Mounting evidence suggests that Hsp90 is present and functionally active in the extracellular space. The biological function of extracellular Hsp90 (eHsp90) remains relatively uncharacterized compared to that of intracellular Hsp90. eHsp90 has been shown to interact with a finite number of extracellular proteins, however, despite the identification of eHsp90 interacting proteins, the function of eHsp90 in these complexes is unknown. Several reports suggest a role for eHsp90α in cell migration and invasion. Reported targets for eHsp90 stimulated cell migration include MMPs, LRP-1, tyrosine kinase receptors and possible others unidentified. Limited studies report a role for eHsp90β. Recently, Hsp90α and Hsp90β were isolated in a complex containing fibronectin (FN) on the surface of MDA-MB-231 breast cancer cells. Herein, we report direct binding of Hsp90α and Hsp90β to FN using a solid phase binding assay and surface plasmon resonance (SPR) spectroscopy. SPR spectroscopy showed that Hsp90β bound the 70 kDa amino-terminal fragment of FN (FN70), but that binding of FN to Hsp90β was not limited to FN70. Confocal microscopy showed regions of colocalization of Hsp90 with extracellular FN matrix fibrils in Hs578T breast cancer cell lines. Treatment of Hs578T breast cancer cells with novobiocin (an Hsp90 inhibitor) and an LRP-1 blocking antibody resulted in a loss of FN matrix and FN endocytosis (novobiocin treated). Addition of exogenous Hsp90β was able to recover such effect after both treatments. FN was shown to colocalize with intracellular LRP-1 in novobiocin treated Hs578T cells. Immunoprecipitation of an LRP-1 containing complex showed the presence of Hsp90 and 70 and 120+ kDa FN fragments. Treatment of Hs578T cells with novobiocin increased the level of FN120+ bound in LRP-1 immunoprecipitate. Exogenous Hsp90β decreased the level of low and high molecular weight FN fragments in a complex with LRP-1, despite the fact that higher levels of lower molecular weight FN fragments were detected in this cell lysate compared to the other treatments. We report FN as a novel interacting protein of eHsp90. Taken together, we provide evidence for a direct role of eHsp90β in FN matrix remodeling. We suggest that Hsp90 plays a direct role in FN matrix dynamics through interaction with FN and LRP-1. The identification of FN as a novel interacting protein of eHsp90 suggests a role for Hsp90 in FN matrix remodeling, which is important for a number of fundamental cellular processes including cell migration and metastasis.

Current dogma suggests that the Heat Shock Protein (Hsp) molecular chaperones and associated co-chaperones function primarily within the cell, although growing evidence suggests a role for these proteins on the plasma membrane of cancer cells. Hsp90 does not function independently in vivo, but instead functions with a variety of partner chaperones and co-chaperones, that include Hsp70 and Hsp90/Hsp70 organising protein (Hop), which are thought to regulate ATP hydrolysis and the binding of Hsp90 to its client proteins. Hsp90 on the plasma membrane appears to have distinct roles in pathways leading to cell motility, invasion and metastasis. We hypothesised that Hsp90 on the plasma membrane is present as part of a multi-chaperone complex that participates in the chaperone-assisted folding of client membrane proteins in a manner analogous to the intracellular chaperone complex. This study characterised the membrane expression of Hsp90, Hsp70 and Hop in different cell models of different adhesive and migratory capacity, namely MDA-MB-231 (metastatic adherent breast cancer cell line), MCF-7 (non-metastatic adherent breast cancer cell line), U937 and THP1 (monocytic leukemia suspension cell lines). Membrane expression of the Hsps was analysed using a combination of subcellular fractionation, biotin-streptavidin affinity purification and immunofluorescence. This study provided evidence to suggest that Hsp90, Hsp70 and Hop are membrane associated in MDA-MB-231 and MCF-7 breast cancer cells. Hsp90, Hsp70 and Hop associated with the plasma membrane such that at least part of the protein is located extracellularly. Immunofluorescence analysis showed that Hsp90, Hsp70 and Hop at the leading edge may localize to membrane ruffles in MDA-MB-231 cells, in accordance with the published role of Hsp90 in migration. An increase in this response was seen in cells stimulated to migrate with SDF-1. By immunoprecipitation, we isolated a putative extracellular membrane associated complex containing Hsp90, Hsp70 and Hop. Using soluble Hsp90 and antibodies against membrane associated Hsp90, we suggested roles for soluble extracellular Hsp90 in mediating migration by wound healing assays and inducing actin reorganisation and vinculin-based focal adhesion formation. The effects of extracellular Hsp90 are mediated by signalling through an ERK1/2 dependent pathway. An anti-Hsp90 antibody against an N-terminal epitope in Hsp90 appeared to be able to overcome the death inducing effects of a combination of SDF-1 and AMD3100, while soluble Hsp90 could not overcome this effect. We propose that this study provides preliminary evidence that extracellular Hsp90 functions as part of a multi-chaperone complex that includes Hsp70 and Hop. The extracellular Hsp90 chaperone complex may mediate cell processes such as migration by modulating the conformation of cell surface receptors, leading to downstream signalling.

To date, a significant portion of research has been devoted to understanding the biological role of the molecular chaperone, heat shock protein 90 (Hsp90), in cancer development and metastasis. Studies have alluded to over 300 clients for intracellular Hsp90, many of which are involved in oncogenic signaling pathways, making Hsp90 a bone fide drug target with several inhibitors already in clinical trials. In recent years, a limited number of extracellular Hsp90 clients have been elucidated with roles in cancer cell migration and invasion. Examples of such clients include matrix metalloproteinase-2 (MMP-2), LRP-1/CD91 and HER-2. Inhibition of extracellular Hsp90 using cellimpermeable inhibitors has been shown to reduce cancer cell migration and metastasis by a hitherto undefined mechanism. Using surface biotinylation and an enzyme linked immunosorbent assay, we provided evidence to support that Hsp90 was found extracellularly in cancers of different origin, cell type and malignancy. Next, we isolated extracellular Hsp90-containing complexes from MDA-MB-231 breast cancer cells using a cell impermeable crosslinker followed by immunoprecipitation and identified by mass spectrometry that the extracellular matrix protein, fibronectin, co-precipitated with Hsp90β. This interaction between Hsp90β and fibronectin was confirmed using pull down assays and surface plasmon resonance spectroscopy with the purified proteins. The ability of exogenous Hsp90β to increase the insoluble fibronectin matrix in Hs578T breast cancer cells indicated a role for Hsp90 in fibronectin matrix stability or fibrillogenesis. Hsp90 knockdown by RNA interference or inhibition with the small molecule inhibitor, novobiocin, resulted in a dose and time-dependent reduction of the extracellular fibronectin matrix. Furthermore, novobiocin was shown to cause the internalization of a fluorescently-labeled exogenous fibronectin matrix incorporated into the extracellular matrix by Hs578T cells. This suggested endocytosis as a possible mechanism for fibronectin turnover. This was supported by the colocalization of fibronectin with key vesicular trafficking markers (Rab-5 and LAMP-1) in small, intracellular vesicles. Furthermore, treatment with the vesicular trafficking inhibitor, methyl-β-cyclodextrin, resulted in a dose-dependent recovery in the extracellular fibronectin matrix following treatment with novobiocin. Taken together, these data provided the first evidence to suggest fibronectin as a new client of Hsp90 and that Hsp90 was involved in regulating extracellular fibronectin matrix dynamics.

