Paget's disease of bone (PDB) is characterised by focal lesions of increased bone turnover driven by overactive osteoclasts, which often contain nuclear and cytoplasmic inclusion bodies. Mutations affecting the sequestosome-1 (SQSTM1) ubiquitin-associated (UBA) domain have been identified in individuals with PDB. SQSTM1, also known as p62, is a ubiquitously expressed multidomain scaffold protein of 62 kDa that functions in multiple signalling pathways important for cell survival and osteoclast activity. The mechanisms by which SQSTM1 mutations cause PDB remain unclear. Using immunohistochemistry, I showed evidence that protein degradation pathway components, both from the UPS and the autophagy pathway, are elevated in osteoclasts in patients with PDB compared with control osteoclasts from patients without PDB. Using molecular and microscopical methods to examine Pagetic bone biopsies, osteoclast cultures and various cell lines, I have identified two isoforms of SQSTM1. In all cell types examined, four SQSTM1 transcripts were detected, differing in their 5′-untranslated region; one transcript encodes p62, while the other three encode a 55 kDa isoform of SQSTM1. The newly identified isoform also contains the UBA domain mutated in PDB. Using biochemical and microscopical methods, I found that both SQSTM1 isoforms are degraded by autophagy. The isoforms interact with each other and form aggregates upon autophagy inhibition. SQSTM1-55 is ~21× more abundant in osteoclasts than SQSTM1/p62. Biochemical and microscopical methods showed that PDB-causing mutations in SQSTM1/p62 impair its autophagic degradation. Cell lines expressing SQSTM1/p62 mutations form paracrystalline inclusion bodies that by immuno-transmission electron microscopy (TEM) were found to contain SQSTM1 and ubiquitin and were ultrastructurally identical to those found in PDB. As observed by TEM, these inclusions can be degraded by autophagy. The effects of mutations in SQSTM1-55 have yet to be characterised. Abstract Taken together, these data show that mutations in SQSTM1 isoforms impair protein degradation and can lead to inclusion body formation suggesting that PDB results from dysregulated protein degradation in osteoclasts.

Thèse--Sc. nat.--Montpellier II, 1981. / Bibliogr. p. 229-274.

<p>The bacterial pathogen <i>Legionella pneumophila</i> modulates host immunity using effectors translocated by its Dot/Icm transporter to facilitate its intracellular replication. A number of these effectors employ diverse mechanisms to interfere with protein ubiquitination, a post-translational modification essential for immunity. Here, we have found that <i>L. pneumophila</i> induces monoubiquitination of the E2 enzyme UBE2N by its Dot/Icm substrate MavC(Lpg2147). Ubiquitination of UBE2N by MavC abolishes its activity in the formation of K63-linked polyubiquitin chains, which dampens NF-kB signaling in the initial phase of bacterial infection. The inhibition of UBE2N activity by MavC creates a conundrum because this E2 enzyme is important in multiple signaling pathways, including some that are important for intracellular <i>L. pneumophila</i> replication. Here we also show that the activity of UBE2N is restored by MvcA(Lpg2148), an ortholog of MavC. MvcA functions to deubiquitinate UBE2N-Ub using the same catalytic triad required for its deamidase activity. Structural analysis of the MvcA-UBE2N-Ub complex reveals a crucial role of the insertion domain in MvcA in substrate recognition. Our findings reveal that two remarkably similar proteins catalyze the forward and reverse reactions to impose temporal regulation of the activity of UBE2N during <i>L. pneumophila</i> infection.</p>

