Dopamine receptor study offers hope for improved treatments with fewer side effects
New York, NY (August 31, 2018)–New work from researchers at Columbia University Vagelos College of Physicians and Surgeons sheds light on how dopamine receptors signal within cells, opening the door for more targeted–and more tolerable–therapeutics to treat an array of neuropsychiatric disorders.
The study's findings have been published in the journal Molecular Psychiatry.
The central nervous system's dopamine receptors play a critical role in a variety of neural processes, including motor control, learning and memory, and reward. The focus of this study, the dopamine D2 receptor (D2R), is an important target in the treatment of disorders such as schizophrenia and Parkinson's disease. Drugs used to treat these conditions either block or activate these receptors to address dysfunctional receptor signaling. Antipsychotic drugs that target D2Rs, however, can have many unpleasant side effects, including weight gain, involuntary movements, and decreased motivation.
Scientists know that D2Rs send signals through two main pathways within cells–either by activating G proteins or by G-protein independent arrestin-signaling. Recent studies of opioid receptors–targeted for pain relief–suggest that it may be possible to maintain the therapeutic effects while avoiding negative side effects, such as respiratory depression, by selectively activating the G protein signaling pathway. "We asked whether these signaling pathways might also lead to different behavioral effects at the D2R, and whether this might provide a new approach to improved antipsychotic drugs with fewer side effects," says Dr. Jonathan Javitch, Lieber Professor of Experimental Therapeutics in Psychiatry and professor of pharmacology at Columbia University Vagelos College of Physicians and Surgeons.
In order to determine whether the two pathways regulate different behaviors, the researchers examined mice that were engineered to carry a mutated D2R that only facilitated the arrestin pathway. In these mice, the mutant dopamine receptor restored motor function just as the non-mutant form of the receptor does, indicating that arrestin recruitment can enhance motor function on its own. In contrast, motivation was enhanced only by wild-type D2R. "This finding was quite exciting as it indicates that the activational component of motivation that enhances locomotion is regulated by a different intracellular mechanism than the reward driven directional component," says Dr. Christoph Kellendonk, associate professor of pharmacology (in Psychiatry) at Columbia University Vagelos College of Physicians and Surgeons. "For the former, arrestin signaling is sufficient whereas the latter requires activation of G-proteins."
"These results offer the exciting possibility that therapeutic approaches targeting specific D2R-mediated signaling pathways could not only treat psychosis, but also avoid some of the adverse side effects experienced by patients taking the existing, less targeted medications," says Javitch.
The study is titled "Arrestin recruitment to dopamine D2 receptor mediates locomotion but not incentive motivation."
The other authors of this paper are Prashant Donthamsetti, PhD (CUIMC), Eduardo F. Gallo, PhD (CUIMC), David C. Buck (VA Portland Health Care System and Oregon Health & Science University), Edward L. Stahl (Scripps Research), Ying Zhu (CUIMC), J. Robert Lane (CUIMC), Laura M. Bohn (Scripps Research), and Kim A. Neve (VA Portland Health Care System and Oregon Health & Science University).
The study was supported by grants from the National Institutes of Health DA044696, MH093672, DA009158, MH54137, DA022413, MH107648, Merit Review Award BX003279 from the US Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Biomedical Laboratory Research, and Development, and by the Lieber Center for Schizophrenia Research, and by the Hope for Depression Research Foundation.
The authors report no financial or other conflicts of interest.
Columbia University Department of Psychiatry
Columbia Psychiatry is among the top ranked psychiatry departments in the nation and has contributed greatly to the understanding and treatment of brain disorders. Co-located at the New York State Psychiatric Institute on the NewYork-Presbyterian Hospital/Columbia University Irving Medical Center campus in Washington Heights, the department enjoys a rich and productive collaborative relationship with physicians in various disciplines at the Columbia University Vagelos College of Physicians and Surgeons. Columbia Psychiatry is home to distinguished clinicians and researchers noted for their clinical and research advances in the diagnosis and treatment of depression, suicide, schizophrenia, bipolar and anxiety disorders, eating disorders, substance use disorders, and childhood psychiatric disorders.
Columbia University Irving Medical Center provides international leadership in basic, preclinical, and clinical research; medical and health sciences education; and patient care. The medical center trains future leaders and includes the dedicated work of many physicians, scientists, public health professionals, dentists, and nurses at the Vagelos College of Physicians and Surgeons, the Mailman School of Public Health, the College of Dental Medicine, the School of Nursing, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. Columbia University Irving Medical Center is home to the largest medical research enterprise in New York City and State and one of the largest faculty medical practices in the Northeast. For more information, visit cumc.columbia.edu or columbiadoctors.org.