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Oral Sessions 軸索輸送、神経細胞死

2O4-1 Concomitant disruption of dynein-mediated retrograde endosome trafficking impedes APP metabolism Nobuyuki Kimura¹，Eriko Samura²，Keiko Suzuki¹，Sachi Okabayashi³，Nobuhiro Shimozawa⁴，Yasuhiro Yasutomi⁴ ¹Dept Alzheimer Dis Res, NCGG，²Dept Neurol, Grad Sch Med, Univ Tokyo，³Corp Prod Res Lab Primates，⁴TPRC, NIBIOHN It is widely accepted that β-amyloid protein (Aβ) plays a pivotal role in Alzheimer’s disease (AD) pathogenesis, and accumulating evidence suggests that endocytic dysfunction correlates with Aβ pathology. The retromer complex is a key element of the endosomal protein sorting machinery, and it mediates the retrograde trafficking of cargos from endosomes to the trans-Golgi network (TGN). Recent genome-wide association studies identified retromer-related genes such as SORL1 and VPS35, and several studies showed that retromer deficiency enhances Aβ pathology both in vitro and in vivo. Cytoplasmic dynein, a microtubule-based motor protein, mediates minus end-directed vesicle transport via interactions with dynactin, another microtubule-associated protein that can interact with retromer. We previously showed that aging attenuates the dynein-dynactin interaction and that dynein dysfunction reproduces age-dependent endocytic disturbance, leading to the intracellular accumulation of β-amyloid precursor protein (APP) and its β-cleavage products including Aβ.  Here, we report that aging disrupts retromer trafficking in nonhuman primate brains, and that dynein dysfunction reproduces age-dependent retromer deficiency such as the endosomal accumulation of retromer-related proteins. Moreover, we demonstrated that the siRNA-mediated disruption of each retrograde endosome trafficking pathway did not alter endogenous APP metabolism such as observed in aged monkey brains and dynein-depleted cells. These findings suggest that dynein dysfunction can cause retromer deficiency and that concomitant disruption of retrograde trafficking pathways may be the key factor underlying age-dependent Aβ pathology.		2O4-2 Axon initial segment cytoskeleton shows a more complicated pattern during brain development. Takeshi Yoshimura¹，Sharon R. Stevens²，Cristophe Leterrier³，Michael C. Stankewich⁴，Genki Amano¹，Sarina Han¹，Sho Shikada¹，Hironori Takamura¹，Ko Miyoshi¹，Matthew N. Rasband²，Taiichi Katayama¹ ¹Dept Child Development & Mol Brain Sci, United Grad Sch Child Development, Osaka Univ，²Dept Neurosci, Baylor College of Medicine，³Aix Marseille Université, CNRS，⁴Dept Pathology, Yale Univ Axon initial segments (AIS) and nodes of Ranvier are highly specialized axonal membrane domains enriched in Na+ channels. These Na+ channel clusters play essential roles in action potential initiation and propagation. AIS and nodal Na+ channel complexes are linked to the actin cytoskeleton through βIV spectrin. However, neuronal βIV spectrin exists as two main splice variants: a longer βIVΣ1 variant with canonical N-terminal actin and αII spectrin-binding domains, and a shorter βIVΣ6 variant lacking these domains. Here, we show that the predominant neuronal βIV spectrin splice variant detected in the developing brain switches from βIVΣ1 to βIVΣ6, and that this switch is correlated with expression changes in ankyrinG splice variants. We show that βIVΣ1 is the predominant splice variant at nascent and developing AIS and nodes of Ranvier, but with increasing age and in adults βIVΣ6 becomes the main splice variant. Remarkably, super-resolution microscopy revealed that the spacing of spectrin tetramers between actin rings remains unchanged, but that shorter spectrin tetramers may also be present. Thus, during development βIV spectrin may undergo a switch in the splice variants found at AIS and nodes of Ranvier.