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2012 / Cell-extracellular matrix (ECM) detachment triggers a cell survival mechanism known as autophagy. A link between attachment and autophagy suggests a form of adhesion-based regulation, involving mechanotransduction of extracellular-originating signals to the cellular machinery controlling autophagy induction. This implies a role for integrin-linked kinase (ILK), which transmits mechanical stimuli to the mammalian target of rapamycin (mTOR) signalling pathway. Cells with a propensity for metastasis may negate these adhesive signals, inducing autophagy inappropriately. Metastasis is a hallmark of transformation frequently associated with human oesophageal squamous cell carcinoma (HOSCC). Additionally, hyperactive mTOR/mTORC1 signalling correlates increasingly with HOSCC. Therefore, the protein expression of significant signal transduction pathway intermediates was investigated in response to both soluble and ECM-originating stimuli. Measurements by SDS-PAGE and western-blotting coupled to semi-quantitative densitometry, during standard tissue culture conditions, revealed that HOSCC’s expressed moderate-to-high levels of mTOR, p-RPS6(Ser 235/236) and mATG-13; indicating elevated levels of autophagy induction despite aberrant signalling through mTOR/mTORC1. Additionally, an 80 kDa mTORβ isoform was identified in HOSCC cells with lower mTOR abundance, presumably to maintain aberrant mTORC1 signalling. A canonical role for the PI3K/PKB pathway was also identified; where autophagy induction accompanied diminished mTORC1 signalling in response to specific PI3K inhibition with LY294002 and serum withdrawal. However, autophagy induction varied in response to a dose-dependent decrease in mTORC1 signalling after exposure of HOSCC cells to rapamycin. Moreover, specific inhibition of p90RSK with BI-D1870, suggests that mTORC1 phosphorylates RPS6(Ser 235/236) in the absence of MAPK signals. Furthermore, ectopic ILK expression indicated an enhanced potential for adhesion-based signalling. Correspondingly, HOSCC cells commonly increased mTOR and p-RPS6(Ser 235/236) expression following growth on fibronectin or collagen. However, co-immunoprecipitation analysis revealed that signals transduction to mTOR precludes a direct interaction with ILK or FAK. Rather, ECM-modulation of mTOR occurs in a integrin-triggered, but PI3K-depedant manner; since specific inhibition of PI3K negated fibronectin-induced increases of mTOR concentration and RPS6(Ser 235/236) phosphorylation. Thus, these data strongly suggest mTOR is a target for adhesion-based signal transduction, where the ECM influences cell survival through mTORC1. Moreover, exploitation of autophagy induction post cell-ECM detachment in HOSCC may promote the survival of metastases during dissemination.

