WPC 2 B P Z Courier 10cpi #| x x 6 X @ 8 ; X @ HP LaserJet III HPLASEII.PRS x @ , t 0 OpX @ #| x 2 Z B X ; HP LaserJet III HPLASEII.PRS x @ , t 0 OpX @Courier 10cpi Helv 12pt (AC) " ^4@@ l 4DDd 8@8dllllllllll<< h t 4d l | |t ||xHdHll4lthtl4tp((h( ptttDd8p` `d`lll ? x x x , k x 6 X @ 8 ; X @ 1 p C 4 , 0iX p 2 P X P 3 ' 3 ' 3 , or1 + 6 > T 6 6 6 | > T t t t | T t | | T 6 6 6 2 R # X p P rk ; 0iX P# 9312414 Terrian Amino acids are utilized as a neurotransmitter by up to 90% of the presynaptic terminals in the human brain. Glutamate is the principal amino acid employed for fast excitatory information transfer between neurons and recent electrophysiological studies suggest that the facilitation of glutamate release may be required for certain forms of memory and learning. Studies of isolated nerve terminals (synaptosomes) have established that activation of protein kinase C (PKC) enhances the release of glutamate and that multiple isoforms of this enzyme are present in synaptosomes. While most neurobiologists agree that the glutamate release apparatus is not dependent on PKC activation to respond to depolarizing stimuli, it is capable of operating more efficiently when PKC substrates have been phosphorylated by PKC. The major hypothesis of Dr. Terrian's proposal is that activated PKC may phosphorylate presynaptic proteins which prepare ("prime") the glutamate release apparatus to respo nd to localized calcium entry and, thus, enhance the probability of release. Specifically, it is hypothesized that PKC activation may increase the number of synaptic vesicles that are available for release by disrupting interactions between actin filaments and the inner surface of the synaptic plasma membrane. This actin-based cytoskeletal network is thought to constitute a barrier which may normally function to limit access of synaptic vesicles to release sites on the plasma membrane. The overall goal of this project is to understand how individual PKC isoforms interact, in concert with one another and their neuronal substrates, to modify the cytoskeletal architecture of presynaptic terminals and sustain an enhancement of glutamate release. The substrates of PKC which mediate this enhancement of glutamate release are unknown, but must exhibit certain defined properties which can be directly examined using synaptosomal preparations. The proposed project will identify the individual isoforms of PKC that are activated under conditions sufficient for the enhancement of glutamate release. Results from this study will direct the focus of subsequent work in which purified PKC, and individual PKC isoforms will be used to identify the individual enzymes and substrate proteins that are functionally-linked to glutamate release. At the same time, a study will be conducted to examine the relationship between PKC activation, reorganization of the synaptosomal cytoskeleton, and movement of synaptic vesicles to release sites on the synaptosomal plasma membrane. ***
