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Aging, Alzheimer's, and APOE genotype influence the expression and neuronal distribution patterns of microtubule motor protein dynactin-P50.

Aboud O, Parcon PA, DeWall KM, Liu L, Mrak RE, Griffin WS - Front Cell Neurosci (2015)

Bottom Line: In contrast, in Alzheimer's, βAPP and dynactin were significantly reduced.It is logical to conclude, then, that as neurons age successfully, there is coordination between retrograde delivery and maintenance and repair, as well as between retrograde delivery and degradation and/or recycling of spent proteins.We conclude that even in disease the ε3 allele is neuroprotective.

View Article: PubMed Central - PubMed

Affiliation: Donald W. Reynolds Department of Geriatrics, University of Arkansas for Medical Sciences Little Rock, AR, USA.

ABSTRACT
Reports from neural cell cultures and experimental animal studies provide evidence of age- and disease-related changes in retrograde transport of spent or misfolded proteins destined for degradation or recycling. However, few studies address these issues in human brain from those who either age without dementia and overt neuropathology, or succumb to Alzheimer's; especially as such propensity may be influenced by APOE genotype. We studied the expression and distribution of the dynein subunit dynactin-P50, the β amyloid precursor protein (βAPP), and hyperphosphorylated tau (P-tau) in tissues and tissue sections of brains from non-demented, neuropathology-free patients and from Alzheimer patients, with either APOE ε3,3 or APOE ε4,4. We found that advanced age in patients without dementia or neuropathological change was associated with coordinated increases in dynactin-P50 and βAPP in neurons in pyramidal layers of the hippocampus. In contrast, in Alzheimer's, βAPP and dynactin were significantly reduced. Furthermore, the dynactin-P50 and βAPP that was present was located primarily in dystrophic neurites in Aβ plaques. Tissues from Alzheimer patients with APOE ε3,3 had less P-tau, more βAPP, dynactin-P50, and synaptophysin than did tissues from Alzheimer patients carrying APOE ε4,4. It is logical to conclude, then, that as neurons age successfully, there is coordination between retrograde delivery and maintenance and repair, as well as between retrograde delivery and degradation and/or recycling of spent proteins. The buildup of proteins slated for repair, synaptic viability, transport, and re-cycling in neuron soma and dystrophic neurites suggest a loss of this coordination in Alzheimer neurons. Inheritance of APOE ε3,3 rather than APOE ε4,4, is associated with neuronal resilience, suggestive of better repair capabilities, more synapses, more efficient transport, and less hyperphosphorylation of tau. We conclude that even in disease the ε3 allele is neuroprotective.

No MeSH data available.


Related in: MedlinePlus

Comparison of tissue levels of dynactin-P50 (DynP50), P-tau, and synaptophysin (Syn) in Alzheimer patients with APOE ε3,3 vs. ε4,4. (A) Dynactin-P50 (green) was less in AD patients with APOE ε4,4, than in those with ε3,3, while (B) P-tau was increased in ε4,4. Representative images. (C) Fluorescence intensity quantification of P-tau and dynactin-P50 levels in AD patients with ε3,3 vs. ε4,4. (D) Steady state protein levels, relative to that of actin, of P-tau in Alzheimer patients with ε3,3 were lower than levels in those with ε4,4, while synaptophysin and dynactin-P50 levels were higher in ε3,3 compared with ε4,4. (E) Western blot comparison of protein levels in AD vs. Control, and between AD ε3,3 vs. AD ε4,4. Actin was used as loading control. Lanes in gray boxes demonstrate a patient with APOE ε3,3 genotype with similar levels of proteins to those in a patient with APOE ε4,4 genotype, suggestive of the possible presence of Alzheimer risk factors aside from APOE genotype. Wilcoxon-Mann-Whitney Rank Sum Test was used for statistical significance, with *denoting p ≤ 0.05 and **denoting p ≤ 0.01. Data reported as group mean with error bars denoting SEM.
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Figure 6: Comparison of tissue levels of dynactin-P50 (DynP50), P-tau, and synaptophysin (Syn) in Alzheimer patients with APOE ε3,3 vs. ε4,4. (A) Dynactin-P50 (green) was less in AD patients with APOE ε4,4, than in those with ε3,3, while (B) P-tau was increased in ε4,4. Representative images. (C) Fluorescence intensity quantification of P-tau and dynactin-P50 levels in AD patients with ε3,3 vs. ε4,4. (D) Steady state protein levels, relative to that of actin, of P-tau in Alzheimer patients with ε3,3 were lower than levels in those with ε4,4, while synaptophysin and dynactin-P50 levels were higher in ε3,3 compared with ε4,4. (E) Western blot comparison of protein levels in AD vs. Control, and between AD ε3,3 vs. AD ε4,4. Actin was used as loading control. Lanes in gray boxes demonstrate a patient with APOE ε3,3 genotype with similar levels of proteins to those in a patient with APOE ε4,4 genotype, suggestive of the possible presence of Alzheimer risk factors aside from APOE genotype. Wilcoxon-Mann-Whitney Rank Sum Test was used for statistical significance, with *denoting p ≤ 0.05 and **denoting p ≤ 0.01. Data reported as group mean with error bars denoting SEM.

