NEUROPEPTIDES & THEIR RECEPTORS IN BRAIN COATED VESICLES

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The main goal of this project is to study the subcellular transport of neuropeptides (NP) and their receptors in brain tissue. It particularly aims to demonstrate transmitter-specific pathways through the use of a panel of pathway-specific monoclonal antibodies. The proposal simply seeks for the answers to two basic questions on the mechanisms of neuronal recycling of NP and their receptor(s), in relation to clathrin coated vesicles. First, are NP and their receptors transported in clathrin coated subcellular organelles? And second, in what molecular form are NP and their receptors expressed in putative pathways-specific clathrin coated vesicles? A panel of monoclonal antibodies has been recently developed and characterized with respect to its ability to recognize putative exocytic and endocytic clathrin coated vesicles. The putative pathway specific CV subpopulations will be isolated by immunoprecipitation assays from whole brain gray matter. The sediments will be assayed for the presence and levels of NP by means of ELISAs, immunoblots, HPLC, and radioimmunoassays (RIA). The latter molecular techniques will be employed to establish the molecular variants of NP present in the diverse subcellular transport subsets, i.e. somatostatin 1-14 versus somatostatin 1- 28. The immunodissected CV subpopulations will also be assayed for the presence of NP receptor molecules. These determinations will rely on the application of equilibrium binding techniques using receptor or receptor-subtype selective labeling ligands. The methodology will allow to assess if specific NP receptor subtypes are expressed in specific subsets of clathrin coated vesicles. The potential findings may be intimately linked to homologous and heterologous receptor interaction systems in the brain. Among the NP and receptor systems to be studied, some bear strong relevance to Alzheimer's disease, Huntington's chorea and Parkinson's disease., In Alzheimer's there is a paradoxical decrease in the levels of somatostatin, but not GABA, two co- existing messengers in brain tissue. The converse occurs in Huntington's chorea. This paradox could be resolved if transmitter-specific pathways existed within a neuron and they are differentially altered in specific disease states.