Calcium-dependent cleavage of endogenous wild-type huntingtin in primary cortical neurons.
Huntington's disease (HD) is caused by a polyglutamine expansion in the amino-terminal region of huntingtin. Mutant huntingtin is proteolytically cleaved by caspases, generating amino-terminal aggregates that are toxic for cells. The addition of calpains to total brain homogenates also leads to cleavage of wild-type huntingtin, indicating that proteolysis of mutant and wild-type huntingtin may play a role in HD. Here we report that endogenous wild-type huntingtin is promptly cleaved by calpains in primary neurons. Exposure of primary neurons to glutamate or 3-nitropropionic acid increases intracellular calcium concentration, leading to loss of intact full-length wild-type huntingtin. This cleavage could be prevented by calcium chelators and calpain inhibitors. Degradation of wild-type huntingtin by calcium-dependent proteases thus occurs in HD neurons, leading to loss of wild-type huntingtin neuroprotective activity.
Department of Pharmacological Sciences and Center of Excellence on Neurodegenerative Diseases, University of Milan, Milano, Italy.
Donato
D
Goffredo
Dorotea
D
Rigamonti
Marzia
M
Tartari
Alberto
A
De Micheli
Claudia
C
Verderio
Michela
M
Matteoli
Chiara
C
Zuccato
Elena
E
Cattaneo
D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002154:Calpain / Q000378:metabolism; D002474:Cell-Free System; D002478:Cells, Cultured; D003720:Densitometry; D018698:Glutamic Acid / Q000494:pharmacology; D000071058:Huntingtin Protein; D007476:Ionophores / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009574:Nitro Compounds; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism*; D011422:Propionates / Q000494:pharmacology; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
C499524:Htt protein, rat; D000071058:Huntingtin Protein; D007476:Ionophores; D009419:Nerve Tissue Proteins; D009574:Nitro Compounds; D009687:Nuclear Proteins; D011422:Propionates; D000001:Calcimycin; D018698:Glutamic Acid; D002154:Calpain; C449000:m-calpain; C015392:3-nitropropionic acid; D002118:Calcium