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1.
BMC Public Health ; 23(1): 848, 2023 05 10.
Article in English | MEDLINE | ID: mdl-37165331

ABSTRACT

BACKGROUND: Hospital staff are often exposed to stressful psychosocial working conditions and report high levels of stress and burnout, which may negatively impact the safety of employees and patients. Managers hold unique knowledge of workplace conditions and needs of employees, but leadership interventions to improve the well-being of managers and employees in hospital settings are scarce. This study evaluates the effects of a leadership intervention based on a health-oriented leadership approach on the well-being and psychosocial work environment aspects of managers and employees. METHODS/DESIGN: The study is designed as a randomized, waitlist-controlled trial with two groups (intervention and waitlist control group) and measurements at baseline, 6- and 12-month follow-up. We aim to include 200 frontline managers in Danish hospital settings and their approximately 5,000 employees. The leadership training comprises five full day modules and four smaller group-training sessions over a period of 5 months. The main aim is to improve stress, burnout, self-care, and perceived level of staff-care among managers and employees. Sickness absence will also be assessed at both manager and employee level. In addition, several psychosocial factors will be assessed at the employee level. A quantitative and qualitative process evaluation will also be conducted. DISCUSSION: Action towards supporting the mental health of hospital employees is important to maintain a strong healthcare system. There is increasing recognition that best practice in workplace mental health requires an integrated approach that prevents harm and promotes positive mental health. There is also increasing understanding of the key role managers' play in maintaining well-being within the workplace, however they often report a lack of knowledge and skills to promote employee mental health. The current leadership training program has been developed for frontline managers working in a hospital setting. The aim is to increase managers' application of strategies to facilitate a healthy psychosocial work environment to benefit well-being and mental health among staff and managers themselves. TRIAL REGISTRATION: The study was retrospectively registered on November 21, 2022 in Clinical Trial.gov with identifier: NCT05623371.


Subject(s)
Burnout, Professional , Working Conditions , Humans , Mental Health , Workplace/psychology , Leadership , Burnout, Professional/prevention & control , Denmark , Randomized Controlled Trials as Topic
2.
Acta Psychiatr Scand ; 133(2): 154-164, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26138003

ABSTRACT

OBJECTIVE: To investigate the role of hippocampal plasticity in the antidepressant effect of electroconvulsive therapy (ECT). METHOD: We used magnetic resonance (MR) imaging including diffusion tensor imaging (DTI) and proton MR spectroscopy (1 H-MRS) to investigate hippocampal volume, diffusivity, and metabolite changes in 19 patients receiving ECT for severe depression. Other regions of interest included the amygdala, dorsolateral prefrontal cortex (DLPFC), orbitofrontal cortex, and hypothalamus. Patients received a 3T MR scan before ECT (TP1), 1 week (TP2), and 4 weeks (TP3) after ECT. RESULTS: Hippocampal and amygdala volume increased significantly at TP2 and continued to be increased at TP3. DLPFC exhibited a transient volume reduction at TP2. DTI revealed a reduced anisotropy and diffusivity of the hippocampus at TP2. We found no significant post-ECT changes in brain metabolite concentrations, and we were unable to identify a spectral signature at ≈1.30 ppm previously suggested to reflect neurogenesis induced by ECT. None of the brain imaging measures correlated to the clinical response. CONCLUSION: Our findings show that ECT causes a remodeling of brain structures involved in affective regulation, but due to their lack of correlation with the antidepressant effect, this remodeling does not appear to be directly underlying the antidepressant action of ECT.

3.
Oncogene ; 34(32): 4199-210, 2015 Aug 06.
Article in English | MEDLINE | ID: mdl-25362855

ABSTRACT

Antiestrogen resistance is a major problem in breast cancer treatment. Therefore, the search for new therapeutic targets and biomarkers for antiestrogen resistance is crucial. In this study, we performed a kinase inhibitor screen on antiestrogen responsive MCF-7 cells and a panel of MCF-7-derived tamoxifen- and fulvestrant-resistant cell lines. Our focus was to identify common and distinct molecular mechanisms involved in tamoxifen- and fulvestrant-resistant cell growth. We identified 18 inhibitors, of which the majority was common for both tamoxifen- and fulvestrant-resistant cell lines. Two compounds, WP1130 and JNJ-7706621, exhibiting prominent preferential growth inhibition of antiestrogen-resistant cell lines, were selected for further studies. WP1130, a deubiquitinase inhibitor, induced caspase-mediated cell death in both tamoxifen- and fulvestrant-resistant cell lines by destabilization of the anti-apoptotic protein Mcl-1. Mcl-1 expression was found upregulated in the antiestrogen-resistant cell lines and depletion of Mcl-1 in resistant cells caused decreased viability. JNJ-7706621, a dual Aurora kinase and cyclin-dependent kinase inhibitor, specifically inhibited growth and caused G2 phase cell cycle arrest of the tamoxifen-resistant cell lines. Knockdown studies showed that Aurora kinase A is essential for growth of the tamoxifen-resistant cells and inhibition of Aurora kinase A resensitized tamoxifen-resistant cells to tamoxifen treatment. Preferential growth inhibition by WP1130 and JNJ-7706621 was also found in T47D-derived tamoxifen-resistant cell lines, pointing at Mcl-1 and Aurora kinase A as potential treatment targets. In addition, tumor samples from 244 estrogen receptor-positive breast cancer patients treated with adjuvant tamoxifen showed that higher expression level of Aurora kinase A was significantly associated with shorter disease-free and overall survival, demonstrating the potential of Aurora kinase A as a biomarker for tamoxifen resistance.


Subject(s)
Aurora Kinase A/antagonists & inhibitors , Drug Resistance, Neoplasm/drug effects , Estrogen Antagonists/pharmacology , Myeloid Cell Leukemia Sequence 1 Protein/antagonists & inhibitors , Protein Kinase Inhibitors/pharmacology , Apoptosis/drug effects , Apoptosis/genetics , Aurora Kinase A/genetics , Aurora Kinase A/metabolism , Biomarkers, Tumor/genetics , Biomarkers, Tumor/metabolism , Breast Neoplasms/drug therapy , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Caspases/metabolism , Cell Line, Tumor , Cell Proliferation/drug effects , Cell Proliferation/genetics , Cyanoacrylates/pharmacology , Drug Resistance, Neoplasm/genetics , Drug Screening Assays, Antitumor , Estradiol/analogs & derivatives , Estradiol/pharmacology , Fulvestrant , G2 Phase Cell Cycle Checkpoints/drug effects , G2 Phase Cell Cycle Checkpoints/genetics , Humans , MCF-7 Cells , Myeloid Cell Leukemia Sequence 1 Protein/genetics , Myeloid Cell Leukemia Sequence 1 Protein/metabolism , Pyridines/pharmacology , RNA Interference , Receptors, Estrogen/metabolism , Survival Analysis , Tamoxifen/pharmacology , Triazoles/pharmacology
4.
Cancer Biomark ; 5(1): 41-9, 2009.
Article in English | MEDLINE | ID: mdl-19242061

ABSTRACT

Uncontrolled growth of cancer cells can be related to dysfunctional cell cycle control, including entry into S-phase, initiating cell division. Cyclin CCND3 and CCNE1 along with CDK2 and CDK6 regulate this checkpoint, and genetic changes, detectable by fluorescence in situ hybridization, are hypothesized to increase the aggressiveness of breast cancer, thereby influencing patient survival. Genomic change was investigated in 106 primary breast cancer samples, where the combined gene copy number changes in one of these four cell cycle regulatory factors was observed in 22% of the 98 tumors of successful analysis, distributed with 15 deletions and 7 amplifications. A trend towards decreased survival was observed with the aberrations, suggesting a prognostic potential of this set of markers, which was supported by an association with tumor grade. For validation of the new set of FISH probes for the G1/S-phase cell cycle factors, two additional markers, frequently amplified in breast cancers, were included in this study: The G1/S phase control gene CCND1 and the proliferation marker MYC. Both markers were amplified in 14% and deleted in 5% of the cases. This is the first report of genomic deletions of MYC in breast cancer.


