Image_1_Amyloid Beta Is Internalized via Macropinocytosis, an HSPG- and Lipid Raft-Dependent and Rac1-Mediated Process.TIFF

Intracellular amyloid β peptide (Aβ) accumulation has drawn attention in relation to the pathophysiology of Alzheimer’s disease in addition to its extracellular deposition as senile plaque. Cellular uptake of extracellular Aβ is one of the possible mechanisms by which intracellular Aβ deposits form. Given the relevance of Aβ inside cells, it is important to understand the mechanism by which it is taken up by them. In this study, we elucidated that Neuro2A and SH-SY5Y cells internalize specifically oligomerized Aβ in a time- and dose-dependent manner. The depletion of plasma membrane cholesterol with methyl-β-cyclodextrin or treatment with trypsin diminished the internalization of oAβ, suggesting that the oAβ uptake might be both a lipid raft-dependent and heparan sulfate proteoglycan-mediated process. Treatment with a macropinocytosis inhibitor (ethylisopropyl amiloride and wortmannin) also drastically reduced the uptake of oligomer-Aβ (oAβ). oAβ-treated cells exhibited an increase in Rac1 activity, indicating that macropinocytosis induced by oAβ is regulated by these small GTPases. These findings suggest that macropinocytosis is a major endocytic route through which oAβ42 enters cells.</p

Image_2_Amyloid Beta Is Internalized via Macropinocytosis, an HSPG- and Lipid Raft-Dependent and Rac1-Mediated Process.TIFF

Intracellular amyloid β peptide (Aβ) accumulation has drawn attention in relation to the pathophysiology of Alzheimer’s disease in addition to its extracellular deposition as senile plaque. Cellular uptake of extracellular Aβ is one of the possible mechanisms by which intracellular Aβ deposits form. Given the relevance of Aβ inside cells, it is important to understand the mechanism by which it is taken up by them. In this study, we elucidated that Neuro2A and SH-SY5Y cells internalize specifically oligomerized Aβ in a time- and dose-dependent manner. The depletion of plasma membrane cholesterol with methyl-β-cyclodextrin or treatment with trypsin diminished the internalization of oAβ, suggesting that the oAβ uptake might be both a lipid raft-dependent and heparan sulfate proteoglycan-mediated process. Treatment with a macropinocytosis inhibitor (ethylisopropyl amiloride and wortmannin) also drastically reduced the uptake of oligomer-Aβ (oAβ). oAβ-treated cells exhibited an increase in Rac1 activity, indicating that macropinocytosis induced by oAβ is regulated by these small GTPases. These findings suggest that macropinocytosis is a major endocytic route through which oAβ42 enters cells.</p

List of primary antibodies.

<p>List of primary antibodies.</p

Representative confocal laser scanning micrograph.

<p>Double immunofluorescence labeling and merged images in muscle sections from patients with s-IBM for CHMP2B (green) and pTDP43 (red) (A), caspase3 (green) and pTDP43 (red) (B), CDK5 (green) and pTDP43 (red) (C), CK1δ (green) and pTDP43 (red) (D), JNK (green) and pTDP43 (red) (E), LRRK2 (green) and pTDP43 (red) (F), annexin 2 (green) and pTDP43 (red) (G), and flotillin-1 (green) and pTDP43 (red) (H). Arrows indicate RVs. Scale bar  = 20 µm.</p

Subject characteristics.

<p>s-IBM, sporadic inclusion body myositis; DMRV, distal myopathy with rimmed vacuoles; F, female; M, male</p

Immunohistochemistry for GVD markers in muscle fibers of s-IBM cases.

<p>Anti-CHMP2B (A), anti-caspase3 (B, C), anti-CDK5 (D), anti- CK1δ (E, F), anti-JNK (G, H), anti-LRRK2 (I), anti-annexin2 (J, K), anti-flotillin-1 (L, M), and anti-pTDP43 (N, O). (B, C), (E, F), (G,H), (J, K), (L, M) and (N, O) indicate 2 independent antibodies for the identification of each protein. Arrows indicate RVs. Scale bar  = 20 µm.</p

Immunohistochemistry for CHMP2B in muscle fibers of s-IBM and DMRV cases.

<p>RVs in all s-IBM (A–C) and distal myopathy with RVs (DMRV) (D) cases detected by anti- CHMP2B antibody. Arrows indicate RVs. Scale bar  = 20 µm.</p

First report of a Japanese family with spinocerebellar ataxia type 10: The second report from Asia after a report from China

<div><p>Spinocerebellar ataxia type 10 (SCA10) is an autosomal-dominant cerebellar ataxia that is variably accompanied by epilepsy and other neurological disorders. It is caused by an expansion of the ATTCT pentanucleotide repeat in intron 9 of the <i>ATXN10</i> gene. Until now, SCA10 was almost exclusively found in the American continents, while no cases had been identified in Japan. Here, we report the first case of an SCA10 family from Japan. The clinical manifestations in our cases were cerebellar ataxia accompanied by epilepsy, hyperreflexia and cognitive impairment. Although the primary pathology in SCA10 in humans is reportedly the loss of Purkinje cells, brain MRI revealed frontal lobe atrophy with white matter lesions. This pathology might be associated with cognitive dysfunction, indicating that the pathological process is not limited to the cerebellum. Examination of the SNPs surrounding the SCA10 locus in the proband showed the “C-expansion-G-G-C” haplotype, which is consistent with previously reported SCA10-positive individuals. This result was consistent with the findings that the SCA10 mutation may have occurred before the migration of Amerindians from East Asia to North America and the subsequent spread of their descendants throughout North and South America.</p></div

Fluorescent repeat-primed PCR analysis in SCA10.

<p>Fluorescent repeat-primed PCR analysis of the <i>ATXN10</i> gene revealed an expanded ATTCT pentanucleotide repeat in the proband (IV-1) and in her mother (III-3).</p

Southern blot analysis in SCA10.

<p>Lane 1 is a size marker, lane 2 is a negative control (13/14 repeats), and lanes 3 and 4 are DNA samples from the proband and her mother, respectively. Southern blot analysis shows an SCA10 repeat expansion of approximately 1,500 repeats in the proband (IV-1) and in her mother (III-3). The arrow shows expanded alleles and arrow head shows normal alleles.</p