Target-related and intrinsic neuronal death in Lurcher mutant mice are both mediated by caspase-3 activation.
The Lurcher (Lc) mutation in the delta2 glutamate receptor gene leads to the presence of a constitutive inward current in the cerebellar Purkinje cells of Lurcher heterozygous mice and to the postnatal degeneration of these neurons. In addition, cerebellar granule cells and olivary neurons of Lc/+ mice die as an indirect effect of the mutation after the loss of their target Purkinje cells. The apoptotic nature of Lc/+ Purkinje cell death remains controversial. To address this question, we studied the involvement of caspase-3, a key effector of apoptosis, in the neurodegenerative processes occurring in Lc/+ cerebellum. Several antibodies recognizing different regions of caspase-3 were used in immunoblotting and immunohistochemical experiments. We demonstrate that pro-caspase-3 is specifically upregulated in the dying Lc/+ Purkinje cells, but not in granule cells and olivary neurons, suggesting that different death-inducing signals trigger variant apoptotic pathways in the CNS. The subcellular localization of pro-caspase-3 was shown to be cytoplasmic and mitochondrial. Active caspase-3 as well as DNA fragmentation was found in numerous granule cells and some Purkinje cells of the Lc/+ cerebellum. Thus, caspase-3 activation is involved in both the direct and indirect neuronal death induced by the Lurcher mutation, strongly supporting the idea that the Lc/+ Purkinje cell dies by apoptosis.
Selimi
F
F
Laboratoire Développement et Vieillissement du Système Nerveux, Institut des Neurosciences, Unité Mixte de Recherche 7624, Centre National de la Recherche Scientifique et Université Pierre et Marie Curie, Paris, France. Fekrije.Selimi@snv.jussieu.fr
Doughty
M
M
Delhaye-Bouchaud
N
N
Mariani
J
J
D000818:Animals; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D053938:DNA Fragmentation; D004789:Enzyme Activation / Q000502:physiology; D004792:Enzyme Precursors / Q000378:metabolism; D051379:Mice; D008818:Mice, Neurologic Mutants / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D011689:Purkinje Cells / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure; D012016:Reference Values; D014018:Tissue Distribution
D004792:Enzyme Precursors; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases