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STIP1/HOP regulates the actin cytoskeleton through interactions with actin and changes in actin-binding proteins cofilin and profilin:

- Beckley, Samantha Joy, Hunter, Morgan C, Kituyi, Sarah N, Wingate, Ianthe, Chakraborty, Abantika, Schwarz, Kelly, Makhubu, Matodzi P, Rousseau, Robert P, Ruck, Duncan K, de la Mare, Jo-Anne, Blatch, Gregory L, Edkins, Adrienne L

  • Authors: Beckley, Samantha Joy , Hunter, Morgan C , Kituyi, Sarah N , Wingate, Ianthe , Chakraborty, Abantika , Schwarz, Kelly , Makhubu, Matodzi P , Rousseau, Robert P , Ruck, Duncan K , de la Mare, Jo-Anne , Blatch, Gregory L , Edkins, Adrienne L
  • Date: 2020
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165373 , vital:41238 , https://doi.org/10.3390/ijms21093152
  • Description: Cell migration plays a vital role in both health and disease. It is driven by reorganization of the actin cytoskeleton, which is regulated by actin-binding proteins cofilin and profilin. Stress-inducible phosphoprotein 1 (STIP1) is a well-described co-chaperone of the Hsp90 chaperone system, and our findings identify a potential regulatory role of STIP1 in actin dynamics. We show that STIP1 can be isolated in complex with actin and Hsp90 from HEK293T cells and directly interacts with actin in vitro via the C-terminal TPR2AB-DP2 domain of STIP1, potentially due to a region spanning two putative actin-binding motifs. We found that STIP1 could stimulate the in vitro ATPase activity of actin, suggesting a potential role in the modulation of F-actin formation. Interestingly, while STIP1 depletion in HEK293T cells had no major effect on total actin levels, it led to increased nuclear accumulation of actin, disorganization of F-actin structures, and an increase and decrease in cofilin and profilin levels, respectively. This study suggests that STIP1 regulates the cytoskeleton by interacting with actin, or via regulating the ratio of proteins known to affect actin dynamics.
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  • Date Issued: 2020

HOP expression is regulated by p53 and RAS and characteristic of a cancer gene signature

- Mattison, Stacey A, Blatch, Gregory L, Edkins, Adrienne L

  • Authors: Mattison, Stacey A , Blatch, Gregory L , Edkins, Adrienne L
  • Date: 2018
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/66278 , vital:28928 , https://doi.org/10.1007/s12192-016-0755-8
  • Description: publisher version , The Hsp70/Hsp90 organising protein (HOP) is a co-chaperone essential for client protein transfer from Hsp70 to Hsp90 within the Hsp90 chaperone machine. Although HOP is upregulated in various cancers, there is limited information from in vitro studies on how HOP expression is regulated in cancer. The main objective of this study was to identify the HOP promoter and investigate its activity in cancerous cells. Bioinformatic analysis of the -2500 to +16 bp region of the HOP gene identified a large CpG island and a range of putative cis-elements. Many of the cis-elements were potentially bound by transcription factors which are activated by oncogenic pathways. Luciferase reporter assays demonstrated that the upstream region of the HOP gene contains an active promoter in vitro. Truncation of this region suggested that the core HOP promoter region was -855 to +16 bp. HOP promoter activity was highest in Hs578T, HEK293T and SV40- transformed MEF1 cell lines which expressed mutant or inactive p53. In a mutant p53 background, expression of wild-type p53 led to a reduction in promoter activity, while inhibition of wild-type p53 in HeLa cells increased HOP promoter activity. Additionally, in Hs578T and HEK293T cell lines containing inactive p53, expression of HRAS increased HOP promoter activity. However, HRAS activation of the HOP promoter was inhibited by p53 overexpression. These findings suggest for the first time that HOP expression in cancer may be regulated by both RAS activation and p53 inhibition. Taken together, these data suggest that HOP may be part of the cancer gene signature induced by a combination of mutant p53 and mutated RAS that is associated with cellular transformation.
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  • Date Issued: 2018

Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective

- Edkins, Adrienne L, Price, John T, Pockley, A Graham, Blatch, Gregory L

  • Authors: Edkins, Adrienne L , Price, John T , Pockley, A Graham , Blatch, Gregory L
  • Date: 2017
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/164332 , vital:41109 , DOI: 10.1098/rstb.2016.0521
  • Description: Many heat shock proteins (HSPs) are essential to survival as a consequence of their role as molecular chaperones, and play a critical role in maintaining cellular proteostasis by integrating the fundamental processes of protein folding and degradation. HSPs are arguably among the most prominent classes of proteins that have been broadly linked to many human disorders, with changes in their expression profile and/or intracellular/extracellular location now being described as contributing to the pathogenesis of a number of different diseases. Although the concept was initially controversial, it is now widely accepted that HSPs have additional biological functions over and above their role in proteostasis (so-called ‘protein moonlighting’).
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  • Date Issued: 2017

Hsp40 Co-chaperones as drug targets: towards the development of specific inhibitors

- Pesce, Eva-Rachele, Blatch, Gregory L, Edkins, Adrienne L

  • Authors: Pesce, Eva-Rachele , Blatch, Gregory L , Edkins, Adrienne L
  • Date: 2016
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/66335 , vital:28937 , https://doi.org/10.1007/7355_2015_92
  • Description: publisher version , The heat shock protein 40 (Hsp40/DNAJ) family of co-chaperones modulates the activity of the major molecular chaperone heat shock protein 70 (Hsp70) protein group. Hsp40 stimulates the basal ATPase activity of Hsp70 and hence regulates the affinity of Hsp70 for substrate proteins. The number of Hsp40 genes in most organisms is substantially greater than the number of Hsp70 genes. Therefore, different Hsp40 family members may regulate different activities of the same Hsp70. This fact, along with increasing knowledge of the function of Hsp40 in diseases, has led to certain Hsp40 isoforms being considered promising drug targets. Here we review the role of Hsp40 in human disease and recent developments towards the creation of Hsp40-specific inhibitors.
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  • Date Issued: 2016

Hsp70/Hsp90 organising protein (hop): beyond interactions with chaperones and prion proteins

- Baindur-Hudson, Swati, Edkins, Adrienne L, Blatch, Gregory L

  • Authors: Baindur-Hudson, Swati , Edkins, Adrienne L , Blatch, Gregory L
  • Date: 2015
  • Language: English
  • Type: text , book
  • Identifier: http://hdl.handle.net/10962/164852 , vital:41178 , ISBN 978-3-319-11730-0 , DOI: 10.1007/978-3-319-11731-7_3
  • Description: The Hsp70/Hsp90 organising protein (Hop), also known as stress-inducible protein 1 (STI1), has received considerable attention for diverse cellular functions in both healthy and diseased states. There is extensive evidence that intracellular Hop is a co-chaperone of the major chaperones Hsp70 and Hsp90, playing an important role in the productive folding of Hsp90 client proteins. Consequently, Hop is implicated in a number of key signalling pathways, including aberrant pathways leading to cancer. However, Hop is also secreted and it is now well established that Hop also serves as a receptor for the prion protein, PrPC.
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  • Date Issued: 2015

Sequence and domain conservation of the coelacanth Hsp40 and Hsp90 chaperones suggests conservation of function

- Tastan Bishop, Özlem, Edkins, Adrienne L, Blatch, Gregory L

  • Authors: Tastan Bishop, Özlem , Edkins, Adrienne L , Blatch, Gregory L
  • Date: 2014
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/126932 , vital:35936 , https://doi.10.1002/jez.b.22541
  • Description: Molecular chaperones and their associated co‐chaperones play an important role in preserving and regulating the active conformational state of cellular proteins. The chaperone complement of the Indonesian Coelacanth, Latimeria menadoensis, was elucidated using transcriptomic sequences. Heat shock protein 90 (Hsp90) and heat shock protein 40 (Hsp40) chaperones, and associated cochaperones were focused on, and homologous human sequences were used to search the sequence databases. Coelacanth homologs of the cytosolic, mitochondrial and endoplasmic reticulum (ER) homologs of human Hsp90 were identified, as well as all of the major co‐chaperones of the cytosolic isoform. Most of the human Hsp40s were found to have coelacanth homologs, and the data suggested that all of the chaperone machinery for protein folding at the ribosome, protein translocation to cellular compartments such as the ER and protein degradation were conserved. Some interesting similarities and differences were identified when interrogating human, mouse, and zebrafish homologs. For example, DnaJB13 is predicted to be a non‐functional Hsp40 in humans, mouse, and zebrafish due to a corrupted histidine‐proline‐aspartic acid (HPD) motif, while the coelacanth homolog has an intact HPD. These and other comparisons enabled important functional and evolutionary questions to be posed for future experimental studies.
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  • Date Issued: 2014