Cheung Siu Chung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 86-91). / Abstracts in English and Chinese. / Thesis Committee --- p.ii / Statement --- p.iii / Acknowledgements --- p.iv / Abstract --- p.v / 摘要 --- p.vii / Table of Contents --- p.viii / List of Tables --- p.xiii / List of Figures --- p.xiv / Lists of Abbreviations --- p.xvii / Chapter Chapter 1 --- General Introduction / Chapter 1.1 --- The plant secretory pathways --- p.2 / Chapter 1.1.1 --- Three different protein sorting pathways to plant vacuoles --- p.3 / Chapter 1.1.2 --- VSD and VSR --- p.6 / Chapter 1.2 --- Prevacuolar compartments --- p.7 / Chapter 1.2.1 --- Lytic PVC --- p.7 / Chapter 1.2.2 --- BP-80 reporter as a lytic PVC marker --- p.8 / Chapter 1.2.3 --- PVC of PSV --- p.9 / Chapter 1.2.4 --- α-TIP CT reporter as a PVC of PSV marker --- p.10 / Chapter 1.3 --- Project objectives --- p.11 / Chapter Chapter 2 --- Development of Transgenic Tobacco BY-2 Cell Lines Expressing Fluorescent Reporters for Golgi and Prevacuolar Compartments / Chapter 2.1 --- Introduction --- p.13 / Chapter 2.2 --- Materials and Methods --- p.15 / Chapter 2.2.1 --- Chemicals --- p.15 / Chapter 2.2.2 --- Oligonucleotides: Primers and Adapters --- p.15 / Chapter 2.2.3 --- Bacterial Strains --- p.17 / Chapter 2.2.4 --- "Preparation of single-reporter constructs (GONST1 -CFP, CFP-BP-80 and CFP-a-TIP CT reporters)" --- p.17 / Chapter 2.2.4.1 --- "Cloning of pGONSTl-CFPK, a Golgi marker" --- p.17 / Chapter 2.2.4.2 --- "Cloning of pCFP-BP-80K, a lytic PVC marker" --- p.20 / Chapter 2.2.4.3 --- "Cloning of pCFP-α-TIP CTK, a putative marker for PVC of PSV" --- p.22 / Chapter 2.2.5 --- "Preparation of double-reporter constructs (CFP-BP-80-GONST1 - YFP, CFP-α-TIP CT-GONST1-YFP, CFP-BP-80-YFP-α-TIP CT and CFP-α-TIP CT-YFP-BP-80 reporters)" --- p.24 / Chapter 2.2.5.1 --- Insertion ofAdapter-XH to pCFP-BP-80K and pCFP-α-TIP CTK --- p.24 / Chapter 2.2.5.2 --- "Cloning of pCFP-BP-80-GONST 1 -YFPK, pCFP-α-TIP CT- GONST 1-YFPK, pCFP-BP-80-YFP-α-TIP CTK and pCFP- α-TIP CT-YFP-BP-80K" --- p.26 / Chapter 2.2.6 --- Agrobacterium electroporation --- p.30 / Chapter 2.2.7 --- Agrobacterium-mediated transformation of tobacco BY-2 cells --- p.30 / Chapter 2.2.8 --- Selection and screening of transformed BY-2 cells --- p.31 / Chapter 2.2.8.1 --- Antibiotic selection --- p.31 / Chapter 2.2.8.2 --- Fluorescence microscopic screening --- p.31 / Chapter 2.2.9 --- Detection of CFP and YFP reporter genes and their expressions --- p.32 / Chapter 2.2.9.1 --- CTAB genomic DNA extraction --- p.32 / Chapter 2.2.9.2 --- PCR test for CFP (and YFP) transgene in genomic DNA --- p.33 / Chapter 2.2.9.3 --- Subcellular fractionation and protein extraction --- p.33 / Chapter 2.2.9.4 --- Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot analysis --- p.34 / Chapter 2.2.9.5 --- Confocal microscopic study --- p.35 / Chapter 2.3 --- Results --- p.36 / Chapter 2.3.1 --- Establishment of kanamycin-resistant BY-2 cells expressing CFP (and YFP) reporters --- p.36 / Chapter 2.3.2 --- Fluorescence microscopic screening of transgenic BY-2 cell lines --- p.37 / Chapter 2.3.3 --- CFP (and YFP) reporter was successfully integrated into transgenic BY-2 cell genome --- p.41 / Chapter 2.3.4 --- CFP (and YFP) reporter was expressed in transgenic BY-2 cell lines --- p.44 / Chapter 2.3.5 --- Punctate CFP (and YFP) signals were detected in transgenic BY-2 cell lines expressing single (or double) reporter --- p.48 / Chapter 2.4 --- Discussion --- p.53 / Chapter 2.4.1 --- "Transgenic BY-2 cell lines expressing single reporter marking Golgi, lytic PVC and putative PVC of PSV have been developed" --- p.53 / Chapter 2.4.2 --- "Golgi, lytic PVC and putative PVC of PSV were separate and distinct organelles" --- p.53 / Chapter 2.4.3 --- Transgenic BY-2 cell lines expressing double reporter were not yet suitable for subsequent study --- p.55 / Chapter Chapter 3 --- Characterization of Transgenic Tobacco BY-2 Cell Lines Expressing Fluorescent Reporters for Prevacuolar Compartments / Chapter 3.1 --- Introduction --- p.58 / Chapter 3.2 --- Materials and Methods --- p.60 / Chapter 3.2.1 --- Confocal immunofluorescence study --- p.60 / Chapter 3.2.2 --- Drug treatment study (for single-reporter transgenic tobacco BY-2 cell line) --- p.62 / Chapter 3.2.2.1 --- Wortmannin treatment --- p.62 / Chapter 3.2.2.1.1 --- Dosage effect --- p.62 / Chapter 3.2.2.1.2 --- Time-course study --- p.62 / Chapter 3.2.2.2 --- Brefeldin A treatment --- p.63 / Chapter 3.2.2.1.1 --- Dosage effect --- p.63 / Chapter 3.2.2.1.2 --- Time-course study --- p.63 / Chapter 3.2.3 --- Drug treatment study (for double-reporter transgenic tobacco BY-2 cell line) --- p.64 / Chapter 3.2.3.1 --- Wortmannin treatment --- p.64 / Chapter 3.2.3.2 --- Brefeldin A treatment --- p.64 / Chapter 3.3 --- Results --- p.65 / Chapter 3.3.1 --- CFP-α-TIP CT reporter-marked compartment was not Golgi apparatus --- p.65 / Chapter 3.3.2 --- Wortmannin induced CFP-α-TIP CT reporter-marked compartment to vacuolate --- p.69 / Chapter 3.3.3 --- BFA induced CFP-α-TIP CT reporter-marked compartment to form aggregates --- p.72 / Chapter 3.3.4 --- Wortmannin and BFA treatment caused lytic PVC to form small vacuole and Golgi to form aggregate respectively in transgenic BY-2 cell lines expressing double-reporter --- p.75 / Chapter 3.4 --- Discussion --- p.77 / Chapter 3.4.1 --- CFP-α-TIP CT reporter-marked compartment was not Golgi apparatus --- p.77 / Chapter 3.4.2 --- CFP-α-TIP CT reporter-marked compartment was not lytic PVC --- p.77 / Chapter 3.4.3 --- Transgenic BY-2 cell lines expressing double reporter could successfully mark two compartments simultaneously in the same cell --- p.78 / Chapter Chapter 4 --- Summary and Future Prospects / Chapter 4.1 --- Summary --- p.80 / Chapter 4.1.1 --- Hypothesis --- p.80 / Chapter 4.1.2 --- Development of transgenic tobacco BY-2 cell lines --- p.81 / Chapter 4.1.3 --- Characterization of α-TIP CT reporter-marked PVC-like compartment --- p.82 / Chapter 4.2 --- Conclusions --- p.84 / Chapter 4.3 --- Future prospects --- p.85 / References --- p.86

No description available.

Wang, Hao. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 83-93). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Cui, Yong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 73-84). / Abstracts in English and Chinese. / Thesis/Assessment Committee --- p.ii / Statement --- p.iii / Acknowledgements --- p.iv / Abstract --- p.v / 摘要 --- p.vi / Table of Contents --- p.vii / List of Figures --- p.xi / List of Supplemental Tables --- p.xiii / List of Abbreviations --- p.xiii / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter 1.1 --- The plant secretory and endocytosis pathways --- p.2 / Chapter 1.2 --- Rab proteins --- p.4 / Chapter 1.2.1 --- Overview of the small GTPases --- p.4 / Chapter 1.2.2 --- Function of Rab proteins in Arabidopsis --- p.6 / Chapter 1.3 --- Prevacuolar compartments --- p.9 / Chapter 1.3.1 --- PVCs in mammalian and yeast cells --- p.9 / Chapter 1.3.2 --- PVCs in plant cells --- p.9 / Chapter 1.4 --- Vacuolar Sorting Receptors --- p.10 / Chapter 1.5 --- Project objectives --- p.10 / Chapter CHAPTER 2 --- Early and Late Prevacuolar Compartments in Arabidopsis thaliana Cells --- p.12 / Chapter 2.1 --- Introduction --- p.13 / Chapter 2.2 --- MATERIALS AND METHODS --- p.19 / Chapter 2.2.1 --- Plasmid Construction --- p.19 / Chapter 2.2.2 --- Plants