AB-type protein toxins such as cholera toxin (CT) consist of a catalytic A subunit and a cell-binding B subunit. CT proceeds through the secretory pathway in reverse, termed retrograde trafficking, and is delivered to the endoplasmic reticulum (ER). In order for the catalytic A1 subunit to become active it must separate from the rest of the holotoxin, and this dissociation event occurs in the ER lumen. CTA1 assumes an unfolded conformation upon dissociation from the holotoxin and is recognized by ERassociated degradation (ERAD), a quality control system that recognizes and exports misfolded proteins to the cytosol for degradation by the 26S proteasome. CTA1 is not degraded by the 26S proteasome because it has few sites for poly-ubitiquination, which is recognized by the cap of the 26S proteasome for degradation. Thus, CTA1 escapes the degradation of ERAD while at the same time using it as a transport mechanism into the cytosol. It was originally proposed that CTA1 is thermally stable and that ER chaperones actively unfolded CTA1 for translocation to the cytosol. In contrast, we hypothesized that the dissociated CTA1 subunit would unfold spontaneously at 37°C. This study focused on the three conditions linked to CTA1 instability and translocation: (i) CTA1 dissociation from the holotoxin, (ii) the translocation-competent conformation of CTA1, and the extraction of CTA1 from the ER into the cytosol. Disruption of any of these events will confer resistance to the toxin. The original model suggested that PDI actively unfolds CTA1 to allow for translocation. However, Fourier transform infrared iv spectroscopy (FTIR) and surface plasmon resonance (SPR) data we have gathered demonstrated that PDI dislodges CTA1 from the rest of the holotoxin without unfolding CTA1. Once released by the holotoxin, CTA1 spontaneously unfolds. PDI is thus required for the toxicity of CT, but not as an unfoldase as originally proposed. CTA1 must maintain an unfolded conformation to keep its translocation-competent state. Based on our model, if CTA1 is stabilized then it will not be able to activate the ERAD translocation system. Our SPR and toxicity results demonstrated that treatment with 4- phenylbutyrate (PBA), a chemical chaperone, stabilizes the structure of CTA1. This stabilization resulted in a decrease in translocation from the ER to the cytosol and a block of intoxication, which makes it a viable candidate for a therapeutic. Because CTA1 exits the ER in an unfolded state, there must be a driving force for this translocation. We hypothesized that Hsp90, a cytosolic chaperone, is responsible for the translocation of CTA1 across the membrane. Previous research had shown Hsp90 to be present on the cytosolic face of the ER and had also shown that Hsp90 will refold exogenously added proteins that enter the cytosol. Using drug treatments and RNAi, we found that Hsp90 is required for the translocation of CTA1 from the ER lumen to the cytosol, a brand new function for this chaperone. We have provided evidence to support a new, substantially different model of CTA1 translocation. CTA1 does not masquerade as a misfolded protein in order to utilize ERAD for entry into the cytosol; it actually becomes misfolded and is treated as any other ERAD substrate. The spontaneous unfolding of CTA1 is the key to its v recognition by ERAD and ultimately its translocation into the cytosol. Host factors play very important roles in intoxication by AB toxins and are targets for blocking intoxication.

No description available.

Ascaris suum were exposed to a number of stressors, including heavy metals and both high (40°C) and low (18°C) temperatures. The 70kD and 90kD heat shock proteins (HSPs) in the different A. suum tissues were analyzed by Western blot and quantitated by Macintosh Image Program.

