A calcium/calcineurin signaling cascade regulates neuronal cannabinoid receptors

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DESCRIPTION (provided by applicant): This project will test the hypothesis that a Ca2+ and calmodulin-dependent phosphatase, calcineurin, regulates the transcription of type 1 cannabinoid receptors (CB1) in neurons. CB1 is the primary target for plant and endogenous cannabinoids in mammalian brain. CB1 agonists are being studied as treatments for acute and chronic neuronal degeneration, whereas antagonists appear promising to treat addictions to nicotine, alcohol, cocaine, heroin, morphine, as well as obesity. Thus there is intense interest in defining the physiological, therapeutic and pathological effects of CB1 signaling. Currently, we understand a great deal about the behavioral and pharmacological effects of cannabinoids, and CB1 structure, function and signaling. However, we know almost nothing about factors regulating the transcription CB1. My laboratory has demonstrated that a depolarization and Ca2+-dependent signaling cascade regulates expression of CB1 mRNA and protein in primary cultures of granule neurons from rodent cerebellar cortex. Our preliminary data point to primary role for calcineurin (CaN) in this process. We propose 2 specific aims. AIM 1. To test the hypothesis that Ca2+-dependent activation of CaN represses the transcription of CB1 mRNA in granule neurons from rodent cerebellar cortex. We will definitively determine the role of CaN and its downstream effector, NFAT, in CB1 transcription using a combination of biochemical, immunochemical, molecular biological and microscopic techniques. AIM 2. To test the hypothesis that CaN-dependent repression of the CB1 gene is via a promoter region containing multiple NFAT responsive sites and lying in the 5' untranslated region. PUBLIC HEALTH RELEVANCE: Cannabis is the most abused illegal drug in adolescents and chronic consumption predisposes young abusers to more serious addictions. Cannabinoid receptor (CB1) antagonists are being tested as treatments for a variety of drug addictions, including nicotine, alcohol, cocaine, and opiates. Thus, there is intense interest in defining the physiological, therapeutic and pathological effects of CB1 signaling. This project will test the hypothesis that a Ca2+ and calmodulin-dependent phosphatase, calcineurin, regulates the transcription of type 1 cannabinoid receptors (CB1) in cultured neurons from the cerebellum. Our results in cultured neurons will serve as a basis for future functional studies in animals.