materials and growth conditions --- p.19 / Chapter 2.2.3 --- Transient Expression of Arabidopsis suspension cultured cells --- p.20 / Chapter 2.2.4 --- Confocal imaging studies --- p.21 / Chapter 2.3 --- RESULTS --- p.23 / Chapter 2.3.1 --- Organelle markers serve as a tool to study biogenesis and turnover of PVCs --- p.23 / Chapter 2.3.2 --- AtRab5 and AtRab7 proteins show distinct but closely associated patterns in the PVC-to-Vacuole pathway --- p.26 / Chapter 2.3.3 --- AtRab5 and AtRab7 proteins localize on the distinct organellein Arabidopsis thaliana protoplasts --- p.32 / Chapter 2.3.4 --- AtRab5 proteins are closely associated with AtRab7 proteins --- p.35 / Chapter 2.3.5 --- ARA7-Q69L proteins recruit a SNARE complex onto the enlarged PVCs --- p.37 / Chapter 2.4 --- Discussion --- p.40 / Chapter 2.4.1 --- PVC dynamics in Arabidopsis cells --- p.40 / Chapter 2.4.2 --- AtVSR and its point mutation form defined different stages of PVCs in Arabidopsis thaliana protoplasts --- p.41 / Chapter 2.4.3 --- AtRab7 proteins localized on the tonoplast and newly defined late PVCs --- p.41 / Chapter CHAPTER 3 --- AtRab7 proteins play a critical role in mediating vacuolar trafficking in Arabidopsis thaliana Cells --- p.43 / Chapter 3.1 --- Introduction --- p.44 / Chapter 3.2 --- MATERIALS AND METHODS --- p.45 / Chapter 3.2.1 --- Plasmid Construction --- p.45 / Chapter 3.2.2 --- Plants materials and growth conditions --- p.45 / Chapter 3.2.3 --- Transient Expression of Arabidopsis suspension cultured cells --- p.45 / Chapter 3.2.4 --- Confocal imaging studies --- p.45 / Chapter 3.2.5 --- Drug treatment --- p.46 / Chapter 3.3 --- RESULTS --- p.48 / Chapter 3.3.1 --- Mutations at GTP-binding motifs and the effector domain affect the subcellular localization of AtRabG3e --- p.48 / Chapter 3.3.2 --- "AtRabG3e-T22N induced vacuolation of YFP-ARA7 marked PVCs, which remains separated from ER, Golgi and TGN but colocalizes with early PVC markers" --- p.51 / Chapter 3.3.3 --- AtRab7-T22N inhibits vacuolar trafficking of cargo proteins --- p.54 / Chapter 3.3.4 --- Wortmannin-induced vacuolation of late PVCs in transgenic plants --- p.57 / Chapter 3.4 --- Discussion --- p.59 / Chapter 3.4.1 --- The proper targeting of AtRab7 proteins --- p.59 / Chapter 3.4.2 --- AtRab5 and AtRab7 proteins are essential for vacuolar protein trafficking --- p.59 / Chapter CHAPTER 4 --- Summary and Future Perspectives --- p.61 / Chapter 4.1 --- Summary --- p.62 / Chapter 4.1.1 --- Localization of AtRab5 and AtRab7 proteins on different populations of PVCs --- p.62 / Chapter 4.1.2 --- Functions of AtRab7 proteins in Arabidopsis cells --- p.63 / Chapter 4.1.3 --- The Rab conversion maturation model --- p.63 / Chapter 4.2 --- Future perspectives --- p.64 / References --- p.73

Liu, Yang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 99-104). / Abstracts in English and Chinese. / Table of Contents / Thesis/Assessment Committee --- p.ii / Statement --- p.iii / Abstract --- p.iv / 摘要 --- p.vi / Acknowledgements --- p.vii / Table of Contents --- p.viii / List of Tables --- p.xi / List of Figures --- p.xii / List of Abbreviations --- p.xiv / Chapter Chapter 1 --- General Introduction --- p.1 / Chapter 1. --- The plant secretory pathway --- p.2 / Chapter 2. --- Vesicular pathways in plant cells --- p.3 / Chapter 3. --- Prevacuolar Compartments --- p.6 / Chapter 4. --- Vacuolar sorting receptors (VSRs) --- p.7 / Chapter 5. --- BP-80 & Arabidopsis VSR Proteins --- p.8 / Chapter 6. --- Research Objectives --- p.9 / Chapter Chapter 2 --- Development and Expression of GFP-OsVSRs Fusion Reporters in Tobacco BY-2 and Rice Suspension Cultured Cells --- p.11 / Chapter 1. --- Introduction --- p.12 / Chapter 2. --- Materials and methods --- p.14 / Chapter 2.1 --- Construction of GFP-OsVSR chimeric reporters --- p.14 / Chapter 2.2 --- Construction of Golgi Marker and PVC marker --- p.18 / Chapter 2.3 --- Agrobacterium electroporation --- p.27 / Chapter 2.4 --- Transformation of tobacco BY-2 cells --- p.27 / Chapter 2.5 --- Transient expression of GFP-OsVSRs in protoplasts of tobacco BY-2 cells and rice suspension cultured cells --- p.28 / Chapter 2.6 --- Screening of transgenic BY-2 cells expressing GFP-OsVSR reporters --- p.30 / Chapter 2.7 --- Chemicals --- p.33 / Chapter 3. --- Results --- p.34 / Chapter 3.1 --- Study subcellular localization of OsVSR proteins with chimeric GFP-OsVSR reporters --- p.34 / Chapter 3.2 --- Generation of transgenic tobacco BY-2 cell lines expressing GFP-OsVSR reporter constructs --- p.38 / Chapter 3.3 --- Transient expression of GFP-OsVSR reporters in tobacco BY-2 and rice cell protoplasts --- p.40 / Chapter 4. --- Conclusion --- p.42 / Chapter Chapter 3 --- Subcellular Localization of GFP-OsVSR Fusion Reporters in Tobacco BY-2 and Rice Suspension Cultured Cells --- p.43 / Chapter 1. --- Introduction --- p.44 / Chapter 2. --- Materials and methods --- p.45 / Chapter 2.1 --- Confocal immunofluorescence studies --- p.45 / Chapter 2.2 --- Antibodies --- p.46 / Chapter 2.3 --- Wortmannin and BFA drug treatment --- p.46 / Chapter 2.4 --- Electron microscopy of resin-embedded cells --- p.47 / Chapter 2.5 --- Two-dimensional (2-D) gel analysis --- p.47 / Chapter 3 --- Results --- p.49 / Chapter 3.1 --- "Distinct subcellular localizations of GFP-OsVSRl, GFP-OsVSR2 and GFP-OsVSR4 reporters in transgenic BY-2 cell lines" --- p.49 / Chapter 3.2 --- "Subcellular localizations of GFP-OsVSRl, GFP-OsVSR2 and GFP-OsVSR4 in protoplasts of rice suspension cultured cells" --- p.58 / Chapter 3.3 --- Distinct localizations of GFP-OsVSR3 and GFP-OsVSR5 --- p.62 / Chapter 3.4 --- Immunogold EM localization of VSR proteins in rice suspension cultured cells --- p.65 / Chapter 3.5 --- 2-D western blot detection of VSR proteins in various plants --- p.68 / Chapter 4. --- Conclusions --- p.70 / Chapter Chapter 4 --- Summary and Discussion --- p.71 / Chapter 1. --- The significance of this study --- p.72 / Chapter 2. --- The hypothesis in this study --- p.73 / Chapter 3. --- A reporter system to study subcellular localization of OsVSR proteins in both tobacco BY-2 cells and rice suspension cultured cells --- p.75 / Chapter 4. --- Transiently expression of GFP-OsVSR reporters in BY-2 and rice protoplasts ..… --- p.76 / Chapter 5. --- Distinct PVC and Golgi localizations of GFP-OsVSR fusions --- p.77 / Chapter 6. --- Summary and future perspective --- p.78 / Appendix --- p.79 / Characterization of A Novel Rice Protein --- p.79 / Chapter 1. --- Introduction --- p.80 / Chapter 2. --- Materials and methods --- p.83 / Chapter 2.1 --- Antibodies --- p.83 / Chapter 2.2 --- Sodium dodecyl sulfate-polyacrylamide (SDS-PAGE) and western blot analysis of proteins from different plant species --- p.84 / Chapter 2.3 --- Sucrose gradient fractionation with protein F antibody --- p.84 / Chapter 2.4 --- Confocal immunofluorescence studies --- p.85 / Chapter 2.5 --- Affinity purification of Protein F by its antibody --- p.85 / Chapter 3. --- Results --- p.87 / Chapter 3.1 --- Protein F is presented in different plant species --- p.87 / Chapter 3.2 --- Protein F is an integral membrane protein --- p.89 / Chapter 3.3 --- Subcelluar localization of Protein F --- p.91 / Chapter 3.4 --- Affinity purification of Protein F for identification --- p.95 / Chapter 4. --- Summary and future perspectives --- p.97 / Chapter 4.1 --- Summary --- p.97 / Chapter 4.2 --- Future Perspectives --- p.97 / References --- p.99