Mentions: Marked differences in fluorescence intensity were noted in AD patients depending on their APOE genotype. Those with ε3,3 genotypes had overall higher dynactin-P50 levels and lower P-Tau levels compared to their ε4,4 counterparts (Figures 6A,B, representative images, Figure 6C, fluorescence quantification). This was confirmed in Western blot: relative to actin steady-state levels, overall, the expression of hyperphosphorylated tau is higher in Alzheimer patients with APOE ε4,4 than in patients with APOE ε3,3, while dynactin and synaptophysin were lower (Figures 6D,E). As synaptophysin is commonly used as a marker for healthy functional synapses, this implies a connection between APOE genotype, retrograde transport, and synaptic integrity. Interestingly, in comparing the right-most lanes in the Alzheimer ε3,3 and ε4,4 western blot (Figure 6E, gray boxes), the hyperphosphorylated tau, synaptophysin, and dynactin-P50 levels are almost identical, perhaps explained by risk factors other than APOE genotype.


Aging, Alzheimer's, and APOE genotype influence the expression and neuronal distribution patterns of microtubule motor protein dynactin-P50.

Aboud O, Parcon PA, DeWall KM, Liu L, Mrak RE, Griffin WS - Front Cell Neurosci (2015)

Comparison of tissue levels of dynactin-P50 (DynP50), P-tau, and synaptophysin (Syn) in Alzheimer patients with APOE ε3,3 vs. ε4,4. (A) Dynactin-P50 (green) was less in AD patients with APOE ε4,4, than in those with ε3,3, while (B) P-tau was increased in ε4,4. Representative images. (C) Fluorescence intensity quantification of P-tau and dynactin-P50 levels in AD patients with ε3,3 vs. ε4,4. (D) Steady state protein levels, relative to that of actin, of P-tau in Alzheimer patients with ε3,3 were lower than levels in those with ε4,4, while synaptophysin and dynactin-P50 levels were higher in ε3,3 compared with ε4,4. (E) Western blot comparison of protein levels in AD vs. Control, and between AD ε3,3 vs. AD ε4,4. Actin was used as loading control. Lanes in gray boxes demonstrate a patient with APOE ε3,3 genotype with similar levels of proteins to those in a patient with APOE ε4,4 genotype, suggestive of the possible presence of Alzheimer risk factors aside from APOE genotype. Wilcoxon-Mann-Whitney Rank Sum Test was used for statistical significance, with *denoting p ≤ 0.05 and **denoting p ≤ 0.01. Data reported as group mean with error bars denoting SEM.
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Figure 6: Comparison of tissue levels of dynactin-P50 (DynP50), P-tau, and synaptophysin (Syn) in Alzheimer patients with APOE ε3,3 vs. ε4,4. (A) Dynactin-P50 (green) was less in AD patients with APOE ε4,4, than in those with ε3,3, while (B) P-tau was increased in ε4,4. Representative images. (C) Fluorescence intensity quantification of P-tau and dynactin-P50 levels in AD patients with ε3,3 vs. ε4,4. (D) Steady state protein levels, relative to that of actin, of P-tau in Alzheimer patients with ε3,3 were lower than levels in those with ε4,4, while synaptophysin and dynactin-P50 levels were higher in ε3,3 compared with ε4,4. (E) Western blot comparison of protein levels in AD vs. Control, and between AD ε3,3 vs. AD ε4,4. Actin was used as loading control. Lanes in gray boxes demonstrate a patient with APOE ε3,3 genotype with similar levels of proteins to those in a patient with APOE ε4,4 genotype, suggestive of the possible presence of Alzheimer risk factors aside from APOE genotype. Wilcoxon-Mann-Whitney Rank Sum Test was used for statistical significance, with *denoting p ≤ 0.05 and **denoting p ≤ 0.01. Data reported as group mean with error bars denoting SEM.
Mentions: Marked differences in fluorescence intensity were noted in AD patients depending on their APOE genotype. Those with ε3,3 genotypes had overall higher dynactin-P50 levels and lower P-Tau levels compared to their ε4,4 counterparts (Figures 6A,B, representative images, Figure 6C, fluorescence quantification). This was confirmed in Western blot: relative to actin steady-state levels, overall, the expression of hyperphosphorylated tau is higher in Alzheimer patients with APOE ε4,4 than in patients with APOE ε3,3, while dynactin and synaptophysin were lower (Figures 6D,E). As synaptophysin is commonly used as a marker for healthy functional synapses, this implies a connection between APOE genotype, retrograde transport, and synaptic integrity. Interestingly, in comparing the right-most lanes in the Alzheimer ε3,3 and ε4,4 western blot (Figure 6E, gray boxes), the hyperphosphorylated tau, synaptophysin, and dynactin-P50 levels are almost identical, perhaps explained by risk factors other than APOE genotype.

