Rainer Reinscheid, PhD - US grants

DESCRIPTION (provided by applicant): G protein-coupled receptors (GPCRs) form the largest gene family in the human genome and are the most successful biochemical targets of pharmaceutical drugs. For about 140 GPCRs the natural ligands are unknown and they are thus called "orphan" receptors. Identification of these natural ligands is the crucial step to start studying their function and holds the potential for development of novel therapeutic drugs. We have developed a strategy to isolate such natural ligands by expressing the cloned receptors in suitable cell lines and monitoring activation of the receptors after adding fractions of tissue extracts. This strategy will ultimately allow us to purify the active molecules and determine their structure. In this application, we propose to isolate, identify and characterize pharmacologically the natural ligands of two such orphan GPCRs which are structurally related to endothelin receptors. Following the isolation of the natural ligands, we will characterize their pharmacological effects, study their biosynthesis by cloning the precursor proteins that encode them and analyze their distribution in the brain and peripheral organs. These receptors do not bind the known endothelin peptides but have been conserved during evolution across various species, showing that they must serve an important function. Both receptors are highly expressed in the brain and one of them was recently identified as a substrate for parkin, the gene product which is mutated in an autosomal recessive form of Parkinson's disease. Identification of the natural ligands will enable us to study the physiological functions of these two orphan GPCRs under normal and pathological conditions.

DESCRIPTION (provided by applicant): We have identified a novel neuropeptide, termed NPS, that is predominantly expressed in a cluster of previously unidentified neurons in close vicinity to the noradrenergic locus coeruleus. The locus coeruleus is a brainstem structure involved in regulating sleep-wake cycles, arousal, attention and stress. Dysfunction of this brain area has been implicated in a number of disorders such as insomnia, narcolepsy and attention deficit hyperactivity disorder. More widespread expression of the NPS receptor is found in several brain areas, including cortex, thalamus and hypothalamus. Our preliminary results show that NPS promotes arousal when injected in mice. NPS also induces wakefulness while suppressing REM sleep and deep sleep in rats. Furthermore, NPS appears to produce anxiolytic-like effects. Therefore, NPS could represent a new transmitter system involved in neuronal modulation of vigilance and stress. We propose to study in detail the anatomical distribution of this novel transmitter system and the pharmacology of its receptor. We will determine the coexistence of NPS with known transmitters and its effect on the release of other transmitters involved in arousal. Furthermore, we will investigate its role in sleep and wakefulness and a possible involvement in attention and anxiety. Since no antagonist to the NPS receptor is currently available, we propose a genetic approach to delete the NPS gene in mice and study the behavioral consequences of NPS deficiency. Together, these studies will lay the foundation for understanding the physiological functions of NPS which may also yield new insights into human psychiatric disorders. A mutation in the human NPS receptor was recently found to be associated with increased risk of asthma. We will study the pharmacology of the mutant receptor isoforms which may help to understand the physiological consequences of the mutation in human airway tissue.

DESCRIPTION (provided by applicant): As our society grows progressively older, age-related memory loss is posing an increasing problem, not only for quality of life of elderly people, but also for relatives, caregivers and the health care system in general. While the biological mechanisms of cognitive decline are poorly understood, both environmental and genetic factors are known to contribute. It is therefore important to understand how the brain and one of its major functions, i.e. memory, age during human life and identify specific biochemical targets and mechanisms that are associated with age-related impairment of learning and memory. Neuropeptide S (NPS) is a recently identified transmitter in the brain. NPS produces arousal and wakefulness and reduces behavioral signs of anxiety in rodents. Recent studies in our lab demonstrate that NPS can potently enhance learning and memory. A naturally occurring mutation in the human NPS receptor gene changes the sensitivity of the receptor significantly, which may have a behavioral impact on memory. These evidences make the NPS system an interesting candidate for development of new drugs with pro-cognitive effects that can help to alleviate symptoms of age-related memory decline. The first part of this proposal will test the effects of NPS on memory formation in very old mice, which are an established model to study age-related memory deficits. Since NPS can enhance memory formation in young mice, we expect to see similar effects in aged mice. Second, we will analyze the pharmacology and signal transduction of a number of naturally occurring variants of the human NPS receptor in order to identify particular versions of the gene that respond differently to activation by NPS. Since these mutations in the NPS receptor occur with high frequency in the human population, we will next address the question whether different forms of the receptor may contribute to age-related cognitive decline or exert a protective function. For this part of the study, we will analyze NPS receptor genotypes in participants of a very large geriatric study: the "90+ Study". We will specifically test whether more sensitive or attenuated NPS receptor gene variants are associated with memory performance, onset and progression of memory decline, or other mental capabilities in these oldest-old members of our society (over 90 years old at time of enrollment). Together, we intend to validate the NPS system as a novel drug target for treatment of age-related cognitive decline. Results from these studies will greatly advance our knowledge about neural mechanisms underlying cognitive aging. PUBLIC HEALTH RELEVANCE: Age-related cognitive decline is a tremendous burden for affected individuals, society, and the health care system, while the underlying neurobiological mechanisms remain largely unknown. In the current proposal, we plan to use translational animal models, in vitro pharmacology, and human molecular genetic tools to explore the potential of the Neuropeptide S system as an emerging target for treatment of age-related cognitive decline. Analyzing naturally occurring polymorphisms in the human NPS receptor gene that are associated with cognitive performance may have practical implications to assess individual risk for developing cognitive decline that would warrant early prevention. The study is both exploratory and translational and could lead to a better understanding of neural mechanisms underlying cognitive aging.