Deregulation of cdk5, hyperphosphorylation, and cytoskeletal pathology in the Niemann-Pick type C murine model.
NPC-1 gene mutations cause Niemann-Pick type C (NPC), a neurodegenerative storage disease resulting in premature death in humans. Spontaneous mutation of the NPC-1 gene in mice generates a similar phenotype, usually with death ensuing by 12 weeks of age. Both human and murine NPC are characterized neuropathologically by ballooned neurons distended with lipid storage, axonal spheroid formation, demyelination, and widespread neuronal loss. To elucidate the biochemical mechanism underlying this neuropathology, we have investigated the phosphorylation of neuronal cytoskeletal proteins in the brains of npc-1 mice. A spectrum of antibodies against phosphorylated epitopes in neurofilaments (NFs) and MAP2 and tau were used in immunohistochemical and immunoblotting analyses of 4- to 12-week-old mice. Multiple sites in NFs, MAP2, and tau were hyperphosphorylated as early as 4 weeks of age and correlated with a significant increase in activity of the cyclin-dependent kinase 5 (cdk5) and accumulation of its more potent activator, p25, a proteolytic fragment of p35. At 5 weeks of age, the development of axonal spheroids was noted in the pons. p25 and cdk5 coaccumulated with hyperphosphorylated cytoskeletal proteins in axon spheroids. These various abnormalities escalated with each additional week of age, spreading to other regions of the brainstem, basal ganglia, cerebellum, and eventually, the cortex. Our data suggest that focal deregulation of cdk5/p25 in axons leads to cytoskeletal abnormalities and eventual neurodegeneration in NPC. The npc-1 mouse is a valuable in vivo model for determining how and when cdk5 becomes deregulated and whether cdk5 inhibitors would be useful in blocking NPC neurodegeneration.
Bu
Bitao
B
Department of Pathology, University of Washington, Seattle, Washington 98195, USA.
Li
Jin
J
Davies
Peter
P
Vincent
Inez
I
D000818:Animals; D001369:Axons / Q000378:metabolism / Q000473:pathology; D001921:Brain / Q000378:metabolism / Q000473:pathology*; D051360:Cyclin-Dependent Kinase 5; D018844:Cyclin-Dependent Kinases / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism / Q000473:pathology*; D004195:Disease Models, Animal; D018450:Disease Progression; D004789:Enzyme Activation; D015151:Immunoblotting; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008818:Mice, Neurologic Mutants; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D016900:Neurofilament Proteins / Q000378:metabolism; D000077296:Niemann-Pick C1 Protein; D009542:Niemann-Pick Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D010766:Phosphorylation; D011506:Proteins / Q000235:genetics; D016875:tau Proteins / Q000378:metabolism
D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins; D000077296:Niemann-Pick C1 Protein; C106831:Npc1 protein, mouse; D011506:Proteins; C089495:neuronal Cdk5 activator (p25-p35); D016875:tau Proteins; C051774:neurofilament protein H; C061195:neurofilament protein M; D051360:Cyclin-Dependent Kinase 5; C495906:Cdk5 protein, mouse; D018844:Cyclin-Dependent Kinases