Palmitoylation is required for TNF-R1 signaling.

BACKGROUND: Binding of tumor necrosis factor (TNF) to TNF-receptor 1 (TNF-R1) can induce either cell survival or cell death. The selection between these diametrically opposed effects depends on the subcellular location of TNF-R1: plasma membrane retention leads to survival, while endocytosis leads to cell death. How the respective TNF-R1 associated signaling complexes are recruited to the distinct subcellular location is not known. Here, we identify palmitoylation of TNF-R1 as a molecular mechanism to achieve signal diversification. METHODS: Human monocytic U937 cells were analyzed. Palmitoylated proteins were enriched by acyl resin assisted capture (AcylRAC) and analyzed by western blot and mass spectrometry. Palmitoylation of TNF-R1 was validated by metabolic labeling. TNF induced depalmitoylation and involvement of APT2 was analyzed by enzyme activity assays, pharmacological inhibition and shRNA mediated knock-down. TNF-R1 palmitoylation site analysis was done by mutated TNF-R1 expression in TNF-R1 knock-out cells. Apoptosis (nuclear DNA fragmentation, caspase 3 assays), NF-κB activation and TNF-R1 internalization were used as biological readouts. RESULTS: We identify dynamic S-palmitoylation as a new mechanism that controls selective TNF signaling. TNF-R1 itself is constitutively palmitoylated and depalmitoylated upon ligand binding. We identified the palmitoyl thioesterase APT2 to be involved in TNF-R1 depalmitoylation and TNF induced NF-κB activation. Mutation of the putative palmitoylation site C248 interferes with TNF-R1 localization to the plasma membrane and thus, proper signal transduction. CONCLUSIONS: Our results introduce palmitoylation as a new layer of dynamic regulation of TNF-R1 induced signal transduction at a very early step of the TNF induced signaling cascade. Understanding the underlying mechanism may allow novel therapeutic options for disease treatment in future.

Ethik First - extracurricular support for medical students and young physicians facing moral dilemmas in hospital routine.

Introduction: Moral value conflicts play an increasingly central role in everyday hospital life. Clinical ethics, however, is only marginally represented in the compulsory curriculum for human medicine and the additional education regulations. The aim of the Ethik First project at the University Medical Center Schleswig-Holstein, Campus Kiel is to close this gap with an extracurricular offer and to support medical students from the fifth clinical semester onward and during their practical year as well as assistant doctors in dealing with moral dilemmas in everyday hospital life. The project has taken the concomitant learning objectives from the national competency-based learning objective catalog for medicine. According to the target group, the address in particular, showed higher taxonomy levels. Project description: The multimodal concept is based on three pillars: In monthly principle-based case conferences, participants practice ethical reflection and moral judgment primarily on the basis of concrete cases introduced by them using the methods of problem-based learning and consideration-based deliberation. If participants do not bring forth a case, they discuss ethical aspects of current political relevance. Moreover, there is an annual public speaker event. Results: Since the project began in 2017, ~20 students and interns have taken part in Ethik First one or more times. In a web-based interim evaluation (N=13), all respondents fully agreed that they considered the format helpful for dealing with ethical questions at the clinic. They rated the relevance for their later profession as high. There is evidence for support in moral dilemma situations. Discussion: The first evaluation results of the voluntary extracurricular offer show the acceptance of the selected format, which goes beyond pure teaching in its conception in that it addresses moral stress as well and strengthens the participants' individual resilience. Conclusion: Ethik First reinforces the role of ethical aspects in the training of (prospective) doctors and focuses on reflecting on cases they have experienced firsthand. We formulate a desideratum for appropriate advanced training concepts both in medical studies and in advanced medical training such that the training and development of comparable projects at medical faculties and at medical associations with student participation can be discussed.