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. 2007 Jun 27;27(26):7011-20.
doi: 10.1523/JNEUROSCI.4272-06.2007.

Impairments in fast axonal transport and motor neuron deficits in transgenic mice expressing familial Alzheimer's disease-linked mutant presenilin 1

Orly Lazarov  1 , Gerardo A Morfini, Gustavo Pigino, Archana Gadadhar, Xiangjun Chen, John Robinson, Hanson Ho, Scott T Brady, Sangram S Sisodia
Affiliations

Impairments in fast axonal transport and motor neuron deficits in transgenic mice expressing familial Alzheimer's disease-linked mutant presenilin 1

Orly Lazarov et al. J Neurosci. .

Abstract

Presenilins (PS) play a central role in gamma-secretase-mediated processing of beta-amyloid precursor protein (APP) and numerous type I transmembrane proteins. Expression of mutant PS1 variants causes familial forms of Alzheimer's disease (FAD). In cultured mammalian cells that express FAD-linked PS1 variants, the intracellular trafficking of several type 1 membrane proteins is altered. We now report that the anterograde fast axonal transport (FAT) of APP and Trk receptors is impaired in the sciatic nerves of transgenic mice expressing two independent FAD-linked PS1 variants. Furthermore, FAD-linked PS1 mice exhibit a significant increase in phosphorylation of the cytoskeletal proteins tau and neurofilaments in the spinal cord. Reductions in FAT and phosphorylation abnormalities correlated with motor neuron functional deficits. Together, our data suggests that defects in anterograde FAT may underlie FAD-linked PS1-mediated neurodegeneration through a mechanism involving impairments in neurotrophin signaling and synaptic dysfunction.