In another study, hyperthermic treatment was applied to study whether HSP27 expression would be induced in un-injured RGCs, and whether this treatment performed after axotomy would have effects on HSP27 expression, RGC survival and/or regeneration into PN graft. Brief duration of heat shock that elevate the body temperature to 42°C did not up-regulate HSP27 in normal retina. About 8-10% increase in RGC survival in the hyperthermia group was observed compared to those received a 37°C treatment at one week post-axotomy and it depended on the number of post-injury heat treatments applied. At the same time, the number of HSP27-RGCs was also doubled, although the same increase occurred was irrespective of the number of hyperthermic treatments. Multiple heat shock application also significantly enhanced RGC regeneration into PN graft through increased the number of HSP27 regenerating RGCs. These results suggest that post-injury hyperthermic treatment enhance HSP27 induction in RGCs and lead to their successful regeneration into the PNG, whereas further studies are necessary to determine whether the protective effect on survival by heat shock is due to the increase in a subset of HSP27-RGCs. (Abstract shortened by UMI.) / In the second study, different neurotrophic factors were injected into the vitreous to enhance RGC survival and/or regeneration. Brain-derived neurotrophic factor (BDNF) significantly reduced RGC death transiently at 14 days after ON cut, but the expression of HSP27 was reduced compared to bovine serum albumin-injected controls. In peripheral nerve (PN)-grafted retina, BDNF suppressed RGC regeneration via reducing the number of HSP27-RGCs regenerating into the PN graft. In ciliary neurotrophic factor (CNTF)-injected group, although there was only a 10% increase in RGC survival, a 5-fold drastic increase in the number of RGCs which expressed HSP27 was observed, and some of these were found to undergo intra-retinal sprouting similar to VPN-transplanted retina. Combined treatment of intra-vitreal CNTF injection with PNG resulted in a 5 fold-increase in the number of regenerating RGCs as well as increasing the proportion of cells which expressed HSP27 from about 60% to about 80%. The data indicates that HSP27 participates in axonal regrowth especially under synergistic interaction of CNTF and PNG. Intra-vitreal injection of hepatocyte growth factor (HGF) significantly sustained RGC survival compared to BDNF at 28 days after axotomy, but the HSP27 expression in RGCs did not change correspondingly. In the PN-ON grafted retina, HGF promoted more RGCs regenerate without altering the number of HSP27-RGCs regrowing into the PNG. Such results indicate that some trophic factors can specifically enhance or suppress RGC regeneration by modulating HSP27 expression, while other trophic factors promote regeneration which is independent to HSP27. Therefore, it suggests that RGCs may regenerate through at least two different mechanisms. / In this study, the detailed in vivo expression of HSP27 in retinal ganglion cells (RGCs) of golden hamster following axotomy and regeneration stimulated by peripheral nerve grafting and neurotrophic factors have been examined. / In whole-mount normal retinas, HSP27 was constitutively expressed in astrocytes and blood vessels, but not in RGCs. Three days after optic nerve (ON) transection, a small subset of surviving RGC began to express HSP27, the number of which peaked at 7 days and dropped to a minimal level at two weeks post-axotomy. When axotomy was done more proximally to their cell bodies, RGCs survival was significantly decreased but HSP27 expression did not change. This suggests the HSP27 expression does not correlate with cell survival after axonal injury. When a viable peripheral nerve (VPN) was transplanted intravitreally into the eye after ON cut, it induced intra-retinal sprouting of RGCs. Although it did not promote RGC survival, VPN prolonged HSP27 expression up to 56 days after surgery and significantly increased the number of HSP27-RGCs. This protein was localized in the cell body, and especially, in dendritic sprouts and growth cones, indicating that it was transported to active growing sites where it may have a functional role associated with regenerative sprouting. / Wong, Wai Kai. / Adviser: Eric Cho. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3270. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 159-198). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