Subject(s)
Breast Neoplasms/genetics , Cyclin D1/genetics , G1 Phase , Gene Amplification , Proto-Oncogene Proteins c-myc/genetics , S Phase , Sequence Deletion , Female , Humans , In Situ Hybridization, Fluorescence , Middle Aged , Prognosis , Survival Rate , Tissue Array Analysis
5.
Clin Exp Immunol ; 155(2): 257-65, 2009 Feb.
Article in English | MEDLINE | ID: mdl-19137636

ABSTRACT

Matrix metalloproteinases (MMPs) have been implicated in tissue damage associated with inflammatory bowel disease (IBD).As the role of the intestinal epithelium in this process is unknown, we determined MMP expression and enzyme activity in human colonic epithelial cells (CEC). MMP mRNA expression was assessed by reverse transcription-polymerase chain reaction in HT-29 and DLD-1 cells and in CEC isolated from biopsies from IBD and control patients. Total MMP activity in the cells was measured by a functional assay, based on degradation of a fluorescent synthetic peptide containing the specific bond for MMP cleavage. HT-29 and DLD-1 expressed several MMPs and levels of MMP-3, -10 and -13 mRNA expression were increased significantly by tumour necrosis factor (TNF)-alpha exposure. Transcripts of MMP-1, -3, -7, -9, -10 and -12 were detected in CECs and all, except MMP12, at significantly increased levels in cells from inflamed IBD mucosa. MMP-2 and -8 mRNA were expressed inconsistently and MMP-11, -13 and -14 mRNA undetectable. Proteolytic MMP activity was detected in CEC supernatants and the level was increased significantly in inflamed IBD epithelium. The enzyme activity was inhibited strongly by a specific MMP inhibitor (GM 6001). A significant TNF-alpha-mediated increase in MMP enzyme activity was also detected in HT-29 cells in vitro. In conclusion, the expression of several MMPs as well as the level of functional MMPactivity is increased in CEC from patients with active IBD. The results suggest that MMPs released by the intestinal epithelium may be involved in the pathogenesis of IBD by promoting local mucosal damage.


Subject(s)
Colon/enzymology , Cytokines/pharmacology , Inflammatory Bowel Diseases/enzymology , Intestinal Mucosa/enzymology , Matrix Metalloproteinases/biosynthesis , Adult , Aged , Cell Line, Transformed , Cells, Cultured , Colon/drug effects , Female , Gene Expression Regulation, Enzymologic/drug effects , Humans , Intestinal Mucosa/drug effects , Male , Matrix Metalloproteinases/genetics , Middle Aged , RNA, Messenger/genetics , Reverse Transcriptase Polymerase Chain Reaction/methods , Young Adult
6.
Histopathology ; 52(6): 698-705, 2008 May.
Article in English | MEDLINE | ID: mdl-18393977

ABSTRACT

AIMS: CCND1 and EMSY, on 11q13, are frequently amplified in breast cancer. CCND1 is implicated in cell cycle progression and EMSY is a BRCA2-associated repressor protein. The aim was to investigate gene copy numbers of CCND1 and EMSY and to determine if CCND1 amplification is associated with reduced survival of tamoxifen-treated breast cancer patients. METHODS AND RESULTS: Fluorescence in situ hybridization (FISH) was performed on 111 consecutive and 354 oestrogen receptor (ER)+ tamoxifen-treated breast cancers. In the consecutive set, CCND1 and EMSY were amplified in 14.8% and 7.2%, respectively, and deleted in 8.7% and 13.5%, respectively. In the ER+ set, CCND1 and EMSY were amplified in 20.6% and 9.6%, respectively, and deleted in 1.7% and 4.2%, respectively. CCND1 and EMSY gene amplifications were associated with decreased overall survival (OS) (P = 0.03 and P = 0.04, respectively) of patients in the ER+ set. CONCLUSION: As hypothesized, CCND1 amplifications are associated with poor OS in ER+ patients. EMSY amplification is also associated with poor OS. However, as >70% of EMSY amplifications were CCND1 amplified, EMSY may not have any additional effect on survival of ER+ breast cancer.


Subject(s)
Breast Neoplasms/genetics , Cyclins/genetics , Neoplasm Proteins/genetics , Nuclear Proteins/genetics , Repressor Proteins/genetics , Breast Neoplasms/drug therapy , Cohort Studies , Cyclin D , Female , Gene Dosage , Humans , Middle Aged , Tamoxifen/pharmacology
7.
Histopathology ; 48(7): 787-94, 2006 Jun.
Article in English | MEDLINE | ID: mdl-16722926

ABSTRACT

AIM: Immunohistochemical analysis of protein expression is central to most clinical translational studies and defines patient treatment or selection criteria for novel drugs. Interobserver variation is rarely analysed despite recognition that this is a key area of potential inaccuracy. Therefore our aim was to examine observer variation and suggest the revision of current standards. METHODS AND RESULTS: We analysed inter- and intra-observer variation, by interclass correlation coefficient (ICCC) and kappa statistics, in 8661 samples. Intra-observer assessment of nuclear, cytoplasmic and membrane staining for seven proteins in 1323 samples resulted in an ICCC of 0.94 and a kappa-value of 0.787. Interobserver reproducibility, assessed on 28 proteins by seven observer pairs in 8661 carcinomas, gave an ICCC of 0.90 and a kappa-value of 0.70. No significant effect of either antibody or cellular compartmentalization was observed. CONCLUSION: We have demonstrated that ICCC is a consistent method to assess observer variation when a continuous scoring system is used, compared with kappa statistics, which depends on a categorical system. Given the importance of accurate assessment of protein expression in diagnostic and experimental medicine, we suggest raising thresholds for observer variation: ICCC of 0.7 should be regarded as the minimum acceptable standard, ICCC of 0.8 as good and ICCC of > or = 0.9 as excellent.


Subject(s)
Biomarkers, Tumor/analysis , Immunohistochemistry/standards , Neoplasms/pathology , Observer Variation , Proteins/analysis , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , Cyclooxygenase 2/analysis , Female , Humans , Male , Membrane Proteins/analysis , Neoplasms/metabolism , Ovarian Neoplasms/metabolism , Ovarian Neoplasms/pathology , Prostate-Specific Antigen/analysis , Prostatic Neoplasms/metabolism , Prostatic Neoplasms/pathology , Receptor, ErbB-2/analysis , Receptors, Estrogen/analysis , Receptors, Progesterone/analysis
8.
Gut ; 53(5): 701-9, 2004 May.
Article in English | MEDLINE | ID: mdl-15082589

ABSTRACT

BACKGROUND: Fistulae are a troublesome complication of Crohn's disease but little is known of the final effector molecules responsible for matrix degradation. Although matrix metalloproteinases (MMPs) have been strongly implicated in tissue injury in Crohn's disease, their role in fistula formation is unknown. AIM: To determine the expression pattern of MMPs and tissue inhibitors of metalloproteinases (TIMPs) in fistulae of patients with Crohn's disease. PATIENTS AND METHODS: Resected fistula specimens were obtained from patients with Crohn's disease (n = 11) and classified according to the predominant histological features-that is, acute versus chronic inflammation. Patients with fistulae due to other diseases (n = 9) and normal colon (n = 5) served as controls. MMP and TIMP protein expression was measured by single or double labelled immunohistochemistry, and mRNA expression by in situ hybridisation. MMP activity was measured by gelatin zymography. RESULTS: Compared with normal colon, strong MMP-3 expression was consistently observed in fistulae in Crohn's disease, irrespective of the stage of inflammatory activity. MMP-3 transcripts and protein were localised in large mononuclear cells and fibroblasts. MMP-9 transcripts and protein were expressed in granulocytes and only in fistulae with acute inflammation. Staining for MMP-1 and MMP-7 was weak and negative for MMP-10, whereas MMP-2 was equally expressed in normal colon and fistulae. TIMP-1, TIMP-2, and TIMP-3 expression was low in all samples. Similar expression patterns were found in fistulae of the disease control group. Fistulae also expressed active MMP-2 and MMP-9, as measured by gelatin zymography. CONCLUSION: MMP-3 and MMP-9 are markedly upregulated in intestinal fistulae and may contribute to fistula formation through degradation of the extracellular matrix, irrespective of the underlying disease process.