The networking of chaperones by co-chaperones: control of cellular protein homeostasis

- Edkins, Adrienne L, Blatch, Gregory L

  • Authors: Edkins, Adrienne L , Blatch, Gregory L
  • Date: 2014
  • Language: English
  • Type: text , book
  • Identifier: http://hdl.handle.net/10962/165107 , vital:41209 , ISBN 978-3-319-11731-7
  • Description: Co-chaperones are important mediators of the outcome of chaperone assisted protein homeostasis, which is a dynamic balance between the integrated processes of protein folding, degradation and translocation. The Networking of Chaperones by Co-chaperones describes how the function of the major molecular chaperones is regulated by a cohort of diverse non-client proteins, known as co-chaperones. The second edition includes the current status of the field and descriptions of a number of novel co-chaperones that have been recently identified. This new edition has a strong focus on the role of co-chaperones in human disease and as putative drug targets. The book will be a resource for both newcomers and established researchers in the field of cell stress and chaperones, as well as those interested in cross-cutting disciplines such as cellular networks and systems biology.
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  • Date Issued: 2014

Assessment of potential anti-cancer stem cell activity of marine algal compounds using an in vitro mammosphere assay:

- de la Mare, Jo-Anne, Sterrenberg, Jason N, Sukhthankar, Mugdha G, Chiwakata, Maynard T, Beukes, Denzil R, Blatch, Gregory L, Edkins, Adrienne L

  • Authors: de la Mare, Jo-Anne , Sterrenberg, Jason N , Sukhthankar, Mugdha G , Chiwakata, Maynard T , Beukes, Denzil R , Blatch, Gregory L , Edkins, Adrienne L
  • Date: 2013
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165184 , vital:41216 , DOI: 10.1186/1475-2867-13-39
  • Description: The cancer stem cell (CSC) theory proposes that tumours arise from and are sustained by a subpopulation of cells with both cancer and stem cell properties. One of the key hallmarks of CSCs is the ability to grow anchorage-independently under serum-free culture conditions resulting in the formation of tumourspheres. It has further been reported that these cells are resistant to traditional chemotherapeutic agents.
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  • Date Issued: 2013

Knockdown of Hop downregulates RhoC expression, and decreases pseudopodia formation and migration in cancer cell lines:

- Willmer, Tarryn, Contu, Lara, Blatch, Gregory L, Edkins, Adrienne L

  • Authors: Willmer, Tarryn , Contu, Lara , Blatch, Gregory L , Edkins, Adrienne L
  • Date: 2013
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165196 , vital:41217 , DOI: 10.1016/j.canlet.2012.09.021
  • Description: The Hsp90/Hsp70 organising protein (Hop) is a co-chaperone that mediates the interaction of Hsp90 and Hsp70 molecular chaperones during assembly of Hsp90 complexes in cells. Formation of Hsp90 complexes is a key intermediate step in the maturation and homeostasis of oncoproteins and several hormone receptors. In this paper, we demonstrate that knockdown of Hop decreased migration of Hs578T and MDA-MB-231 breast cancer cells. Hop was identified in isolated pseudopodia fractions; it colocalised with actin in lamellipodia, and co-sedimented with purified actin in vitro. Knockdown of Hop caused a decrease in the level of RhoC GTPase, and significantly inhibited pseudopodia formation in Hs578T cells. Our data suggest that Hop regulates directional cell migration by multiple unknown mechanisms.
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  • Date Issued: 2013

The African coelacanth genome provides insights into tetrapod evolution:

- Amemiya, Chris T, Alföldi, Jessica, Lee, Alison P, Fan, Shaohua, Philippe, Herve´, MacCallum, Iain, Braasch, Ingo, Manousaki, Tereza, Schneider, Igor, Rohner, Nicolas, Organ, Chris, Chalopin, Domitille, Smith, Jeramiah J, Robinson, Mark, Dorrington, Rosemary A, Gerdol, Marco, Aken, Bronwen, Biscotti, Maria Assunta, Barucca, Marco, Baurain, Denis, Berlin, Aaron, Blatch, Gregory L, Buonocore, Francesco, Burmester, Thorsten, Campbell, Michael S, Canapa, Adriana, Cannon, John P, Christoffels, Alan, De Moro, Gianluca, Edkins, Adrienne L, Fan, Lin, Fausto, Anna Maria, Feiner, Nathalie, Forconi, Mariko, Gamieldien, Junaid, Gnerre, Sante, Gnirke, Andreas, Goldstone, Jared V, Haerty, Wilfried, Hahn, Mark E, Hesse, Uljana, Hoffmann, Steve, Johnson, Jeremy, Karchner, Sibel I, Kuraku, Shigehiro, Lara, Marcia, Levin, Joshua Z, Litman, Gary W, Mauceli, Evan, Miyake, Tsutomu, Mueller, M Gail, Nelson, David R, Nitsche, Anne, Olmo, Ettore, Ota, Tatsuya, Pallavicini, Alberto, Panji, Sumir, Picone, Barbara, Ponting, Chris P, Prohaska, Sonja J, Przybylski, Dariusz, Ratan Saha, Nil, Ravi, Vydianathan, Ribeiro, Filipe J, Sauka-Spengler, Tatjana, Scapigliati, Giuseppe, Searle, Stephen M J, Sharpe, Ted, Simakov, Oleg, Stadler, Peter F, Stegeman, John J, Sumiyama, Kenta, Tabbaa, Diana, Tafer, Hakim, Turner-Maier, Jason, van Heusden, Peter, White, Simon, Williams, Louise, Yandell, Mark, Brinkmann, Henner, Volff, Jean-Nicolas, Tabin, Clifford J, Shubin, Neil, Schartl, Manfred, Jaffe, David B, Postlethwait, John H, Venkatesh, Byrappa, Di Palma, Frederica, Lander, Eric S, Meyer, Axel, Lindblad-Toh, Kerstin

Quinones and halogenated monoterpenes of algal origin show anti-proliferative effects against breast cancer cells in vitro:

- de la Mare, Jo-Anne, Lawson, Jessica C, Chiwakata, Maynard T, Beukes, Denzil R, Blatch, Gregory L, Edkins, Adrienne L

  • Authors: de la Mare, Jo-Anne , Lawson, Jessica C , Chiwakata, Maynard T , Beukes, Denzil R , Blatch, Gregory L , Edkins, Adrienne L
  • Date: 2012
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165165 , vital:41214 , DOI: 10.1007/s10637-011-9788-0
  • Description: Red and brown algae have been shown to produce a variety of compounds with chemotherapeutic potential. A recent report described the isolation of a range of novel polyhalogenated monoterpene compounds from the red algae Plocamium corallorhiza and Plocamium cornutum collected off the coast of South Africa, together with the previously described tetraprenylquinone, sargaquinoic acid (SQA), from the brown algae Sargassum heterophyllum. In our study, the algal compounds were screened for anti-proliferative activity against metastatic MDA-MB-231 breast cancer cells revealing that a number of compounds displayed anti-cancer activity with IC50 values in the micromolar range. A subset of the compounds was tested for differential toxicity in the MCF-7/MCF12A system and five of these, including sargaquinoic acid, were found to be at least three times more toxic to the breast cancer than the non-malignant cell line.
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  • Date Issued: 2012

STAT3 interacts directly with Hsp90:

- Prinsloo, Earl, Kramer, Adam H, Edkins, Adrienne L, Blatch, Gregory L

  • Authors: Prinsloo, Earl , Kramer, Adam H , Edkins, Adrienne L , Blatch, Gregory L
  • Date: 2012
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165142 , vital:41212 , DOI: 10.1002/iub.607
  • Description: Heat shock protein 90 (Hsp90) functionally modulates signal transduction. The signal transducer and activator of transcription 3 (STAT3) mediates interleukin‐6 family cytokine signaling. Aberrant activation and mutation of STAT3 is associated with oncogenesis and immune disorders, respectively. Hsp90 and STAT3 have previously been shown to colocalize and coimmunoprecipitate in common complexes.
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  • Date Issued: 2012

Targeting conserved pathways as a strategy for novel drug development: disabling the cellular stress response:

- Edkins, Adrienne L, Blatch, Gregory L

  • Authors: Edkins, Adrienne L , Blatch, Gregory L
  • Date: 2012
  • Language: English
  • Type: text , book
  • Identifier: http://hdl.handle.net/10962/165129 , vital:41211 , ISBN 978-3-642-28174-7 , DOI: 10.1007/978-3-642-28175-4_4
  • Description: The ability to respond to and cope with stress at a molecular level is essential for cell survival. The stress response is conserved across organisms by the expression of a group of molecular chaperones known as heat shock proteins (HSP). HSP are ubiquitous and highly conserved proteins that regulate cellular protein homeostasis and trafficking under physiological and stressful conditions, including diseases such as cancer and malaria. HSP are good drug targets for the treatment of human diseases, as the significant functional and structural data available suggest that they are essential for cell survival and that, despite conservation across species, there are biophysical and biochemical differences between HSP in normal and disease states that allow HSP to be selectively targeted. In this chapter, we review the international status of this area of research and highlight progress by us and other African researchers towards the characterisation and targeting of HSP from humans and parasites from Plasmodium and Trypanosoma as drug targets.
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  • Date Issued: 2012

Hsp90α/β associates with the GSK3β/axin1/phospho-β-catenin complex in the human MCF-7 epithelial breast cancer model:

- Cooper, Leanne C, Prinsloo, Earl, Edkins, Adrienne L, Blatch, Gregory L

  • Authors: Cooper, Leanne C , Prinsloo, Earl , Edkins, Adrienne L , Blatch, Gregory L
  • Date: 2011
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165096 , vital:41208 , DOI: 10.1016/j.bbrc.2011.08.136
  • Description: Hsp90α/β, the signal transduction chaperone, maintains intracellular communication in normal, stem, and cancer cells. The well characterised association of Hsp90α/β with its client kinases form the framework of multiple signalling networks. GSK3β, a known Hsp90α/β client, mediates β-catenin phosphorylation as part of a cytoplasmic destruction complex which targets phospho-β-catenin to the 26S proteasome. The canonical Wnt/β-catenin pathway promotes stem cell self-renewal as well as oncogenesis. The degree of Hsp90α/β involvement in Wnt/β-catenin signalling needs clarification. Here, we describe the association of Hsp90α/β with GSK3β, β-catenin, phospho-β-catenin and the molecular scaffold, axin1, in the human MCF-7 epithelial breast cancer cell model using selective inhibition of Hsp90α/β, confocal laser scanning microscopy and immunoprecipitation. Our findings suggest that Hsp90α/β modulates the phosphorylation of β-catenin by interaction in common complex with GSK3β/axin1/β-catenin.
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  • Date Issued: 2011

Human DNAJ in cancer and stem cells:

- Sterrenberg, Jason N, Edkins, Adrienne L, Blatch, Gregory L

  • Authors: Sterrenberg, Jason N , Edkins, Adrienne L , Blatch, Gregory L
  • Date: 2011
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165118 , vital:41210 , DOI: 10.1016/j.canlet.2011.08.019
  • Description: The heat shock protein 40 kDa (HSP40/DNAJ) co-chaperones constitute the largest and most diverse sub-group of the heat shock protein (HSP) family. DNAJ are widely accepted as regulators of HSP70 function, but also have roles as co-chaperones for the HSP90 chaperone machine, and a growing number of biological functions that may be independent of either of these chaperones. The DNAJ proteins are differentially expressed in human tissues and demonstrate the capacity to function to both promote and suppress cancer development by acting as chaperones for tumour suppressors or oncoproteins. We review the current literature on the function and expression of DNAJ in cancer, stem cells and cancer stem cells. Combining data from gene expression, proteomics and studies in other systems, we propose that DNAJ will be key regulators of cancer, stem cell and possibly cancer stem cell function. The diversity of DNAJ and their assorted roles in a range of biological functions means that selected DNAJ, provided there is limited redundancy and that a specific link to malignancy can be established, may yet provide an attractive target for specific and selective drug design for the development of anti-cancer treatments.
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  • Date Issued: 2011

Theiler’s murine encephalomyelitis virus infection induces a redistribution of heat shock proteins 70 and 90 in BHK-21 cells, and is inhibited by novobiocin and geldanamycin:

- Mutsvunguma, Lorraine Z, Moetlhoa, Boitumelo, Edkins, Adrienne L, Luke, Garry A, Blatch, Gregory L, Knox, Caroline M

