Morphine Antinociceptive Tolerance Revealed in barrestin-2 Knockout Mice. J. Neurosci. 22:0494-10500.

Bohn, L.M., Gainetdinov, R.R., Lin, F.T., Lefkowitz, R.J. and Caron, M.G. (2000) Mu-opioid receptor desensitization by beta-arrestin-2 determines morphine tolerance but not dependence. Nature 408:720-723.

Bohn, L.M., Xu, F., Gainetdinov, R.R. and Caron, M.G. (2000) Potentiated opioid analgesia in norepinephrine transporter knock-out mice. J. Neurosci. 20:9040-9045.

Xu, F., Gainetdinov, R.R., Wetsel, W.C., Jones, S.R., Bohn, L.M., Miller, G.W., Wang, Y.M. and Caron, M.G. (2000) Mice lacking the norepinephrine transporter are supersensitive to psychostimulants. Nature Neurosci. 3:465-471.

Bohn, L.M., Lefkowitz, R.J., Gainetdinov, R.R., Peppel, K., Caron, M.G. and Lin, F.T. (1999) Enhanced morphine analgesia in mice lacking beta-arrestin 2. Science 286:2495-2498.

Bohn, L.M.^* Gainetdinov, R.R.^*, Walker, J.K., Laporte, S.A., Macrae, A.D., Caron, M.G., Lefkowitz, R.J. and Premont, R.T. (1999) Muscarinic supersensitivity and impaired receptor desensitization in G protein-coupled receptor kinase 5-deficient mice. Neuron 24:1029-1036 *equal contribution.