Subject(s)
Crohn Disease/metabolism , Intestinal Fistula/metabolism , Matrix Metalloproteinases/metabolism , Tissue Inhibitor of Metalloproteinases/metabolism , Adolescent , Adult , Colon/enzymology , Colon/metabolism , Crohn Disease/complications , Crohn Disease/enzymology , Female , Gene Expression , Humans , Immunoenzyme Techniques , In Situ Hybridization , Intestinal Fistula/enzymology , Intestinal Fistula/etiology , Male , Matrix Metalloproteinase 3/metabolism , Matrix Metalloproteinase 9/metabolism , Matrix Metalloproteinases/genetics , Middle Aged , RNA, Messenger/genetics
9.
Clin Exp Immunol ; 135(1): 146-53, 2004 Jan.
Article in English | MEDLINE | ID: mdl-14678276

ABSTRACT

Tumour necrosis factor (TNF)-alpha converting enzyme (TACE) releases biologically active, soluble TNF-alpha from transmembrane pro-TNF-alpha and has attracted interest as a specific therapeutic target in inflammatory bowel disease (IBD). Strong immunoreactivity for TACE protein was demonstrated recently in human colonic epithelium, but the function is unknown. We investigated if human colonic epithelial cells express functional TACE activity and how TACE expression is regulated in response to cytokine stimulation. TACE and TNF-alpha mRNA and protein expression were measured in HT-29 and DLD-1 colonic epithelial cells by reverse-transcription polymerase chain reaction, western blotting or enzyme-linked immunosorbent assay. Monocytic THP-1 cells served as positive control. Functional TACE activity was identified and quantified in detergent extracts of cell lines and freshly isolated colonocytes from 14 IBD patients and five controls by a hydrolysis assay using an oligopeptide spanning the cleavage site in pro-TNF-alpha. HT-29 and DLD-1 cells spontaneously expressed TACE mRNA and the active form of TACE protein at levels similar to those of monocytic cells. Functional TACE activity was demonstrated in all cell lines and in cells of controls or IBD patients irrespective of disease activity. TACE mRNA expression and functional activity remained unchanged in cell lines after stimulation with TNF-alpha despite clear induction of TNF-alpha mRNA expression and release of soluble TNF-alpha protein. The release of soluble TNF-alpha protein was almost completely abolished by CH4474, a synthetic TACE inhibitor. We conclude that functional TACE activity is constitutively expressed in human colonic epithelial cells and responsible for processing of the mature, soluble form of TNF-alpha in response to cytokine stimulation.


Subject(s)
Colon/enzymology , Inflammatory Bowel Diseases/enzymology , Intestinal Mucosa/enzymology , Metalloendopeptidases/metabolism , ADAM Proteins , ADAM17 Protein , Adult , Cell Line, Transformed , Cells, Cultured , Cytokines/immunology , Epithelial Cells/enzymology , Female , Gene Expression , Humans , Inflammatory Bowel Diseases/immunology , Male , Metalloendopeptidases/antagonists & inhibitors , Metalloendopeptidases/genetics , Middle Aged , Protease Inhibitors/pharmacology , RNA, Messenger/genetics , Tumor Necrosis Factor-alpha/biosynthesis , Tumor Necrosis Factor-alpha/genetics
10.
Gut ; 51(1): 37-43, 2002 Jul.
Article in English | MEDLINE | ID: mdl-12077089

