Abstract

The regulation of synaptic efficacy is an important mechanism for producing plastic changes in neuronal activity associated with development, learning, and neurological and psychiatric disorders. The modulation of ion channel activity by neurotransmitters has often been proposed to be important in synaptic regulation, although there is little direct evidence to support this. Here we propose to continue studies of the molecular mechanism by which serotonin (5-HT) modulates a specific potassium channel (S channel) in Aplysia sensory neurons and to investigate the role of S channel modulation in facilitation of transmitter release from sensory neuron synaptic terminals. I. Mechanism of S channel modulation. Previously we have shown, using single channel recording, that channel modulation by 5-HT involves a phosphorylation reaction mediated by cyclic AMP dependent protein kinase (cAMP-PK). Here we will extend these findings by studying: 1. The role of membrane protein phosphatases in regulating channel modulation and their possible inhibition by specific proteins. 2. The effects of calcium-calmodulin and calcium-phospholipid dependent protein kinases on S channel activity and the modulation of channel activity by cAMP-PK. 3. Whether or not the S channel itself is the important substrate phosphoprotein by determining the importance of peripheral membrane proteins in modulation. II. Mechanism of presynaptic facilitation. To investigate more directly whether S channel modulation is important in regulating transmitter release by serotonin, we will study 5-HT action in growth cones of Aplysia sensory neurons in culture as these are direct precursors to mature synaptic terminals. We will investigate: 1. Whether or not the S channels are present in growth cones and whether they are modulated by 5-HT via a cAMP-dependent mechanism. 2. The effects of 5-HT and cAMP on other voltage dependent ionic currents. 3. Effects of 5-HT on transmitter release as monitored by membrane capacitance increases associated with transmitter vesicle fusion.

  Funding Agency

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS019569-05
Application #
3399660
Study Section
Physiology Study Section (PHY)
Project Start
1983-04-01
Project End
1989-03-31
Budget Start
1987-04-01
Budget End
1988-03-31
Support Year
5
Fiscal Year
1987
Total Cost
Indirect Cost

  Institution

Name
Columbia University (N.Y.)
Department
Type
Schools of Medicine
DUNS #
064931884
City
New York
State
NY
Country
United States
Zip Code
10027

  Publications

Shuster, M J; Camardo, J S; Siegelbaum, S A (1991) Comparison of the serotonin-sensitive and Ca(2+)-activated K+ channels in Aplysia sensory neurons. J Physiol 440:601-21
Volterra, A; Siegelbaum, S A (1989) Antagonistic modulation of S-K+ channel activity by cyclic AMP and arachidonic acid metabolites. Role for two G proteins. Ann N Y Acad Sci 559:219-36
Volterra, A; Siegelbaum, S A (1988) Role of two different guanine nucleotide-binding proteins in the antagonistic modulation of the S-type K+ channel by cAMP and arachidonic acid metabolites in Aplysia sensory neurons. Proc Natl Acad Sci U S A 85:7810-4
Belardetti, F; Kandel, E R; Siegelbaum, S A (1987) Neuronal inhibition by the peptide FMRFamide involves opening of S K+ channels. Nature 325:153-6
Shuster, M J; Siegelbaum, S A (1987) Pharmacological characterization of the serotonin-sensitive potassium channel of Aplysia sensory neurons. J Gen Physiol 90:587-608
Shuster, M J; Camardo, J S; Siegelbaum, S A et al. (1986) Modulation of the 'S' K+ channel by cAMP-dependent protein phosphorylation in cell-free membrane patches. Prog Brain Res 69:119-32
Belardetti, F; Schacher, S; Siegelbaum, S A (1986) Action potentials, macroscopic and single channel currents recorded from growth cones of Aplysia neurones in culture. J Physiol 374:289-313
Siegelbaum, S A; Belardetti, F; Camardo, J S et al. (1986) Modulation of the serotonin-sensitive potassium channel in Aplysia sensory neurone cell body and growth cone. J Exp Biol 124:287-306
Shuster, M J; Camardo, J S; Siegelbaum, S A et al. (1985) Cyclic AMP-dependent protein kinase closes the serotonin-sensitive K+ channels of Aplysia sensory neurones in cell-free membrane patches. Nature 313:392-5