糖調節蛋白78 (Glucose-regulated protein 78),也稱之Bip,是70kDa熱休克蛋白家族成员之一。已有的研究表明，Bip 是一個具有多功能的蛋白，參與眾多的生物調控過程，包括蛋白折疊，調節鈣平衡，以及作為內質網緊張（ER stress) 的感應器。有研究表明，Bip可以在細胞膜上定位，作為Nodal信號通路的一個輔助受體發揮作用。大量的研究表明，Bip在疾病和代謝方面也發揮重要作用。它參與胰島素的生物合成，並可以提高長期高血糖下β細胞的功能。同時具有抗細胞凋亡的作用。然而Bip在胚胎髮育中的生物功能卻知之甚少。 / 高等脊椎動物腎臟發育中經歷形成3種腎臟形式：前腎，中腎和後腎。腎單位是這3種形式的基本結構和功能單位。在兩棲類，前腎在胚胎時期發揮作用，在胚胎的兩側各只有一個腎單位。這使得爪蟾成為前腎研究的一個非常好的模型。 / 在此項研究中，我們採用非洲爪蛙作為動物模型來研究Bip在胚胎髮育過程中，尤其是在前腎發育中的生物功能。Bip是一個母性因子，在尾芽期，Bip 表達在粘液腺，前腎，肝以及耳囊。 Bip在前腎清晰明確的表達，表明Bip可能在前腎的發育中發揮作用。我們利用BipMO來進行敲低功能實驗，免疫印記顯示BipMO能阻斷帶Flag標記Bip的翻譯。通過原位雜交技術檢測前腎的不同標記基因的表達發現，敲低Bip抑制前腎的形成，表明Bip的正常表達是前腎發育所必須的。 / 為了研究Bip調節前腎的發育的分子機制， 我們使用Affmetrix基因芯片分析在Bip敲低情況下的不同時期胚胎中基因的表達譜，發現在Bip敲低表達的胚胎中，視黃酸信號通路的一些重要的組分的表達受到抑制。爪蛙胚胎原腸胚的動物帽細胞具有多能性， 使用激活素和視黃酸一同處理動物帽細胞可以誘導其分化成為原腎組織。在此體外分化體系中敲低Bip表達，前腎標記基因表達降低，顯示在這一體外系統中前腎的分化受到抑制。該實驗結果與體內實驗結果一致。在體外培養的HEK293T細胞中敲低Bip，抑制視黃酸處理後視黃酸信號通路螢光素報告的活性。 lhx1是前腎發育早期表達標記之一，對於前腎原基的初始化具有重要的作用，同是它也是視黃酸信號通路的靶基因。共同註射BipMO和lhx1表明，前腎的異常可以明顯降低，顯示lhx1可以部份拯救由於Bip缺失所造成的腎臟發育缺陷。該實驗表明Bip通過調節視黃酸信號通路，來調控lhx1的表達前腎的形成。我們進一不發現，敲低Bip後，前腎異常形成的區域內，細胞凋亡增加，增殖減少。該結果在細胞水平上解釋了Bip敲低表達時前腎形成異常的一個原因。 / 综述所述，Bip正確表達对胚胎前肾的发育極為重要。它胚胎发育过程中通过視黃酸信号通路調控lhx1的表達，從而对前肾的形成发挥重要作用。 / Glucose-regulated protein 78 (Grp78), also known as Bip, belongs to heat shock protein 70kDa family. It has been implicated in various biological processes including protein folding, regulation of calcium homeostasis, and serving as a sensor of ER (Endoplasmic Reticulum) stress. Moreover, it can localize in cell membrane, acting as co-receptor of nodal signaling. It is essential for insulin biosynthesis. In addition, Bip plays important roles in a number of diseases. For example, BIP can improve β-cell function in the prolonged hyperglycemia. Knockdown of BIP in β-cell can induce apoptosis. However, little is known about its function during embryonic development. / In high vertebrate, three sets of nephric forms develop successively during embryonic kidney development. They are pronephros, mesonephros, and metanephros. Nephron is the basic structural and functional unit of all these three forms. In amphibian, the pronephros performs function at the embryonic stages, which has only one nephron on either side of the body. It makes Xenopus a very good model for pronephros study. / In this study, we took advantage of Xenopus leavis as an animal model to investigate Bip function during embryonic development, especially its role in pronephros development. We first examined the expression of Bip in developing embryos. Whole mount in situ hybridization showed that Bip was expressed in the cement gland, pronephros, liver and ear vesicle during tailbud stages. It was expressed in the pronephros strongly and clearly which suggested that Bip might play roles in pronephros development. We performed loss-of-function experiment by using morpholino oligonucleotide (MO) knock down translation of endogenous Bip expression. Depletion of Bip impaired formation of pronephros revealed by reduction expression of different pronephros maker genes. The pluripotent animal caps can differentiate into pronephros tissue when treated with activin and all-trans retinoic acid (atRA) in vitro kidney induction assay. In line with our in vivo observation, knockdown of Bip inhibited pronephros differentiation that can normally achieved by combined effects of activin and atRA in animal cap assay. / In order to investigate the molecular mechanisms as how Bip regulated pronephros development, we performed Affymetrix DNA microarray assay to generate gene expression profile in Bip morphants. We found that some components of RA signaling were inhibited when Bip was knockdown. Moreover, knockdown of Bip caused reduction of RA target genes expression after treatment with RA. Consistent with above observations, luciferase activities of RA signaling reporter was reduced in HEK293T cells when BIP expression was depleted by RNAi. lhx1 is one of RA target genes and has been implicated playing essential roles in pronephros development. The inhibition of pronephros formation induced by Bip depletion can be partially rescued by co-overpression, suggesting 1) lhx1 is downstream of Bip in the regulatory network of pronephros formation; and 2) Bip regulates pronephros formation through RA signaling via lhx1. We also found increased apoptosis and decreased cell proliferation at pronephros-forming region in Bip morphants. That could explain the reason of pronephros malformation when Bip is downregulated. / Taken together, Bip is essential for pronephros development. It functions through RA signaling during the complex developmental processes. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Shi, Weili. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 125-143). / Abstracts also in Chinese.

Orientador: Carlos Henrique Inacio Ramos / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-13T20:53:19Z (GMT). No. of bitstreams: 1 Cagliari_ThiagoCarlos_D.pdf: 4482929 bytes, checksum: a1439ac0cca9a21c77eb47d2e163c224 (MD5) Previous issue date: 2009 / Resumo: As proteinas sao macromoleculas que possuem importancia vital para o funcionamento celular, participando da maioria das reacoes biologicas e tambem como componentes estruturais. Para que uma proteina possa exercer sua funcao, precisa atingir sua estrutura nativa atraves de um processo denominado enovelamento proteico. Neste contexto, as chaperonas moleculares sao proteinas capazes de auxiliar no enovelamento de outras proteinas, atuando na prevencao de agregados, desagregacao, translocacao, ativacao, entre outros. Dentre os muitos tipos de chaperonas existentes, neste trabalho foram abordadas as chaperonas das familias Hsp100 e Hsp90, as quais estao relacionadas aos processos de desagregacao e auxilio do enovelamento de proteinas-substrato, respectivamente. O presente trabalho pretendeu produzir as proteinas recombinantes Hsp100 e Hsp82 de cana-de-acucar para a caracterizacao de suas respectivas relacoes estrutura-funcao. Para isto foram empregadas tecnicas como: dicroismo circular, fluorescencia, espalhamento dinamico de luz e ultracentrifugacao analitica. Assim, foi observado que a forca ionica do meio e capaz de influenciar a estrutura quaternaria da proteina Hsp100, a qual se apresenta hexamerica em menores concentracoes de sal. Alem disto, e capaz de reconhecer agregados proteicos formados pelas proteinas luciferase e citrato sintase em ensaios in vitro. Ja a proteina Hsp82 apresentou uma estrutura dimerica, a qual nao e influenciada pela presenca de nucleotideos e apresenta grande estabilidade termica. Finalmente, a proteina p23 humana, a qual e responsavel por auxiliar a proteina Hsp90 no enovelamento de muitas proteinas/complexos proteicos, tambem foi caracterizada. Foram observados indicios de que a regiao C-terminal, rica em residuos de aminoacidos carregados, pode possuir algum grau de estruturacao, apesar de alguns estudos na literatura indicarem o contrario. O estudo das chaperonas de cana-de-acucar foi direcionado por um trabalho previo de anotacao de sequencias relacionadas as chaperonas moleculares no banco de dados do projeto SUCEST (Sugarcane EST Genome Project), o qual foi realizado por nosso grupo de pesquisa. Alem disto, sao apresentados os resultados da anotacao das sequencias relacionadas as chaperonas de eucalipto no banco de dados FORESTs (Eucalyptus Genome Sequencing Project Consortium), possibilitando futuros estudos com estas proteinas. / Abstract: Proteins are macromolecules that are vital to the functioning cell, participating in most of the biological reactions as well as structural components. To perform its function, a protein need to achieve its native structure through a process called protein folding. In this context, the molecular chaperone proteins are able to assist in the folding of other proteins, acting in the prevention of