2004 — 2006 |
Zhao, Haiqing |
R03Activity Code Description: To provide research support specifically limited in time and amount for studies in categorical program areas. Small grants provide flexibility for initiating studies which are generally for preliminary short-term projects and are non-renewable. |
Functional Role of Odorant Receptor Phosphorylation @ Johns Hopkins University
DESCRIPTION (provided by applicant): Olfactory neurons use a large repertoire of G protein-coupled odorant receptors to detect thousands of odors. Ligand-stimulated receptor phosphorylation is a major regulatory mechanism to receptor function for many G-protein coupled receptors (GPCRs) and is essential to the termination of GPCR signal transduction. As with other G protein-coupled signaling, olfactory transduction may use the receptor phosphorylation mechanism to regulate the response to odor stimuli. Yet, there is still lack of a direct and unambiguous evidence for odorant-stimulated odorant receptor phosphorylation. How and how much odorant-stimulated odorant receptor phosphorylation contributes to olfactory signal transduction remains largely unknown. The overall goal of this project is to understand how olfactory signal transduction is regulated at the level of the odorant receptor. Two specific aims proposed in this project include: 1) to demonstrate odorant-stimulated odorant receptor phosphorylation; and 2) to reveal the role of odorant-stimulated odorant receptor phosphorylation in olfactory signal transduction. The first aim will be achieved by expressing an epitope tagged odorant receptor with known ligand specificity in all olfactory neurons in mice through a gene targeting approach. The odorant-stimulated odorant receptor phosphorylation will be displayed by detecting the phosphorylated receptor protein using well-defined antibodies against the epitope tag. The second aim will be achieved by expressing a mutated odorant receptor, in which the potential phosphorylation residues are mutated, in all olfactory neurons in mice. The odor-evoked responses in these mice will be measured by electrophysiological recordings and be compared to responses in the mouse carrying ubiquitous expression of the wild-type receptor. The proposed research will enhance our understanding of how olfactory neurons control their sensitivity and response dynamics to odor stimuli.
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2008 — 2016 |
Zhao, Haiqing |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Regulation of Olfactory Signal Transduction @ Johns Hopkins University
DESCRIPTION (provided by applicant): Olfactory transduction is the process by which olfactory sensory neurons (OSNs) transform odor information into neuronal electrical signals. Over the past two and a half decades, extensive investigations have led to the elucidation of a core transduction pathway in vertebrate OSNs. However, the processes that regulate transduction to allow for proper sensitivity and response kinetics are not well understood. Calcium is a key olfactory transduction regulator. Calcium enters the sensory cilium through the olfactory cyclic nucleotide-gated (CNG) channel during the odor response, amplifies OSN depolarization, and also negatively regulating several olfactory transduction components. This negative regulation governs OSN adaptation--a phenomenon manifested as reduced sensitivity upon sustained or repeated stimulation. In this proposal, we propose to take advantage of multiple genetically modified mouse strains that we generated to: 1) investigate the integration of multiple Ca2+-dependent feedback mechanisms in OSN adaptation (Aim 1); and 2) investigate the role of negative regulatory mechanisms, which function in termination and adaptation, in setting OSN sensitivity at rest (Aim 2). Electrophysiological analysis, at the level of intact olfactory epithelium and the isolated single cell level, will be conducted on mice carrying double or triple mutations for calcium-dependent feedback mechanisms (Aim 1) as well as on mice that lack a calcium-dependent feedback mechanism and also lack efficient calcium extrusion (Aim 2). The long-term goal of this proposal is to elucidate the molecular mechanisms underlying olfaction. The proposed investigation will lead to a better understanding of how OSNs encode the intensity and temporal features of odor stimulations by regulating sensitivity and response kinetics. The knowledge gained from the proposed research will enhance our understanding of normal olfactory function and olfactory dysfunctions.