ABSTRACT

BACKGROUND: Anti-tumour necrosis factor alpha (TNF-alpha) antibodies are effective in Crohn's disease and perhaps ulcerative colitis but antigenicity and the high cost have raised interest in other strategies to block TNF-alpha. These include the TNF-alpha converting enzyme (TACE) which releases soluble TNF-alpha from transmembrane pro-TNF-alpha. AIM: To investigate whether TACE activity is present in human colonic mucosa. MATERIALS AND METHODS: Detergent extracts of cell membranes from colonic biopsies were obtained from 12 controls and 28 patients with inflammatory bowel disease. Enzyme activity was measured by hydrolysis assays using pro-TNF-alpha or oligopeptide substrates spanning the known pro-TNF-alpha cleavage site at Ala(76)-Val(77). Cleavage products were identified by western blotting, high pressure liquid chromatography, or mass spectrometry. TACE protein was localised by immunohistochemistry and identified by western blotting of detergent extracts from purified lamina propria mononuclear cells (LPMNC) or epithelial cells. RESULTS: Detergent extracts released TNF-alpha from pro-TNF-alpha and cleaved a model oligopeptide as predicted. Substrate hydrolysis was sensitive to known TACE/matrix metalloproteinase (MMP) inhibitors, but not trocade which has low activity against TACE. The median TACE level was increased in active ulcerative colitis (147 arbitrary units (AU)/mg; p<0.01) but not in Crohn's disease (81 AU/mg) compared with controls (79 AU/mg). Both the full length proform and the active form of TACE protein were expressed in LPMNC cells and epithelial cells. CONCLUSIONS: Functional TACE activity is ubiquitously expressed in the human colon and increased in ulcerative colitis, raising interest in MMP inhibitors targeting TACE.


Subject(s)
Colitis, Ulcerative/enzymology , Colon/enzymology , Crohn Disease/enzymology , Intestinal Mucosa/enzymology , Metalloendopeptidases/metabolism , ADAM Proteins , ADAM17 Protein , Adult , Aged , Case-Control Studies , Female , Humans , Immunohistochemistry , Male , Middle Aged
11.
Thromb Haemost ; 83(5): 742-51, 2000 May.
Article in English | MEDLINE | ID: mdl-10823273

ABSTRACT

Some monoclonal antibodies against plasminogen activator inhibitor-1 (PAI-1) are able to inhibit its reaction with its target proteinases. We have characterized the effect on PAI-1 of two monoclonal antibodies, Mab-2 and Mab-6, with overlapping epitopes in a sequence encompassing beta-strand 1A, alpha-helix F, and the loop connecting alpha-helix F and beta-strand 3A (the hF/s3A loop). Mab-2 reduced the inhibitory activity of wild type PAI-1 and almost totally abolished the inhibitory activity of a PAI-1 variant harboring an Ala substitution of Lys 325 (335 in the alpha1-proteinase inhibitor template residue numbering) in beta-strand 5A. In both cases, the neutralizing effect of the antibody was strongly potentiated by vitronectin. Mab-6 had no effect on wild type PAI-1, but reduced the inhibitory activity of the K325A variant. The effect of Mab-6 was not potentiated by vitronectin. With both Mab-2 and Mab-6, the neutralization of PAI-1 activity was associated with PAI-1 substrate behaviour. Mab-2, but not Mab-6, prevented vitronectin from rescuing PAI-1 from cold-induced substrate behaviour. We propose that the antibodies act by weakening the anchoring of alpha-helix F to the adjacent structures, resulting in an increased flexibility of beta-strand 5A and the hF/s3A loop and a changed conformational response to the binding of vitronectin in the alpha-helix E region. The potentiating effect of vitronectin on neutralization of PAI-1 by antibodies is a novel concept in the development of compounds for neutralizing PAI-1 in vivo.


Subject(s)
Amino Acid Substitution , Antibodies, Monoclonal/pharmacology , Plasminogen Activator Inhibitor 1/chemistry , Vitronectin/pharmacology , Amino Acid Motifs , Antibodies, Monoclonal/immunology , Antibody Specificity , Epitopes/chemistry , Epitopes/immunology , Humans , Hydrogen Bonding , Macromolecular Substances , Models, Molecular , Plasminogen Activator Inhibitor 1/immunology , Plasminogen Activator Inhibitor 1/metabolism , Protein Binding/drug effects , Protein Conformation/drug effects , Serpins/chemistry , Serpins/metabolism , Structure-Activity Relationship , Substrate Specificity , Temperature
12.
Clin Chim Acta ; 291(2): 223-34, 2000 Feb 15.
Article in English | MEDLINE | ID: mdl-10675725

ABSTRACT

Bone resorption is critical for the development and the maintenance of the skeleton, and improper regulation of bone resorption leads to pathological situations. Proteinases are necessary for this process. In this review, we show that this need of proteinases is not only because they are required for the solubilization of bone matrix, but also because they are key components of the mechanism that determines where and when bone resorption will be initiated. Moreover, there are indications that proteinases may also determine whether resorption will be followed by bone formation. Some of the proteinases involved in these different steps of the resorption processes were recently identified, as for instance cathepsin K, MMP-9 (gelatinase B), and interstitial collagenase. However, there is also increasing evidence showing that the critical proteinase(s) may vary depending on the bone type or on other factors.


Subject(s)
Bone Resorption , Endopeptidases/metabolism , Bone Diseases/enzymology , Extracellular Matrix/enzymology , Humans
13.
Eur J Biochem ; 263(2): 577-86, 1999 Jul.
Article in English | MEDLINE | ID: mdl-10406969

ABSTRACT

The serpin (serine proteinase inhibitor) family is of general protein chemical interest because of its ability to undergo large conformational changes, in which the surface-exposed reactive centre loop (RCL) is inserted as strand 4 in the large central beta-sheet A. Loop insertion is an integral part of the inhibitory mechanism and also takes place at conversion of serpins to the latent state, occurring spontaneously only in plasminogen activator inhibitor-1 (PAI-1). We have investigated the importance of beta-strand 5A residues for the activity and latency transition of PAI-1. An approximately fourfold increase in the rate of latency transition resulted from His-substitution of Gln324 (position 334 in the alpha(1)-proteinase inhibitor template numbering), which interacts with the underlying alpha-helix B. The side chains of Gln321 and Lys325 (template residues 331 and 335, respectively) form hydrogen bonds to the peptide backbone of a loop connecting alpha-helix F and beta-strand 3A. While substitution with Ala of Glu321 had only minor effects on the properties of PAI-1, substitution with Ala of Lys325 led to stabilization of the inhibitory activity at incubation conditions leading to conversion of wild-type PAI-1 to a substrate form, and to an anomalous reaction towards a monoclonal antibody, which induced a delay in the latency transition of the mutant, but not wild-type PAI-1. We conclude that the anchoring of beta-strand 5A plays a crucial role in loop insertion. These findings provide new information about the mechanism of an important example of protein conformational changes.


Subject(s)
Plasminogen Activator Inhibitor 1/chemistry , Amino Acids/chemistry , Humans , Models, Molecular , Mutagenesis, Site-Directed , Plasminogen Activator Inhibitor 1/immunology , Plasminogen Activator Inhibitor 1/pharmacology , Protein Conformation , Protein Engineering/methods , Recombinant Proteins , Temperature , Time Factors
14.
Eur J Biochem ; 253(3): 669-74, 1998 May 01.
Article in English | MEDLINE | ID: mdl-9654064

ABSTRACT

Distinct binding interactions between cell-surface receptors and extracellular matrix components are characteristic of multifunctional adhesion proteins such as vitronectin. The close proximity of binding sites for alpha(v)-integrins and plasminogen activator inhibitor-1 (PAI-1) on vitronectin may have consequences for cell adhesion and migration, or for the localized inhibition of plasminogen activators. In this study, the kinetics and reversibility of vitronectin-dependent cell adhesion via alpha(v)-integrins was investigated using RGD peptides and PAI-1 as competitors. Active, but not latent or cleaved PAI-1, and RGD peptides were effective in preventing cell adhesion to vitronectin provided the inhibitor was present at the time of cell seeding. In a concentration-dependent manner urokinase or thrombin abrogated the inhibitory effect of PAI-1. Following cell seeding onto a vitronectin substratum, delayed addition of RGD peptides or active PAI-1 (10-20 min post-seeding) resulted in the loss of their inhibitory potential. These data were supported by experiments in a purified system where delayed addition of active PAI-1 could no longer prevent vitronectin binding to immobilized alpha(v)beta3, while a cyclic RGD peptide gave some moderate inhibition. The apparent stabilization of vitronectin-integrin contacts was observed with immobilized native or multimeric vitronectin but not with the more rigid form of denatured, aggregated multimers. These results demonstrate that the cell adhesive properties of vitronectin depend on its conformational flexibility and can be tightly regulated in a spatio-temporal manner through direct competition of cellular integrins by soluble or matrix-bound factors such as PAI-1.