  • Authors: Mutsvunguma, Lorraine Z , Moetlhoa, Boitumelo , Edkins, Adrienne L , Luke, Garry A , Blatch, Gregory L , Knox, Caroline M
  • Date: 2011
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165085 , vital:41207 , DOI: 10.1007/s12192-011-0262-x
  • Description: Theiler’s murine encephalomyelitis virus (TMEV) is a positive-sense RNA virus belonging to the Cardiovirus genus in the family Picornaviridae. In addition to other host cellular factors and pathways, picornaviruses utilise heat shock proteins (Hsps) to facilitate their propagation in cells. This study investigated the localisation of Hsps 70 and 90 in TMEV-infected BHK-21 cells by indirect immunofluorescence and confocal microscopy. The effect of Hsp90 inhibitors novobiocin (Nov) and geldanamycin (GA) on the development of cytopathic effect (CPE) induced by infection was also examined. Hsp90 staining was uniformly distributed in the cytoplasm of uninfected cells but was found concentrated in the perinuclear region during late infection where it overlapped with the signal for non-structural protein 2C within the viral replication complex.
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  • Date Issued: 2011

Cancer stem cells in breast cancer and metastasis:

- Lawson, Jessica C, Blatch, Gregory L, Edkins, Adrienne L

  • Authors: Lawson, Jessica C , Blatch, Gregory L , Edkins, Adrienne L
  • Date: 2009
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/165057 , vital:41205 , DOI: 10.1007/s10549-009-0524-9
  • Description: The cancer stem cell theory poses that cancers develop from a subset of malignant cells that possess stem cell characteristics and has been proposed to account for the development of a variety of malignancies, including breast cancer. These cancer stem cells (CSC) possess characteristics of both stem cells and cancer cells, in that they have the properties of self-renewal, asymmetric cell division, resistance to apoptosis, independent growth, tumourigenicity and metastatic potential. A CSC origin for breast cancer can neatly explain both the heterogeneity of breast cancers and the relapse of the tumours after treatment. However, many reports on CSC in the breast are contradictory. There is variation with respect to how breast cancer stem cells should be identified, their characteristics and a possible lack of correlation between clinical outcome and breast cancer stem cell status of a tumour. These combined factors have made breast cancer stem cells a highly contentious issue. In this review, we highlight the progress in the analysis of cancer stem cells, with an emphasis on breast cancer.
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  • Date Issued: 2009

A Trypanosoma cruzi heat shock protein 40 is able to stimulate the adenosine triphosphate hydrolysis activity of heat shock protein 70 and can substitute for a yeast heat shock protein 40

- Edkins, Adrienne L, Ludewig, M H, Blatch, Gregory L

  • Authors: Edkins, Adrienne L , Ludewig, M H , Blatch, Gregory L
  • Date: 2004
  • Language: English
  • Type: Article
  • Identifier: vital:6465 , http://hdl.handle.net/10962/d1005794 , http://dx.doi.org/10.1016/j.biocel.2004.01.016
  • Description: The process of assisted protein folding, characteristic of members of the heat shock protein 70 (Hsp70) and heat shock protein 40 (Hsp40) molecular chaperone families, is important for maintaining the structural integrity of cellular protein machinery under normal and stressful conditions. Hsp70 and Hsp40 cooperate to bind non-native protein conformations in a process of adenosine triphosphate (ATP)-regulated assisted protein folding. We have analysed the molecular chaperone activity of the cytoplasmic inducible Hsp70 from Trypanosoma cruzi (TcHsp70) and its interactions with its potential partner Hsp40s (T. cruzi DnaJ protein 1 [Tcj1] and T. cruzi DnaJ protein 2 [Tcj2]). Histidine-tagged TcHsp70 (His-TcHsp70), Tcj1 (Tcj1-His) and Tcj2 (His-Tcj2) were over-produced in Escherichia coli and purified by nickel affinity chromatography. The in vitro basal specific ATP hydrolysis activity (ATPase activity) of His-TcHsp70 was determined as 40 nmol phosphate/min/mg protein, significantly higher than that reported for other Hsp70s. The basal specific ATPase activity was stimulated to a maximal level of 60 nmol phosphate/min/mg protein in the presence of His-Tcj2 and a model substrate, reduced carboxymethylated α-lactalbumin. In vivo complementation assays showed that Tcj2 was able to overcome the temperature sensitivity of the ydj1 mutant Saccharomyces cerevisiae strain JJ160, suggesting that Tcj2 may be functionally equivalent to the yeast Hsp40 homologue (yeast DnaJ protein 1, Ydj1). These data suggest that Tcj2 is involved in cytoprotection in a similar fashion to Ydj1, and that TcHsp70 and Tcj2 may interact in a nucleotide-regulated process of chaperone-assisted protein folding.
  • Full Text:
  • Date Issued: 2004
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