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Cell type-specific neuroprotective activity of untranslocated prion protein.

Restelli E, Fioriti L, Mantovani S, Airaghi S, Forloni G, Chiesa R - PLoS ONE (2010)

Bottom Line: However, it is not clear how cytosolic PrP localization influences neuronal viability, with either cytotoxic or anti-apoptotic effects reported in different studies.Untranslocated PrP boosted the resistance of cortical and hippocampal neurons to apoptotic insults but had no effect on cerebellar cells.These results indicate cell type-dependent differences in the efficiency of PrP translocation, and argue that cytosolic PrP targeting might serve a physiological neuroprotective function.

View Article: PubMed Central - PubMed

Affiliation: Dulbecco Telethon Institute, Milan, Italy.

ABSTRACT

Background: A key pathogenic role in prion diseases was proposed for a cytosolic form of the prion protein (PrP). However, it is not clear how cytosolic PrP localization influences neuronal viability, with either cytotoxic or anti-apoptotic effects reported in different studies. The cellular mechanism by which PrP is delivered to the cytosol of neurons is also debated, and either retrograde transport from the endoplasmic reticulum or inefficient translocation during biosynthesis has been proposed. We investigated cytosolic PrP biogenesis and effect on cell viability in primary neuronal cultures from different mouse brain regions.

Principal findings: Mild proteasome inhibition induced accumulation of an untranslocated form of cytosolic PrP in cortical and hippocampal cells, but not in cerebellar granules. A cyclopeptolide that interferes with the correct insertion of the PrP signal sequence into the translocon increased the amount of untranslocated PrP in cortical and hippocampal cells, and induced its synthesis in cerebellar neurons. Untranslocated PrP boosted the resistance of cortical and hippocampal neurons to apoptotic insults but had no effect on cerebellar cells.

Significance: These results indicate cell type-dependent differences in the efficiency of PrP translocation, and argue that cytosolic PrP targeting might serve a physiological neuroprotective function.

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Related in: MedlinePlus

SP-PrP does not affect the cerebellar granule neurons' response to serum and potassium deprivation.(A) Cerebellar granule neurons from C57BL/6J mice were shifted to serum-free medium containing 5 mM KCl, and left untreated (-) or treated with 10 μM CAM741 alone or in combination with 10 μM MG132 to induce accumulation of SP-PrP. After 24 h cells were analyzed by Western blot with antibody 12B2 to verify the induction of SP-PrP. (B), Cell survival was quantified by MTT assay and expressed as a percentage of the values for untreated cells. Data are the mean ± SEM of 12 replicates; **p<0.01, ***p<0.001 vs -K+ in Prnp+/+; ##p<0.01 vs -K+ in Prnp0/0 by Bonferroni test.
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pone-0013725-g007: SP-PrP does not affect the cerebellar granule neurons' response to serum and potassium deprivation.(A) Cerebellar granule neurons from C57BL/6J mice were shifted to serum-free medium containing 5 mM KCl, and left untreated (-) or treated with 10 μM CAM741 alone or in combination with 10 μM MG132 to induce accumulation of SP-PrP. After 24 h cells were analyzed by Western blot with antibody 12B2 to verify the induction of SP-PrP. (B), Cell survival was quantified by MTT assay and expressed as a percentage of the values for untreated cells. Data are the mean ± SEM of 12 replicates; **p<0.01, ***p<0.001 vs -K+ in Prnp+/+; ##p<0.01 vs -K+ in Prnp0/0 by Bonferroni test.

Mentions: Next, we tested the effect of SP-PrP in CGN deprived of serum and potassium, a condition that induces apoptotic cell death [38]. After 24 h of deprivation, CGN viability was reduced by ∼30% (Fig. 7B). CAM741 alone, or combined with MG132 to induce accumulation of SP-PrP (Fig. 7A, lanes 7 and 8), caused a small but significant decrease of cell survival (Fig. 7B, gray bars). However, the same happened in CGN from Prnp0/0 mice (Fig. 7B, white bars), indicating that the loss of cell viability was due to a toxic effect of the treatment, independent of SP-PrP.


