The Journal of Neuroscience, March 8, 2006, 26(10):2738-2744; doi:10.1523/JNEUROSCI.4834-05.2006
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Neurobiology of Disease
p35/p25 Is Not Essential for Tau and Cytoskeletal Pathology or Neuronal Loss in NiemannPick Type C Disease
Janice L. Hallows,
Robert E. Iosif,
Rebecca D. Biasell, and
Inez Vincent
Department of Pathology, University of Washington, Seattle, Washington 98195
Correspondence should be addressed to Inez Vincent at her present address: Centre for Molecular Medicine and Therapeutics, University of British Columbia, 950 West 28th Avenue, Vancouver, British Columbia, Canada V5A 4H4. Email: ivincent{at}cmmt.ubc.ca
Hyperactivation of the cyclin-dependent kinase 5 (cdk5), triggered by proteolytic conversion of its neuronal activator, p35, to a more potent byproduct, p25, has been implicated in Alzheimer's disease (AD), amyotrophic lateral sclerosis, and NiemannPick type C disease (NPC). This mechanism is thought to lead to the development of neuropathological hallmarks, i.e., hyperphosphorylated cytoskeletal proteins, neuronal inclusions, and neurodegeneration, that are common to all three diseases. This pathological ensemble is recapitulated in a single model, the npc-1 (npc/) mutant mouse. Previously, we showed that pharmacological cdk inhibitors dramatically reduced hyperphosphorylation, lesion formation, and locomotor defects in npc/ mice, suggesting that cdk activity is required for NPC pathogenesis. Here, we used genetic ablation of the p35 gene to examine the specific involvement of p35, p25, and hence cdk5 activation in NPC neuropathogenesis. We found that lack of p35/p25 does not slow the onset or progression or improve the neuropathology of NPC. Our results provide direct evidence that p35/p25-mediated cdk5 deregulation is not essential for NPC pathology and suggest that similar pathology in AD may also be cdk5 independent.
Key words: Alzheimer's disease; ALS; cdk5; hyperphosphorylation; spheroid; tauopathy
Received Nov. 9, 2005;
revised Jan. 30, 2006;
accepted Feb. 1, 2006.
Correspondence should be addressed to Inez Vincent at her present address: Centre for Molecular Medicine and Therapeutics, University of British Columbia, 950 West 28th Avenue, Vancouver, British Columbia, Canada V5A 4H4. Email: ivincent{at}cmmt.ubc.ca