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Activation of HRI is mediated by Hsp90 during stress through modulation of the HRI-Hsp90 complex. Int J Biol Macromol 2018; 118:1604-1613. [PMID: 30170366 DOI: 10.1016/j.ijbiomac.2018.06.204] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 06/28/2018] [Accepted: 06/30/2018] [Indexed: 12/28/2022]
Abstract
Heme Regulated Inhibitor (HRI) is known to get activated in various stresses such as heme deficiency, heat shock, heavy metal toxicity etc. Heat shock protein 90 (Hsp90), a ubiquitous cytoplasmic protein interacts with HRI in order to regulate protein synthesis. However, it still remains to establish this interaction of HRI and Hsp90 at cellular levels and how this modulation of HRI activity is mediated by Hsp90 during stress. In the present report, using co-immunoprecipitation analysis we show that HRI interacts with Hsp90 and this association is independent of other co-chaperones in in vitro conditions. Further, analysis using truncated domains of HRI revealed that the K1 subdomain is essential for HRI - Hsp90 complex formation. Our in silico protein - protein interaction studies also indicated interaction of Hsp90 with K1 subdomain of HRI. Mammalian two hybrid assay validated this HRI - Hsp90 interaction at cellular levels. When the in vitro kinase assay was carried out with the co-immunoprecipitated complex of HRI - Hsp90, an increase in the kinase activity was observed resulting elevated levels of eIF2α phosphorylation upon heavy metal stress and heat shock. Thus, our results clearly indicate modulation of HRI kinase activity with simultaneous Hsp90 association under stress conditions.
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Bhavnani V, Kaviraj S, Panigrahi P, Suresh CG, Yapara S, Pal J. Elucidation of molecular mechanism of stability of the heme-regulated eIF2α kinase upon binding of its ligand, hemin in its catalytic kinase domain. J Biomol Struct Dyn 2017; 36:2845-2861. [PMID: 28814160 DOI: 10.1080/07391102.2017.1368417] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The eIF2α kinase activity of the heme-regulated inhibitor (HRI) is regulated by heme which makes it a unique member of the family of eIF2α kinases. Since heme concentrations create an equilibrium for the kinase to be active/inactive, it becomes important to study the heme binding effects upon the kinase and understanding its mechanism of functionality. In the present study, we report the thermostability achieved by the catalytic kinase domain of HRI (HRI.CKD) upon ligand (heme) binding. Our CD data demonstrates that the HRI.CKD retains its secondary structure at higher temperatures when it is in ligand bound state. HRI.CKD when incubated with hemin loses its monomeric state and attains a higher order oligomeric form resulting in its stability. The HRI.CKD fails to refold into its native conformation upon mutation of H377A/H381A, thereby confirming the necessity of these His residues for correct folding, stability, and activity of the kinase. Though our in silico study demonstrated these His being the ligand binding sites in the kinase insert region, the spectra-based study did not show significant difference in heme affinity for the wild type and His mutant HRI.CKD.
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Affiliation(s)
- Varsha Bhavnani
- a Department of Biotechnology , Savitribai Phule Pune University , Pune , Maharashtra 411007 , India
| | - Swarnendu Kaviraj
- b Vaccine Formulation & Research Centre , Gennova Biopharmaceuticals Limited , Pune , Maharashtra 411057 , India
| | - Priyabrata Panigrahi
- c Division of Biochemical Sciences , CSIR-National Chemical Laboratory , Pune 411008 , India
| | - C G Suresh
- c Division of Biochemical Sciences , CSIR-National Chemical Laboratory , Pune 411008 , India
| | - SuneelShekar Yapara
- b Vaccine Formulation & Research Centre , Gennova Biopharmaceuticals Limited , Pune , Maharashtra 411057 , India
| | - Jayanta Pal
- a Department of Biotechnology , Savitribai Phule Pune University , Pune , Maharashtra 411007 , India
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Bhavnani V, Swarnendu K, Savergave L, Raghuwanshi AS, Kumar A, Kumar A, Pal J. HRI, a stress response eIF2α kinase, exhibits structural and functional stability at high temperature and alkaline conditions. Int J Biol Macromol 2016; 95:528-538. [PMID: 27888007 DOI: 10.1016/j.ijbiomac.2016.11.071] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 11/14/2016] [Accepted: 11/15/2016] [Indexed: 01/20/2023]
Abstract
The Heme Regulated Inhibitor (HRI) is a key regulator of protein synthesis in mammalian cells. Once activated under heme-deficiency and other stress conditions, it phosphorylates the α subunit of eukaryotic initiation factor 2 (eIF2α) leading to inhibition of protein synthesis. In the present study, our objective was to establish the structural and functional credentials of this kinase so as to qualify it as a stress responsive eIF2α kinase. When the catalytic kinase domain of the HRI (HRI.CKD) protein was subjected to high temperature, 45°C (above mammalian heat shock temperature), it could still phosphorylate the substrate, indicating its potential as a stress response kinase. At a temperature beyond 45°C, loss in secondary structure of the HRI.CKD is attributable to loss of its function. Furthermore, no significant structural changes were observed at the broad pH range of 3.0--10.0. The HRI.CKD incubated at any pH between 8.0-10.0, exhibited more than 60% of its kinase activity, demonstrating structural and functional stability of the kinase at an alkaline pH. These data taken together establish that the structural stability of this kinase at high temperature and alkaline conditions is due to conservation of its secondary structure and that the resulting functional activity qualifies this kinase as a stress responsive kinase.
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Affiliation(s)
- Varsha Bhavnani
- Department of Biotechnology, Savitribai Phule Pune University, Pune, Maharashtra 411007, India
| | - Kaviraj Swarnendu
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Laxman Savergave
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Arjun Singh Raghuwanshi
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Ankit Kumar
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Avinash Kumar
- Vaccine Formulation & Research Centre, Gennova Biopharmaceuticals Limited, Pune, Maharashtra 411057, India
| | - Jayanta Pal
- Department of Biotechnology, Savitribai Phule Pune University, Pune, Maharashtra 411007, India.
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Sreejith RK, Suresh CG, Bhosale SH, Bhavnani V, Kumar A, Gaikwad SM, Pal JK. Conformational Transitions of the Catalytic Domain of Heme-Regulated Eukaryotic Initiation Factor 2α Kinase, a Key Translational Regulatory Molecule. J Fluoresc 2011; 22:431-41. [DOI: 10.1007/s10895-011-0976-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 09/13/2011] [Indexed: 01/18/2023]
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Kulkarni AP, Mittal SPK, Devasagayam TPA, Pal JK. Oxidative stress perturbs cell proliferation in human K562 cells by modulating protein synthesis and cell cycle. Free Radic Res 2009; 43:1090-100. [DOI: 10.1080/10715760903179673] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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Stress-induced overexpression of the heme-regulated eIF-2α kinase is regulated by Elk-1 activated through ERK pathway. Biochem Biophys Res Commun 2009; 379:710-5. [DOI: 10.1016/j.bbrc.2008.12.141] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2008] [Accepted: 12/14/2008] [Indexed: 11/17/2022]
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Xu D, Luo D. Determination of Hemin using a Parallel Catalytic Reduction Wave of its Protoporphyrin IX Ring. ANAL LETT 2007. [DOI: 10.1080/00032710701645737] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Sarkar A, Kulkarni A, Chattopadhyay S, Mogare D, Sharma KK, Singh K, Pal JK. Lead-induced upregulation of the heme-regulated eukaryotic initiation factor 2α kinase is compromised by hemin in human K562 cells. ACTA ACUST UNITED AC 2005; 1732:15-22. [PMID: 16500424 DOI: 10.1016/j.bbaexp.2005.12.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 12/10/2005] [Accepted: 12/19/2005] [Indexed: 11/24/2022]
Abstract
Expression and kinase activity of the heme-regulated-eIF-2alpha kinase or -inhibitor (HRI) are induced during cytoplasmic stresses leading to inhibition of protein synthesis. Using a reporter construct with HRI promoter, we have determined the promoter activity during heat-shock and lead toxicity in human K562 cells. These two conditions induced HRI promoter activity by 2- to 3-fold. Contrary to this, hemin, a suppressor of HRI kinase activity, downregulated HRI promoter activity and stimulated hemoglobin synthesis. Interestingly, when hemin-treated cells were transfected and exposed to lead, hemin compromised lead-effect substantially by downregulating HRI promoter activity, HRI transcription and HRI kinase activity. These results together suggest that heme signaling in relation to translation regulation is not only restricted to the cytoplasm (modulating HRI kinase activity) alone but it also spans to the nucleus modulating HRI expression. Hemin may thus be useful for alleviation of stress-induced inhibition of protein synthesis.
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Affiliation(s)
- Angshuman Sarkar
- Department of Biotechnology, University of Pune, Pune 411 007, India
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Lombardo ME, Araujo LS, Ciccarelli AB, Batlle A. A spectrophotometric method for estimating hemin in biological systems. Anal Biochem 2005; 341:199-203. [PMID: 15907864 DOI: 10.1016/j.ab.2004.11.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Indexed: 11/18/2022]
Abstract
Hemin chlorides exhibit two absorption maxima in the Soret region, one at about 360-380 nm (S' band) and the other between 400 and 430 nm (S band). We present here a simple and fast spectrophotometric assay to determine concentration of hemin between 1.15 and 9.20 microM employing the Soret region (S' band) as a reference. In this method the hemin is quantitatively extracted from biological materials by acidified chloroform. By recording the absorbance of the chloroform extract at its maximum peak at 388, 450, and 330 nm and applying the correction formula A(c)=2A388-(A450+A330), a very good linear correlation between the A(c) and the concentration of hemin is attained. The method can be used to estimate hemin in the presence of protein (0.06-5.00 mg/ml) and porphyrin (0.19-2.97 microM). Compared with the pyridine hemochromogen method, the assay reported here is highly reproducible, with 15- to 30-fold more sensitivity, and it allows the quantification of four times lower hemin concentrations.
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Affiliation(s)
- María Elisa Lombardo
- Centro de Investigaciones sobre Porfirinas y Porfirias-CIPYP (CONICET-FCEN, UBA), Ciudad Universitaria Pabellón II 2do.Piso, 1428 Buenos Aires, Argentina
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Pal JK, Joshi-Purandare M. Dose-dependent differential effect of hemin on protein synthesis and cell proliferation in Leishmania donovani promastigotes cultured in vitro. J Biosci 2001; 26:225-31. [PMID: 11426058 DOI: 10.1007/bf02703646] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Leishmania donovani requires an exogenous source of heme for growth and transformation. In in vitro culture of the free-living promastigotes, exogenously added hemin enhances cell proliferation. In this investigation, the question of the function of heme with particular reference to protein synthesis and cell proliferation has been addressed. The results of in vitro cell culture experiments demonstrated that hemin (10 microM) alone is suitable for supporting optimum level of protein synthesis, and thereby cell proliferation of promastigotes to an extent that it can replace fetal bovine serum. However, in situ labelling experiments along with Western blots revealed that high concentration of hemin (50 microM) reduced the level of protein synthesis in general and of beta-tubulin in particular with a concomitant induction of hsp90, and induced consequent morphological changes that are observed during in situ transformation of promastigotes in mammalian macrophages. These results therefore suggest that sudden exposure to high concentration of heme in mammalian macrophages may be one of the key factors that trigger promastigote to amastigote transformation in L. donovani. Furthermore, hemin with its dual characteristic could be used as a tool to understand molecular mechanism of cell proliferation and transformation in these parasites.
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Affiliation(s)
- J K Pal
- Department of Biotechnology, University of Pune, Pune 411 007, India.
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Hsp90 regulates protein synthesis by activating the heme-regulated eukaryotic initiation factor 2α (eIF-2α) kinase in rabbit reticulocyte lysates. J Biosci 1998. [DOI: 10.1007/bf02936128] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Csermely P, Schnaider T, Soti C, Prohászka Z, Nardai G. The 90-kDa molecular chaperone family: structure, function, and clinical applications. A comprehensive review. Pharmacol Ther 1998; 79:129-68. [PMID: 9749880 DOI: 10.1016/s0163-7258(98)00013-8] [Citation(s) in RCA: 741] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The 90-kDa molecular chaperone family (which comprises, among other proteins, the 90-kDa heat-shock protein, hsp90 and the 94-kDa glucose-regulated protein, grp94, major molecular chaperones of the cytosol and of the endoplasmic reticulum, respectively) has become an increasingly active subject of research in the past couple of years. These ubiquitous, well-conserved proteins account for 1-2% of all cellular proteins in most cells. However, their precise function is still far from being elucidated. Their involvement in the aetiology of several autoimmune diseases, in various infections, in recognition of malignant cells, and in antigen-presentation already demonstrates the essential role they likely will play in clinical practice of the next decade. The present review summarizes our current knowledge about the cellular functions, expression, and clinical implications of the 90-kDa molecular chaperone family and some approaches for future research.
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Affiliation(s)
- P Csermely
- Department of Medical Chemistry, Semmelweis University, Budapest, Hungary
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Heme-regulated eukaryotic initiation factor 2α kinase—A molecular indicator of haemolytic anemia. J Biosci 1997. [DOI: 10.1007/bf02703232] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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15
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hsp 83 mutation is a dominant enhancer of lethality associated with absence of the non-protein codinghsrω locus inDrosophila melanogaster. J Biosci 1996. [DOI: 10.1007/bf02703109] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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