Cellular prion protein (PrPC) protects neuronal cells from the effect of huntingtin aggregation

Abstract

The effect of normal cellular prion protein (PrPC) on abnormal protein aggregation was examined by transfecting huntingtin fragments (Htt) into SN56 neuronal-derived cells depleted of PrPC by RNA interference. PrPC depletion caused an increase in both the number of cells containing granules and the number of apoptotic cells. Consistent with the increase in Htt aggregation, PrPC depletion caused an decrease in proteasome activity and a decrease in the activities of cellular defense enzymes compared with control cells whereas reactive oxygen species (ROS) increased more than threefold. Therefore, PrPC may protect against Htt toxicity in neuronal cells by increasing cellular defense proteins, decreasing ROS and increasing proteasome activity thereby increasing Htt degradation. Depletion of endogenous PrPC in non-neuronal Caco-2 and HT-29 cells did not affect ROS levels or proteasome activity suggesting that only in neuronal cells does PrPC confer protection against Htt toxicity. The protective effect of PrPC was further evident in that overexpression of mouse PrPC in SN56 cells transfected with Htt caused a decrease in both the number of cells with Htt granules and the number of apoptotic cells, whereas there was no effect of PrPC expression in non-neuronal NIH3T3 or CHO cells. Finally, in chronically scrapie (PrPSc)-infected cells, ROS increased more than twofold while proteasome activity was decreased compared to control cells. Although this could be a direct effect of PrPSc, it is also possible that, since PrPC specifically prevents pathological protein aggregation in neuronal cells, partial loss of PrPC itself increases PrPSc aggregation.

Context dependent neuroprotective properties of prion protein (PrP)

“…Crosstalk between PrP and other neurodegenerative disease causing proteins is not limited to AD, as another report has suggested that PrP protects against polyglutamine aggregate toxicity. 40 Tau, our study there was not a significant progressive rotarod deficit in α-synuclein Tg + mice or that the repeated testing had a masking effect on this phenotype ( Fig. 2A).…”

The Chaperone-Like Protein HYPK Acts Together with NatA in Cotranslational N-Terminal Acetylation and Prevention of Huntingtin Aggregation

“…Plasmids encoding V5-tagged hNaa15p, hNaa25p, and hNaa35p were previously described (4,39,40). Plasmids encoding Huntingtin polyQ-enhanced green fluorescent protein (EGFP) fusion proteins (pHttQ25-EGFP, pHttQ72-EGFP, and pHttQ103-EGFP) (24,46) were generously provided by Evan Eisenberg, National Heart, Lung and Blood Institute, Bethesda, MD. Plasmids encoding EGFP-Huntingtin polyQ fusion proteins (pEGFP-HttQ23 and pEGFP-HttQ74) (45) were generously provided by David C. Rubinsztein, University of Cambridge, United Kingdom.…”

Reduction of PrPC in human cerebrospinal fluid after spinal cord injury

“…While suggested roles for PrP C include cell signaling, differentiation and adhesion, an increasing number of studies have implicated PrP C in neuroprotection against oxidative stress, ischemia and toxic protein aggregation. [27][28][29][30][31][32][33][34][35][36]38,46 Given the proposed neuroprotective role for PrP C , low levels of PrP C in CSF following spinal cord injury may well create a window in which neurons are susceptible to damage. CSF reduction in PrP C following spinal cord injury is specific (Figs.…”

“…Under normal conditions PrP C is released from cells into the CSF. [22][23][24][25][26] We evaluated PrP C in CSF samples for two reasons: First, PrP C has been hypothesized to be neuroprotective [27][28][29][30][31][32][33][34][35][36][37][38] and it follows that changes in CSF PrP C expression levels might influence neural cell survival. Secondly, CSF from some CJD patients is infectious 39 and changes in the CSF levels of PrP C may well alter the rate of PrP Sc replication.…”