2004 — 2009 |
Smith, Corey |
N/AActivity Code Description: No activity code was retrieved: click on the grant title for more information |
Mechanisms of Endocytosis in Adrenal Chromaffin Cells. @ Case Western Reserve University
Mechanisms of Endocytosis in Adrenal Chromaffin Cells Corey B. Smith Case Western Reserve University
Stress is a physiological response to a hostile environment. Stress causes chromaffin cells of the adrenal gland to increase their release of chemical transmitters, including adrenaline, into the blood stream. This release is achieved by fusion of transmitter containing packets, called secretory granules, with the inside cell surface, causing their contents to be expelled from the cell. Under normal conditions, chromaffin cells release low levels of adrenaline and set the organism in a 'breed and feed' state of energy storage by directing blood flow to the internal organs, focusing the eye on nearby objects and increasing insulin release from the pancreas. With stress, chromaffin cells release elevated levels of adrenaline, contributing to the 'fight or flight' response. In this state, the elevated adrenaline diverts blood flow to skeletal muscle, focuses they eye on distant objects and increases blood sugar levels. In addition, stress-activation causes chromaffin cells to release analgesic compounds, termed enkephalins. Together these signaling molecules place the organism into a state for escape or defense. Thus, regulated transmitter release from chromaffin cells plays a critical role in determining the physiological and metabolic status of an organism. It is the overall goal of this laboratory to provide a fundamental understanding of the chromaffin cell as a primary contributor to the 'breed and feed' as well as the 'fight or flight' state. This proposal focuses on the mechanisms utilized by chromaffin cells for transmitter release under basal versus stress activation.
Sustained transmitter release requires the recycling of the transmitter-containing secretory granules. Without recycling the cell would soon exhaust its supply. Specialized granule components are retrieved from the cell surface and refilled with transmitter molecules for re-use. It was assumed that this recycling occurred by the same mechanism under all conditions. However, it was recently demonstrated that differences in recycling processes exist under basal versus stress-activation. This proposal outlines a series of experiments designed to test signature events that delineate recycling mechanisms under conditions of basal versus stress activation in mouse adrenal chromaffin cells. It provides experiments that will test the degree of granule fusion and collapse during transmitter release and the degree to which the granule and cell surface components mix, thus defining the complexity of the recycling process required prior to re-generation of viable secretory granules. It will also determine the role of key molecules involved in the recycling mechanism, thus defining points of potential regulation for the re-generation of secretory granules. Techniques employed in these experiments include electrophysiological measures of the surface area of single cells, electrochemical determination of the amount of transmitter released, quantitative fluorescence imaging of cell surface components and molecular disruption of the recycling mechanism. Thus a fundamental description of the mechanisms utilized by adrenal chromaffin cells for the sustained release of adrenaline and enkephalin during the normal 'breed and feed' as well as the 'fight or flight' stress-activated state will be provided.
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0.915 |
2005 |
Smith, Corey B |
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. |
Mechanisms of the Adrenal Medulla Stress Response @ Case Western Reserve University
DESCRIPTION (provided by applicant): Stress is a physiological response of the sympathetic nervous system to environmental pressures. If left unchecked it can lead to patho-physiologies such as hypertension and diabetes. Chromaffin cells of the adrenal medulla are a primary endocrine output of the sympathetic nervous system and secrete a host of transmitter molecules, including catecholamines and peptide transmitters, through the fusion of dense core secretory granules. At basal firing rates, set by the sympathetic tone, catecholamine output regulates homeostatic processes such as enteric function, vascular tone and insulin secretion. Stress-mediated sympathetic activation leads to elevated catecholamine secretion, increasing cardiac output and glucagon levels. Stress also evokes peptide transmitter release, including enkephalin which acts as an analgesic and allows the organism to focus on escape and defense. Our goal is to understand how chromaffin cells regulate the release of catecholamine and signaling peptides under physiological basal-firing and stress activation. Cellular mechanisms for catecholamine release have been studied, but peptide transmitter release is less well understood under these conditions. In this proposal we will test that, under basal firing, chromaffin granules undergo a restricted fusion with the cell surface and selectively release catecholamine. We will test that stress-activation induces a full fusion and collapse of the granule leading to release of both catecholamine and peptide cargos. We will employ electrophysiological, electrochemical, fluorescence imaging, immunocytochemical and biochemical approaches. We will test for exocytosis of catecholamine and protein cargo from chromaffin granules under basal-firing and stress-activated states. We will test the roles of key molecules in the exo-endocytic mechanism and we will measure the degree granule collapse into the cell surface during the exo-endocytic cycle. This data will provide a fundamental understanding of the cellular and molecular mechanisms for the endocrine stress response in chromaffin cells.
