CALBINDIN-D28K--ROLE IN NEURODEGENERATION

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Calbindin-D28k (CaBP), a calcium-binding protein that is present in defined neuronal populations in the brain and spinal cord, appears to protect cells from calcium-mediated cellular degeneration. CaBP is found in the hippocampal neurons that are spared cell loss caused by experimentally induced seizures and excitotoxins. The neurons that do not contain CaBP appear to die as a result of toxic levels of intracellular Ca2+. Recent data from our laboratory indicate that the specific midbrain dopaminergic (DA) neurons that contain CaBP are preserved in patients with Parkinson's disease, and in monkeys and mice treated with 1-methyl- 4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, a neurotoxin which produces a parkinsonian syndrome). However, those DA neurons that do not contain CaBP are most vulnerable to Parkinson's disease and MPTP. The purpose of the present grant is-to determine whether CaBP protects midbrain DA neurons from the neurotoxic effects of MPTP in the mouse. First, we will use immunohistochemical staining for CaBP, computer imaging, CaBP in situ hybridization, 14C-MPTP in vivo autoradiography, and monoamine biochemical measuring techniques to determine whether endogenous CaBP protects specific midbrain DA neurons from MPTP-induced degeneration. Secondly, we will develop animal models in which to test the protective effects of CaBP against MPTP by generating transgenic mice which express CaBP within all of the midbrain DA neurons. We will use the tyrosine hydroxylase promoter and the neuron specific enolase promoter to ex-press CaBP, and determine whether the presence of this protein will specifically protect MPTP-sensitive areas of the midbrain (substantia nigra). These experiments will: (I) determine whether CaBP protects midbrain DA neurons from MPTP-induced parkinsonism; and (2) provide animal models of other neurodegenerative diseases where calcium-mediated neurodegeneration may play a major etiologic role (e.g., Alzheimer's disease, Huntington's disease).