The long-range objective of this project, now in its 14th year, is to define the sequence of steps and mechanisms involved in the regeneration of synapses. It has focused on the neuromuscular synapse because of its convenience for experimentation. The experiments outlined in this proposal concern the mechanisms that regulate formation of the structural specializations in axon terminals and muscle fibers crucial for synaptic transmission. Most of the experiments are directed toward defining the structure, function and regulation of the protein agrin. Such studies will enable us to test the hypothesis that agrin at the neuromuscular junction mediates the nerve-induced aggregation of acetylcholine receptors, acetylcholinesterase and other molecules that compose the synaptic specializations on muscle fibers. Some of the studies are also directed toward determining the molecular basis of the muscle-induced formation of synaptic specializations in axon terminals.
The specific aims are: 1. To determine the cellular source of agrin active at the neuromuscular synapse. 2. To identify and characterize function domains in agrin. 3. To study the regulation of agrin during development and regeneration. 4. To identify and characterize molecules that induce the formation of presynaptic apparatus in regenerating axon terminals. These experiments will involve light and electron microscopy, immunocytochemistry and molecular genetics and will be conducted on a variety of nerve-muscle preparations. Studies such as these are requisite for understanding the cellular and molecular basis of neuromuscular disease and for devising ways to enhance restoration of neuromuscular function after trauma. Because synapses in the brain have pre- and postsynaptic specializations similar to those at the neuromuscular synapse, these studies may also provide insight as to the mechanisms involved in CNS synapse formation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS014506-21
Application #
2379570
Study Section
Neurology B Subcommittee 2 (NEUB)
Project Start
1979-04-01
Project End
1998-05-31
Budget Start
1997-03-01
Budget End
1998-05-31
Support Year
21
Fiscal Year
1997
Total Cost
Indirect Cost
Name
Stanford University
Department
Biology
Type
Schools of Medicine
DUNS #
800771545
City
Stanford
State
CA
Country
United States
Zip Code
94305
Jung, Jae H; Szule, Joseph A; Stouder, Kylee et al. (2018) Active Zone Material-Directed Orientation, Docking, and Fusion of Dense Core Vesicles Alongside Synaptic Vesicles at Neuromuscular Junctions. Front Neuroanat 12:72
Jung, Jae Hoon; Szule, Joseph A; Marshall, Robert M et al. (2016) Variable priming of a docked synaptic vesicle. Proc Natl Acad Sci U S A 113:E1098-107
Szule, Joseph A; Jung, Jae Hoon; McMahan, Uel J (2015) The structure and function of 'active zone material' at synapses. Philos Trans R Soc Lond B Biol Sci 370:
Harlow, Mark L; Szule, Joseph A; Xu, Jing et al. (2013) Alignment of synaptic vesicle macromolecules with the macromolecules in active zone material that direct vesicle docking. PLoS One 8:e69410
Szule, Joseph A; Harlow, Mark L; Jung, Jae Hoon et al. (2012) Regulation of synaptic vesicle docking by different classes of macromolecules in active zone material. PLoS One 7:e33333
Nagwaney, Sharuna; Harlow, Mark Lee; Jung, Jae Hoon et al. (2009) Macromolecular connections of active zone material to docked synaptic vesicles and presynaptic membrane at neuromuscular junctions of mouse. J Comp Neurol 513:457-68
Ress, David B; Harlow, Mark L; Marshall, Robert M et al. (2004) Methods for generating high-resolution structural models from electron microscope tomography data. Structure 12:1763-74
Mathiesen, I; Rimer, M; Ashtari, O et al. (1999) Regulation of the size and distribution of agrin-induced postsynaptic-like apparatus in adult skeletal muscle by electrical muscle activity. Mol Cell Neurosci 13:207-17
Ress, D; Harlow, M L; Schwarz, M et al. (1999) Automatic acquisition of fiducial markers and alignment of images in tilt series for electron tomography. J Electron Microsc (Tokyo) 48:277-87
Rimer, M; Cohen, I; Lomo, T et al. (1998) Neuregulins and erbB receptors at neuromuscular junctions and at agrin-induced postsynaptic-like apparatus in skeletal muscle. Mol Cell Neurosci 12:1-15

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