aggregation, disaggregation, translocation, activation, among others. From all types of existing chaperones, here were highlight the Hsp100 and Hsp90 families, which are related to processes of disaggregation and assistance of substrateprotein folding, respectively. This study sought to produce the recombinant proteins Hsp100 and Hsp82 from sugar cane for the characterization of their structure-function relationships. In order to do this, some techniques were employed such as: circular dichroism, fluorescence, dynamic light scattering and analytical ultracentrifugation. As a result, it was observed that the ionic strength of the solvent is capable of influencing the quaternary structure of protein Hsp100, which presents as a hexamer in lower salt concentrations. Furthermore, it is capable of recognizing protein aggregates formed by luciferase protein and citrate synthase in in vitro essays. The Hsp82 protein showed a dimeric structure, which was not influenced by the presence of nucleotides and presented a great thermal stability. Finally, the human protein p23, which is responsible for assisting in the Hsp90 protein folding of many proteins/protein complexes, was also characterized. In spite of some studies indicating the contrary, we observed evidence that the C-terminal region, which is rich in charged amino acid residues, can possible have some structure. The sugarcane chaperones study was guided by a previous chaperone sequence annotation work in the SUCEST (Sugarcane EST Genome Project) databank performed by our research group. In addition, results regarding chaperone sequences annotation in the eucalyptus databank (FORESTs - Eucalyptus Genome Sequencing Project Consortium) were presented here as well, which can also lead to future chaperone proteins function and structure studies. / Doutorado

Indiana University-Purdue University Indianapolis (IUPUI) / The function of major histocompatability complex (MHC) class II molecules is to present antigenic peptides to CD4+ T cells. Typically, MHC class II molecules present peptides derived from exogenous sources. Yet, certain endogenous antigens (Ags) have been found to be presented by class II molecules. Studies suggest that specific heat shock protein family members may play a role in Ag processing and subsequent class II presentation. The studies presented here using B lymphoblasts demonstrate the importance of HSP90α, HSP90β, and possibly HSP70 in selectively regulating MHC class II presentation. Inactivation of HSP90 function using pharmacological inhibitors inhibited class II presentation of exogenous and endogenous GAD, but did not perturb the presentation of several other intra- and extracellular Ags. Individual knockdown of HSP90 isoforms using isoform specific siRNA selectively inhibited GAD Ag presentation. These results demonstrate a requirement for HSP90α and HSP90β in regulating MHC class II presentation of select Ags. Studies to explore mechanistically the roles of HSP90α and HSP90β in regulating GAD Ag presentation were pursued. The pathways of exogenous and endogenous MHC class II presentation of GAD Ag are distinct yet converge with shared terminal processing of GAD within endosomal/lysosomal vesicles. The effect of HSP90 manipulation on various shared components of the MHC class II pathway was examined. The studies presented here suggest that HSP90α and HSP90β regulate MHC class II presentation of GAD Ag at discrete steps most likely involving HSP90 binding to GAD Ag rather than perturbing overall MHC class II function. vi Studying the role of HSP90 in MHC class II presentation in B cells revealed the potential requirement for HSP70 in the presentation of select Ags. The studies presented here demonstrate a possible role for HSP70 in the presentation of Ags such as SMA or Ig kappa by MHC class II molecules. Also included in this work is a study of a rare case of diabetes caused by type B insulin resistance due to development of insulin receptor autoantibodies during the treatment of hepatitis C with interferon alpha and ribavirin. Clinical and laboratory findings in the case are presented.