E2F1 in neurons is cleaved by calpain in an NMDA receptor-dependent manner in a model of HIV-induced neurotoxicity.

TitleE2F1 in neurons is cleaved by calpain in an NMDA receptor-dependent manner in a model of HIV-induced neurotoxicity.
Publication TypeJournal Article
Year of Publication2015
AuthorsZyskind, JW, Wang, Y, Cho, G, Ting, JH, Kolson, DL, Lynch, DR, Jordan-Sciutto, KL
JournalJ Neurochem
Volume132
Issue6
Pagination742-55
Date Published03/2015
ISSN1471-4159
KeywordsAnimals, Calpain, Cells, Cultured, E2F1 Transcription Factor, HIV Infections, Humans, Mice, Mice, 129 Strain, Mice, Inbred C57BL, Mice, Transgenic, Neurons, Rats, Rats, Sprague-Dawley, Receptors, N-Methyl-D-Aspartate
Abstract

The transcription factor E2F1 activates gene targets required for G1 -S phase progression and for apoptosis, and exhibits increased expression levels in neurons in several CNS diseases including HIV encephalitis, Alzheimer disease, and Parkinson's Disease. While E2F1 is known to regulate cell viability through activation of caspases, here we present evidence supporting the involvement of E2F1 in N-methyl-d-aspartate (NMDA) receptor-dependent, HIV-induced neuronal death mediated by calpains. Using an in vitro model of HIV-induced neurotoxicity that is dependent on NMDA receptor and calpain activation, we have shown that cortical neurons lacking functional E2F1 are less susceptible to neuronal death. In addition, we report that neuronal E2F1 is cleaved by calpain to a stable 55-kiloDalton fragment following NR2B-dependent NMDA receptor stimulation. This cleavage of E2F1 is protein conformation-dependent and involves at least two cleavage events, one at each terminus of the protein. Intriguingly, the stabilized E2F1 cleavage product is produced in post-mitotic neurons of all ages, but fails to be stabilized in cycling cells. Finally, we show that a matching E2F1 cleavage product is produced in human fetal neurons, suggesting that calpain cleavage of E2F1 may be produced in human cortical tissue. These results suggest neuronal E2F1 is processed in a novel manner in response to NMDA receptor-mediated toxicity, a mechanism implicated in HIV-associated neurocognitive disorders pathogenesis as well as several other diseases of the CNS. After crossing the blood-brain barrier, HIV-infected monocytes differentiate into macrophages and release excitotoxins and inflammatory factors including glutamate into the brain parenchyma (1). These factors stimulate neuronal N-Methyl-d-aspartate (NMDA) receptors (2), causing calcium influx (3) and subsequent activation of the cysteine protease calpain (4). Activated calpain cleaves multiple substrates including E2F1, producing a stabilized protein fragment with truncations at the N- and C-terminus (5). Calpain-cleaved E2F1 may contribute to calpain-mediated neuronal damage observed in NMDA receptor-mediated neurotoxicity (6).

DOI10.1111/jnc.12956
Alternate JournalJ. Neurochem.
PubMed ID25279448
PubMed Central IDPMC4359652
Grant ListNS071787 / NS / NINDS NIH HHS / United States
R01 NS041202 / NS / NINDS NIH HHS / United States
NS041202 / NS / NINDS NIH HHS / United States
P30 AI045008 / AI / NIAID NIH HHS / United States
NS043994 / NS / NINDS NIH HHS / United States
R01 MH095671 / MH / NIMH NIH HHS / United States
NS074942 / NS / NINDS NIH HHS / United States