Release of transmitters and hormones from neurons plays a critical role in transmission of information between neighboring cells and distant tissues. Revealing mechanisms that control neurosecretion is vital to our understanding of both homeostasis of a wide variety of physiological systems and disease processes that occur when this transmission breaks down. Our long-term goal is to understand neural control of peptide secretion and its impact on physiology and behavior. The broad aim of this proposal is to reveal and study underlying cellular and molecular events regulating synthesis and secretion of a neurohormone (egg laying hormone, ELH) using the bag cell neurons of Aplysia as a model system. We are now able to monitor membrane excitability and ELH secretion from bag cell neurons of freely-behaving animals, from bag cell neurons in excised neural tissue maintained in vitro, and from single bag cell neurons in culture. This gives us a relatively unique ability to move between studies addressing molecular and cell physiological issues and those addressing systems and behavioral questions using a single neuroendocrine system. There are three specific aims of this proposal.
The first aim i s to determine the role of calcium from intracellular stores in regulating the pattern of ELH secretion. We will use electrophysiology, calcium imaging, and RIA measurement of hormone secretion to determine the pattern of intracellular calcium in response to electrical afterdischarge, the effects of manipulating intracellular calcium on ELH secretion, and the source of intracellular calcium controlling ELH secretion in response to afterdischarge.
The second aim i s to investigate protein kinase A (PKA), protein kinase C (PKC), and CaM kinase in bag cell neurons. We plan to monitor kinase activities using both a traditional radiolabeling approach, as well as newly developed optical imaging techniques. In addition, we will investigate the role of CaM kinase II in regulating ELH secretion. The third specific aim is to understand cellular and molecular events that mediate the stimulatory effects of afterdischarge on ELH biosynthesis. We will investigate the effects of afterdischarge on specific steps along the translation pathway, and the roles of the calcium, PKA and PKC signaling pathways in regulating specific translational events leading to alterations in ELH biosynthesis. The outcome of this work should enable us to develop a detailed model of cellular mechanisms that link membrane excitation to neurohormone secretion and neurohormone synthesis.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS033548-08
Application #
6624811
Study Section
Special Emphasis Panel (ZRG1-IFCN-2 (01))
Program Officer
Mitler, Merrill
Project Start
1994-12-01
Project End
2004-11-30
Budget Start
2002-12-01
Budget End
2004-11-30
Support Year
8
Fiscal Year
2003
Total Cost
$194,178
Indirect Cost
Name
University of California Los Angeles
Department
Physiology
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Lee, Wenjau; Wayne, Nancy L (2004) Secretion of locally synthesized neurohormone from neurites of peptidergic neurons. J Neurochem 88:532-7
Wayne, Nancy L; Lee, Wenjau; Michel, Stephan et al. (2004) Post-afterdischarge depolarization does not stimulate prolonged neurohormone secretion but is required for activity-dependent stimulation of neurohormone biosynthesis from peptidergic neurons. Endocrinology 145:1678-84
Wayne, Nancy L; Michel, Stephan (2004) Synaptic stimulation of Aplysia peptidergic neurons can activate hormone secretion in the absence of an afterdischarge. Neurosci Lett 362:249-52
Wayne, Nancy L; Lee, Wenjau; Michel, Stephan et al. (2004) Activity-dependent regulation of neurohormone synthesis and its impact on reproductive behavior in aplysia. Biol Reprod 70:277-81
Dyer, John R; Michel, Stephan; Lee, Wenjau et al. (2003) An activity-dependent switch to cap-independent translation triggered by eIF4E dephosphorylation. Nat Neurosci 6:219-20
Michel, Stephan; Wayne, Nancy L (2002) Neurohormone secretion persists after post-afterdischarge membrane depolarization and cytosolic calcium elevation in peptidergic neurons in intact nervous tissue. J Neurosci 22:9063-9
Lee, Wenjau; Jones, Andrea M; Ono, Joyce K et al. (2002) Regional differences in processing of locally translated prohormone in peptidergic neurons of Aplysia californica. J Neurochem 83:1423-30
Wayne, N L; Lee, W; Kim, Y J (1999) Persistent activation of calcium-activated and calcium-independent protein kinase C in response to electrical afterdischarge from peptidergic neurons of aplysia. Brain Res 834:211-3
Wayne, N L; Kim, Y J; Yong-Montenegro, R J (1998) Seasonal fluctuations in the secretory response of neuroendocrine cells of Aplysia californica to inhibitors of protein kinase A and protein kinase C. Gen Comp Endocrinol 109:356-65
Wayne, N L; Kim, J; Lee, E (1998) Prolonged hormone secretion from neuroendocrine cells of Aplysia is independent of extracellular calcium. J Neuroendocrinol 10:529-37

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