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Ciesielski GL, Plotka M, Manicki M, Schilke BA, Dutkiewicz R, Sahi C, Marszalek J, Craig EA. Nucleoid localization of Hsp40 Mdj1 is important for its function in maintenance of mitochondrial DNA. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2233-43. [PMID: 23688635 PMCID: PMC3750215 DOI: 10.1016/j.bbamcr.2013.05.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 05/09/2013] [Accepted: 05/10/2013] [Indexed: 11/26/2022]
Abstract
Faithful replication and propagation of mitochondrial DNA (mtDNA) is critical for cellular respiration. Molecular chaperones, ubiquitous proteins involved in protein folding and remodeling of protein complexes, have been implicated in mtDNA transactions. In particular, cells lacking Mdj1, an Hsp40 co-chaperone of Hsp70 in the mitochondrial matrix, do not maintain functional mtDNA. Here we report that the great majority of Mdj1 is associated with nucleoids, DNA-protein complexes that are the functional unit of mtDNA transactions. Underscoring the importance of Hsp70 chaperone activity in the maintenance of mtDNA, an Mdj1 variant having an alteration in the Hsp70-interacting J-domain does not maintain mtDNA. However, a J-domain containing fragment expressed at the level that Mdj1 is normally present is not competent to maintain mtDNA, suggesting a function of Mdj1 beyond that carried out by its J-domain. Nevertheless, loss of mtDNA function upon Mdj1 depletion is retarded when the J-domain, is overexpressed. Analysis of Mdj1 variants revealed a correlation between nucleoid association and DNA maintenance activity, suggesting that localization is functionally important. We found that Mdj1 has DNA binding activity and that variants retaining DNA-binding activity also retained nucleoid association. Together, our results are consistent with a model in which Mdj1, tethered to the nucleoid via DNA binding, thus driving a high local concentration of the Hsp70 machinery, is important for faithful DNA maintenance and propagation. J-protein co-chaperone Mdj1 is critical for maintenance of functional mtDNA. Majority of Mdj1 localizes to the nucleoid, likely via interaction with mtDNA. Nucleoid localization of Mdj1 is necessary for mtDNA maintenance. Function of Mdj1 in mtDNA maintenance requires cooperation with Hsp70.
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Real-time observation of the conformational dynamics of mitochondrial Hsp70 by spFRET. EMBO J 2013; 32:1639-49. [PMID: 23624933 DOI: 10.1038/emboj.2013.89] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 03/21/2013] [Indexed: 11/08/2022] Open
Abstract
The numerous functions of the important class of molecular chaperones, heat shock proteins 70 (Hsp70), rely on cycles of intricate conformational changes driven by ATP-hydrolysis and regulated by cochaperones and substrates. Here, we used Förster resonance energy transfer to study the conformational dynamics of individual molecules of Ssc1, a mitochondrial Hsp70, in real time. The intrinsic dynamics of the substrate-binding domain of Ssc1 was observed to be uncoupled from the dynamic interactions between substrate- and nucleotide-binding domains. Analysis of the fluctuations in the interdomain separation revealed frequent transitions to a nucleotide-free state. The nucleotide-exchange factor Mge1 did not induce ADP release, as expected, but rather facilitated binding of ATP. These results indicate that the conformational cycle of Ssc1 is more elaborate than previously thought and provide insight into how the Hsp70s can perform a wide variety of functions.
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53
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Varabyova A, Stojanovski D, Chacinska A. Mitochondrial protein homeostasis. IUBMB Life 2013; 65:191-201. [PMID: 23341326 DOI: 10.1002/iub.1122] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 11/29/2012] [Indexed: 11/09/2022]
Abstract
Mitochondria use 800-1,500 proteins to perform their biological functions in the eukaryotic cells. Distinct transport and sorting mechanisms are responsible for the delivery of proteins to the correct location within mitochondria. Mitochondrial proteins undergo processing events and form functional assemblies. Finally, non-functional proteins are cleared to maintain healthy mitochondria. We provide an overview of the processes collectively contributing to the maintenance of mitochondrial protein homeostasis, which is critical for cell physiology and survival.
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Affiliation(s)
- Aksana Varabyova
- International Institute of Molecular and Cell Biology, 02-109 Warsaw, Poland
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Sahi C, Kominek J, Ziegelhoffer T, Yu HY, Baranowski M, Marszalek J, Craig EA. Sequential duplications of an ancient member of the DnaJ-family expanded the functional chaperone network in the eukaryotic cytosol. Mol Biol Evol 2013; 30:985-98. [PMID: 23329686 DOI: 10.1093/molbev/mst008] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Across eukaryotes, Hsp70-based chaperone machineries display an underlying unity in their sequence, structure, and biochemical mechanism of action, while working in a myriad of cellular processes. In good part, this extraordinary functional versatility is derived from the ability of a single Hsp70 to interact with an array of J-protein cochaperones to form a functional chaperone network. Among J-proteins, the DnaJ-type is the most prevalent, being present in all three kingdoms and in several different compartments of eukaryotic cells. However, because these ancient DnaJ-type proteins diverged at the base of the eukaryotic phylogeny, little is understood about the evolutionary basis of their diversification and thus the functional expansion of the chaperone network. Here, we report results of evolutionary and experimental analyses of two more recent members of the cytosolic DnaJ family of Saccharomyces cerevisiae, Xdj1 and Apj1, which emerged by sequential duplications of the ancient YDJ1 in Ascomycota. Sequence comparison and molecular modeling revealed that both Xdj1 and Apj1 maintained a domain organization similar to that of multifunctional Ydj1. However, despite these similarities, both Xdj1 and Apj1 evolved highly specialized functions. Xdj1 plays a unique role in the translocation of proteins from the cytosol into mitochondria. Apj1's specialized role is related to degradation of sumolyated proteins. Together these data provide the first clear example of cochaperone duplicates that evolved specialized functions, allowing expansion of the chaperone functional network, while maintaining the overall structural organization of their parental gene.
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Affiliation(s)
- Chandan Sahi
- Department of Biochemistry, University of Wisconsin-Madison, USA
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55
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Kakoi S, Yorimitsu T, Sato K. COPII machinery cooperates with ER-localized Hsp40 to sequester misfolded membrane proteins into ER-associated compartments. Mol Biol Cell 2013; 24:633-42. [PMID: 23303252 PMCID: PMC3583666 DOI: 10.1091/mbc.e12-08-0639] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Proteins that fail to fold in the endoplasmic reticulum (ER) are subjected to ER-associated degradation (ERAD). Certain transmembrane ERAD substrates are segregated into specialized ER subdomains, termed ER-associated compartments (ERACs), before targeting to ubiquitin-proteasome degradation. The traffic-independent function of several proteins involved in COPII-mediated ER-to-Golgi transport have been implicated in the segregation of exogenously expressed human cystic fibrosis transmembrane conductance regulator (CFTR) into ERACs in Saccharomyces cerevisiae. Here we focus on the properties of COPII components in the sequestration of enhanced green fluorescent protein (EGFP)-CFTR into ERACs. It has been demonstrated that the temperature-sensitive growth defects in many COPII mutants can be suppressed by overexpressing other genes involved in COPII vesicle formation. However, we show that these suppression abilities are not always correlated with the ability to rescue the ERAC formation defect, suggesting that COPII-mediated EGFP-CFTR entry into ERACs is independent of its ER-to-Golgi trafficking function. In addition to COPII machinery, we find that ER-associated Hsp40s are also involved in the sequestration process by directly interacting with EGFP-CFTR. COPII components and ER-associated Hsp40, Hlj1p, act in the same pathway to sequester EGFP-CFTR into ERACs. Our findings point to an as-yet-undefined role of COPII proteins in the formation of ERACs.
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Affiliation(s)
- Shogo Kakoi
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
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56
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Petitjean C, Moreira D, López-García P, Brochier-Armanet C. Horizontal gene transfer of a chloroplast DnaJ-Fer protein to Thaumarchaeota and the evolutionary history of the DnaK chaperone system in Archaea. BMC Evol Biol 2012. [PMID: 23181628 PMCID: PMC3564930 DOI: 10.1186/1471-2148-12-226] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Background In 2004, we discovered an atypical protein in metagenomic data from marine thaumarchaeotal species. This protein, referred as DnaJ-Fer, is composed of a J domain fused to a Ferredoxin (Fer) domain. Surprisingly, the same protein was also found in Viridiplantae (green algae and land plants). Because J domain-containing proteins are known to interact with the major chaperone DnaK/Hsp70, this suggested that a DnaK protein was present in Thaumarchaeota. DnaK/Hsp70, its co-chaperone DnaJ and the nucleotide exchange factor GrpE are involved, among others, in heat shocks and heavy metal cellular stress responses. Results Using phylogenomic approaches we have investigated the evolutionary history of the DnaJ-Fer protein and of interacting proteins DnaK, DnaJ and GrpE in Thaumarchaeota. These proteins have very complex histories, involving several inter-domain horizontal gene transfers (HGTs) to explain the contemporary distribution of these proteins in archaea. These transfers include one from Cyanobacteria to Viridiplantae and one from Viridiplantae to Thaumarchaeota for the DnaJ-Fer protein, as well as independent HGTs from Bacteria to mesophilic archaea for the DnaK/DnaJ/GrpE system, followed by HGTs among mesophilic and thermophilic archaea. Conclusions We highlight the chimerical origin of the set of proteins DnaK, DnaJ, GrpE and DnaJ-Fer in Thaumarchaeota and suggest that the HGT of these proteins has played an important role in the adaptation of several archaeal groups to mesophilic and thermophilic environments from hyperthermophilic ancestors. Finally, the evolutionary history of DnaJ-Fer provides information useful for the relative dating of the diversification of Archaeplastida and Thaumarchaeota.
