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Signalling pathways involved in neurodegeneration in the striatum

Objective

To analyse cellular and molecular events leading to apoptosis in striatal neurones in culture and in striatal slices in response to a glutamate-induced rise of intracellular Ca2+ combined (or not) with a mitochondrial chain toxin treatment.
To determine the adaptive changes linked to the activation of cortical afferents in physiological and pathological conditions on cortico-striatal slices.
To characterise the morphological, cytochemical, neurochemical, and electrophysiological changes in an in vivo model of striatal neurone degeneration.
To define the organisational principles of the cortico-striatal projections to correlate the selective susceptibility of striatal neurones to degenerative processes.

The aim of the present project is to analyse in experimental models fundamental mechanisms leading to apoptosis of neurones in the striatum which are selectively affected in an inherited neurological disorder: Huntington's disease (HD). The selective degeneration of striatal neurones in HD will be reproduced by combining raise of intracellular levels of Ca (by increasing excitatory transmission) and failure of mitochondrial chain metabolism (with the inhibitor 3-nitropropionic acid, 3-NP). Cellular and molecular events underlying the progressive processes of apoptosis will be examined first in primary cultures of rat striatal neurones. We will test the hypothesis that the proliferative phase that occurs in the very early stages of HD is associated with the activation of extracellular signal regulated kinase (ERK), a MAP kinase which has been described to play a role in proliferation and differentiation of cells. We will also analyse the degenerative phase that leads to apoptosis, and the activation of two other MAP kinase pathways implicated in adaptive response of cells to environmental stress, namely the c-Jun N terminal kinase/stress activated protein kinase(JNK/SAPK) and p38. In both cases we will investigate the activation of the convergent nuclear target of these MAP kinase pathways, the transcription factor Elk-1.

We will test the putative role of these kinases and of Elk-1 in early events leading to apoptosis by tranfecting cells with mutated forms of kinases and Elk-1.Secondly electrophysiological recordings and intracellular calcium imaging will be carried out to characterise the properties of striatal neurons inslices under physiological (e.g. sustained activation of corticostriatalafferents) and pathophysiological (e.g. combined activation of corticostriatalafferents and 3-NP treatment) conditions. The involvement of ERK and JNK/SAPK, p38 pathways will be analysed in both conditions. Any possible linkage will be confirmed and further defined using pharmacological agent that specifically and selectively affects the MAP kinase pathways. Thirdly, using an in vivo model of HD we will reproduce the progressive neuro-degeneration of striatal neurones by injecting increasing doses of 3-NP.multidisciplinary approach will allow us to analyse, at the single cell level, morphological (dendritic spines), neuro-chemical (MAP kinase and Elk-1activation) and electrophysiological (responsiveness of neurones to corticostriatal stimulation) changes associated with the proliferative phase and the early phase of apoptosis.

In view of the importance of corticostriatal projection in the control of the activity of striatal neurones and its role in the degeneration of striatal neurones we will characterize the organisational principles of the corticostriatal projections. This proposal, which requires the association and collaboration of highly, specialised partners at a pan-European level by bringing together experts in intracellular signalling pathways, in vitro and in vivo intracellular electrophysiological recordings and advanced anatomical techniques. This combined approach will provide new insights, into the fundamental knowledge of signalling cascades utilised in neurones in physiological and patho-physiological conditions. The knowledge gained from this project will have important industrial repercussions by providing new insights into possible therapeutic intervention in neurological disorders that are associated with neuro-degeneration, a crucial problem that might be of growing importance in Europe. 01

Coordinator

Université Pierre et Marie Curie - Paris VI
Address
9,Quai Saint-bernard
75005 Paris
France

Participants (4)

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
France
Address
Route De Mende 1919
34293 Montpellier
Centre National de la Recherche Scientifique
France
Address
Avenue De La Terrasse
91198 Gif-sur-yvette
MEDICAL RESEARCH COUNCIL
United Kingdom
Address
Mansfield Road
OX1 3TH Oxford
UNIVERSITÀ DEGLI STUDI DI ROMA TOR VERGATA
Italy
Address
135,Via Di Tor Vergata 135
00133 Roma