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Figures

Figure 1.
Figure 1.
Reduction in anterograde FAT of full-length APP in ligated sciatic nerves of FAD-linked PS1 variants. A, Fl-APP, APP is accumulated at the proximal stump of ligated nerves 6 h after ligation in mice harboring PS1HWT. Although steady-state levels of APP are comparable between intact sciatic nerve segments of PS1HWT and PS1ΔE9 mice, accumulation of APP at the proximal stump of ligated nerves is significantly reduced in PS1ΔE9 mice. Similarly, transgenic mice harboring APPswe × PS1ΔE9 exhibit reduced accumulation of APP at the proximal stump of the ligated sciatic nerve compared with APPswe mice. Levels of APP accumulated at the distal site of the ligation remained unchanged in all cases. Expression of full-length PS1, PS1NTF, or full-length PS1ΔE9 is unchanged in the intact and ligated sciatic nerve of FAD-linked PS1 and APP variants. Immunoblot using anti-α-tubulin antibodies was used to control for equal amounts of protein loading. B, Densitometric analysis of APP accumulation in nerves of FAD-linked APP and PS1 variants 6 h after ligation as shown in A. Graphs show APP levels normalized to α-tubulin levels. C, APP accumulation at the proximal stump of the ligature is also reduced in the sciatic nerve of mice harboring PS1M146L compared with mice harboring PS1HWT. D, Densitometric analysis of APP accumulation in nerves of FAD-linked PS1HWT and PS1M146L variants 6 h after ligation as shown in D, Fl-APP panel. Fl-APP, Full-length APP; I, intact nerve segment; P, proximal nerve segment; D, distal nerve segment. Molecular weight markers are indicated in kilodaltons.
Figure 2.
Figure 2.
Reduced rate of anterograde FAT of selected membrane proteins in ligated nerves of FAD-linked PS1ΔE9 mutant compared with PS1HWT. The levels of APP, Trk receptor, KHC, and KLC accumulated at the proximal stump of the ligation site in sciatic nerve of PS1ΔE9 mice are reduced compared with levels observed in nerves of PS1HWT mice. However, accumulation of PrP molecules in the proximal stump is comparable in sciatic nerves of PS1HWT and PS1ΔE9. α-Tubulin was used as loading control. I, Intact nerve segment; P, proximal nerve segment. Molecular weight markers are in kilodaltons. B, Densitometric analysis of data in A. Graphs show APP, Trk, PrP, KHC, and KLC levels normalized to α-tubulin levels. A.U., Arbitrary units.
Figure 3.
Figure 3.
FAD-linked mutant PS1ΔE9 mice exhibit impaired motor performance. Average running time (minutes) on the rotorod for transgenic mice harboring PS1HWT (gray bar) or PS1ΔE9 (black bar) at 5 and 10 months of age. FAD-linked PS1ΔE9 mice exhibit impaired performance on the rotorod with shorter time periods spent on the cylinder (*p ≤ 0.005, ANOVA).
Figure 4.
Figure 4.
Conduction velocity, muscle tissue morphology, and myelination are intact in sciatic nerve of FAD-linked PS1 variants. A, CMAPs were recorded after distal and proximal stimulation of sciatic nerves of transgenic mice harboring FAD-linked PS1HWT and PS1ΔE9. Waveform, latencies, and amplitudes of CMAPs were found to be similar in both groups. DL, Distal latency; PL, proximal latency; CV, conduction velocity; AMP (D), distal amplitude (DA); AMP (P), proximal amplitude (PA). Ba, Bc, Muscle sections of PS1HWT (a) and FAD-linked PS1ΔE9 (c) mice. Immunostaining with antibodies raised against slow-tonic myosin heavy chain isoforms, indicating muscle morphology (green), and with antibodies raised against collagen IV (red) revealed no signs of muscular atrophy. Scale bar, 10 μm. Bb, Bd, Nodal and paranodal structures of sciatic nerves of PS1HWT (b) and FAD-linked PS1ΔE9 (d) mice were visualized using antibodies raised against pan VGSC (red) and antibodies raised against paranodin/Caspr (green), respectively. No morphological abnormalities could be detected in PS1ΔE9 mice. Scale bar, 50 μm.
Figure 5.
Figure 5.
Neuropathology in lumbar spinal cord of FAD-linked PS1ΔE9 mice. A, Western blot analysis of tau phosphorylation in detergent-soluble protein extracts of lumbar spinal cord of PS1HWT and PS1ΔE9 mice. Note the increased immunoreactivity for PHF-1 in the spinal cord of PS1ΔE9 compared with PS1HWT mice. No significant change in the expression of total tau (Tau5) was observed between PS1ΔE9 and PS1HWT mice samples. Tau isoforms of medium (arrows) and high (arrows) molecular weight are indicated. B, Distribution and localization of PHF-1 expression in lumbar spinal cord sections of PS1ΔE9 and PS1HWT mice. Low-power (a, b) and high-power (c–f) images of PHF-1 immunoreactivity in spinal cord sections of PS1HWT (b, d, f) and PS1ΔE9 (a, c, e) show increased PHF-1 immunoreactivity in spinal cord sections of PS1ΔE9 mice. Higher levels of PHF-1 immunoreactivity were detected in white matter and in cell bodies in the ventral horn (arrowheads). Scale bars: a, b, 750 μm; c, d, 110 μm; e, f, 65 μm. C, Phosphorylation of NF-M is markedly increased in detergent-soluble protein extracts of lumbar spinal cord of PS1ΔE9 mice compared with PS1HWT mice, as shown by SMI34 and SMI31immunoreactivity. These antibodies recognize a phosphorylated epitope on both NF-H and NF-M subunits. Note that not all phospho-epitopes on NF-M are altered in PS1ΔE9, as shown by RM055, a monoclonal phospho-specific antibody that binds to a phosphorylated epitope in the tail domain of NF-M (Virginia Lee, personal communication).
Figure 6.
Figure 6.
FAD-linked mutant PS1-induced neuropathology. Appropriate neurotrophic support and synaptic function depends on kinesin 1-mediated transport of neurotrophin receptors (Trk) and synaptic cargoes to their final sites of utilization. In a model encompassing our data, expression of FAD-linked PS1 mutants (mut PS1) results in increased GSK-3 activation (Pigino et al., 2003), possibly by altering the activity of phospho-transferases involved in GSK-3 regulation (Beffert et al., 2002; Morfini et al., 2004). Activated GSK-3 phosphorylates KLC (P), which in turn promotes dissociation of kinesin-1 from its transported cargo (Morfini et al., 2002b), resulting in impaired anterograde FAT of critical axonal cargoes (Pigino et al., 2003). Additionally, increased GSK-3 activation leads to the characteristic increases in tau and neurofilament (NF) phosphorylation, widely reported in AD. FAD-linked mutant PS1-induced reductions in FAT would result in impaired neurotrophin signaling and synaptic dysfunction. PIP3, Phosphatidylinositol 3,4,5-triphosphate; PP1, protein phosphatase-1; CDK5, cyclin-dependent kinase-5.
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References

    1. Annaert WG, Esselens C, Baert V, Boeve C, Snellings G, Cupers P, Craessaerts K, De Strooper B. Interaction with telencephalin and the amyloid precursor protein predicts a ring structure for presenilins. Neuron. 2001;32:579–589. - PubMed
    1. Assini A, Terreni L, Borghi R, Giliberto L, Piccini A, Loqui D, Fogliarino S, Forloni G, Tabaton M. Pure spastic paraparesis associated with a novel presenilin 1 R278K mutation. Neurology. 2003;60:150. - PubMed
    1. Bajaj NP, Miller CC. Phosphorylation of neurofilament heavy-chain side-arm fragments by cyclin-dependent kinase-5 and glycogen synthase kinase-3alpha in transfected cells. J Neurochem. 1997;69:737–743. - PubMed
    1. Baki L, Shioi J, Wen P, Shao Z, Schwarzman A, Gama-Sosa M, Neve R, Robakis NK. PS1 activates PI3K thus inhibiting GSK-3 activity and tau overphosphorylation: effects of FAD mutations. EMBO J. 2004;23:2586–2596. - PMC - PubMed
    1. Beffert U, Morfini G, Bock HH, Reyna H, Brady ST, Herz J. Reelin-mediated signaling locally regulates protein kinase B/Akt and glycogen synthase kinase 3beta. J Biol Chem. 2002;277:49958–49964. - PubMed

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