MAPT/Tau accumulation represses autophagy flux by disrupting IST1-regulated ESCRT-III complex formation: a vicious cycle in Alzheimer neurodegeneration

Macroautophagy/autophagy deficit induces intracellular MAPT/tau accumulation, the hallmark pathology in Alzheimer disease (AD) and other tauopathies; however, the reverse role of MAPT accumulation in autophagy and neurodegeneration is not clear. Here, we found that overexpression of human wild-type full-length MAPT, which models MAPT pathologies as seen in sporadic AD patients, induced autophagy deficits via repression of autophagosome-lysosome fusion leading to significantly increased LC3 (microtubule-associated protein 1 light chain 3)-II and SQSTM1/p62 (sequestosome 1) protein levels with autophagosome accumulation. At the molecular level, intracellular MAPT aggregation inhibited expression of IST1 (IST1 factor associated with ESCRT-III), a positive modulator for the formation of ESCRT (the Endosomal Sorting Complex Required for Transport) complex that is required for autophagosome-lysosome fusion. Upregulating IST1 in human MAPT transgenic mice attenuated autophagy deficit with reduced MAPT aggregation and ameliorated synaptic plasticity and cognitive functions, while downregulating IST1 per se induced autophagy deficit with impaired synapse and cognitive function in naïve mice. IST1 can facilitate association of CHMP2B (charged multivesicular body protein 2B) and CHMP4B/SNF7-2 to form ESCRT-III complex, while lack of IST1 impeded the complex formation. Finally, we demonstrate that MAPT accumulation suppresses IST1 transcription with the mechanisms involving the ANP32A-regulated mask of histone acetylation. Our findings suggest that the AD-like MAPT accumulation can repress autophagosome-lysosome fusion by deregulating ANP32A-INHAT-IST1-ESCRT-III pathway, which also reveals a vicious cycle of MAPT accumulation and autophagy deficit in the chronic course of AD neurodegeneration.Abbreviations: AAV: adeno-associated virus; Aβ: β-amyloid; aCSF: artificial cerebrospinal fluid; AD: Alzheimer disease; ANP32A: acidic nuclear phosphoprotein 32 family member A; ATG: autophagy related; AVs: autophagic vacuoles; CEBPB: CCAAT enhancer binding protein beta; CHMP: charged multivesicular body protein; DMEM: Dulbecco's modified eagle's medium; EBSS: Earle's balanced salt solution; EGFR: epidermal growth factor receptor; ESCRT: endosomal sorting complex required for transport; fEPSPs: field excitatory postsynaptic potentials; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GSK3B: glycogen synthase kinase 3 beta; HAT: histone acetyl transferase; HDAC: histone deacetylase; INHAT: inhibitor of histone acetyl transferase; IST1: IST1 factor associated with ESCRT-III; LAMP2: lysosomal associated membrane protein 2; LTP: long-term potentiation; MAP1LC3: microtubule associated protein 1 light chain 3; MAPT/tau: microtubule associated protein tau; MVB: multivesicular bodies; MWM: Morris water maze; PBS: phosphate-buffered saline solution; RAB7: member RAS oncogene family; SNAREs: soluble N-ethylmaleimide-sensitive factor attachment protein receptors; SQSTM1/p62: sequestosome 1.

Tau accumulation triggers STAT1-dependent memory deficits by suppressing NMDA receptor expression

Intracellular tau accumulation forming neurofibrillary tangles is hallmark pathology of Alzheimer's disease (AD), but how tau accumulation induces synapse impairment is elusive. By overexpressing human full-length wild-type tau (termed hTau) to mimic tau abnormality as seen in the brain of sporadic AD patients, we find that hTau accumulation activates JAK2 to phosphorylate STAT1 (signal transducer and activator of transcription 1) at Tyr701 leading to STAT1 dimerization, nuclear translocation, and its activation. STAT1 activation suppresses expression of N-methyl-D-aspartate receptors (NMDARs) through direct binding to the specific GAS element of GluN1, GluN2A, and GluN2B promoters, while knockdown of STAT1 by AAV-Cre in STAT1^flox/flox mice or expressing dominant negative Y701F-STAT1 efficiently rescues hTau-induced suppression of NMDAR expression with amelioration of synaptic functions and memory performance. These findings indicate that hTau accumulation impairs synaptic plasticity through JAK2/STAT1-induced suppression of NMDAR expression, revealing a novel mechanism for hTau-associated synapse and memory deficits.