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Affiliation(s)
- Céline Petitjean
- UPR CNRS 9043, Laboratoire de Chimie Bactérienne, Université d’Aix-Marseille (AMU), 13402 Marseille, Cedex 20, France
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A bacteriophage-encoded J-domain protein interacts with the DnaK/Hsp70 chaperone and stabilizes the heat-shock factor σ32 of Escherichia coli. PLoS Genet 2012; 8:e1003037. [PMID: 23133404 PMCID: PMC3486835 DOI: 10.1371/journal.pgen.1003037] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 09/04/2012] [Indexed: 01/21/2023] Open
Abstract
The universally conserved J-domain proteins (JDPs) are obligate cochaperone partners of the Hsp70 (DnaK) chaperone. They stimulate Hsp70's ATPase activity, facilitate substrate delivery, and confer specific cellular localization to Hsp70. In this work, we have identified and characterized the first functional JDP protein encoded by a bacteriophage. Specifically, we show that the ORFan gene 057w of the T4-related enterobacteriophage RB43 encodes a bona fide JDP protein, named Rki, which specifically interacts with the Escherichia coli host multifunctional DnaK chaperone. However, in sharp contrast with the three known host JDP cochaperones of DnaK encoded by E. coli, Rki does not act as a generic cochaperone in vivo or in vitro. Expression of Rki alone is highly toxic for wild-type E. coli, but toxicity is abolished in the absence of endogenous DnaK or when the conserved J-domain of Rki is mutated. Further in vivo analyses revealed that Rki is expressed early after infection by RB43 and that deletion of the rki gene significantly impairs RB43 proliferation. Furthermore, we show that mutations in the host dnaK gene efficiently suppress the growth phenotype of the RB43 rki deletion mutant, thus indicating that Rki specifically interferes with DnaK cellular function. Finally, we show that the interaction of Rki with the host DnaK chaperone rapidly results in the stabilization of the heat-shock factor σ32, which is normally targeted for degradation by DnaK. The mechanism by which the Rki-dependent stabilization of σ32 facilitates RB43 bacteriophage proliferation is discussed. Bacteriophages are the most abundant biological entities on earth. As a consequence, they represent the largest reservoir of unexplored genetic information. They control bacterial growth, mediate horizontal gene transfer, and thus exert profound influence on microbial ecology and growth. One of the striking features of bacteriophages is that they code for many open reading frames of thus far unknown biological function (called ORFans), which have been referred to as the dark matter of our biosphere. Here we have extensively characterized such a novel ORFan-encoded protein, Rki, encoded by the large, virulent enterobacteriaceae bacteriophage RB43. We show that Rki functions to control the host stress-response during the early stages of bacteriophage infection, specifically by interacting with the host DnaK/Hsp70 chaperone to stabilize the major host heat-shock factor, σ32.
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58
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Witt SN. Molecular chaperones, α-synuclein, and neurodegeneration. Mol Neurobiol 2012; 47:552-60. [PMID: 22923346 DOI: 10.1007/s12035-012-8325-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 08/10/2012] [Indexed: 12/17/2022]
Abstract
Parkinson's disease (PD) is a devastating neurological condition that affects about 1 % of people older than 65 years of age. In PD, dopaminergic neurons in the mid-brain slowly accumulate cytoplasmic inclusions (Lewy bodies, LBs) of the protein alpha-synuclein (α-syn) and then gradually lose function and die off. Cell death is thought to be causally linked to the aggregation/fibrillization of α-syn. This review focuses on new findings about the structure of α-syn, about how α-syn cooperates with Hsp70 and Hsp40 chaperones to promote neurotransmitter release, and about cell-to-cell transfer of pathogenic forms of α-syn and how Hsp70 might protect against this disease process.
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Affiliation(s)
- Stephan N Witt
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center at Shreveport, Shreveport, LA, USA.
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59
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Griesemer M, Young C, Robinson A, Petzold L. Spatial localisation of chaperone distribution in the endoplasmic reticulum of yeast. IET Syst Biol 2012; 6:54-63. [PMID: 22519358 DOI: 10.1049/iet-syb.2011.0006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
In eukaryotes, the endoplasmic reticulum (ER) serves as the first membrane-enclosed organelle in the secretory pathway, with functions including protein folding, maturation and transport. Molecular chaperones, of the Hsp70 family of proteins, participate in assisting these processes and are essential to cellular function and survival. BiP is a resident Hsp70 chaperone in the ER of Saccharomyces cerevisiae. In this study the authors have created a partial differential equation model to examine how BiP interacts with the membrane-bound co-chaperone Sec63 in translocation, a process in which BiP assists in guiding a nascent protein into the ER lumen. It has been found that when Sec63 participates in translocation through localisation at the membrane, the spatial distribution of BiP is inhomogeneous, with more BiP at the surface. When translocation is inhibited through a disabling of Sec63's membrane tether, the concentration of BiP throughout the ER becomes homogeneous. The computational simulations suggest that Sec63's localisation and the resulting binding to BiP near the membrane surface of the ER enable a heterogeneous distribution of BiP within the ER, and may facilitate BiP's role in translocation. [Includes supplementary material].
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Affiliation(s)
- M Griesemer
- Department of Computer Science, University of California, Santa Barbara, CA, USA
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60
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Zhou W, Zhou T, Li MX, Zhao CL, Jia N, Wang XX, Sun YZ, Li GL, Xu M, Zhou RG, Li B. The Arabidopsis J-protein AtDjB1 facilitates thermotolerance by protecting cells against heat-induced oxidative damage. THE NEW PHYTOLOGIST 2012; 194:364-378. [PMID: 22356282 DOI: 10.1111/j.1469-8137.2012.04070.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
AtDjB1 belongs to the J-protein family in Arabidopsis thaliana. Its biological functions in plants are largely unknown. In this study, we examined the roles of AtDjB1 in resisting heat and oxidative stresses in A. thaliana using reverse genetic analysis. AtDjB1 knockout plants (atj1-1) were more sensitive to heat stress than wildtype plants, and displayed decreased concentrations of ascorbate (ASC), and increased concentrations of hydrogen peroxide (H(2)O(2)) and oxidative products after heat shock. Application of H(2)O(2) accelerated cell death and decreased seedling viability in atj1-1. Exogenous ASC conferred much greater thermotolerance in atj1-1 than in wildtype plants, suggesting that a lower concentration of ASC in atj1-1 could be responsible for the increased concentration of H(2)O(2) and decreased thermotolerance. Furthermore, AtDjB1 was found to localize to mitochondria, directly interact with a mitochondrial heat-shock protein 70 (mtHSC70-1), and stimulate ATPase activity of mtHSC70-1. AtDjB1 knockout led to the accumulation of cellular ATP and decreased seedling respiration, indicating that AtDjB1 modulated the ASC concentration probably through affecting the function of mitochondria. Taken together, these results suggest that AtDjB1 plays a crucial role in maintaining redox homeostasis, and facilitates thermotolerance by protecting cells against heat-induced oxidative damage.
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Affiliation(s)
- Wei Zhou
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
- Institute of Genetics and Physiology, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang 050051, China
- College of Biology and Engineering, Hebei University of Economics and Business, Shijiazhuang 050061, China
| | - Ting Zhou
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
| | - Mi-Xin Li
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
| | - Chun-Lan Zhao
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
| | - Ning Jia
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
| | - Xing-Xing Wang
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
| | - Yong-Zhen Sun
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
| | - Guo-Liang Li
- Institute of Genetics and Physiology, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang 050051, China
| | - Meng Xu
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
| | - Ren-Gang Zhou
- Institute of Genetics and Physiology, Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang 050051, China
| | - Bing Li
- Hebei Key Laboratory of Molecular and Cellular Biology, College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
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Thakur A, Chitoor B, Goswami AV, Pareek G, Atreya HS, D'Silva P. Structure and mechanistic insights into novel iron-mediated moonlighting functions of human J-protein cochaperone, Dph4. J Biol Chem 2012; 287:13194-205. [PMID: 22367199 PMCID: PMC3339945 DOI: 10.1074/jbc.m112.339655] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
J-proteins are obligate cochaperones of Hsp70s and stimulate their ATPase activity via the J-domain. Although the functions of J-proteins have been well understood in the context of Hsp70s, their additional co-evolved "physiological functions" are still elusive. We report here the solution structure and mechanism of novel iron-mediated functional roles of human Dph4, a type III J-protein playing a vital role in diphthamide biosynthesis and normal development. The NMR structure of Dph4 reveals two domains: a conserved J-domain and a CSL-domain connected via a flexible linker-helix. The linker-helix modulates the conformational flexibility between the two domains, regulating thereby the protein function. Dph4 exhibits a unique ability to bind iron in tetrahedral coordination geometry through cysteines of its CSL-domain. The oxidized Fe-Dph4 shows characteristic UV-visible and electron paramagnetic resonance spectral properties similar to rubredoxins. Iron-bound Dph4 (Fe-Dph4) also undergoes oligomerization, thus potentially functioning as a transient "iron storage protein," thereby regulating the intracellular iron homeostasis. Remarkably, Fe-Dph4 exhibits vital redox and electron carrier activity, which is critical for important metabolic reactions, including diphthamide biosynthesis. Further, we observed that Fe-Dph4 is conformationally better poised to perform Hsp70-dependent functions, thus underlining the significance of iron binding in Dph4. Yeast Jjj3, a functional ortholog of human Dph4 also shows a similar iron-binding property, indicating the conserved nature of iron sequestration across species. Taken together, our findings provide invaluable evidence in favor of additional co-evolved specialized functions of J-proteins, previously not well appreciated.
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Affiliation(s)
- Anushikha Thakur
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, India
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62
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Arockiaraj J, Vanaraja P, Easwvaran S, Singh A, Othman RY, Bhassu S. Gene expression and functional studies of small heat shock protein 37 (MrHSP37) from Macrobrachium rosenbergii challenged with infectious hypodermal and hematopoietic necrosis virus (IHHNV). Mol Biol Rep 2012; 39:6671-82. [DOI: 10.1007/s11033-012-1473-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 01/24/2012] [Indexed: 11/29/2022]
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63
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Dingus J, Hildebrandt JD. Synthesis and assembly of G protein βγ dimers: comparison of in vitro and in vivo studies. Subcell Biochem 2012; 63:155-80. [PMID: 23161138 DOI: 10.1007/978-94-007-4765-4_9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The heterotrimeric GTP-binding proteins (G proteins) are the canonical cellular machinery used with the approximately 700 G protein-coupled receptors (GPCRs) in the human genome to transduce extracellular signals across the plasma membrane. The synthesis of the constituent G protein subunits, and their assembly into Gβγ dimers and G protein heterotrimers, determines the signaling repertoire for G-protein/GPCR signaling in cells. These synthesis/assembly -processes are intimately related to two other overlapping events in the intricate pathway leading to formation of G protein signaling complexes, posttranslational modification and intracellular trafficking of G proteins. The assembly of the Gβγ dimer is a complex process involving multiple accessory proteins and organelles. The mechanisms involved are becoming increasingly appreciated, but are still incompletely understood. In vitro and in vivo (cellular) studies provide different perspectives of these processes, and a comparison of them can provide insight into both our current level of understanding and directions to be taken in future investigations.
