Modulation of Mitochondria-Endoplasmic Reticulum Contacts (MERCs) by Small Molecules as a New Strategy for Restoring Lipid Metabolism in an Amyotrophic Lateral Sclerosis Model.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease without effective treatment. The progressive motoneuron death in ALS is associated with alterations in lipid metabolism. As its regulation occurs in mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs), modulation of mitochondria-ER contacts (MERCs) is emerging as a crucial factor in MAM formation and lipid metabolism control.

Targeting mitochondrial metabolism by the mitotoxin bromoxib in leukemia and lymphoma cells.

Targeting mitochondrial metabolism represents a promising approach for cancer treatment. Here, we investigated the mitotoxic potential of the polybrominated diphenyl ether bromoxib, a natural compound isolated from the marine sponge Dysidea family. We could show that bromoxib comprised strong cytotoxicity in different leukemia and lymphoma cell lines (such as HL60, HPBALL, Jurkat, K562, KOPTK1, MOLT4, SUPB15 and Ramos), but also in solid tumor cell lines (such as glioblastoma cell lines SJ-GBM2 and TP365MG).

Iron-Induced Lipid Oxidation Alters Membrane Mechanics Favoring Permeabilization.

Ferroptosis is a form of regulated necrosis characterized by the iron-dependent accumulation of lipid peroxides in cell membranes. However, how lipid oxidation via iron-mediated Fenton reactions affects the biophysical properties of cellular membranes and how these changes contribute to the opening of plasma membrane pores are major questions in the field. Here, we characterized the dynamics of membrane alterations during lipid oxidation induced onsite by Fenton reactions in chemically defined model membrane systems.

The regulation of the apoptotic pore-An immunological tightrope walk.

Apoptotic pore formation in mitochondria is the pivotal point for cell death during mitochondrial apoptosis. It is regulated by BCL-2 family proteins in response to various cellular stress triggers and mediates mitochondrial outer membrane permeabilization (MOMP). This allows the release of mitochondrial contents into the cytosol, which triggers rapid cell death and clearance through the activation of caspases.

Lipid unsaturation promotes BAX and BAK pore activity during apoptosis.

BAX and BAK are proapoptotic members of the BCL2 family that directly mediate mitochondrial outer membrane permeabilition (MOMP), a central step in apoptosis execution. However, the molecular architecture of the mitochondrial apoptotic pore remains a key open question and especially little is known about the contribution of lipids to MOMP. By performing a comparative lipidomics analysis of the proximal membrane environment of BAK isolated in lipid nanodiscs, we find a significant enrichment of unsaturated species nearby BAK and BAX in apoptotic conditions.

Nanobodies as novel tools to monitor the mitochondrial fission factor Drp1.

In cells, mitochondria undergo constant fusion and fission. An essential factor for fission is the mammalian dynamin-related protein 1 (Drp1). Dysregulation of Drp1 is associated with neurodegenerative diseases including Parkinson's, cardiovascular diseases and cancer, making Drp1 a pivotal biomarker for monitoring mitochondrial status and potential pathophysiological conditions.

Many paths lead to immunology.

While some people pore over the textbook and train through the classics of the field, many scientists come to immunology when they discover it intersecting with their "first love" interests. Five of these "accidental immunologists" tell us how they found their way to a fascination with the immune system.

Novel meriolin derivatives activate the mitochondrial apoptosis pathway in the presence of antiapoptotic Bcl-2.

Meriolin derivatives represent a new class of kinase inhibitors with a pronounced cytotoxic potential. Here, we investigated a newly synthesized meriolin derivative (termed meriolin 16) that displayed a strong apoptotic potential in Jurkat leukemia and Ramos lymphoma cells. Meriolin 16 induced apoptosis in rapid kinetics (within 2-3 h) and more potently (IC: 50 nM) than the previously described derivatives meriolin 31 and 36 [1].

A guideline on the molecular ecosystem regulating ferroptosis.