Abstract P2-05-03: Clinical implication of APOBEC3A and 3B in Korean patients with breast cancer

Background: Apolipoprotein B mRNA-editing enzyme, catalytic polypeptide-like (APOBEC) family is known to function in innate immune system that protects against retrovirus by deaminating cytosine to uracil in single-stranded DNA. APOBEC family has emerged as an endogenous mutator to contribute to the mutation burden in many cancers. We aimed to evaluate the expression of APOBEC3A (A3A), 3B (A3B) mRNA and APOBEC3A-3B deletion polymorphism in Korean breast cancer patients and investigate the correlation between their expression and clinicopathological characteristics.

Methods: One hundred thirty-eight patients who underwent surgery for breast cancer in Uijeongbu St. Mary's Hospital between January 2013 and December 2016 were evaluated. RNA and DNA were extracted from 138 breast cancer tissues and 10 adjacent normal breast tissues. The levels of A3A and A3B mRNA transcripts were determined using real-time quantitative PCR. Insertion and deletion PCR assays were performed to detect the APOBEC3A-3B deletion allele. Mutation hotspots in exon 2-11 of TP53 and exon 9/20 of PIK3CA were evaluated using direct sequencing method.

Results: The expression of A3B was increased in breast cancer tissues than in normal breast tissues. The median A3B mRNA expression levels in both triple-negative breast cancer and human epidermal growth factor 2-positive breast cancer were significantly higher than in hormone receptor-positive breast cancer. Old age and high ki-67 expression were associated with increased expression of A3A and A3B. Advanced stage, presence of lymph node involvement, and high histological grade were associated with increased expression of A3A. The APOBEC3B deletion allele was found in 78 (56%) tumor samples. There was no significant association between A3A, A3B mRNA levels and the presence of APOBEC3B deletion allele. There was no difference in clinicopathological characteristics according to the presence of APOBEC3B deletion allele except histological grade. The frequency of high histological grade was significantly higher in tumors with APOBEC3B deletion allele than tumors without APOBEC3B deletion allele. TP53 mutations were identified in 12 (8.7%) cases and PIK3CA mutations were identified in 31 (22.5%) cases. There were no significant differences in the levels of A3A and A3B mRNA expression by TP53 mutation status. The presence of a PIK3CA mutation was significantly associated with lower A3A expression.

Conclusions: The levels of A3B mRNA expression showed a difference according to breast cancer subtype, and triple-negative breast cancer showed the highest levels of A3B mRNA expression. The high levels of A3A and A3B mRNA expression were associated with an aggressive phenotype including high proliferation index. The APOBEC3A-3B deletion polymorphism was found in about half of the patients, but there was no difference in clinicopathological factors according to the presence of APOBEC3B deletion allele except histological grade.

Citation Format: Won HS, Sun DS, Ko YH, You SH, Kim YS, Kim JS. Clinical implication of APOBEC3A and 3B in Korean patients with breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-05-03.

Correction to: CDK5 Regulates PD-L1 Expression and Cell Maturation in Dendritic Cells of CRSwNP

The article CDK5 Regulates PD-L1 Expression and Cell Maturation in Dendritic Cells of CRSwNP, written by C. C. Liu, H. L. Zhang, L. L. Zhi, P. Jin, L. Zhao, T. Li, X. M. Zhou, D. S. Sun, G. H. Cheng, Q. Xin, L. Shi, and M. Xia was originally published electronically on the publisher's internet.

