Loss of Hsp70 exacerbates pathogenesis but not levels of fibrillar aggregates in a mouse model of Huntington's disease.
Endogenous protein quality control machinery has long been suspected of influencing the onset and progression of neurodegenerative diseases characterized by accumulation of misfolded proteins. Huntington's disease (HD) is a fatal neurodegenerative disorder caused by an expansion of a polyglutamine (polyQ) tract in the protein huntingtin (htt), which leads to its aggregation and accumulation in inclusion bodies. Here, we demonstrate in a mouse model of HD that deletion of the molecular chaperones Hsp70.1 and Hsp70.3 significantly exacerbated numerous physical, behavioral and neuropathological outcome measures, including survival, body weight, tremor, limb clasping and open field activities. Deletion of Hsp70.1 and Hsp70.3 significantly increased the size of inclusion bodies formed by mutant htt exon 1, but surprisingly did not affect the levels of fibrillar aggregates. Moreover, the lack of Hsp70s significantly decreased levels of the calcium regulated protein c-Fos, a marker for neuronal activity. In contrast, deletion of Hsp70s did not accelerate disease in a mouse model of infectious prion-mediated neurodegeneration, ruling out the possibility that the Hsp70.1/70.3 mice are nonspecifically sensitized to all protein misfolding disorders. Thus, endogenous Hsp70s are a critical component of the cellular defense against the toxic effects of misfolded htt protein in neurons, but buffer toxicity by mechanisms independent of the deposition of fibrillar aggregates.
Wacker
Jennifer L
JL
Department of Pharmacology, University of Washington, Seattle, Washington 98195, USA.
Huang
Shao-Yi
SY
Steele
Andrew D
AD
Aron
Rebecca
R
Lotz
Gregor P
GP
Nguyen
QuangVu
Q
Giorgini
Flaviano
F
Roberson
Erik D
ED
Lindquist
Susan
S
Masliah
Eliezer
E
Muchowski
Paul J
PJ
D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D005786:Gene Expression Regulation / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000172:deficiency; D050884:HSP72 Heat-Shock Proteins / Q000145:classification / Q000172:deficiency*; D006816:Huntington Disease / Q000150:complications / Q000235:genetics* / Q000401:mortality / Q000473:pathology*; D002479:Inclusion Bodies / Q000473:pathology; D053208:Kaplan-Meier Estimate; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009043:Motor Activity / Q000235:genetics; D009069:Movement Disorders / Q000209:etiology / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009460:Neurologic Examination / Q000379:methods; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D019680:Trinucleotide Repeat Expansion / Q000235:genetics; D015431:Weight Loss / Q000235:genetics
D002868:Chromosomal Proteins, Non-Histone; D018840:HSP70 Heat-Shock Proteins; D050884:HSP72 Heat-Shock Proteins; C498550:Hsp70.3 protein, mouse; D009419:Nerve Tissue Proteins; D016760:Proto-Oncogene Proteins c-fos; C047458:fibrillarin; C081884:heat-shock protein 70.1