Cell type-specific neuroprotective activity of untranslocated prion protein.

Restelli E, Fioriti L, Mantovani S, Airaghi S, Forloni G, Chiesa R - PLoS ONE (2010)

SP-PrP does not affect the cerebellar granule neurons' response to serum and potassium deprivation.(A) Cerebellar granule neurons from C57BL/6J mice were shifted to serum-free medium containing 5 mM KCl, and left untreated (-) or treated with 10 μM CAM741 alone or in combination with 10 μM MG132 to induce accumulation of SP-PrP. After 24 h cells were analyzed by Western blot with antibody 12B2 to verify the induction of SP-PrP. (B), Cell survival was quantified by MTT assay and expressed as a percentage of the values for untreated cells. Data are the mean ± SEM of 12 replicates; **p<0.01, ***p<0.001 vs -K+ in Prnp+/+; ##p<0.01 vs -K+ in Prnp0/0 by Bonferroni test.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2965675&req=5

pone-0013725-g007: SP-PrP does not affect the cerebellar granule neurons' response to serum and potassium deprivation.(A) Cerebellar granule neurons from C57BL/6J mice were shifted to serum-free medium containing 5 mM KCl, and left untreated (-) or treated with 10 μM CAM741 alone or in combination with 10 μM MG132 to induce accumulation of SP-PrP. After 24 h cells were analyzed by Western blot with antibody 12B2 to verify the induction of SP-PrP. (B), Cell survival was quantified by MTT assay and expressed as a percentage of the values for untreated cells. Data are the mean ± SEM of 12 replicates; **p<0.01, ***p<0.001 vs -K+ in Prnp+/+; ##p<0.01 vs -K+ in Prnp0/0 by Bonferroni test.
Mentions: Next, we tested the effect of SP-PrP in CGN deprived of serum and potassium, a condition that induces apoptotic cell death [38]. After 24 h of deprivation, CGN viability was reduced by ∼30% (Fig. 7B). CAM741 alone, or combined with MG132 to induce accumulation of SP-PrP (Fig. 7A, lanes 7 and 8), caused a small but significant decrease of cell survival (Fig. 7B, gray bars). However, the same happened in CGN from Prnp0/0 mice (Fig. 7B, white bars), indicating that the loss of cell viability was due to a toxic effect of the treatment, independent of SP-PrP.

Bottom Line: However, it is not clear how cytosolic PrP localization influences neuronal viability, with either cytotoxic or anti-apoptotic effects reported in different studies.Untranslocated PrP boosted the resistance of cortical and hippocampal neurons to apoptotic insults but had no effect on cerebellar cells.These results indicate cell type-dependent differences in the efficiency of PrP translocation, and argue that cytosolic PrP targeting might serve a physiological neuroprotective function.

View Article: PubMed Central - PubMed

Affiliation: Dulbecco Telethon Institute, Milan, Italy.

ABSTRACT

Background: A key pathogenic role in prion diseases was proposed for a cytosolic form of the prion protein (PrP). However, it is not clear how cytosolic PrP localization influences neuronal viability, with either cytotoxic or anti-apoptotic effects reported in different studies. The cellular mechanism by which PrP is delivered to the cytosol of neurons is also debated, and either retrograde transport from the endoplasmic reticulum or inefficient translocation during biosynthesis has been proposed. We investigated cytosolic PrP biogenesis and effect on cell viability in primary neuronal cultures from different mouse brain regions.

Principal findings: Mild proteasome inhibition induced accumulation of an untranslocated form of cytosolic PrP in cortical and hippocampal cells, but not in cerebellar granules. A cyclopeptolide that interferes with the correct insertion of the PrP signal sequence into the translocon increased the amount of untranslocated PrP in cortical and hippocampal cells, and induced its synthesis in cerebellar neurons. Untranslocated PrP boosted the resistance of cortical and hippocampal neurons to apoptotic insults but had no effect on cerebellar cells.

Significance: These results indicate cell type-dependent differences in the efficiency of PrP translocation, and argue that cytosolic PrP targeting might serve a physiological neuroprotective function.

Show MeSH
Related in: MedlinePlus