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Affiliation(s)
- Jane Dingus
- Department of Cell and Molecular Pharmacology, Medical University of South Carolina, Charleston, SC, 29425, USA
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64
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Pais JE, Schilke B, Craig EA. Reevaluation of the role of the Pam18:Pam16 interaction in translocation of proteins by the mitochondrial Hsp70-based import motor. Mol Biol Cell 2011; 22:4740-9. [PMID: 22031295 PMCID: PMC3237618 DOI: 10.1091/mbc.e11-08-0715] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Pam18, the J-protein cochaperone of the Hsp70-based mitochondrial import motor, forms a heterodimer with the structurally related protein Pam16. Genetic and biochemical studies suggest a critical role of this interaction in maintaining Pam18's association with the translocon rather than its previously proposed regulatory role. The heat-shock protein 70 (Hsp70)–based import motor, associated with the translocon on the matrix side of the mitochondrial inner membrane, drives translocation of proteins via cycles of binding and release. Stimulation of Hsp70's ATPase activity by the translocon-associated J-protein Pam18 is critical for this process. Pam18 forms a heterodimer with the structurally related protein Pam16, via their J-type domains. This interaction has been proposed to perform a critical regulatory function, inhibiting the ATPase stimulatory activity of Pam18. Using biochemical and genetic assays, we tested this hypothesis by assessing the in vivo function of Pam18 variants having altered abilities to stimulate Hsp70's ATPase activity. The observed pattern of genetic interactions was opposite from that predicted if the heterodimer serves an inhibitory function; instead the pattern was consistent with that of mutations known to cause reduction in the stability of the heterodimer. Analysis of a previously uncharacterized region of Pam16 revealed its requirement for formation of an active Pam18:Pam16 complex able to stimulate Hsp70's ATPase activity. Together, our data are consistent with the idea that Pam18 and Pam16 form a stable heterodimer and that the critical role of the Pam18:Pam16 interaction is the physical tethering of Pam18 to the translocon via its interaction with Pam16.
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Affiliation(s)
- June E Pais
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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65
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Zorzi E, Bonvini P. Inducible hsp70 in the regulation of cancer cell survival: analysis of chaperone induction, expression and activity. Cancers (Basel) 2011; 3:3921-56. [PMID: 24213118 PMCID: PMC3763403 DOI: 10.3390/cancers3043921] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 09/26/2011] [Accepted: 10/10/2011] [Indexed: 12/31/2022] Open
Abstract
Understanding the mechanisms that control stress is central to realize how cells respond to environmental and physiological insults. All the more important is to reveal how tumour cells withstand their harsher growth conditions and cope with drug-induced apoptosis, since resistance to chemotherapy is the foremost complication when curing cancer. Intensive research on tumour biology over the past number of years has provided significant insights into the molecular events that occur during oncogenesis, and resistance to anti-cancer drugs has been shown to often rely on stress response and expression of inducible heat shock proteins (HSPs). However, with respect to the mechanisms guarding cancer cells against proteotoxic stresses and the modulatory effects that allow their survival, much remains to be defined. Heat shock proteins are molecules responsible for folding newly synthesized polypeptides under physiological conditions and misfolded proteins under stress, but their role in maintaining the transformed phenotype often goes beyond their conventional chaperone activity. Expression of inducible HSPs is known to correlate with limited sensitivity to apoptosis induced by diverse cytotoxic agents and dismal prognosis of several tumour types, however whether cancer cells survive because of the constitutive expression of heat shock proteins or the ability to induce them when adapting to the hostile microenvironment remains to be elucidated. Clear is that tumours appear nowadays more "addicted" to heat shock proteins than previously envisaged, and targeting HSPs represents a powerful approach and a future challenge for sensitizing tumours to therapy. This review will focus on the anti-apoptotic role of heat shock 70kDa protein (Hsp70), and how regulatory factors that control inducible Hsp70 synthesis, expression and activity may be relevant for response to stress and survival of cancer cells.
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Affiliation(s)
- Elisa Zorzi
- OncoHematology Clinic of Pediatrics, University-Hospital of Padova, 35100 Padova, Italy; E-Mail:
| | - Paolo Bonvini
- OncoHematology Clinic of Pediatrics, University-Hospital of Padova, 35100 Padova, Italy; E-Mail:
- Fondazione Città della Speranza, 36030 Monte di Malo, Vicenza, Italy
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66
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Reidy M, Masison DC. Modulation and elimination of yeast prions by protein chaperones and co-chaperones. Prion 2011; 5:245-9. [PMID: 22052352 DOI: 10.4161/pri.17749] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The yeast system has provided considerable insight into the biology of amyloid and prions. Here we focus on how alterations in abundance or function of protein chaperones and co-chaperones affect propagation of yeast prions. In spite of a considerable amount of information, a clear understanding of the molecular mechanisms underlying these effects remains wanting.
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Affiliation(s)
- Michael Reidy
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
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67
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Abstract
Mutations at the APM1 and APM2 loci in the green alga Chlamydomonas reinhardtii confer resistance to phosphorothioamidate and dinitroaniline herbicides. Genetic interactions between apm1 and apm2 mutations suggest an interaction between the gene products. We identified the APM1 and APM2 genes using a map-based cloning strategy. Genomic DNA fragments containing only the DNJ1 gene encoding a type I Hsp40 protein rescue apm1 mutant phenotypes, conferring sensitivity to the herbicides and rescuing a temperature-sensitive growth defect. Lesions at five apm1 alleles include missense mutations and nucleotide insertions and deletions that result in altered proteins or very low levels of gene expression. The HSP70A gene, encoding a cytosolic Hsp70 protein known to interact with Hsp40 proteins, maps near the APM2 locus. Missense mutations found in three apm2 alleles predict altered Hsp70 proteins. Genomic fragments containing the HSP70A gene rescue apm2 mutant phenotypes. The results suggest that a client of the Hsp70-Hsp40 chaperone complex may function to increase microtubule dynamics in Chlamydomonas cells. Failure of the chaperone system to recognize or fold the client protein(s) results in increased microtubule stability and resistance to the microtubule-destabilizing effect of the herbicides. The lack of redundancy of genes encoding cytosolic Hsp70 and Hsp40 type I proteins in Chlamydomonas makes it a uniquely valuable system for genetic analysis of the function of the Hsp70 chaperone complex.
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68
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Kumar DP, Vorvis C, Sarbeng EB, Cabra Ledesma VC, Willis JE, Liu Q. The four hydrophobic residues on the Hsp70 inter-domain linker have two distinct roles. J Mol Biol 2011; 411:1099-113. [PMID: 21762702 DOI: 10.1016/j.jmb.2011.07.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Revised: 06/13/2011] [Accepted: 07/01/2011] [Indexed: 12/14/2022]
Abstract
The ubiquitous molecular chaperone 70-kDa heat shock proteins (Hsp70) play key roles in maintaining protein homeostasis. Hsp70s contain two functional domains: a nucleotide binding domain and a substrate binding domain. The two domains are connected by a highly conserved inter-domain linker, and allosteric coupling between the two domains is critical for chaperone function. The auxiliary chaperone 40-kDa heat shock proteins (Hsp40) facilitate all the biological processes associated with Hsp70s by stimulating the ATPase activity of Hsp70s. Although an overall essential role of the inter-domain linker in both allosteric coupling and Hsp40 interaction has been suggested, the molecular mechanisms remain largely unknown. Previously, we reported a crystal structure of a full-length Hsp70 homolog, in which the inter-domain linker forms a well-ordered β strand. Four highly conserved hydrophobic residues reside on the inter-domain linker. In DnaK, a well-studied Hsp70, these residues are V389, L390, L391, and L392. In this study, we biochemically dissected their roles. The inward-facing side chains of V389 and L391 form extensive hydrophobic contacts with the nucleotide binding domain, suggesting their essential roles in coupling the two functional domains, a hypothesis confirmed by mutational analysis. On the other hand, L390 and L392 face outward on the surface. Mutation of either abolishes DnaK's in vivo function, yet intrinsic biochemical properties remain largely intact. In contrast, Hsp40 interaction is severely compromised. Thus, for the first time, we separated the two essential roles of the highly conserved Hsp70 inter-domain linker: coupling the two functional domains through V389 and L391 and mediating the interaction with Hsp40 through L390 and L392.
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Affiliation(s)
- Divya Prasanna Kumar
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA 23298, USA
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69
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Expression of a malarial Hsp70 improves defects in chaperone-dependent activities in ssa1 mutant yeast. PLoS One 2011; 6:e20047. [PMID: 21625512 PMCID: PMC3098276 DOI: 10.1371/journal.pone.0020047] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Accepted: 04/11/2011] [Indexed: 01/06/2023] Open
Abstract
Plasmodium falciparum causes the most virulent form of malaria and encodes a large number of molecular chaperones. Because the parasite encounters radically different environments during its lifecycle, many members of this chaperone ensemble may be essential for P. falciparum survival. Therefore, Plasmodium chaperones represent novel therapeutic targets, but to establish the mechanism of action of any developed therapeutics, it is critical to ascertain the functions of these chaperones. To this end, we report the development of a yeast expression system for PfHsp70-1, a P. falciparum cytoplasmic chaperone. We found that PfHsp70-1 repairs mutant growth phenotypes in yeast strains lacking the two primary cytosolic Hsp70s, SSA1 and SSA2, and in strains harboring a temperature sensitive SSA1 allele. PfHsp70-1 also supported chaperone-dependent processes such as protein translocation and ER associated degradation, and ameliorated the toxic effects of oxidative stress. By introducing engineered forms of PfHsp70-1 into the mutant strains, we discovered that rescue requires PfHsp70-1 ATPase activity. Together, we conclude that yeast can be co-opted to rapidly uncover specific cellular activities mediated by malarial chaperones.
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70
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Hines JK, Li X, Du Z, Higurashi T, Li L, Craig EA. [SWI], the prion formed by the chromatin remodeling factor Swi1, is highly sensitive to alterations in Hsp70 chaperone system activity. PLoS Genet 2011; 7:e1001309. [PMID: 21379326 PMCID: PMC3040656 DOI: 10.1371/journal.pgen.1001309] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Accepted: 01/12/2011] [Indexed: 11/24/2022] Open
Abstract
The yeast prion [SWI+], formed of heritable amyloid aggregates of the Swi1 protein, results in a partial loss of function of the SWI/SNF chromatin-remodeling complex, required for the regulation of a diverse set of genes. Our genetic analysis revealed that [SWI+] propagation is highly dependent upon the action of members of the Hsp70 molecular chaperone system, specifically the Hsp70 Ssa, two of its J-protein co-chaperones, Sis1 and Ydj1, and the nucleotide exchange factors of the Hsp110 family (Sse1/2). Notably, while all yeast prions tested thus far require Sis1, [SWI+] is the only one known to require the activity of Ydj1, the most abundant J-protein in yeast. The C-terminal region of Ydj1, which contains the client protein interaction domain, is required for [SWI+] propagation. However, Ydj1 is not unique in this regard, as another, closely related J-protein, Apj1, can substitute for it when expressed at a level approaching that of Ydj1. While dependent upon Ydj1 and Sis1 for propagation, [SWI+] is also highly sensitive to overexpression of both J-proteins. However, this increased prion-loss requires only the highly conserved 70 amino acid J-domain, which serves to stimulate the ATPase activity of Hsp70 and thus to stabilize its interaction with client protein. Overexpression of the J-domain from Sis1, Ydj1, or Apj1 is sufficient to destabilize [SWI+]. In addition, [SWI+] is lost upon overexpression of Sse nucleotide exchange factors, which act to destabilize Hsp70's interaction with client proteins. Given the plethora of genes affected by the activity of the SWI/SNF chromatin-remodeling complex, it is possible that this sensitivity of [SWI+] to the activity of Hsp70 chaperone machinery may serve a regulatory role, keeping this prion in an easily-lost, meta-stable state. Such sensitivity may provide a means to reach an optimal balance of phenotypic diversity within a cell population to better adapt to stressful environments. Yeast prions are heritable genetic elements, formed spontaneously by aggregation of a single protein. Prions can thus generate diverse phenotypes in a dominant, non-Mendelian fashion, without a corresponding change in chromosomal gene structure. Since the phenotypes caused by the presence of a prion are thought to affect the ability of cells to survive under different environmental conditions, those that have global effects on cell physiology are of particular interest. Here we report the results of a study of one such prion, [SWI+], formed by a component of the SWI/SNF chromatin-remodeling complex, which is required for the regulation of a diverse set of genes. We found that, compared to previously well-studied prions, [SWI+] is highly sensitive to changes in the activities of molecular chaperones, particularly components of the Hsp70 machinery. Both under- and over-expression of components of this system initiated rapid loss of the prion from the cell population. Since expression of molecular chaperones, often known as heat shock proteins, are known to vary under diverse environmental conditions, such “chaperone sensitivity” may allow alteration of traits that under particular environmental conditions convey a selective advantage and may be a common characteristic of prions formed from proteins involved in global gene regulation.
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Affiliation(s)
- Justin K. Hines
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Xiaomo Li
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Zhiqiang Du
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
| | - Takashi Higurashi
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
| | - Liming Li
- Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States of America
- * E-mail: (EAC); (LL)
| | - Elizabeth A. Craig
- Department of Biochemistry, University of Wisconsin–Madison, Madison, Wisconsin, United States of America
- * E-mail: (EAC); (LL)
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71
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Fan AC, Young JC. Function of cytosolic chaperones in Tom70-mediated mitochondrial import. Protein Pept Lett 2011; 18:122-31. [PMID: 20955164 PMCID: PMC5026486 DOI: 10.2174/092986611794475020] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2010] [Accepted: 09/17/2010] [Indexed: 11/22/2022]
Abstract
The great majority of mitochondrial proteins are synthesized by cytosolic ribosomes and then imported into the organelle post-translationally. The translocase of the outer membrane (TOM) is a proteinaceous machinery that contains surface receptors for preprotein recognition and also serves as the main entry gateway into mitochondria. Mitochondrial targeting requires various cytosolic factors, in particular the molecular chaperones Hsc70/Hsp70 and Hsp90. The chaperone activity of Hsc70/Hsp70 and Hsp90 occurs in coordinated cycles of ATP hydrolysis and substrate binding, and is regulated by a number of co-chaperone proteins. The import receptor Tom70 is a member of the tetratricopeptide repeat (TPR) co-chaperone family and contains a conserved TPR clamp domain for interaction with Hsc70 and Hsp90. Such interaction is essential for the initiation of the import process. This review will discuss the roles of Hsc70 and Hsp90 in mitochondrial import and summarize recent progress in understanding these pathways.
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Affiliation(s)
- Anna C.Y. Fan
- Department of Biochemistry, McGill University, 3649 Promenade Sir William Osler, Montreal, Quebec, Canada, H3G 0B1; Groupe de Recherche Axé sur la Structure des Protéines (GRASP)
| | - Jason C. Young
- Department of Biochemistry, McGill University, 3649 Promenade Sir William Osler, Montreal, Quebec, Canada, H3G 0B1; Groupe de Recherche Axé sur la Structure des Protéines (GRASP)
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72
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Marcinowski M, Höller M, Feige MJ, Baerend D, Lamb DC, Buchner J. Substrate discrimination of the chaperone BiP by autonomous and cochaperone-regulated conformational transitions. Nat Struct Mol Biol 2011; 18:150-8. [PMID: 21217698 DOI: 10.1038/nsmb.1970] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Accepted: 11/01/2010] [Indexed: 01/13/2023]
Abstract
The endoplasmic reticulum is the site of folding, assembly and quality control for proteins of the secretory pathway. The ATP-regulated Hsp70 chaperone BiP (heavy chain-binding protein), together with cochaperones, has important roles in all of these processes. The functional cycle of Hsp70s is determined by conformational transitions that are required for substrate binding and release. Here, we used the intrinsically disordered C(H)1 domain of antibodies as an authentic substrate protein and analyzed the conformational cycle of BiP by single-molecule and ensemble Förster resonance energy transfer (FRET) measurements. Nucleotide binding resulted in concerted domain movements of BiP. Conformational transitions of the lid domain allowed BiP to discriminate between peptide and protein substrates. A major BiP cochaperone in antibody folding, ERdj3, modulated the conformational space of BiP in a nucleotide-dependent manner, placing the lid subdomain in an open, protein-accepting state.
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73
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Goeckeler JL, Brodsky JL. Molecular chaperones and substrate ubiquitination control the efficiency of endoplasmic reticulum-associated degradation. Diabetes Obes Metab 2010; 12 Suppl 2:32-8. [PMID: 21029298 PMCID: PMC3071497 DOI: 10.1111/j.1463-1326.2010.01273.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The endoplasmic reticulum (ER) must contend with a large protein flux, which is especially notable in cells dedicated to secreting hormone-regulated gene products. Because of the complexity of the protein folding pathway and the potential for genetic or stochastic errors, a significant percentage of these nascent secreted proteins fail to acquire their native conformations. If these species cannot be cleared from the ER, they may aggregate, which leads to cell death. To lessen the effects of potentially toxic polypeptides, aberrant ER proteins are destroyed via a process known as ER-associated degradation (ERAD). ERAD substrates are selected by molecular chaperones and chaperone-like proteins, and prior to degradation most substrates are ubiquitin-modified. Together with the unfolded protein response, the ERAD pathway is a critical component of the protein quality control machinery in the ER. Although emerging data continue to link ERAD with human diseases, most of our knowledge of this pathway arose from studies using a model eukaryote, the yeast Saccharomyces cerevisiae. In this review, we will summarize the discoveries that led to our current understanding of this pathway, focusing primarily on experiments in yeast. We will also indicate links between ERAD and disease and emphasize future research avenues.
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Affiliation(s)
- J L Goeckeler
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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74
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Liu Y, Gierasch LM, Bahar I. Role of Hsp70 ATPase domain intrinsic dynamics and sequence evolution in enabling its functional interactions with NEFs. PLoS Comput Biol 2010; 6. [PMID: 20862304 PMCID: PMC2940730 DOI: 10.1371/journal.pcbi.1000931] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2010] [Accepted: 08/16/2010] [Indexed: 12/16/2022] Open
Abstract
Catalysis of ADP-ATP exchange by nucleotide exchange factors (NEFs) is central to the activity of Hsp70 molecular chaperones. Yet, the mechanism of interaction of this family of chaperones with NEFs is not well understood in the context of the sequence evolution and structural dynamics of Hsp70 ATPase domains. We studied the interactions of Hsp70 ATPase domains with four different NEFs on the basis of the evolutionary trace and co-evolution of the ATPase domain sequence, combined with elastic network modeling of the collective dynamics of the complexes. Our study reveals a subtle balance between the intrinsic (to the ATPase domain) and specific (to interactions with NEFs) mechanisms shared by the four complexes. Two classes of key residues are distinguished in the Hsp70 ATPase domain: (i) highly conserved residues, involved in nucleotide binding, which mediate, via a global hinge-bending, the ATPase domain opening irrespective of NEF binding, and (ii) not-conserved but co-evolved and highly mobile residues, engaged in specific interactions with NEFs (e.g., N57, R258, R262, E283, D285). The observed interplay between these respective intrinsic (pre-existing, structure-encoded) and specific (co-evolved, sequence-dependent) interactions provides us with insights into the allosteric dynamics and functional evolution of the modular Hsp70 ATPase domain. The heat shock protein 70 (Hsp70) serves as a housekeeper in the cell, assisting in the correct folding, trafficking, and degradation of many proteins. The ATPase domain is the control unit of this molecular machine and its efficient functioning requires interactions with co-chaperones, including, in particular, the nucleotide exchange factors (NEFs). We examined the molecular motions of the ATPase domain in both NEF-bound and -unbound forms. We found that the NEF-binding surface enjoys large global movements prior to NEF binding, which presumably facilitates NEF recognition and binding. NEF binding stabilizes the ATPase domain in an open form and thereby facilitates the nucleotide exchange step of the chaperone cycle. A series of highly correlated amino acids were distinguished at the NEF-binding sites of the Hsp70 ATPase domain, which highlights the adaptability of the ATPase domain, both structurally and sequentially, to recognize NEFs. In contrast, the nucleotide-binding residues are tightly held near a global hinge center and are highly conserved. The contrasting properties of these two groups of residues point to an evolutionarily optimized balance between conserved/constrained and co-evolved/mobile amino acids, which enables the functional interactions of the modular Hps70 ATPase domains with NEFs.
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Affiliation(s)
- Ying Liu
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - Lila M. Gierasch
- Department of Biochemistry and Molecular Biology, and Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America
| | - Ivet Bahar
- Department of Computational and Systems Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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75
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Kampinga HH, Craig EA. The HSP70 chaperone machinery: J proteins as drivers of functional specificity. Nat Rev Mol Cell Biol 2010; 11:579-92. [PMID: 20651708 PMCID: PMC3003299 DOI: 10.1038/nrm2941] [Citation(s) in RCA: 1208] [Impact Index Per Article: 86.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Heat shock 70 kDa proteins (HSP70s) are ubiquitous molecular chaperones that function in a myriad of biological processes, modulating polypeptide folding, degradation and translocation across membranes, and protein-protein interactions. This multitude of roles is not easily reconciled with the universality of the activity of HSP70s in ATP-dependent client protein-binding and release cycles. Much of the functional diversity of the HSP70s is driven by a diverse class of cofactors: J proteins. Often, multiple J proteins function with a single HSP70. Some target HSP70 activity to clients at precise locations in cells and others bind client proteins directly, thereby delivering specific clients to HSP70 and directly determining their fate.
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Affiliation(s)
- Harm H Kampinga
- Department of Cell Biology, University of Groningen, University Medical Center, 713 AV Groningen, The Netherlands.
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76
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Uhrigshardt H, Singh A, Kovtunovych G, Ghosh M, Rouault TA. Characterization of the human HSC20, an unusual DnaJ type III protein, involved in iron-sulfur cluster biogenesis. Hum Mol Genet 2010; 19:3816-34. [PMID: 20668094 DOI: 10.1093/hmg/ddq301] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The importance of mitochondrial iron-sulfur cluster (ISC) biogenesis for human health has been well established, but the roles of some components of this critical pathway still remain uncharacterized in mammals. Among them is human heat shock cognate protein 20 (hHSC20), the putative human homolog of the specialized DnaJ type co-chaperones, which are crucial for bacterial and fungal ISC assembly. Here, we show that the human HSC20 protein can complement for its counterpart in yeast, Jac1p, and interacts with its proposed human partners, hISCU and hHSPA9. hHSC20 is expressed in various human tissues and localizes mainly to the mitochondria in HeLa cells. However, small amounts were also detected extra-mitochondrially. RNA interference-mediated depletion of hHSC20 specifically reduced the activities of both mitochondrial and cytosolic ISC-containing enzymes. The recovery of inactivated ISC enzymes was markedly delayed after an oxidative insult of hHSC20-deficient cells. Conversely, overexpression of hHSC20 substantially protected cells from oxidative insults. These results imply that hHSC20 is an integral component of the human ISC biosynthetic machinery that is particularly important in the assembly of ISCs under conditions of oxidative stress. A cysteine-rich N-terminal domain, which clearly distinguishes hHSC20 from the specialized DnaJ type III proteins of fungi and most bacteria, was found to be important for the integrity and function of the human co-chaperone.
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Affiliation(s)
- Helge Uhrigshardt
- Molecular Medicine Program, The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
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77
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Stetler RA, Gan Y, Zhang W, Liou AK, Gao Y, Cao G, Chen J. Heat shock proteins: cellular and molecular mechanisms in the central nervous system. Prog Neurobiol 2010; 92:184-211. [PMID: 20685377 DOI: 10.1016/j.pneurobio.2010.05.002] [Citation(s) in RCA: 206] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Revised: 05/23/2010] [Accepted: 05/27/2010] [Indexed: 12/30/2022]
Abstract
Emerging evidence indicates that heat shock proteins (HSPs) are critical regulators in normal neural physiological function as well as in cell stress responses. The functions of HSPs represent an enormous and diverse range of cellular activities, far beyond the originally identified roles in protein folding and chaperoning. HSPs are now understood to be involved in processes such as synaptic transmission, autophagy, ER stress response, protein kinase and cell death signaling. In addition, manipulation of HSPs has robust effects on the fate of cells in neurological injury and disease states. The ongoing exploration of multiple HSP superfamilies has underscored the pluripotent nature of HSPs in the cellular context, and has demanded the recent revamping of the nomenclature referring to these families to reflect a re-organization based on structure and function. In keeping with this re-organization, we first discuss the HSP superfamilies in terms of protein structure, regulation, expression and distribution in the brain. We then explore major cellular functions of HSPs that are relevant to neural physiological states, and from there we discuss known and proposed HSP impacts on major neurological disease states. This review article presents a three-part discussion on the array of HSP families relevant to neuronal tissue, their cellular functions, and the exploration of therapeutic targets of these proteins in the context of neurological diseases.
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Affiliation(s)
- R Anne Stetler
- Geriatric Research, Educational and Clinical Center, Veterans Affairs Pittsburgh Health Care System, Pittsburgh, PA 15261, United States.
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78
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Vembar SS, Jonikas MC, Hendershot LM, Weissman JS, Brodsky JL. J domain co-chaperone specificity defines the role of BiP during protein translocation. J Biol Chem 2010; 285:22484-94. [PMID: 20430885 DOI: 10.1074/jbc.m110.102186] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hsp70 chaperones can potentially interact with one of several J domain-containing Hsp40 co-chaperones to regulate distinct cellular processes. However, features within Hsp70s that determine Hsp40 specificity are undefined. To investigate this question, we introduced mutations into the ER-lumenal Hsp70, BiP/Kar2p, and found that an R217A substitution in the J domain-interacting surface of BiP compromised the physical and functional interaction with Sec63p, an Hsp40 required for ER translocation. In contrast, interaction with Jem1p, an Hsp40 required for ER-associated degradation, was unaffected. Moreover, yeast expressing R217A BiP exhibited defects in translocation but not in ER-associated degradation. Finally, the genetic interactions of the R217A BiP mutant were found to correlate with those of known translocation mutants. Together, our results indicate that residues within the Hsp70 J domain-interacting surface help confer Hsp40 specificity, in turn influencing distinct chaperone-mediated cellular activities.
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Affiliation(s)
- Shruthi S Vembar
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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79
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Goswami AV, Chittoor B, D'Silva P. Understanding the functional interplay between mammalian mitochondrial Hsp70 chaperone machine components. J Biol Chem 2010; 285:19472-82. [PMID: 20392697 PMCID: PMC2885226 DOI: 10.1074/jbc.m110.105957] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondria biogenesis requires the import of several precursor proteins that are synthesized in the cytosol. The mitochondrial heat shock protein 70 (mtHsp70) machinery components are highly conserved among eukaryotes, including humans. However, the functional properties of human mtHsp70 machinery components have not been characterized among all eukaryotic families. To study the functional interactions, we have reconstituted the components of the mtHsp70 chaperone machine (Hsp70/J-protein/GrpE/Hep) and systematically analyzed in vitro conditions for biochemical functions. We observed that the sequence-specific interaction of human mtHsp70 toward mitochondrial client proteins differs significantly from its yeast counterpart Ssc1. Interestingly, the helical lid of human mtHsp70 was found dispensable to the binding of P5 peptide as compared with the other Hsp70s. We observed that the two human mitochondrial matrix J-protein splice variants differentially regulate the mtHsp70 chaperone cycle. Strikingly, our results demonstrated that human Hsp70 escort protein (Hep) possesses a unique ability to stimulate the ATPase activity of mtHsp70 as well as to prevent the aggregation of unfolded client proteins similar to J-proteins. We observed that Hep binds with the C terminus of mtHsp70 in a full-length context and this interaction is distinctly different from unfolded client-specific or J-protein binding. In addition, we found that the interaction of Hep at the C terminus of mtHsp70 is regulated by the helical lid region. However, the interaction of Hep at the ATPase domain of the human mtHsp70 is mutually exclusive with J-proteins, thus promoting a similar conformational change that leads to ATPase stimulation. Additionally, we highlight the biochemical defects of the mtHsp70 mutant (G489E) associated with a myelodysplastic syndrome.
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Affiliation(s)
- Arvind Vittal Goswami
- Department of Biochemistry, Indian Institute of Science, Bangalore 560012, Karnataka, India
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80
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Buck TM, Kolb AR, Boyd CR, Kleyman TR, Brodsky JL. The endoplasmic reticulum-associated degradation of the epithelial sodium channel requires a unique complement of molecular chaperones. Mol Biol Cell 2010; 21:1047-58. [PMID: 20110346 PMCID: PMC2836957 DOI: 10.1091/mbc.e09-11-0944] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 01/06/2010] [Accepted: 01/15/2010] [Indexed: 12/28/2022] Open
Abstract
The epithelial sodium channel (ENaC) is composed of a single copy of an alpha-, beta-, and gamma-subunit and plays an essential role in water and salt balance. Because ENaC assembles inefficiently after its insertion into the ER, a substantial percentage of each subunit is targeted for ER-associated degradation (ERAD). To define how the ENaC subunits are selected for degradation, we developed novel yeast expression systems for each ENaC subunit. Data from this analysis suggested that ENaC subunits display folding defects in more than one compartment and that subunit turnover might require a unique group of factors. Consistent with this hypothesis, yeast lacking the lumenal Hsp40s, Jem1 and Scj1, exhibited defects in ENaC degradation, whereas BiP function was dispensable. We also discovered that Jem1 and Scj1 assist in ENaC ubiquitination, and overexpression of ERdj3 and ERdj4, two lumenal mammalian Hsp40s, increased the proteasome-mediated degradation of ENaC in vertebrate cells. Our data indicate that Hsp40s can act independently of Hsp70 to select substrates for ERAD.
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Affiliation(s)
- Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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81
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Pukszta S, Schilke B, Dutkiewicz R, Kominek J, Moczulska K, Stepien B, Reitenga KG, Bujnicki JM, Williams B, Craig EA, Marszalek J. Co-evolution-driven switch of J-protein specificity towards an Hsp70 partner. EMBO Rep 2010; 11:360-5. [PMID: 20224575 DOI: 10.1038/embor.2010.29] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 01/15/2010] [Accepted: 02/04/2010] [Indexed: 11/09/2022] Open
Abstract
Molecular mechanisms by which protein-protein interactions are preserved or lost after gene duplication are not understood. Taking advantage of the well-studied yeast mtHsp70:J-protein molecular chaperone system, we considered whether changes in partner proteins accompanied specialization of gene duplicates. Here, we report that existence of the Hsp70 Ssq1, which arose by duplication of the gene encoding multifunction mtHsp70 and specializes in iron-sulphur cluster biogenesis, correlates with functional and structural changes in the J domain of its J-protein partner Jac1. All species encoding this shorter alternative version of the J domain share a common ancestry, suggesting that all short JAC1 proteins arose from a single deletion event. Construction of a variant that extended the length of the J domain of a 'short' Jac1 enhanced its ability to partner with multifunctional Hsp70. Our data provide a causal link between changes in the J protein partner and specialization of duplicate Hsp70.
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Affiliation(s)
- Sebastian Pukszta
- Department of Molecular and Cellular Biology, Faculty of Biotechnology, University of Gdansk, Gdansk, Poland
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82
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Fujikawa T, Munakata T, Kondo SI, Satoh N, Wada S. Stress response in the ascidian Ciona intestinalis: transcriptional profiling of genes for the heat shock protein 70 chaperone system under heat stress and endoplasmic reticulum stress. Cell Stress Chaperones 2010; 15:193-204. [PMID: 19629754 PMCID: PMC2866982 DOI: 10.1007/s12192-009-0133-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2008] [Revised: 07/02/2009] [Accepted: 07/03/2009] [Indexed: 10/20/2022] Open
Abstract
The genome of Ciona intestinalis contains eight genes for HSP70 superfamily proteins, 36 genes for J-proteins, a gene for a J-like protein, and three genes for BAG family proteins. To understand the stress responses of genes in the HSP70 chaperone system comprehensively, the transcriptional profiles of these 48 genes under heat stress and endoplasmic reticulum (ER) stress were studied using real-time reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Heat stress treatment increased the messenger RNA (mRNA) levels of six HSP70 superfamily genes, eight J-protein family genes, and two BAG family genes. In the cytoplasmic group of the DnaK subfamily of the HSP70 family, Ci-HSPA1/6/7-like was the only heat-inducible gene and Ci-HSPA2/8 was the only constitutively active gene which showed striking simplicity in comparison with other animals that have been examined genome-wide so far. Analyses of the time course and temperature dependency of the heat stress responses showed that the induction of Ci-HSPA1/6/7-like expression rises to a peak after heat stress treatment at 28 degrees C (10 degrees C upshift from control temperature) for 1 h. ER stress treatment with Brefeldin A, a drug that is known to act as ER stress inducer, increased the mRNA levels of four HSP70 superfamily genes and four J-protein family genes. Most stress-inducible genes are conserved between Ciona and vertebrates, as expected from a close evolutionary relationship between them. The present study characterized the stress responses of HSP70 chaperone system genes in Ciona for the first time and provides essential data for comprehensive understanding of the functions of the HSP70 chaperone system.
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Affiliation(s)
- Tetsuya Fujikawa
- Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga 526-0829 Japan
| | - Takeo Munakata
- Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga 526-0829 Japan
| | - Shin-ichi Kondo
- Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga 526-0829 Japan
| | - Nori Satoh
- Marine Genomics Unit, Okinawa Institute of Science and Technology Promotion Corporation, Uruma, Okinawa 904-2234 Japan
| | - Shuichi Wada
- Department of Bioscience, Faculty of Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga 526-0829 Japan
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83
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Cwc23, an essential J protein critical for pre-mRNA splicing with a dispensable J domain. Mol Cell Biol 2010; 30:33-42. [PMID: 19822657 DOI: 10.1128/mcb.00842-09] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
J proteins are structurally diverse, obligatory cochaperones of Hsp70s, each with a highly conserved J domain that plays a critical role in the stimulation of Hsp70's ATPase activity. The essential protein, Cwc23, is one of 13 J proteins found in the cytosol and/or nucleus of Saccharomyces cerevisiae. We report that a partial loss-of-function CWC23 mutant has severe, global defects in pre-mRNA splicing. This mutation leads to accumulation of the excised, lariat form of the intron, as well as unspliced pre-mRNA, suggesting a role for Cwc23 in spliceosome disassembly. Such a role is further supported by the observation that this mutation results in reduced interaction between Cwc23 and Ntr1 (SPP382), a known component of the disassembly pathway. However, Cwc23 is a very atypical J protein. Its J domain, although functional, is dispensable for both cell viability and pre-mRNA splicing. Nevertheless, strong genetic interactions were uncovered between point mutations encoding alterations in Cwc23's J domain and either Ntr1 or Prp43, a DExD/H-box helicase essential for spliceosome disassembly. These genetic interactions suggest that Hsp70-based chaperone machinery does play a role in the disassembly process. Cwc23 provides a unique example of a J protein; its partnership with Hsp70 plays an auxiliary, rather than a central, role in its essential cellular function.
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84
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New Insights into the Roles of Molecular Chaperones in Chlamydomonas and Volvox. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 285:75-113. [DOI: 10.1016/b978-0-12-381047-2.00002-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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85
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Meyer AE, Hoover LA, Craig EA. The cytosolic J-protein, Jjj1, and Rei1 function in the removal of the pre-60 S subunit factor Arx1. J Biol Chem 2009; 285:961-8. [PMID: 19901025 DOI: 10.1074/jbc.m109.038349] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Although the biogenesis of ribosomal subunits occurs predominantly in the nucleus, final remodeling steps take place in the cytosol. One cytosolic step has two components: 1) the removal of the maturation factor Arx1, which transits from the nucleus to the cytosol with the pre-60 S subunit, and 2) its subsequent transport back into the nucleus. Two cytosolic proteins, Rei1 and Jjj1, are required, but their individual contributions to this step are not understood. Here we report that Rei1 and Jjj1 directly interact. This interaction is mediated by a C-terminal segment of Jjj1 encompassing a region rich in charged residues, flanked by C(2)H(2)-type zinc fingers. Deletion of the charged region results in defects in 60 S subunit biogenesis in vivo. In addition, we report resolution of an apparent contradiction in the literature regarding the association of Arx1 with the pre-60 S subunit in the absence of Rei1. The association of Arx1 with ribosomes is sensitive to the concentration of magnesium ions when Rei1 is absent. At near physiological concentrations, Arx1 remains associated with the pre-60 S particle, as it does in the absence of Jjj1; at higher concentrations, Arx1 dissociates in the absence of Rei1 but not in the absence of Jjj1. As both Rei1 and Jjj1 are required for dissociation of Arx1 from the pre-60 S subunit, and the region of Jjj1 that mediates interaction with Rei1 is required in vivo for 60 S subunit biogenesis, our data support the idea that the primary role of both Rei1 and Jjj1 is the first step of the Arx1 removal/recycling process.
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Affiliation(s)
- Alison E Meyer
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
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86
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Sharma D, Masison DC. Hsp70 structure, function, regulation and influence on yeast prions. Protein Pept Lett 2009; 16:571-81. [PMID: 19519514 DOI: 10.2174/092986609788490230] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heat shock proteins protect cells from various conditions of stress. Hsp70, the most ubiquitous and highly conserved Hsp, helps proteins adopt native conformation or regain function after misfolding. Various co-chaperones specify Hsp70 function and broaden its substrate range. We discuss Hsp70 structure and function, regulation by co-factors and influence on propagation of yeast prions.
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Affiliation(s)
- Deepak Sharma
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes, Digestive and Kidney Diseases, National institutes of Health, Bethesda, MD 20892-0851, USA
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87
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Vembar SS, Jin Y, Brodsky JL, Hendershot LM. The mammalian Hsp40 ERdj3 requires its Hsp70 interaction and substrate-binding properties to complement various yeast Hsp40-dependent functions. J Biol Chem 2009; 284:32462-71. [PMID: 19748898 DOI: 10.1074/jbc.m109.000729] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Heat shock proteins of 70 kDa (Hsp70s) and their J domain-containing Hsp40 cofactors are highly conserved chaperone pairs that facilitate a large number of cellular processes. The observation that each Hsp70 partners with many J domain-containing proteins (JDPs) has led to the hypothesis that Hsp70 function is dictated by cognate JDPs. If this is true, one might expect highly divergent Hsp70-JDP pairs to be unable to function in vivo. However, we discovered that, when a yeast cytosolic JDP, Ydj1, was targeted to the mammalian endoplasmic reticulum (ER), it interacted with the ER-lumenal Hsp70, BiP, and bound to BiP substrates. Conversely, when a mammalian ER-lumenal JDP, ERdj3, was directed to the yeast cytosol, it rescued the temperature-sensitive growth phenotype of yeast-containing mutant alleles in two cytosolic JDPs, HLJ1 and YDJ1, and activated the ATP hydrolysis rate of Ssa1, the yeast cytosolic Hsp70 that partners with Hlj1 and Ydj1. Surprisingly, ERdj3 mutants that were compromised for substrate binding were unable to rescue the hlj1ydj1 growth defect even though they stimulated the ATPase activity of Ssa1. Yet, J domain mutants of ERdj3 that were defective for interaction with Ssa1 restored the growth of hlj1ydj1 yeast. Taken together, these data suggest that the substrate binding properties of certain JDPs, not simply the formation of unique Hsp70-JDP pairs, are critical to specify in vivo function.
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Affiliation(s)
- Shruthi S Vembar
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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88
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Rajan VBV, D'Silva P. Arabidopsis thaliana J-class heat shock proteins: cellular stress sensors. Funct Integr Genomics 2009; 9:433-46. [PMID: 19633874 DOI: 10.1007/s10142-009-0132-0] [Citation(s) in RCA: 122] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Revised: 07/06/2009] [Accepted: 07/06/2009] [Indexed: 12/22/2022]
Abstract
Plants are sessile organisms that have evolved a variety of mechanisms to maintain their cellular homeostasis under stressful environmental conditions. Survival of plants under abiotic stress conditions requires specialized group of heat shock protein machinery, belonging to Hsp70:J-protein family. These heat shock proteins are most ubiquitous types of chaperone machineries involved in diverse cellular processes including protein folding, translocation across cell membranes, and protein degradation. They play a crucial role in maintaining the protein homeostasis by reestablishing functional native conformations under environmental stress conditions, thus providing protection to the cell. J-proteins are co-chaperones of Hsp70 machine, which play a critical role by stimulating Hsp70s ATPase activity, thereby stabilizing its interaction with client proteins. Using genome-wide analysis of Arabidopsis thaliana, here we have outlined identification and systematic classification of J-protein co-chaperones which are key regulators of Hsp70s function. In comparison with Saccharomyces cerevisiae model system, a comprehensive domain structural organization, cellular localization, and functional diversity of A. thaliana J-proteins have also been summarized.
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89
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Wright CM, Seguin SP, Fewell SW, Zhang H, Ishwad C, Vats A, Lingwood CA, Wipf P, Fanning E, Pipas JM, Brodsky JL. Inhibition of Simian Virus 40 replication by targeting the molecular chaperone function and ATPase activity of T antigen. Virus Res 2009; 141:71-80. [PMID: 19200446 DOI: 10.1016/j.virusres.2008.12.018] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 12/29/2008] [Accepted: 12/29/2008] [Indexed: 01/23/2023]
Abstract
Polyomaviruses such as BK virus and JC virus have been linked to several diseases, but treatments that thwart their propagation are limited in part because of slow growth and cumbersome culturing conditions. In contrast, the replication of one member of this family, Simian Virus 40 (SV40), is robust and has been well-characterized. SV40 replication requires two domains within the viral-encoded large tumor antigen (TAg): The ATPase domain and the N-terminal J domain, which stimulates the ATPase activity of the Hsp70 chaperone. To assess whether inhibitors of polyomavirus replication could be identified, we examined a recently described library of small molecules, some of which inhibit chaperone function. One compound, MAL2-11B, inhibited both TAg's endogenous ATPase activity and the TAg-mediated activation of Hsp70. MAL2-11B also reduced SV40 propagation in plaque assays and compromised DNA replication in cell culture and in vitro. Furthermore, the compound significantly reduced the growth of BK virus in a human kidney cell line. These data indicate that pharmacological inhibition of TAg's chaperone and ATPase activities may provide a route to combat polyomavirus-mediated disease.
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Affiliation(s)
- Christine M Wright
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA
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90
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Select pyrimidinones inhibit the propagation of the malarial parasite, Plasmodium falciparum. Bioorg Med Chem 2009; 17:1527-33. [PMID: 19195901 DOI: 10.1016/j.bmc.2009.01.024] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Revised: 01/01/2009] [Accepted: 01/08/2009] [Indexed: 01/30/2023]
Abstract
Plasmodium falciparum, the Apicomplexan parasite that is responsible for the most lethal forms of human malaria, is exposed to radically different environments and stress factors during its complex lifecycle. In any organism, Hsp70 chaperones are typically associated with tolerance to stress. We therefore reasoned that inhibition of P. falciparum Hsp70 chaperones would adversely affect parasite homeostasis. To test this hypothesis, we measured whether pyrimidinone-amides, a new class of Hsp70 modulators, could inhibit the replication of the pathogenic P. falciparum stages in human red blood cells. Nine compounds with IC(50) values from 30 nM to 1.6 micrOM were identified. Each compound also altered the ATPase activity of purified P. falciparum Hsp70 in single-turnover assays, although higher concentrations of agents were required than was necessary to inhibit P. falciparum replication. Varying effects of these compounds on Hsp70s from other organisms were also observed. Together, our data indicate that pyrimidinone-amides constitute a novel class of anti-malarial agents.
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91
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Rosales-Hernandez A, Beck KE, Zhao X, Braun AP, Braun JEA. RDJ2 (DNAJA2) chaperones neural G protein signaling pathways. Cell Stress Chaperones 2009; 14:71-82. [PMID: 18595009 PMCID: PMC2673899 DOI: 10.1007/s12192-008-0056-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2008] [Accepted: 05/28/2008] [Indexed: 12/11/2022] Open
Abstract
A number of structurally divergent proteins with J domains, called J proteins, interact with and activate the ATPase of Hsp70s, thereby harnessing the ATPase activity for conformational work on target proteins. The precise role of most mammalian J proteins remains undefined. In this paper, we demonstrate that transient expression of the J protein, Rdj2, in HEK 293 cells increased cellular cyclic adenosine monophosphate (cAMP) levels in the presence of the beta-adrenergic agonist isoproterenol. In CNS-derived catecholaminergic neuronal cell line (CAD) neuroblastoma cells, expression of Rdj2 increased isoproterenol-stimulated phosphorylation of cAMP response element binding protein (CREB). Moreover, we have characterized the binding properties of Rdj2 and observed a direct interaction between Rdj2 and receptor-coupled trimeric GTP-binding proteins (G proteins). We further show that the composition of the Rdj2-chaperone complex and the cysteine string protein (CSPalpha)-chaperone complex, another J protein, is distinct. Our data demonstrate that Rdj2 modulates G protein signaling and further suggest that chaperoning G proteins is an emerging theme of the J protein network.
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Affiliation(s)
- Alma Rosales-Hernandez
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, Calgary, AB Canada T2N 4N1
| | - Katy E. Beck
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, Calgary, AB Canada T2N 4N1
| | - Xiaoxi Zhao
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, Calgary, AB Canada T2N 4N1
| | - Andrew P. Braun
- Libin Cardiovascular Institute of Alberta, Department of Pharmacology and Therapeutics, University of Calgary, Calgary, AB Canada T2N 4N1
| | - Janice E. A. Braun
- Hotchkiss Brain Institute, Department of Physiology and Biophysics, University of Calgary, Calgary, AB Canada T2N 4N1
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92
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Stehling O, Sheftel AD, Lill R. Chapter 12 Controlled expression of iron-sulfur cluster assembly components for respiratory chain complexes in mammalian cells. Methods Enzymol 2009; 456:209-31. [PMID: 19348891 DOI: 10.1016/s0076-6879(08)04412-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Three of the respiratory chain complexes contain essential iron-sulfur (Fe/S) cluster prosthetic groups. Besides respiration, these ancient inorganic cofactors are also necessary for numerous other fundamental biochemical processes in virtually every known organism. Both the synthesis of Fe/S clusters and their delivery to apoproteins depend on the concerted function of specialized, often dedicated, proteins located in the mitochondria and cytosol of eukaryotes. Impaired function of the mitochondria-located Fe/S cluster (ISC) assembly machinery affects all cellular Fe/S proteins, including enzymes of the respiratory chain, NADH: ubiquinone oxidoreductase (complex I; eight Fe/S clusters), succinate: ubiquinone oxidoreductase (complex II; three Fe/S clusters), and cytochrome bc(1) complex (complex III; one Fe/S cluster). Here, we describe strategies and techniques both to deprive respiratory chain proteins of their Fe/S cofactors and to study changes in activity and composition of these proteins. As examples, we present the results of the depletion of two types of Fe/S biogenesis proteins, huNfs1 and huInd1, in a human tissue culture model. The ISC assembly component huNfs1 is required for biogenesis of all cellular Fe/S proteins, its loss exerting pleiotropic effects, whereas huInd1 is specific for Fe/S cluster maturation of complex I. Disorders in Fe/S cluster assembly are candidate causes for defects in respiratory complex assembly of unknown etiology.
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Affiliation(s)
- Oliver Stehling
- Institut für Zytobiologie and Zytopathologie, Philipps-Universität, Marburg, Germany
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93
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Specificity of the J-protein Sis1 in the propagation of 3 yeast prions. Proc Natl Acad Sci U S A 2008; 105:16596-601. [PMID: 18955697 DOI: 10.1073/pnas.0808934105] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Yeast prions, such as [PSI(+)], [RNQ(+)], and [URE3], are heritable elements formed by proteins capable of acquiring self-perpetuating conformations. Their propagation is dependent on fragmentation of the amyloid protein complexes formed to generate the additional seeds necessary for conversion of nascent soluble protein to the prion conformation. We report that, in addition to its known role in [RNQ(+)] propagation, Sis1, a J-protein cochaperone of Hsp70 Ssa, is also specifically required for propagation of [PSI(+)] and [URE3]. Whereas both [RNQ(+)] and [URE3] are cured rapidly upon SIS1 repression, [PSI(+)] loss is markedly slower. This disparity cannot be explained simply by differences in seed number, as [RNQ(+)] and [PSI(+)] are lost with similar kinetics upon inhibition of Hsp104, a remodeling protein required for propagation of all yeast prions. Rather, in the case of [PSI(+)], our results are consistent with the partial impairment, rather than the complete abolition, of fragmentation of prion complexes upon Sis1 depletion. We suggest that a common set of molecular chaperones, the J-protein Sis1, the Hsp70 Ssa, and the AAA+ ATPase Hsp104, act sequentially in the fragmentation of all yeast prions, but that the threshold of Sis1 activity required for each prion varies.