Alzheimer’s disease (AD) is an age-related neurodegenerative disorder, characterized by global cognitive decline and progressive memory loss. As many other neurological disorders characterized by “proteinopathy”, pathology of AD includes beta-amyloid plaques and tau neurofibrillary tangles, which imply a crucial role of the cellular degradation systems in maintaining homeostasis of protein turnover. This is especially important for post-mitotic neuronal cells since aggravating protein crisis cannot be alleviated by cell division. Autophagy is a cellular degradation process that removes or recycles long-lived proteins and damaged organelles, with its enhancement being remarkably implicated during the progression of Alzheimer’s disease (AD). The majority of studies have hitherto focused on the mechanism of how oligomeric Ah, as one of the potent toxic species in AD, activates autophagy. However, how autophagy is activated remains to be elucidated. The goal of this study is to reveal the underlying mechanisms of autophagy and the subsequent events. Using imaging and biochemical analysis in primary cultures of rat hippocampal neurons, I found that oligomeric An-induced autophagy was initiated by aggregation of the endoplasmic reticulum (ER), in an mTOR-independent pathway. Ao-triggered autophagosomes were derived from omegasomes, starting from the ER aggregation sites. Aggregation of the ER facilitated the clustering of Atg14L to propel the recruitment of Beclin1 and Vps34, which contributes to generation of omegasomes. I further found that p62 targeted to ER aggregates possibly through the enhanced ubiquitinated ER chaperones trapped at ER aggregation sites, implicating the underlying mechanism for how p62 are recruited to autophagosome formation sites (omegasomes). Herein, I report key steps for activation of AH-triggered autophagy, whereby a mechanistic link between ER aggregation, autophagic activation and recruitment of p62 to autophagosome formation sites is revealed. First, Ao-induced ER aggregation triggers autophagy, via the recruitment of Beclin 1 and Vps34 to Atg14L clusters, which is a promoting factor for omegasome formation at the ER aggregation site. Second, the recruitment of p62 to omegasomes is likely mediated by the attraction of the underlying accumulation of ubiquitinated ER chaperones at the ER aggregation site. Up-regulation of autophagy is an early sign of AD. The activation of autophagy without tightly manipulation may contribute to neuronal damage in AD. In addition, how the autophagic substrates can be efficiently incorporated into the autophagic pathway is important for understanding the sustainability of autophagy. Therefore, my study on elucidating how ER aggregation initiates autophagy and the autophagic substrate/cargo receptor p62 are loaded onto autophagosome formation sites may help us to identify a potential therapeutic strategy or target for AD patients. / published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy