Sangwon Kim - US grants

[unreadable] DESCRIPTION (provided by applicant): Schizophrenia is commonly recognized by its psychotic symptoms such as delusions and hallucinations, which often leads to social and functional impairment. Glutamate-NMDA neurotransmission has been strongly implicated in the genesis of schizophrenia. Recently, we have discovered that Dexrasl was found originally to bind to the Peripheral Benzodiazepine Receptor Associated Protein (PAP7), a protein of unknown function which binds to cyclic AMP dependent protein kinase and the peripheral benzodiazepine receptor. PAP7 also binds to the Divalent Metal Transporter (DMT1), an iron import channel. We have identified a novel signaling cascade in neurons whereby stimulation of glutamate-NMDA receptors activates nNOS, leading to S-nitrosylation of Dexrasl and a physiological increase in iron uptake through DMT1. In this proposal we plan to continue extensive investigations to further define the role of Dexrasl on brain iron homeostasis and study its implications in pathophysiological conditions and mental illness. We will employ both cellular and animal models to dissect out the detailed signaling cascades and the role of individual components. We will also extend our study to the Dexrasl homologous protein, Rhes (Ras Homologous Enriched in Striatum) which is enriched in striatum and up-regulated by thyroid hormone, which is known to influence the development and the function of CMS. We will employ molecular and cellular approaches to characterize the functions and roles of Rhes in the brain. The findings from our research will improve our understandings of CNS iron homeostasis and possibly lead to development of new strategies for treatment of patients with neurological dysfunctions and mental illness. [unreadable] [unreadable] [unreadable]

Schizophrenia is commonly recognized by its psychotic symptoms such as delusions and hallucinations, which often leads to social and functional impairment. Glutamate-NMDA neurotransmission has been strongly implicated in the genesis of schizophrenia. Recently, we have discovered that Dexrasl was found originally to bind to the Peripheral Benzodiazepine Receptor Associated Protein (PAP7), a protein of unknown function which binds to cyclic AMP dependent protein kinase and the peripheral benzodiazepine receptor. PAP7 also binds to the Divalent Metal Transporter (DMT1), an iron import channel. We have identified a novel signaling cascade in neurons whereby stimulation of glutamate-NMDA receptors activates nNOS, leading to S-nitrosylation of Dexrasl and a physiological increase in iron uptake through DMT1. In this proposal we plan to continue extensive investigations to further define the role of Dexrasl on brain iron homeostasis and study its implications in pathophysiological conditions and mental illness. We will employ both cellular and animal models to dissect out the detailed signaling cascades and the role of individual components. We will also extend our study to the Dexrasl homologous protein, Rhes (Ras Homologous Enriched in Striatum) which is enriched in striatum and up-regulated by thyroid hormone, which is known to influence the development and the function of CMS. We will employ molecular and cellular approaches to characterize the functions and roles of Rhes in the brain. The findings from our research will improve our understandings of CNS iron homeostasis and possibly lead to development of new strategies for treatment of patients with neurological dysfunctions and mental illness.

DESCRIPTION (provided by applicant): Antipsychotic drugs relieve symptoms of schizophrenia as well as manic-depressive illness. The first generation drugs, however, were ineffective in many patients and failed to alleviate features such as emotional withdrawal reflecting the negative symptoms of schizophrenia. A new generation, atypical antipsychotic drugs (AAPDs), help non-responders, ameliorate negative symptoms, have fewer side-effects and so have emerged as some of the most widely used of all drugs. However, their use has been hampered by adverse metabolic side effects including severe weight gain elicited by some of those agents, sometimes doubling patient weights and with no clear cut explanation. We have found that the drugs that cause weight gain potently and selectively activate the enzyme AMP-kinase (AMPK) in the hypothalamic area of the brain in discrete nuclei which regulate eating behavior. This activation occurs secondary to the drugs' blocking the histamine H1 receptor for histamine, which, besides its roles in allergy, is a neurotransmitter in the feeding centers of the hypothalamus. Our preliminary studies indicate that inositol polyphosphate multikinase (IPMK), which utilizes one of the downstream molecules (inositol 1,4,5-triphosphate) produced upon histamine H1 receptor activation, is required for AMPK regulation. Also, the expression level of IPMK in the hypothalamus is modulated by energy balance. These intriguing observations led us to hypothesize that IPMK is the main mediator between histamine H1 receptor and AMPK regulation in the hypothalamus. Hence, in this proposal we will investigate the novel role of IPMK on AMPK modulation and energy homeostasis. We will characterize the molecular mechanism by which IPMK regulates AMPK modulation in the hypothalamus (Aim1). Moreover, we will investigate the posttranslational modification of IPMK, which can lead to a change of eating behavior via AMPK modulation (Aim 2). Finally, the contribution of IPMK in energy homeostasis and AAPDs-mediated weight gain in animal model will be investigated utilizing ipmkloxP/loxP mice (Aim3). Together, these studies will unveil not only the molecular basis of AAPD-mediated weight gain but also a novel signaling mechanism by which appetite is regulated in the hypothalamus. Accordingly, more efficient and effective strategies could be developed to manage the patients experiencing APPD-related metabolic side effects.

? DESCRIPTION (provided by applicant): Smoking is the largest preventable cause of death and disease in the United States, with about 46 million U.S. adults currently smoking. Though there are medications approved by the FDA to treat nicotine addiction, they are minimally effective and at least 80% of those seeking treatment relapse within one year. Rewarding aspects of nicotine as well as aversive properties, such as those associated with abstinence, may act synergistically to direct the behavior of smokers toward tobacco consumption. Symptoms associated with nicotine withdrawal include increased anxiety and cognitive deficits. To date, few studies have investigated the molecular and cellular changes that occur during chronic exposure to nicotine and how these molecules are altered during withdrawal. Previously, we and others have established that the transcription factor CREB is a central mediator of addictive behaviors. We now made the discovery that one of the targets of CREB in the brain is the LKB1/AMPK pathway. AMP-activated kinase (AMPK) is an evolutionarily conserved serine/threonine kinase that has a major role in the periphery in sensing cellular energy status and regulating fuel availability. Its role in the brain is virtually unknown. Preliminary data indicates that the AMPK pathway and its downstream targets are misregulated during nicotine exposure and withdrawal. The proposed mechanistic and translational studies will determine the functional role of this protein on nicotine reward behavior and withdrawal symptoms and will afford the development of novel or repurposed pharmacological treatments designed to promote smoking cessation.

PROJECT SUMMARY/ABSTRACT (30 LINES MAX) The human gut is a unique site with enormous burden of foreign antigens from diet and microbes all the time. Among those antigens, the immune system should actively suppress inflammatory responses against harmless ones while mounting effector response to eliminate pathogens in case of their invasion. Imbalance of this pro- and anti-inflammatory responses in the intestine can lead to inflammatory bowel disease (IBD). Different subsets of T cells in the intestine can mediate both local pathogenesis and suppression of inflammation, and T cells use distinct strategies for homing to the small and the large intestine. While these homing processes have been considered as attractive therapeutic targets for IBD, ligand-receptor pairs specific for the large intestine are relatively unexplored. Our long-term goal is to characterize how T cell recruitment to the large intestine is accomplished. Our central hypothesis is that novel host protein C10orf99 is the ligand for homing receptors, such as GPR15, for the large intestine. Guided by strong preliminary data, we have generated novel mouse models that will enable us to test this hypothesis. We propose to pursue the following three aims: (1) To characterize the role of C10orf99 in T cell homing to the large intestine, we will test its role during physiological T cell activation and migration to the large intestine upon encountering microbial antigens in chronological order. To determine its relevance to colitis development, we will: (2) Examine the role of C10orf99 in the mouse model of colitis; (3) Characterize the expression pattern of C10orf99 within the large intestine and also during colonic inflammation in both mouse and human. Our findings will significantly advance understanding of T cell homing to the large intestine and will help to develop novel therapeutic strategies to treat inflammatory bowel disease.

PROJECT SUMMARY/ABSTRACT It is critical that the host immune system does not mount outright inflammatory responses against foreign antigens abundant in the lumen of the intestine (such as dietary antigens exposed through the small intestine mucosa and microbial antigens coming predominantly from the lumen of the large intestine). Failure in this process leads to a significant health threat to the host as evidenced by prevalence of celiac disease and inflammatory bowel diseases. Regulatory T cells (Tregs) have evolved to play a critical role to ensure this tolerance. Dietary antigens are known to generate inducible Tregs (iTregs) and systemic tolerance against those antigens is achieved by circulation of these iTregs throughout the body (oral tolerance). In contrast, it may not be beneficial for the host to establish systemic, Treg-mediated tolerance against antigens from the large intestine since self-replicating microbes, the primary source of antigens in the large intestine, can easily escape and invade tissues outside of the intestine. Our long-term goal is to characterize how Treg-mediated tolerance against antigens from the large intestine is accomplished. Our central hypotheses are that activation of the aryl hydrocarbon receptor (AHR) in T cells induces GPR15 expression and promotes iTreg differentiation simultaneously to produce GPR15+ iTregs and that the GPR15-C10orf99 receptor-ligand pair mediates the retention of Tregs in the large intestine and prevents systemic dissemination of iTregs, accomplishing local tolerance by GPR15+ iTregs. Guided by strong preliminary data, we have generated novel mouse models that will enable us to test these hypotheses. We propose to pursue the following two aims: (1) To characterize Treg-mediated immune tolerance against microbial antigens in the large intestine compared to systemic oral tolerance against dietary antigens from the small intestine, we will check whether GPR15-C10orf99 mediate trafficking of Tregs inside the large intestine lamina propria and Treg retention, in addition to their known function during extravasation. We will also determine the fate of GPR15+ iTregs and the consequences in Treg-mediated tolerance against gut microbial antigens after inducible deletion of GPR15. (2) To characterize the effect of AHR signaling on iTreg differentiation and GPR15 induction, we will test chemicals with reported AHR ligand activity for their ability to induce FOXP3 and GPR15 expression. We will also examine mechanisms underlying AHR-induced increase of GPR15+ Tregs in vivo at the cellular level. To understand the molecular mechanisms for AHR-mediated expression of FOXP3 and GPR15, we will perform CHIPseq analysis in T cells after AHR activation by specific ligands that we will identify. Our findings will significantly advance understanding of Treg-mediated tolerance and will help to develop novel therapeutic strategies to treat various immunological disorders.