2O4-3 Regulation of CCL2 (MCP-1) expression from human mesenchymal stem/stromal cells after ischemia through inflammatory cytokines Hirokazu Ohtaki¹，Kazumichi Yagura¹，Jun Watanabe²，Kazuyuki Miyamoto³，Kenji Dohi³，Kazuho Honda¹ ¹Dept Anat, Showa Univ Sch Med，²Centr Biotech, Showa Univ，³Dept Emergency & Critical Care Med, Showa Univ Sch Med We have reported that transplanted human mesenchymal stem/stromal cells (hMSCs) suppressed neuronal damage after ischemia and spinal cord injury. However, it is still unclear how hMSCs responded in the CNS parenchyma after the transplantation. The purpose of present study is to determine and understand the cell-cell communication between hMSCs and recipient tissues during CNS diseases. The culturing hMSCs were exposed condition media of mouse hippocampal homogenate which obtained from 1day after transient forebrain ischemia (ischemic brain condition medium: ibCM) to mimic hippocampal state of brain. Then, the cells were surveyed the transcriptome in comparison with non-ischemic hippocampal homogenate (brain condition medium: bCM). The hMSCs exposed by ibCM increased 98 genes >2-fold more and decreased 78 genes <2-fold more to compare with those by bCM. The top category of gene ontology included several chemokines such as CCL2 (MCP-1). Exposing the ibCM from different region of the brain, MCP-1 was increased in the media after hippocampal ibCM, but not cortical and cerebellar ibCM by ELISA. Moreover, gene expression of CCL2 were increased by the application of recombinant mouse IL-1β or TNFα in a dose-dependent manner, but not IFNγ, IL-4, IL-13 and IL-10. Then, the hMSCs were exposed ibCM in IL-1α/β and TNFα knockout (KO) mice. The increased MCP-1 with ibCM of wild-type mice was suppressed by the ibCM in IL-1 and TNFα KO mice. Co-application of IL-1β and TNFα further increased CCL2 expression on hMSCs. Interestingly, Co-application of these proinflammatiory cytokines and IL-4 or IL-10 into hMSCs culture also further increased the expression of CCL2. These results suggest that enhancing of the MCP-1 in hMSCs might be regulated by pro-inflammatory cytokines.		2O4-4 S6 kinase and insulin/IGF signaling regulates accumulation and toxicity of tau through Ser262 phosphorylation in a Drosophila model of tauopathy Kanae Ando^1,2，Motoki Hayashishita¹，Tomoki Chiku²，Taro Saito^1,2，Akiko Asada^1,2，Shin-ichi Hisanaga^1,2，Koichi M Iijima^3,4 ¹Dept of Biol. Sci. Grad Sch Sci & Eng. TMU，²Dept of Biol Sci, Sch of Sci & Eng, TMU，³Dept Alzheimer’s Disease Res, NCGG，⁴Dept Exp Gerontology, Grad Sch Pharm Sci, Nagoya City Univ Accumulation of microtubule-associated protein tau is associated with Alzheimer disease (AD) and a family of related neurodegenerative diseases called tauopathies. In disease brains, tau is hyperphosphorylated and accumulated, which is thought to cause neuron loss. The insulin/insulin-like growth factor (IGF) signaling is important for neuronal growth, synaptic maintenance and neuroprotection, and disrupted in AD brains. However, how the insulin/IGF signaling affects tau metabolism and toxicity has not been fully elucidated. Here we report that an insulin/IGF signaling, insulin-responsive kinase ribosomal protein S6 kinase (S6K) and insulin receptor substrate (IRS), regulates accumulation and toxicity of tau in a Drosophila model. We found that S6K knockdown increased total tau levels and enhanced tau-induced neurodegeneration in the fly eyes. Tau is reported to be stabilized by its phosphorylation at a disease-associated site Ser262, and we found that increase in tau levels caused by S6K is depending on Ser262 phosphorylation. S6K is known to be activated by insulin/IGF signaling and subsequently induce negative feedback of this pathway by promoting degradation of Insulin receptor substrate (IRS). In fact, S6K knockdown increased the levels of chico, the Drosophila homolog of IRS. Interestingly, chico knockdown reduced tau phosphorylated at Ser262, suggesting that S6K regulates tau levels via IRS. These results suggest that disruption of the insulin/ IGF signaling causes abnormal phosphorylation of tau at Ser262, resulting in its accumulation and enhanced neurodegeneration. Further study of this pathway may reveal of molecular links between metabolic diseases and AD and other tauopathies.