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1 |
2006 — 2008 |
Smith, Corey B |
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. |
Mechanisms of the Adrenal Medulla Stress Response. @ Case Western Reserve University
DESCRIPTION (provided by applicant): Stress is a physiological response of the sympathetic nervous system to environmental pressures. If left unchecked it can lead to patho-physiologies such as hypertension and diabetes. Chromaffin cells of the adrenal medulla are a primary endocrine output of the sympathetic nervous system and secrete a host of transmitter molecules, including catecholamines and peptide transmitters, through the fusion of dense core secretory granules. At basal firing rates, set by the sympathetic tone, catecholamine output regulates homeostatic processes such as enteric function, vascular tone and insulin secretion. Stress-mediated sympathetic activation leads to elevated catecholamine secretion, increasing cardiac output and glucagon levels. Stress also evokes peptide transmitter release, including enkephalin which acts as an analgesic and allows the organism to focus on escape and defense. Our goal is to understand how chromaffin cells regulate the release of catecholamine and signaling peptides under physiological basal-firing and stress activation. Cellular mechanisms for catecholamine release have been studied, but peptide transmitter release is less well understood under these conditions. In this proposal we will test that, under basal firing, chromaffin granules undergo a restricted fusion with the cell surface and selectively release catecholamine. We will test that stress-activation induces a full fusion and collapse of the granule leading to release of both catecholamine and peptide cargos. We will employ electrophysiological, electrochemical, fluorescence imaging, immunocytochemical and biochemical approaches. We will test for exocytosis of catecholamine and protein cargo from chromaffin granules under basal-firing and stress-activated states. We will test the roles of key molecules in the exo-endocytic mechanism and we will measure the degree granule collapse into the cell surface during the exo-endocytic cycle. This data will provide a fundamental understanding of the cellular and molecular mechanisms for the endocrine stress response in chromaffin cells.
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1 |
2012 — 2015 |
Smith, Corey B |
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. |
Molecular Control of Differential Peptide Transmitter Exocytosis. @ Case Western Reserve University
DESCRIPTION (provided by applicant): Environmental threat, physical exertion or injury and psychological strain all lead to the initiation of the sympatho-adrenal fight or flight stress response. Neuroendocrine adrenal medullary chromaffin cells receive excitatory synaptic input from the sympathetic splanchnic nerve. Splanchnic activation causes adrenal chromaffin cells to release catecholamines as well as a diverse array of neuro- and vaso-active peptide transmitters into the circulation. Different levels of stress result in the differential release of catecholamine versus peptide transmitters to formulate the appropriate physiological response. All secreted hormones, catecholamines as well as multiple species of peptide transmitters, are co-packaged in the same secretory granules. Thus, differential hormone release is regulated at a step after granule fusion. Under basal chromaffin cell excitation, set by the sympathetic tone, selective release of freely-soluble catecholamine occurs through a transient fusion event, characterized by a narrow, structured exocytic fusion pore between the granule lumen and the extracellular space. Under sympathetic tone, selective and modest catecholamine release plays an important role in the rest and digest metabolic status of energy storage, regulating homeostatic physiological functions including pancreatic insulin secretion, increased blood flow to the viscera and maintenance of basal cardiac activity. In response to stress, increased chromaffin cell stimulation modulates the mode of secretory granule fusion, leading to the expansion of the exocytic fusion pore to maximize catecholamine release and facilitate exocytosis of the co-packaged adrenal peptide transmitters. Elevated serum catecholamine levels, in combination with adrenal-derived peptide transmitters, are core effectors of the sympathetic fight or flight stress response. Together they regulate multiple processes that prepare for defense or escape, including generalized analgesia (enkephalin), increased cardiac output (elevated catecholamines), blood flow to skeletal muscle (atrial natriuretic factor, Neuropeptide Y) and blood glucose (pancreastatin). Thus, regulated expansion of the