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Protein kinase Calpha and beta1 isoforms are regulators of alpha-secretory proteolytic processing of amyloid
S Rossner1, K Mendla, R Schliebs
1Department of Neurochemistry, Paul Flechsig Institute for Brain Research, Jahnallee 59, 04109 Leipzig, Germany. rossn@medizin.uni-leipzig.de
Abstract:
We have recently shown that in utero treatment of guinea pigs with the DNA methylating substance methylazoxymethanol acetate (MAM) results in neocortical microencephalopathy, increased protein kinase C (PKC) activity and altered processing of the amyloid precursor protein (APP) in neocortex of offspring. Here we show that PKCalpha and PKCbeta1 are the key regulators of alpha-secretory APP processing in guinea pig neocortex under these experimental conditions in vivo. This conclusion is based on the selective translocation of PKCalpha and PKCbeta1 isoforms to the cell membrane in MAM-treated guinea pigs, as revealed by Western blot analysis and by immunocytochemistry. Additionally, we observed that [3H]phorbol ester binding to protein kinase C increased by 38% and enhanced basal PKC activity by 58% in the neocortex of microencephalic guinea pigs. Inhibition of PKCalpha/PKCbeta1 by Gö6976 abolished this difference, suggesting that constitutive overactivation of these PKC isoforms accounts for the increase in total PKC activity. We also observed a strong positive correlation between levels of alpha-secretase-processed APP and PKC activity in the neocortex of individual animals, providing further evidence for a significant role of classical PKC isoforms in nonamyloidogenic APP processing.
Insights
In utero exposure to methylazoxymethanol acetate (MAM) causes brain abnormalities and alters amyloid precursor protein (APP) processing. PKCalpha and PKCbeta1 are key regulators of non-amyloidogenic APP processing in affected guinea pigs.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Molecular Biology
Background:
- In utero exposure to methylazoxymethanol acetate (MAM) induces neocortical microencephalopathy in guinea pigs.
- This exposure alters amyloid precursor protein (APP) processing and increases protein kinase C (PKC) activity in the offspring's neocortex.
Purpose of the Study:
- To identify the specific protein kinase C (PKC) isoforms regulating alpha-secretory APP processing in MAM-induced neocortical microencephalopathy.
- To investigate the role of PKCalpha and PKCbeta1 in non-amyloidogenic APP processing in vivo.
Main Methods:
- Western blot analysis and immunocytochemistry to detect PKC isoform translocation.
- Measurement of [3H]phorbol ester binding to assess PKC activity.
- Pharmacological inhibition of PKCalpha/PKCbeta1 using Gö6976.
- Correlation analysis between APP processing and PKC activity.
Main Results:
- Selective translocation of PKCalpha and PKCbeta1 to the cell membrane in MAM-treated guinea pigs.
- Significant increase in [3H]phorbol ester binding and basal PKC activity in microencephalic neocortex.
- Inhibition of PKCalpha/PKCbeta1 abolished the observed increase in PKC activity.
- Strong positive correlation between alpha-secretase-processed APP levels and PKC activity.
Conclusions:
- PKCalpha and PKCbeta1 are the primary regulators of alpha-secretory APP processing in MAM-induced neocortical microencephalopathy.
- Constitutive overactivation of PKCalpha and PKCbeta1 contributes to increased total PKC activity.
- Classical PKC isoforms play a significant role in non-amyloidogenic APP processing in this model.