Pseudomonas aeruginosa lectin LecB inhibits tissue repair processes by triggering β-catenin degradation

Pseudomonas aeruginosa is an opportunistic pathogen that induces severe lung infections such as ventilator-associated pneumonia and acute lung injury. Under these conditions, the bacterium diminishes epithelial integrity and inhibits tissue repair mechanisms, leading to persistent infections. Understanding the involved bacterial virulence factors and their mode of action is essential for the development of new therapeutic approaches. In our study we discovered a so far unknown effect of the P. aeruginosa lectin LecB on host cell physiology. LecB alone was sufficient to attenuate migration and proliferation of human lung epithelial cells and to induce transcriptional activity of NF-κB. These effects are characteristic of impaired tissue repair. Moreover, we found a strong degradation of β-catenin, which was partially recovered by the proteasome inhibitor lactacystin. In addition, LecB induced loss of cell-cell contacts and reduced expression of the β-catenin targets c-myc and cyclin D1. Blocking of LecB binding to host cell plasma membrane receptors by soluble l-fucose prevented these changes in host cell behavior and signaling, and thereby provides a powerful strategy to suppress LecB function. Our findings suggest that P. aeruginosa employs LecB as a virulence factor to induce β-catenin degradation, which then represses processes that are directly linked to tissue recovery.

Uptake of Marasmius oreades agglutinin disrupts integrin-dependent cell adhesion

BACKGROUND

Fruiting body lectins have been proposed to act as effector proteins in the defense of fungi against parasites and predators. The Marasmius oreades agglutinin (MOA) is a lectin from the fairy ring mushroom with specificity for Galα1-3Gal containing carbohydrates. This lectin is composed of an N-terminal carbohydrate-binding domain and a C-terminal dimerization domain. The dimerization domain of MOA shows in addition calcium-dependent cysteine protease activity, similar to the calpain family.

METHODS

Cell detachment assay, cell viability assay, immunofluorescence, live cell imaging and Western blot using MDCKII cell line.

RESULTS

In this study, we demonstrate in MDCKII cells that after internalization, MOA protease activity induces profound physiological cellular responses, like cytoskeleton rearrangement, cell detachment and cell death. These changes are preceded by a decrease in FAK phosphorylation and an internalization and degradation of β1-integrin, consistent with a disruption of integrin-dependent cell adhesion signaling. Once internalized, MOA accumulates in late endosomal compartments.

CONCLUSION

Our results suggest a possible toxic mechanism of MOA, which consists of disturbing the cell adhesion and the cell viability.

GENERAL SIGNIFICANCE

After being ingested by a predator, MOA might exert a protective role by diminishing host cell integrity.

The interplay of autophagy and β-Catenin signaling regulates differentiation in acute myeloid leukemia

The major feature of leukemic cells is an arrest of differentiation accompanied by highly active proliferation. In many subtypes of acute myeloid leukemia, these features are mediated by the aberrant Wnt/β-Catenin pathway. In our study, we established the lectin LecB as inducer of the differentiation of the acute myeloid leukemia cell line THP-1 and used it for the investigation of the involved processes. During differentiation, functional autophagy and low β-Catenin levels were essential. Corresponding to this, a high β-Catenin level stabilized proliferation and inhibited autophagy, resulting in low differentiation ability. Initiated by LecB, β-Catenin was degraded, autophagy became active and differentiation took place within hours. Remarkably, the reduction of β-Catenin sensitized THP-1 cells to the autophagy-stimulating mTOR inhibitors. As downmodulation of E-Cadherin was sufficient to significantly reduce LecB-mediated differentiation, we propose E-Cadherin as a crucial interaction partner in this signaling pathway. Upon LecB treatment, E-Cadherin colocalized with β-Catenin and thereby prevented the induction of β-Catenin target protein expression and proliferation. That way, our study provides for the first time a link between E-Cadherin, the aberrant Wnt/β-Catenin signaling, autophagy and differentiation in acute myeloid leukemia. Importantly, LecB was a valuable tool to elucidate the underlying molecular mechanisms of acute myeloid leukemia pathogenesis and may help to identify novel therapy approaches.

Identification of a dithiol-disulfide switch in collapsin response mediator protein 2 (CRMP2) that is toggled in a model of neuronal differentiation

Vertebrate-specific glutaredoxin 2 (Grx2) is expressed in at least two isoforms, mitochondrial Grx2a and cytosolic Grx2c. We have previously shown that cytosolic Grx2 is essential for embryonic development of the brain. In particular, we identified collapsin response mediator protein 2 (CRMP2/DPYSL2), a mediator of the semaphorin-plexin signaling pathway, as redox-regulated target of Grx2c and demonstrated that this regulation is required for normal axonal outgrowth. In this study, we demonstrate the molecular mechanism of this regulation, a specific and reversible intermolecular Cys-504-Cys-504 dithiol-disulfide switch in homotetrameric CRMP2. This switch determines two conformations of the quaternary CRMP2 complex that controls axonal outgrowth and thus neuronal development.

Modulation of growth factor binding properties of alpha2-macroglobulin by enzyme therapy

PURPOSE

To investigate the binding of transforming growth factor-beta (TGF-beta) to human alpha2-macroglobulin upon oral treatment of patients with proteases.