secretory fusion pore represents a key element of the acute stress response. It is our overall goal to understand the molecular mechanism responsible for pore expansion. We summarize previous work and provide preliminary data to formulate 3 specific aims to test an activity-dependent dynamin I de- phosphorylation event, subsequent recruitment of a multimeric pore-expansion complex, and requirement for myosin motor activity in the regulation of fusion pore expansion. In the execution of these aims, we employ state of the art electrophysiological, electrochemical and quantitative fluorescence microscopy as well as a newly-developed silicon nanowire-based field effect transistor (SiNW-FET) biosensor to measure specific peptide release. The data obtained will provide a molecular understanding of the key regulators of the acute sympatho-adrenal stress response as well as pathologies resulting from its improper regulation. PUBLIC HEALTH RELEVANCE: Environmental or physical threat increases firing of the autonomic sympathetic nervous system to activate the acute fight or flight stress response. Through an as-of-yet poorly understood process, different sympathetic activity levels result in unique hormonal profiles to elicit appropriate physiological responses. This proposal will test a molecular signaling cascade for the specific activity-dependent differential release of hormone transmitters into the circulation and thus provide the mechanistic basis for the sympatho-adrenal acute stress response.
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1 |
2017 — 2020 |
Ardell, Jeffrey L [⬀] Kipke, Daryl R (co-PI) [⬀] Shivkumar, Kalyanam (co-PI) [⬀] Smith, Corey B (co-PI) [⬀] |
U01Activity 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. |
Bioelectric Monitoring and Control of the Heart @ University of California Los Angeles
Project Summary/Abstract Cardiovascular disease, such as heart failure, atrial and ventricular arrhythmias, hypertensive and valvular heart disease is the leading cause of morbidity and mortality in the USA and the world. Importantly, over 500,000 cardiac surgeries and procedures, which require detailed cardiac diagnostics and intense monitoring, are performed to treat arrhythmias and structural heart disease in the US each year, which together carry a morbidity and mortality risk of 1-30%, depending on a patient's comorbidities. Cardiovascular specialists are required to monitor the heart routinely during interventions and almost exclusively rely on surface ECG and pressure measurements from the heart and vascular compartments and in selected cases electrical mapping of the heart. Current state-of-art technologies for cardiac electrophysiological and surgical therapies for management of complex atrial and ventricular arrhythmias provide limited and time-disparate data to guide interventions and monitor patients, primarily relying on hemodynamic parameters, gross and time-consuming point-by-point electrophysiological mapping techniques, and intermittent evaluation of blood chemistries. At present these data, in addition to being limited, often have substantial time delays from sampling to usable readouts leading to increase intraoperative and post-operative recovery time. This proposal outlines development of a conceptually new approach to cardiac monitoring that can impact diagnostics, therapeutics, and ultimately lead to closed-loop bioelectronics control of the heart. For Quantum Phase 1, three aims are proposed: Aim 1: Development of bioelectronic interfaces, platforms/modules, and analytical tools for real-time assessments of the cardiac interstitial and vascular parameters (catecholamine levels, acid-base and metabolic indices), along with high-density thin-film microarrays for mapping of cardiac electrical function and recording of peripheral cardiac autonomic neural activity. Aim 2: Integration of monitoring platforms, technologies, and analytics for cardiac electrophysiological mapping, multi-point cardiac pacing, hemodynamics, autonomic function, and real-time assessments of interstitial (and plasma) neurotransmitters and neuropeptide levels, acid-base levels, and metabolic factors. Aim 3: Discovery and validation of critical autonomic, metabolic, and electrophysiological parameters that precede and predict adverse cardiac events in infarcted porcine hearts and initial proof-of-concept human studies. Developing and optimizing new mapping arrays and systems for real-time measurement and evaluation of multiple electrophysiological parameters simultaneously with instantaneous ?read-outs? of regional autonomic function (neural and cardiac interstitial neurotransmitters) has the potential to revolutionize the practice of medicine and patient care.
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0.931 |