Bottom Line: In contrast, in Alzheimer's, βAPP and dynactin were significantly reduced.It is logical to conclude, then, that as neurons age successfully, there is coordination between retrograde delivery and maintenance and repair, as well as between retrograde delivery and degradation and/or recycling of spent proteins.We conclude that even in disease the ε3 allele is neuroprotective.

View Article: PubMed Central - PubMed

Affiliation: Donald W. Reynolds Department of Geriatrics, University of Arkansas for Medical Sciences Little Rock, AR, USA.

ABSTRACT
Reports from neural cell cultures and experimental animal studies provide evidence of age- and disease-related changes in retrograde transport of spent or misfolded proteins destined for degradation or recycling. However, few studies address these issues in human brain from those who either age without dementia and overt neuropathology, or succumb to Alzheimer's; especially as such propensity may be influenced by APOE genotype. We studied the expression and distribution of the dynein subunit dynactin-P50, the β amyloid precursor protein (βAPP), and hyperphosphorylated tau (P-tau) in tissues and tissue sections of brains from non-demented, neuropathology-free patients and from Alzheimer patients, with either APOE ε3,3 or APOE ε4,4. We found that advanced age in patients without dementia or neuropathological change was associated with coordinated increases in dynactin-P50 and βAPP in neurons in pyramidal layers of the hippocampus. In contrast, in Alzheimer's, βAPP and dynactin were significantly reduced. Furthermore, the dynactin-P50 and βAPP that was present was located primarily in dystrophic neurites in Aβ plaques. Tissues from Alzheimer patients with APOE ε3,3 had less P-tau, more βAPP, dynactin-P50, and synaptophysin than did tissues from Alzheimer patients carrying APOE ε4,4. It is logical to conclude, then, that as neurons age successfully, there is coordination between retrograde delivery and maintenance and repair, as well as between retrograde delivery and degradation and/or recycling of spent proteins. The buildup of proteins slated for repair, synaptic viability, transport, and re-cycling in neuron soma and dystrophic neurites suggest a loss of this coordination in Alzheimer neurons. Inheritance of APOE ε3,3 rather than APOE ε4,4, is associated with neuronal resilience, suggestive of better repair capabilities, more synapses, more efficient transport, and less hyperphosphorylation of tau. We conclude that even in disease the ε3 allele is neuroprotective.

No MeSH data available.


Related in: MedlinePlus