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2017 — 2021 |
Brown, Ronald Lane Robinson, Phyllis R Zhao, Haiqing |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Regulation of the Intrinsic Melanopsin-Based Light Response in Iprgcs @ Johns Hopkins University
Proposal Summary/Abstract: In the mammalian retina, there is a small subset of retinal ganglion cells (RGCs) that function as autonomous photoreceptors and exhibit light responses independent of rod/cone-driven synaptic input. These intrinsically photosensitive RGCs (known as, ipRGCs) relay light information to the brain to regulate several light-dependent processes, such as circadian photoentrainment, the pupillary light reflex (PLR), sleep, and mood. ipRGCs use the photopigment melanopsin and a G-protein coupled phototransduction cascade to respond to light, and are now known to comprise 5 different subtypes (M1-5) that can be differentiated based on morphological and electrophysiological criteria, projection targets, and transcription factor expression. Currently, there exists a major gap in our understanding of how the regulation of melanopsin and its downstream phototransduction pathways in different ipRGC subtypes govern distinct light-mediated behaviors. Based on our preliminary data, the goal of the proposed research is to determine, in Aim I, the role of melanopsin posttranslational modifications in ipRGC-mediated behaviors in vivo, and in Aim II, the phototransduction components that allow distinct ipRGC subtypes to intrinsically detect light and influence ipRGC-subtype specific behaviors. These studies will provide a critical understanding of the biochemical and molecular mechanisms by which light influences a wide range effects on human health and performance through the regulation of circadian rhythms, sleep, mood, and learning & memory.
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2018 |
Zhao, Haiqing |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Role of Mammalian Retinal Photoreceptors in Non-Image-Forming Visual Functions @ Johns Hopkins University
DESCRIPTION (provided by applicant): Light has profound influences on many non-image forming (NIF) visual functions including circadian rhythms, sleep, mood, body temperature and the pupillary light reflex. In mammals, light influences these NIF functions through three retinal photoreceptors, namely the classical photoreceptors, rods and cones, and the intrinsically photosensitive retinal ganglion cells (ipRGCs), which express the photopigment melanopsin. As ganglion cells, ipRGCs integrate rod/cone input with their own intrinsic melanopsin-based phototransduction to serve as the sole conduits to signal light information to brain regions important for these NIF functions. However, how ipRGCs, a seemingly homogeneous population, integrate extrinsic light input from rods and cones with their own intrinsic melanopsin-based light responses to coordinate diverse behaviors is poorly understood. The overall goal of this competitive renewal is to address this fundamental question at three levels. In Aim I, we will determine the functional circuits by which rod, cone and melanopsin-based signals are integrated in ipRGCs to drive NIF functions. Recently, we found that ipRGCs are much more diverse than previously appreciated, consisting of multiple morphologically and electrophysiologically distinct subtypes. Additionally, ipRGCs appear to be unique among retinal ganglion cells in that they co-express two neurotransmitters, glutamate and a neuropeptide, PACAP. Thus, in Aim II, we will define the relative contribution of glutamatergic and peptidergic neurotransmission to diverse NIF functions. In Aim III, we will elucidate the functional contribution of individual ipRGC subtypes to NIF functions. These studies will advance our current understanding of the role of ipRGCs in controlling light- mediated behaviors that are essential to human health and a better quality of life.
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2018 — 2021 |
Zhao, Haiqing |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
The Role of Cfap69 in Olfaction @ Johns Hopkins University
Necessary steps towards understanding the sense of smell include characterizing the relevant molecular components that regulate olfactory sensory neuron (OSN) responses and analyzing behaviors of animal models that harbor abnormal odor coding. Our initial studies in mice suggest that Cilia- and Flagella-Associated Protein 69 (CFAP69), an evolutionarily conserved and poorly studied protein, plays a critical, yet unconventional, role in regulating olfactory transduction kinetics, odor stimuli coding of OSNs and also olfactory behavior. CFAP69 is enriched in OSN cilia, where olfactory signal transduction occurs. OSNs from CFAP69 conditional knockout mice display faster response kinetics in both on- and off- phases of the response with little change in response size, and can fire action potentials more faithfully to repeated stimuli than the control OSNs. CFAP69 conditional knockout mice, despite having higher temporal resolution in coding odor stimuli at the peripheral sensory neuron level, performed inferiorly in a challenging olfactory task. In this proposal, we will: 1) Determine the role of CFAP69 in regulating OSN sensitivity, adaptation and action potential coding by detailed electrophysiological analysis of odor responses at the levels of intact olfactory epithelium and isolated single cells from OSN-specific conditional knockout mice; 2) Investigate the mechanisms by which CFAP69 exerts its effect by using both a combined pharmacological and electrophysiological approach to determine the site of CFAP69 action in the transduction cascade and a biochemical approach to identify its interaction protein partners; and 3) Investigate how altered OSN response and odor stimuli coding affect olfactory behavior in OSN-specific conditional knockout mice. The proposed research will bring new knowledge and new perspective to the understanding of the olfactory transduction process, olfactory stimuli coding of OSNs and olfactory perception. The research will enhance our understanding of the fundamental biology of olfaction and olfactory dysfunction.
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