Subject(s)
Antigens, CD/metabolism , Cell Adhesion , Oligopeptides , Plasminogen Activator Inhibitor 1/metabolism , Vitronectin/metabolism , Amino Acid Sequence , Antigens, CD/chemistry , Binding Sites , Carcinoma, Squamous Cell , Cell Adhesion/drug effects , Humans , Integrin alphaV , Kinetics , Oligopeptides/pharmacology , Plasminogen Activator Inhibitor 1/chemistry , Protein Conformation , Thrombin/pharmacology , Tumor Cells, Cultured , Urokinase-Type Plasminogen Activator/metabolism , Urokinase-Type Plasminogen Activator/pharmacology , Vitronectin/chemistry
15.
Exp Cell Res ; 232(2): 420-9, 1997 May 01.
Article in English | MEDLINE | ID: mdl-9168821

ABSTRACT

Cell migration involves the integrins, their extracellular matrix ligands, and pericellular proteolytic enzyme systems. We have studied the role of plasminogen activator inhibitor-1 (PAI-1) in cell migration, using human amnion WISH cells and human epidermoid carcinoma HEp-2 cells in an assay measuring migration from microcarrier beads and a modified Boyden-chamber assay. Active, but not latent or reactive center-cleaved, PAI-1 inhibited migration. A PAI-1 mutant without ability to inhibit plasminogen activation was as active as wild-type PAI-1 as a migration inhibitor, showing that inhibition of plasminogen activation was not involved. PAI-1 specifically interfered with intergrin- and vitronectin-mediated migration: Migration onto vitronectin-coated but not onto fibronectin-coated surfaces was inhibited by PAI-1, a cyclic RGD peptide inhibited migration, and both cell lines expressed vitronectin-binding alpha v-integrins. In addition, active PAI-1, but not latent or reactive center-cleaved PAI-1, inhibited vitronectin binding to integrins in an in vitro binding assay, without affecting binding of fibronectin. Monoclonal antibodies against the urokinase receptor, another vitronectin binding protein, did not affect cell migration in the beads assay, while some inhibitory effect was observed in the Boyden-chamber assay. We conclude that PAI-1, independently of its role as a proteinase inhibitor, inhibits cell migration by competing for vitronectin binding to integrins, while the interference of PAI-1 with binding of vitronectin to the urokinase receptor may play a secondary role. These data define a novel function for the serpin PAI-1, enabling it to regulate cell migration over vitronectin-rich extracellular matrix in the body.


Subject(s)
Cell Movement/drug effects , Integrins/physiology , Plasminogen Activator Inhibitor 1/physiology , Vitronectin/physiology , Amnion/cytology , Carcinoma, Squamous Cell/pathology , Cell Line , Culture Media, Serum-Free , Enzyme Activation/drug effects , Extracellular Matrix/metabolism , Humans , Neoplasm Proteins/physiology , Oligopeptides/pharmacology , Peptides, Cyclic/pharmacology , Plasminogen/metabolism , Plasminogen Activator Inhibitor 1/chemistry , Plasminogen Activator Inhibitor 1/pharmacology , Protein Conformation , Receptors, Cell Surface/physiology , Receptors, Urokinase Plasminogen Activator , Tumor Cells, Cultured , Urokinase-Type Plasminogen Activator/physiology
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