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Early apoptotic and late necrotic components associated with altered Ca 2+ homeostasis in a peptide‐delivery model of polyglutamine‐induced neuronal death
Author(s) -
Suzuki Mari,
Koike Tatsuro
Publication year - 2005
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.20461
Subject(s) - mitochondrial permeability transition pore , microbiology and biotechnology , programmed cell death , biology , mitochondrion , apoptosis , phosphorylation , cytochrome c , depolarization , biochemistry , biophysics
The mechanisms by which polyglutamine expansion causes common features of neuronal death remain unclear. Here we describe an approach for delivering polyglutamine expansions directly into cultured sympathetic neurons. Glutamine (Q) residues (n = 10, 22, 30) were conjugated with a peptide possessing translocation properties across plasma membranes (PDP) and a nuclear localization signal (NLS). These peptides were rapidly incorporated into sympathetic neurons and showed neurotoxicity in a length‐ and dose‐dependent manner. A robust induction of c‐jun and cyclin D1 occurred following treatment with PDP‐Q22‐NLS. Enhanced c‐Jun phosphorylation showed c‐Jun N‐terminal kinase (JNK) activation. Coincidentally, TrkA tyrosine phosphorylation was decreased in association with loss of phospho‐Akt, the downstream target of PI‐3 kinase. Despite such proapoptotic signals, neither release of cytochrome c from mitochondria nor caspase‐3/7 activation was detected. TdT‐mediated dUTP nick‐end labeling‐positive nuclear condensation, but no fragmentation, occurred. At 24 hr of treatment, cytoplasmic Ca 2+ levels began to become elevated, and the cellular level of ATP was decreased. Cytoplasmic Ca 2+ responses to KCl depolarization displayed a delayed recovery, providing evidence for lack of Ca 2+ homeostasis. The neurons became committed to death at about 36 hr when mitochondrial Ca 2+ uptake declined concurrently with loss of mitochondrial membrane potential. Collectively, these results show that, despite induction of early apoptotic signals, nonapoptotic neuronal cell death occurred via perturbed Ca 2+ homeostasis and suggest that mitochondrial permeability transition may play important roles in this model of neuronal death. © 2005 Wiley‐Liss, Inc.