Intraportal donor bone marrow transplantation improves intestinal allograft survival in rats under FK506-based immunosuppression

Donor-specific immunosuppression is important in transplant surgery. We examined the effect of intraportal donor-specific bone marrow transplantation on heterotopic small bowel transplantation in the high responder rat combination, ACI to Lewis. The study comprised five treatment groups: untreated controls (group 1); FK506 alone (group 2); low-dose predonine + FK506 (group 3); high-dose predonine + FK506 (group 4); and intraportal donor-specific bone marrow transplantation + FK506 (group 5). Intraportal transplantation was performed pre-operatively and FK506 and predonine given post-operatively. Intestinal allograft survival and changes of intragraft cytokine expression were analysed using the reverse transcription polymerase chain reaction. Allograft survival (mean +/- SD) was lowest in group 1 and greatest in group 5. The group 5 treatment regimen also down-regulated interferon-gamma and interleukin-2 transcription in the transplanted intestine. Intraportal donor bone marrow transplant combined with FK506 immunosuppression was found therefore to be the most beneficial treatment regimen.

Restricted expression of LUZP in neural lineage cells: a study in embryonic stem cells

A novel protein LUZP with 3 leucine zipper motifs at its amino terminus is predominantly expressed in the adult brain. A modified gene targeting approach was employed in an attempt to establish in vitro and in vivo models in which Luzp is knock-out (KO) for phenotype assessment and a reporter gene lacZ is knock-in (KI) for tracing its expression. We report in this study the molecular cloning of the Luzp gene, its targeting vector construction and Luzp-KO/lacZ-KI embryonic stem (ES) clone selection. Since LUZP is also expressed in ES cells, the possibility of embryonic lethality cannot be excluded when attempting to establish Luzp-null mutant mice. We have therefore examined the development of homozygous Luzp-KO/lacZ-KI clones in nude mice. Tissue types derived from all three embryonic germ layers were observed in teratomas developed in nude mice. In situ X-gal staining further revealed restricted expression of LUZP in neural lineage cells.

Essential role of Drosophila Hdac1 in homeotic gene silencing

Deacetylation of the N-terminal tails of core histones plays a crucial role in gene silencing. Rpd3 and Hda1 represent two major types of genes encoding trichostatin A-sensitive histone deacetylases. Although they have been widely found, their cellular and developmental roles remain to be elucidated in metazoa. We show that Drosophila Hdac1, an Rpd3-type gene, interacts cooperatively with Polycomb group repressors in silencing the homeotic genes that are essential for axial patterning of body segments. The biochemical copurification and cytological colocalization of HDAC1 and Polycomb group repressors strongly suggest that HDAC1 is a component of the silencing complex for chromatin modification on specific regulatory regions of homeotic genes.

Identification, molecular characterization, and chromosomal localization of the cDNA encoding a novel leucine zipper motif-containing protein

cDNA clones encoding a novel protein (LUZP) with three leucine zipper motifs were first identified from a murine bone marrow cDNA library. After screening two additional cDNA libraries of activated peritoneal exudate cells, 32 positive clones were obtained from 1.3 x 10(7) phage plaques. Four overlapping clones constituting a total of 7399 bp were sequenced on both strands. The complete open reading frame of LUZP is 1067 amino acids. In addition to three leucine zipper motifs located at the NH2 terminus, there are three nuclear localization signals and a large number of putative Ser/Thr phosphorylation sites. Western blot analyses indicate that LUZP is predominantly expressed in brain, whereas immunocytochemistry data clearly reveal its presence in the nucleus of neurons. Interspecific backcross analyses have mapped Luzp to mouse chromosome 4 in proximity to Gpcr14. Comparative mapping data suggest that the human homolog of Luzp will map to human chromosome 1p36.