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94
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Regulated association of misfolded endoplasmic reticulum lumenal proteins with P58/DNAJc3. EMBO J 2008; 27:2862-72. [PMID: 18923430 DOI: 10.1038/emboj.2008.199] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2008] [Accepted: 09/05/2008] [Indexed: 02/07/2023] Open
Abstract
P58/DNAJc3 defends cells against endoplasmic reticulum (ER) stress. Most P58 molecules are translocated into the ER lumen, and here we report selective and stable binding to misfolded proteins by P58's TPR-containing N-terminal domain. In vitro, too, P58 binds selectively to a model misfolded protein and challenge of that complex with physiological concentrations of the ER lumenal Hsp70-type chaperone BiP encourages disassembly. BiP-induced dissociation of P58 from its substrate depends on the presence of ATP and on interactions with P58's J-domain, which are mediated by invariant residues BiP(R197) and P58(H422). A functional J-domain also accelerates dissociation of P58 from a model substrate, VSV-G(ts045), on the latter's re-folding in vivo. However, J-domain binding can be separated from the ability to promote substrate dissociation by the mutant BiP(E201G) and a wild-type J-domain fused ectopically to P58(H422Q) rescues the latter's inability to dissociate from substrate in response to BiP and ATP. These findings are consistent with a model whereby localized activation of the Hsp70-type partner is sufficient to promote substrate handover from the J-domain co-chaperone.
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95
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Han MJ, Yun H, Lee SY. Microbial small heat shock proteins and their use in biotechnology. Biotechnol Adv 2008; 26:591-609. [PMID: 18789382 DOI: 10.1016/j.biotechadv.2008.08.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2008] [Revised: 08/01/2008] [Accepted: 08/03/2008] [Indexed: 11/29/2022]
Abstract
Small heat shock proteins (sHsps) exist in almost all organisms. Most organisms have more than one sHsp, but their number can be as high as 65, as found in the eukaryote, Vitis vinifera. The function of sHsps is well-known; they confer thermotolerance to cellular cultures and proteins in cellular extracts during prolonged incubations at elevated temperatures. This demonstrates the ability of sHsps to protect cellular proteins, and to maintain cellular viability under conditions of intensive stress, such as heat shock or chemical treatments. sHsps have several properties that distinguish them from heat shock proteins (Hsps): they function as ATP-independent chaperones, require the flexible assembly and reassembly of oligomeric complex structures for their activation, and exhibit a wide range of substrate-binding capacities. Recent studies indicate that sHsps have important biological functions in thermostability, disaggregation, and proteolysis inhibition. These functions can be harnessed for various applications, including nanobiotechnology, proteomics, bioproduction, and bioseparation. In this review, we discuss the properties and diversity of microbial sHsps, as well as their potential uses in the biotechnology industry.
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Affiliation(s)
- Mee-Jung Han
- Metabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical & Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 305-701, Republic of Korea
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96
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Ydj1 protects nascent protein kinases from degradation and controls the rate of their maturation. Mol Cell Biol 2008; 28:4434-44. [PMID: 18443039 DOI: 10.1128/mcb.00543-08] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Ydj1 is a Saccharomyces cerevisiae Hsp40 molecular chaperone that functions with Hsp70 to promote polypeptide folding. We identified Ydj1 as being important for maintaining steady-state levels of protein kinases after screening several chaperones and cochaperones in gene deletion mutant strains. Pulse-chase analyses revealed that a portion of Tpk2 kinase was degraded shortly after synthesis in a ydj1Delta mutant, while the remainder was capable of maturing but with reduced kinetics compared to the wild type. Cdc28 maturation was also delayed in the ydj1Delta mutant strain. Ydj1 protects nascent kinases in different contexts, such as when Hsp90 is inhibited with geldanamycin or when CDC37 is mutated. The protective function of Ydj1 is due partly to its intrinsic chaperone function, but this is minor compared to the protective effect resulting from its interaction with Hsp70. SIS1, a type II Hsp40, was unable to suppress defects in kinase accumulation in the ydj1Delta mutant, suggesting some specificity in Ydj1 chaperone action. However, analysis of chimeric proteins that contained the chaperone modules of Ydj1 or Sis1 indicated that Ydj1 promotes kinase accumulation independently of its client-binding specificity. Our results suggest that Ydj1 can both protect nascent chains against degradation and control the rate of kinase maturation.
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97
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Yang C, Owen HA, Yang P. Dimeric heat shock protein 40 binds radial spokes for generating coupled power strokes and recovery strokes of 9 + 2 flagella. ACTA ACUST UNITED AC 2008; 180:403-15. [PMID: 18227282 PMCID: PMC2213584 DOI: 10.1083/jcb.200705069] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
T-shape radial spokes regulate flagellar beating. However, the precise function and molecular mechanism of these spokes remain unclear. Interestingly, Chlamydomonas reinhardtii flagella lacking a dimeric heat shock protein (HSP) 40 at the spokehead-spokestalk juncture appear normal in length and composition but twitch actively while cells jiggle without procession, resembling a central pair (CP) mutant. HSP40(-) cells begin swimming upon electroporation with recombinant HSP40. Surprisingly, the rescue doesn't require the signature DnaJ domain. Furthermore, the His-Pro-Asp tripeptide that is essential for stimulating HSP70 adenosine triphosphatase diverges in candidate orthologues, including human DnaJB13. Video microscopy reveals hesitance in bend initiation and propagation as well as irregular stalling and stroke switching despite fairly normal waveform. The in vivo evidence suggests that the evolutionarily conserved HSP40 specifically transforms multiple spoke proteins into stable conformation capable of mechanically coupling the CP with dynein motors. This enables 9 + 2 cilia and flagella to bend and switch to generate alternate power strokes and recovery strokes.
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Affiliation(s)
- Chun Yang
- Department of Biological Sciences, Marquette University, Milwaukee, WI 53233, USA
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98
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Bettencourt BR, Hogan CC, Nimali M, Drohan BW. Inducible and constitutive heat shock gene expression responds to modification of Hsp70 copy number in Drosophila melanogaster but does not compensate for loss of thermotolerance in Hsp70 null flies. BMC Biol 2008; 6:5. [PMID: 18211703 PMCID: PMC2257928 DOI: 10.1186/1741-7007-6-5] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 01/22/2008] [Indexed: 06/12/2024] Open
Abstract
Background The heat shock protein Hsp70 promotes inducible thermotolerance in nearly every organism examined to date. Hsp70 interacts with a network of other stress-response proteins, and dissecting the relative roles of these interactions in causing thermotolerance remains difficult. Here we examine the effect of Hsp70 gene copy number modification on thermotolerance and the expression of multiple stress-response genes in Drosophila melanogaster, to determine which genes may represent mechanisms of stress tolerance independent of Hsp70. Results Hsp70 copy number in four strains is positively associated with Hsp70 expression and inducible thermotolerance of severe heat shock. When assayed at carefully chosen temperatures, Hsp70 null flies are almost entirely deficient in thermotolerance. In contrast to expectations, increasing Hsp70 expression levels induced by thermal pretreatment are associated with increasing levels of seven other inducible Hsps across strains. In addition, complete Hsp70 loss causes upregulation of the inducible Hsps and six constitutive stress-response genes following severe heat shocks. Conclusion Modification of Hsp70 copy number quantitatively and qualitatively affects the expression of multiple other stress-response genes. A positive association between absolute expression levels of Hsp70 and other Hsps after thermal pretreatment suggests novel regulatory mechanisms. Severe heat shocks induce both novel gene expression patterns and almost total mortality in the Hsp70 null strain: alteration of gene expression in this strain does not compensate for Hsp70 loss but suggests candidates for overexpression studies.
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Affiliation(s)
- Brian R Bettencourt
- Department of Biological Sciences, University of Massachusetts Lowell, 1 University Avenue, Lowell, MA 01854, USA.
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Pyrimidinone-peptoid hybrid molecules with distinct effects on molecular chaperone function and cell proliferation. Bioorg Med Chem 2007; 16:3291-301. [PMID: 18164205 DOI: 10.1016/j.bmc.2007.12.014] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2007] [Revised: 12/04/2007] [Accepted: 12/06/2007] [Indexed: 02/04/2023]
Abstract
The Hsp70 molecular chaperones are ATPases that play critical roles in the pathogenesis of many human diseases, including breast cancer. Hsp70 ATP hydrolysis is relatively weak but is stimulated by J domain-containing proteins. We identified pyrimidinone-peptoid hybrid molecules that inhibit cell proliferation with greater potency than previously described Hsp70 modulators. In many cases, anti-proliferative activity correlated with inhibition of J domain stimulation of Hsp70.
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100
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D'Silva PR, Schilke B, Hayashi M, Craig EA. Interaction of the J-protein heterodimer Pam18/Pam16 of the mitochondrial import motor with the translocon of the inner membrane. Mol Biol Cell 2007; 19:424-32. [PMID: 18003975 DOI: 10.1091/mbc.e07-08-0748] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Import of proteins across the inner mitochondrial membrane through the Tim23:Tim17 translocase requires the function of an essential import motor having mitochondrial 70-kDa heat-shock protein (mtHsp70) at its core. The heterodimer composed of Pam18, the J-protein partner of mtHsp70, and the related protein Pam16 is a critical component of this motor. We report that three interactions contribute to association of the heterodimer with the translocon: the N terminus of Pam16 with the matrix side of the translocon, the inner membrane space domain of Pam18 (Pam18(IMS)) with Tim17, and the direct interaction of the J-domain of Pam18 with the J-like domain of Pam16. Pam16 plays a major role in translocon association, as alterations affecting the stability of the Pam18:Pam16 heterodimer dramatically affect association of Pam18, but not Pam16, with the translocon. Suppressors of the growth defects caused by alterations in the N terminus of Pam16 were isolated and found to be due to mutations in a short segment of TIM44, the gene encoding the peripheral membrane protein that tethers mtHsp70 to the translocon. These data suggest a model in which Tim44 serves as a scaffold for precise positioning of mtHsp70 and its cochaperone Pam18 at the translocon.
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Affiliation(s)
- Patrick R D'Silva
- Department of Biochemistry, University of Wisconsin, Madison, Madison, WI 53706, USA
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