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How does day-to-day stress appraisal relate to coping among office workers in academia? An ecological momentary assessment study. Stress Health 2023. [PMID: 37724331 DOI: 10.1002/smi.3315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2022] [Revised: 07/30/2023] [Accepted: 08/24/2023] [Indexed: 09/20/2023]
Abstract
Existing literature indicates that academic staff experience increasing levels of work stress. This study investigated associations between day-to-day threat and challenge appraisal and day-to-day problem-focused coping, emotion-focused coping, and seeking social support among academic office workers. This study is based on an Ecological Momentary Assessment (EMA) design with a 15-working day data collection period utilising our self-developed STRAW smartphone application. A total of 55 office workers from academic institutions in Belgium (n = 29) and Slovenia (n = 26) were included and 3665 item measurements were analysed. Participants were asked approximately every 90 min about their appraisal of stressful events (experienced during the working day) and their coping styles. For data analysis, we used an unstructured covariance matrix in our linear mixed models. Challenge appraisal predicted problem-focused coping and threat appraisal predicted emotion-focused coping. Our findings suggest an association between threat appraisal as well as challenge appraisal and seeking social support. Younger and female workers chose social support more often as a coping style. While working from home, participants were less likely to seek social support. The findings of our EMA study confirm previous research on the relationship between stress appraisal and coping with stress. Participants reported seeking social support less while working from home compared to working at the office, making the work location an aspect that deserves further research.
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The association between day-to-day stress experiences and work-life interference among office workers in academia: an ecological momentary assessment study. Int Arch Occup Environ Health 2023; 96:201-212. [PMID: 36104629 PMCID: PMC9474273 DOI: 10.1007/s00420-022-01915-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 08/14/2022] [Indexed: 02/08/2023]
Abstract
PURPOSE We investigated relations between day-to-day job demands, job control, job strain, social support at work, and day-to-day work-life interference among office workers in academia. METHODS This study is based on a 15-working day data collection period using an Ecological Momentary Assessment (EMA) implemented in our self-developed STRAW smartphone application. We recruited office workers from two academic settings in Belgium and Slovenia. Participants were repeatedly asked to complete EMAs including work stressors and work interfering with personal life (WIPL) as well as personal life interfering with work (PLIW). We applied fixed-effect model testing with random intercepts to investigate within- and between-participant levels. RESULTS We included 55 participants with 2261 analyzed observations in this study. Our data showed that researchers with a PhD reported higher WIPL compared to administrative and technical staff (β = 0.37, p < 0.05). We found significant positive associations between job demands (β = 0.53, p < 0.001), job control (β = 0.19, p < 0.01), and job strain (β = 0.61, p < 0.001) and WIPL. Furthermore, there was a significant interaction effect between job control and social support at work on WIPL (β = - 0.24, p < 0.05). Additionally, a significant negative association was found between job control and PLIW (β = - 0.20, p < 0.05). CONCLUSION Based on our EMA study, higher job demands and job strain were correlated with higher WIPL. Furthermore, we found associations going in opposite directions; higher job control was correlated with higher WIPL and lower PLIW. Higher job control leading to higher imbalance stands out as a novel result.
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Work environment risk factors causing day-to-day stress in occupational settings: a systematic review. BMC Public Health 2022; 22:240. [PMID: 35123449 PMCID: PMC8818147 DOI: 10.1186/s12889-021-12354-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 11/29/2021] [Indexed: 01/24/2023] Open
Abstract
Abstract
Background
While chronic workplace stress is known to be associated with health-related outcomes like mental and cardiovascular diseases, research about day-to-day occupational stress is limited. This systematic review includes studies assessing stress exposures as work environment risk factors and stress outcomes, measured via self-perceived questionnaires and physiological stress detection. These measures needed to be assessed repeatedly or continuously via Ecological Momentary Assessment (EMA) or similar methods carried out in real-world work environments, to be included in this review. The objective was to identify work environment risk factors causing day-to-day stress.
Methods
The search strategies were applied in seven databases resulting in 11833 records after deduplication, of which 41 studies were included in a qualitative synthesis. Associations were evaluated by correlational analyses.
Results
The most commonly measured work environment risk factor was work intensity, while stress was most often framed as an affective response. Measures from these two dimensions were also most frequently correlated with each other and most of their correlation coefficients were statistically significant, making work intensity a major risk factor for day-to-day workplace stress.
Conclusions
This review reveals a diversity in methodological approaches in data collection and data analysis. More studies combining self-perceived stress exposures and outcomes with physiological measures are warranted.
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From Opioid Pain Management to Opioid Crisis in the USA: How Can Public-Private Partnerships Help? Front Med (Lausanne) 2019; 6:106. [PMID: 31157226 PMCID: PMC6528705 DOI: 10.3389/fmed.2019.00106] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 04/29/2019] [Indexed: 11/13/2022] Open
Abstract
The current opioid crisis in the USA arose from (at first) successful opioid pain management in three waves, starting in the'90s. Today, USA patients consume opioid drugs on a massive scale. Considering their potential for tolerance, as well as their potential for lethality in relatively small overdose, the overuse of opioids form an urgent threat to public health in the USA. Since the opioid crisis is a complex phenomenon, several stakeholders are needed to tackle the problem. Both public and private stakeholders should collaborate, e.g., in Public-Private Partnerships. Those collaborations should focus on different aspects related to the opioid crisis such as medical and societal (e.g., pain management process, including addressing opioid use disorders), as well as economical and regulatory issues (e.g., incentivizing the search for alternative non-addictive pain medication and banning aggressive marketing tactics used by the pharmaceutical industry). Additionally, collaborations should cover interdisciplinary education and training of various healthcare actors involved. In conclusion, interdisciplinary collaboration on the various opioid abuse-related aspects is urgently needed to tackle the opioid crisis in the USA.
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A Personal Decision Support System for Heart Failure Management (HeartMan): study protocol of the HeartMan randomized controlled trial. BMC Cardiovasc Disord 2018; 18:186. [PMID: 30261836 PMCID: PMC6161437 DOI: 10.1186/s12872-018-0921-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 09/17/2018] [Indexed: 12/28/2022] Open
Abstract
Background Heart failure (HF) is a highly prevalent chronic disease, for which there is no cure available. Therefore, improving disease management is crucial, with mobile health (mHealth) being a promising technology. The aim of the HeartMan study is to evaluate the effect of a personal mHealth system on top of standard care on disease management and health-related quality of life (HRQoL) in HF. Methods HeartMan is a randomized controlled 1:2 (control:intervention) proof-of-concept trial, which will enrol 120 stable ambulatory HF patients with reduced ejection fraction across two European countries. Participants in the intervention group are equipped with a multi-monitoring health platform with the HeartMan wristband sensor as the main component. HeartMan provides guidance through a decision support system on four domains of disease management (exercise, nutrition, medication adherence and mental support), adapted to the patient’s medical and psychological profile. The primary endpoint of the study is improvement in self-care and HRQoL after a six-months intervention. Secondary endpoints are the effects of HeartMan on: behavioural outcomes, illness perception, clinical outcomes and mental state. Discussion HeartMan is technologically the most innovative HF self-management support system to date. This trial will provide evidence whether modern mHealth technology, when used to its full extent, can improve HRQoL in HF. Trial registration This trial has been registered on https://clinicaltrials.gov/ct2/show/NCT03497871, on April 13 2018 with registration number NCT03497871.
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Abstract
BACKGROUND Suicide is a tremendous public health issue and worldwide the second leading cause of death among young people. In 2015, Greenland had the highest burden of disease due to self-harm with loss of 2,952.97 disability-adjusted life years per 100,000 inhabitants, more than six times as many as Denmark. AIMS What are possible reasons for Greenland's higher youth suicide rate compared to Denmark, despite being one kingdom of Denmark? METHOD Mixed methods in the form of qualitative, semi-structured interviews, the analysis of available data for 2003-2016 and a literature review were conducted with the aim to answer this question. RESULTS Several exposures cause this difference, most significantly adverse effects of the colonial past, such as social issues and experienced traumas in Greenland compared to its former coloniser Denmark. CONCLUSION The ongoing burden of youth suicide in Greenland requires enhanced actions of all stakeholders involved in suicide prevention, intervention and postvention.
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Abstract
With 12% of all injuries concerning the shoulder, acromioclavicular (AC) joint dislocations are a common injury especially in young and active patients. The Rockwood classification is widely accepted, which differentiates between six types depending on the degree of injury and the vertical dislocation. Because the classification does not adequately address the horizontal instability, its benefits are questionable and there is currently no consensus. For this reason, the classification and the therapy of these injuries are increasingly becoming the subject of scientific investigations. Whereas conservative treatment for type I and II injuries and operative treatment for type IV-VI injuries are widely accepted, there is still no agreement in treating type III lesions. The goal of this review article is to present the current evidence for the diagnostics, different classifications and therapeutic possibilities.
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[Lack of adequate personnel threatens patient safety]. KRANKENPFLEGE. SOINS INFIRMIERS 2016; 109:27-29. [PMID: 27051906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
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Abstract
Coronal plane deformity has been found to be one of the main risk factors for poor clinical results, higher complication rates and failure of total ankle replacements. Initially, many authors considered a malalignment of more than 10° to be a contraindication for total ankle replacement, however, several publications later underlined the usefulness of the distinction of different etiologies of hindfoot malalignment. This subsequently led to suggestions for additional procedures in order to avoid early implant failure.The aim of the present article is to illustrate the different causes of varus malaligned arthritic ankles and to present procedures to balance these ankles at the time of replacement.
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Subtalar and talonavicular arthrodesis through a single medial approach for the correction of severe planovalgus deformity. ACTA ACUST UNITED AC 2009; 91:612-5. [DOI: 10.1302/0301-620x.91b5.21727] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We describe a retrospective review of the clinical and radiological parameters of 32 feet in 30 patients (10 men and 20 women) who underwent correction for malalignment of the hindfoot with a modified double arthrodesis through a medial approach. The mean follow-up was 21 months (13 to 37). Fusion was achieved in all feet at a mean of 13 weeks (6 to 30). Apart from the calcaneal pitch angle, all angular measurements improved significantly after surgery. Primary wound healing occurred without complications. The isolated medial approach to the subtalar and talonavicular joints allows good visualisation which facilitated the reduction and positioning of the joints. It was also associated with fewer problems with wound healing than the standard lateral approach.
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Identification and functional characterization of the zeta-chain dimerization motif for TCR surface expression. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1999; 163:3867-76. [PMID: 10490986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
We recognized a common dimerization motif between the transmembrane (TM) domain of zeta-chain family members and glycophorin A. We have shown that a glycine within the zeta-dimerization motif is critical for zeta-homodimerization and also for its association with the TCR/CD3 complex. Similarly, two residues within the CD3 delta gamma TM domains have proven to be critical for their interaction with the zeta-homodimer. A three-dimensional homology model of the zeta-chain TM domain highlights potential residues preferentially involved either in the zeta 2-CD3 or zeta 2-TCR alpha beta association, confirming our experimental findings. These results indicate that, for symmetrical reasons, the zeta-homodimer participates in the TCR/CD3 complex assembly by interacting with CD3 gamma delta TM domains, thereby masking their degradation signals located in the cytoplasmic tails.
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MESH Headings
- Amino Acid Sequence
- Amino Acids/chemistry
- Amino Acids/genetics
- Amino Acids/metabolism
- Animals
- Conserved Sequence
- Dimerization
- Glycophorins/chemistry
- Glycophorins/metabolism
- Membrane Proteins/biosynthesis
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mice
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Peptide Fragments/chemistry
- Peptide Fragments/genetics
- Peptide Fragments/metabolism
- Point Mutation
- Receptor-CD3 Complex, Antigen, T-Cell/chemistry
- Receptor-CD3 Complex, Antigen, T-Cell/metabolism
- Receptors, Antigen, T-Cell/biosynthesis
- Receptors, Antigen, T-Cell/chemistry
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/metabolism
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T cell receptor (TCR) antagonism without a negative signal: evidence from T cell hybridomas expressing two independent TCRs. J Exp Med 1999; 189:253-64. [PMID: 9892608 PMCID: PMC2192976 DOI: 10.1084/jem.189.2.253] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Antagonist peptides inhibit T cell responses by an unknown mechanism. By coexpressing two independent T cell receptors (TCRs) on a single T cell hybridoma, we addressed the question of whether antagonist ligands induce a dominant-negative signal that inhibits the function of a second, independent TCR. The two receptors, Valpha2Vbeta5 and Valpha2Vbeta10, restricted by H-2Kb and specific for the octameric peptides SIINFEKL and SSIEFARL, respectively, were coexpressed on the same cell. Agonist stimulation demonstrated that the two receptors behaved independently with regard to antigen-induced TCR downregulation and intracellular biochemical signaling. The exposure of one TCR (Valpha2Vbeta5) to antagonist peptides could not inhibit a second independent TCR (Valpha2Vbeta10) from responding to its antigen. Thus, our data clearly demonstrate that these antagonist ligands do not generate a dominant-negative signal which affects the responsiveness of the entire cell. In addition, a kinetic analysis showed that even 12 h after engagement with their cognate antigen and 10 h after reaching a steady-state of TCR internalization, T cells were fully inhibited by the addition of antagonist peptides. The window of susceptibility to antagonist ligands correlated exactly with the time required for the responding T cells to commit to interleukin 2 production. The data support a model where antagonist ligands can competitively inhibit antigenic peptides from productively engaging the TCR. This competitive inhibition is effective during the entire commitment period, where sustained TCR engagement is essential for full T cell activation.
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The extracellular domain of the zeta-chain is essential for TCR function. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1999; 162:878-85. [PMID: 9916711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
The zeta-chain homodimer is a key component in the TCR complex and exerts its function through its cytoplasmic immunoreceptor-tyrosine activation motif (1). The zeta-chain extracellular (EC) domain is highly conserved; however, its functional and structural contributions to the TCR signaling have not been elucidated. We show that the EC domain of the zeta homodimer is essential for TCR surface expression. To gain a more detailed structural and functional information about the zeta-chain EC domain, we applied a cysteine scanning mutagenesis to conserved amino acids of the short domain. The results showed that the interchain disulfide bridge can be displaced by seven or eight amino acids along the EC domain. The TCR signaling efficacy was dramatically reduced during peptide/MHC engagement in the zeta mutants containing the displaced disulfide bond. These signaling defective zeta mutants produced an unconventional early tyrosine phosphorylation pattern. While the tyrosine phosphorylated forms of zeta (p21 and p23) could be observed during Ag stimulation, downstream signaling events such as the generation of phospho-p36, higher m.w. forms of phospho-zeta, and phospho-zeta/ZAP-70 complexes were impaired. Together these results suggest an important function of the phylogenetically conserved zeta-EC domain.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antigens/immunology
- Apoproteins/immunology
- Cell Line
- Columbidae/immunology
- Cysteine/genetics
- Cytochrome c Group/immunology
- Cytochromes c
- Disulfides/chemistry
- Disulfides/metabolism
- Extracellular Space/chemistry
- Extracellular Space/immunology
- Extracellular Space/metabolism
- Humans
- Hybridomas/metabolism
- Immunophenotyping
- Lymphocyte Activation/genetics
- Membrane Proteins/biosynthesis
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Membrane Proteins/physiology
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Phosphorylation
- Protein Structure, Tertiary
- Receptors, Antigen, T-Cell/biosynthesis
- Receptors, Antigen, T-Cell/genetics
- Receptors, Antigen, T-Cell/metabolism
- Receptors, Antigen, T-Cell/physiology
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The chicken TCR zeta-chain restores the function of a mouse T cell hybridoma. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1998; 160:1552-4. [PMID: 9469409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The TCR/CD3 complex has been intensively studied in mammals, but it has been difficult to isolate homologues in other vertebrates. Here, we characterize the chicken zeta-chain, the first nonmammalian homologue identified. The comparison of mammalian and chicken zeta proteins revealed high identity of the transmembrane and the C-terminal cytoplasmic domains. Transfection of a mouse zeta-deficient cell line, with the chicken zeta gene, restored surface expression of the murine TCR/CD3 complex. The chicken zeta-chain was stably associated with the mouse TCR/CD3 components and fully restored its signaling capacity upon stimulation with Ab, superantigen, and peptide Ag. This is the first report of a nonmammalian TCR component that is capable of fully restoring a mammalian TCR in every aspect analyzed, thus demonstrating the enormous selective pressure to maintain the zeta-chain as a structural and signaling component over a period of 300 million years.
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The short extracellular domain of the T cell receptor zeta chain is involved in assembly and signal transduction. Mol Immunol 1997; 34:819-27. [PMID: 9464517 DOI: 10.1016/s0161-5890(97)00122-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The zeta chain is required in the TCR complex to guarantee its surface expression and function. However, an understanding of the interaction(s) between the zeta chain and the other proteins in the TCR/CD3 has not yet been achieved. In this report, we attempt to assign a functional role to the short extracellular (EC) domain of the zeta chain by studying its unique positive charge, a lysine at position 9, because of its interesting location to the interchain disulphide bond of the zeta chain homodimer. We show that amino acid exchanges of lysine 9 to glycine, serine, cysteine or asparagine generate TCR complexes which are clearly defective in antigenic signalling. Interestingly, the non-conservative point mutations were segregating TCR complex signalling pathways. However, lysine 9 is not critical for TCR complex surface expression unless the positively charged lysine is exchanged for the negatively charged amino acid aspartic acid. The zeta chain mutant bearing a lysine to cysteine exchange is the sole mutant to be inefficiently co-precipitated with the TCR/CD3 complex suggesting a loose interaction of the zeta chain within the TCR complex.
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Acidic receptor domains on both sides of the outer membrane mediate translocation of precursor proteins into yeast mitochondria. EMBO J 1995; 14:6318-26. [PMID: 8557051 PMCID: PMC394756 DOI: 10.1002/j.1460-2075.1995.tb00322.x] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Mitochondrial precursor proteins made in the cytosol bind to a hetero-oligomeric protein import receptor on the mitochondrial surface and then pass through the translocation channel across the outer membrane. This translocation step is accelerated by an acidic domain of the receptor subunit Mas22p, which protrudes into the intermembrane space. This 'trans' domain of Mas22p specifically binds functional mitochondrial targeting peptides with a Kd of < 1 microM and is required to anchor the N-terminal targeting sequence of a translocation-arrested precursor in the intermembrane space. If this Mas22p domain is deleted, respiration-driven growth of the cells is compromised and import of different precursors into isolated mitochondria is inhibited 3- to 8-fold. Binding of precursors to the mitochondrial surface appears to be mediated by cytosolically exposed acidic domains of the receptor subunits Mas20p and Mas22p. Translocation of a precursor across the outer membrane thus appears to involve sequential binding of the precursor's basic and amphiphilic targeting signal to acidic receptor domains on both sides of the membrane.
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Dynamic interaction between Isp45 and mitochondrial hsp70 in the protein import system of the yeast mitochondrial inner membrane. Proc Natl Acad Sci U S A 1994; 91:12818-22. [PMID: 7809127 PMCID: PMC45531 DOI: 10.1073/pnas.91.26.12818] [Citation(s) in RCA: 148] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The protein import system of the yeast mitochondrial inner membrane includes at least three membrane proteins that presumably form a transmembrane channel as well as several chaperone proteins that mediate the import and refolding of precursor proteins. We show that one of the membrane proteins, Isp45, spans the mitochondrial inner membrane yet is extracted from this membrane at high pH. Solubilization of mitochondria with a nonionic detergent releases Isp45 as a complex with the chaperones mitochondrial hsp70 (mhsp70) and GrpEp. Both chaperones reversibly dissociate from Isp45 upon addition of ATP or adenosine 5'-[gamma-thio]triphosphate, suggesting that dissociation requires the binding of ATP. Control experiments indicate that the interaction between mhsp70 and Isp45 occurs in the intact mitochondria. We propose that Isp45 lines the inside of a proteinaceous channel across the inner membrane and that it is the membrane anchor for an ATP-driven "import motor" composed of mhsp70 and GrpEp. This arrangement is reminiscent of the protein transport systems of the yeast endoplasmic reticulum and the bacterial plasma membrane.
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A mitochondrial homolog of bacterial GrpE interacts with mitochondrial hsp70 and is essential for viability. EMBO J 1994; 13:1998-2006. [PMID: 8168496 PMCID: PMC395042 DOI: 10.1002/j.1460-2075.1994.tb06469.x] [Citation(s) in RCA: 134] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mitochondrial hsp70 (mhsp70) is located in the matrix and an essential component of the mitochondrial protein import system. To study the function of mhsp70 and to identify possible partner proteins we constructed a yeast strain in which all mhsp70 molecules carry a C-terminal hexa-histidine tag. The tagged mhsp70 appears to be functional in vivo. When an ATP depleted mitochondrial extract was incubated with a nickel-derivatized affinity resin, the resin bound not only mhsp70, but also a 23 kDa protein. This protein was dissociated from mhsp70 by ATP. ADP and GTP were much less effective in promoting dissociation whereas CTP and TTP were inactive. We cloned the gene encoding the 23 kDa protein. This gene, termed GRPE, encodes a 228 residue protein, whose sequence closely resembles that of the bacterial GrpE protein. Microsequencing the purified 23 kDa protein established it as the product of the yeast GRPE gene. Yeast GrpEp is made as a precursor that is cleaved upon import into isolated mitochondria. GrpEp is essential for viability. We suggest that this protein interacts with mhsp70 in a manner analogous to that of GrpE with DnaK of E.coli.
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Protein import into yeast mitochondria: the inner membrane import site protein ISP45 is the MPI1 gene product. EMBO J 1993; 12:3035-41. [PMID: 8344245 PMCID: PMC413568 DOI: 10.1002/j.1460-2075.1993.tb05972.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein import across both mitochondrial membranes is mediated by the cooperation of two distinct protein transport systems, one in the outer and the other in the inner membrane. Previously we described a 45 kDa yeast mitochondrial inner membrane protein (ISP45) that can be cross-linked to a partially translocated precursor protein (Scherer et al., 1992). We have now purified ISP45 to homogeneity and identified it as the product of the nuclear MPI1 gene. Identity of ISP45 with the MPI1 gene product was shown by microsequencing of three tryptic ISP45 peptides and by demonstrating that an antibody against an Mpi1p-beta-galactosidase fusion protein specifically recognizes ISP45. Antibodies monospecific for ISP45 inhibited protein import into right-side-out mitochondrial inner membrane vesicles, but not into intact mitochondria. On solubilizing mitochondria, ISP45 was rapidly converted to a 40 kDa proteolytic fragment unless mitochondria were first denatured with trichloroacetic acid. The combined genetic and biochemical evidence identifies ISP45/Mpi1p as a component of the protein import system of the yeast mitochondrial inner membrane.
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