METHODS

Volunteers were given a cocktail of active proteinases (Phlogenzym) composed of trypsin, bromelain and the additive rutoside orally over a period of 7 days at low dose followed by a bolus application. Before and after medication plasma was immediately withdrawn and binding of 125I-TGF-beta to the proteinase inhibitor alpha2-macroglobulin was determined by electrophoresis and gamma-counting. Cell culture experiments were performed to study the effect of transformed alpha2-macroglobulin on TGF-beta-stimulated proliferation of skin fibroblasts.

RESULTS

Ingestion of proteinases was found to trigger the formation of intermediate forms of alpha2-macroglobulin displaying high affinity to TGF-beta. Maximum binding of TGF-beta was observed 1-2 h after bolus ingestion, and steadily levelled off with time. In vitro experiments demonstrated that complex formation of diverse proteinases (trypsin, alpha-chymotrypsin, bromelain and plasmin) with alpha2-macroglobulin conferred binding of 125I-TGF-beta, alpha2-Macroglobulin transformed by methylamine or proteinases was found to abolish the TGF-beta effect on fibroblasts in cell culture.

CONCLUSIONS

Intestinal absorption of proteinases triggers the formation of TGF-beta binding species of alpha2-macroglobulin in blood. Mediated by this process high concentrations of TGF-beta might be reduced via enhanced clearance of alpha2-macroglobulin-TGF-beta complexes. Thus, proteinase therapy may have beneficial effects in treatment of fibrosis and certain cancers accompanied by excessively high TGF-beta concentrations.

Adaptation to chronic illness and disability and its relationship to perceptions of independence and dependence

This study extends research on living with chronic physical illness and disability by examining how adaptation processes are associated with different activity domains and how the combination of adaptations and activity domains relate to older adults' perceptions of their independence and dependence, helplessness, emotional reactivity, and coping efficacy. The study investigated the behavioral efforts that 286 older adults with osteoarthritis and/or osteoporosis used to adapt to disability arising from their condition. The findings revealed that adults used a wide range of adaptations, including compensations for loss, optimizing performance, limiting or restricting activities, and gaining help from others. The relative use of each of these adaptations varied across 5 domains of activity: personal care, in-home mobility, community mobility, household activities, and valued activities. Moreover, older adults' perceptions of their independence, dependence, helplessness, emotional reactivity, and coping efficacy varied depending on the domain of activity examined and the type of adaptation used.

A conceptual model of independence and dependence for adults with chronic physical illness and disability

This paper presents a conceptual model of physical independence and dependence as it relates to adult onset, chronic physical illness and disability. Physical independence and dependence are presented as two separate, continuous, and multiply determined constructs, and illustrations are provided of situations where people can be independent, dependent, not independent, or experience imposed dependence. The paper also discusses potential determinants of physical independence and dependence, including different domains of disability, the role of subjective perceptions, demographics, the physical and social/political environments, personal resources, attitudes and coping resources, illness and efficacy appraisals, and the nature of the assistive relationship. The paper extends work on physical independence and dependence by synthesizing the findings from previous studies and incorporating the findings from other relevant areas of research into the area. It also expands on the concepts of physical independence and dependence, as well as their determinants, and relates independence and dependence to other outcomes of interest such as service delivery.

"We decide, you carry it out": a social network analysis of multidisciplinary long-term care teams

The purpose of this study was to describe the structure of multidisciplinary long-term care teams by identifying the pattern of relationships that develop amongst staff as they go about their work. Using a social network analysis approach, team members were classified as occupying the same structural position based on their patterns of relationships with other team members. The analysis was based on the results of a self-administered survey of 93 health care workers on three teams in the same multilevel geriatric care facility in Metropolitan Toronto. A common structure of the teams was identified consisting of two sub-teams: a multiprofessional sub-team and a nursing sub-team, each of which has a different structure indicating differential involvement in different types of teamwork. The multiprofessional sub-team has an "organic" structure and is mainly involved in teamwork that involves decision-making and problem-solving, whereas the nursing sub-team has a "mechanistic" structure and is mainly involved in task oriented work. The findings of this analysis indicate that while teamwork may be increasing the participation in decision-making by health professionals other than medicine, rather than flattening the hierarchical structure throughout the health care division of labour, its effects are limited to a group of higher status professionals. The clearly defined hierarchy remains for the lower status subdisciplines, and "I decide, you carry it out" has simply become "We decide, you carry it out".

Goal-setting in physical therapy practice

Goal-setting is traditionally used by physical therapists; however, factors identified in the literature as increasing goal achievement are often not considered. The purpose of this paper is to describe the potential use of goal-setting in improving and measuring effectiveness in physical therapy practice. Factors identified in the literature for effective goal-setting include setting specific and measurable goals, degree of goal difficulty, goal acceptance, and feedback. Active participation by the client in the goal-setting process is of primary importance. In order to maximize the use of goal-setting in physical therapy practice, reliable, valid, and sensitive clinical measures need to be identified and developed. There appears to be a potential for further use of goal-setting in physical therapy practice both as a means of improving treatment effectiveness and as a method for measuring effectiveness of treatment programs.