Ferroptosis, an intricately regulated form of cell death characterized by uncontrolled lipid peroxidation, has garnered substantial interest since this term was first coined in 2012. Recent years have witnessed remarkable progress in elucidating the detailed molecular mechanisms that govern ferroptosis induction and defence, with particular emphasis on the roles of heterogeneity and plasticity. In this Review, we discuss the molecular ecosystem of ferroptosis, with implications that may inform and enable safe and effective therapeutic strategies across a broad spectrum of diseases.

Expanding roles of BCL-2 proteins in apoptosis execution and beyond.

The proteins of the BCL-2 family are known as key regulators of apoptosis, with interactions between family members determining permeabilisation of the mitochondrial outer membrane (MOM) and subsequent cell death. However, the exact mechanism through which they form the apoptotic pore responsible for MOM permeabilisation (MOMP), the structure and specific components of this pore, and what roles BCL-2 proteins play outside of directly regulating MOMP are incompletely understood. Owing to the link between apoptosis dysregulation and disease, the BCL-2 proteins are important targets for drug development.

Exploring the Binding Affinity of the ARR2 GARP DNA Binding Domain via Comparative Methods.

Plants have evolved signaling mechanisms such as the multi-step phosphorelay (MSP) to respond to different internal and external stimuli. MSP responses often result in gene transcription regulation that is modulated through transcription factors such as B-type Arabidopsis response regulator (ARR) proteins. Among these proteins, ARR2 is a key component that is expressed ubiquitously and is involved in many aspects of plant development.

Pyroptosis Induction and Visualization at the Single-Cell Level Using Optogenetics.

Pyroptosis has been identified as a pro-inflammatory form of programmed cell death. It can be triggered by different stimuli including pathogen invasion or cell stress/danger signals releasing hundreds of proteins upon lysis that cause complex responses in neighboring cells. Pyroptosis is executed by the gasdermin (GSDM) family of proteins which, upon cleavage by caspases, form transmembrane pores that release cytokines to induce inflammation.

Mechanisms of BCL-2 family proteins in mitochondrial apoptosis.

The proteins of the BCL-2 family are key regulators of mitochondrial apoptosis, acting as either promoters or inhibitors of cell death. The functional interplay and balance between the opposing BCL-2 family members control permeabilization of the outer mitochondrial membrane, leading to the release of activators of the caspase cascade into the cytosol and ultimately resulting in cell death. Despite considerable research, our knowledge about the mechanisms of the BCL-2 family of proteins remains insufficient, which complicates cell fate predictions and does not allow us to fully exploit these proteins as targets for drug discovery.

Calcium as a master regulator of ferroptosis and other types of regulated necrosis.

Regulation of proliferation and cell death is fundamental for organismal development and for restoring tissue homeostasis after biological stress. During the last years, several forms of regulated cell death have been discovered that share the loss of plasma membrane integrity as a common hallmark and that are collectively known as regulated necrosis (RN) pathways. During RN, plasma membrane damage is sensed by the cell by increases in the levels of intracellular calcium.

Apoptotic cell death in disease-Current understanding of the NCCD 2023.

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions.

Real-Time Growth Kinetics Analysis of Macromolecular Assemblies in Cells with Single Molecule Resolution.

Single molecule fluorescence microscopy has the unique advantage to provide real-time information on the spatiotemporal assembly of individual protein complexes in cellular membranes. This includes the assembly of proteins into oligomer species of numerous copy numbers. However, there is a need for improved tracing analysis of the real-time growth kinetics of these assemblies in cells with single molecule resolution.

Mitochondrial pores at the crossroad between cell death and inflammatory signaling.

Mitochondria are cellular organelles with a major role in many cellular processes, including not only energy production, metabolism, and calcium homeostasis but also regulated cell death and innate immunity. Their proteobacterial origin makes them a rich source of potent immune agonists, normally hidden within the mitochondrial membrane barriers. Alteration of mitochondrial permeability through mitochondrial pores thus provides efficient mechanisms not only to communicate mitochondrial stress to the cell but also as a key event in the integration of cellular responses.

Reversible Live-Cell Labeling with Retro-engineered HaloTags Enables Long-Term High- and Super-Resolution Imaging.

Self-labeling enzymes (SLE) such as the HaloTag have emerged as powerful tools in high and super-resolution fluorescence microscopy. Newly developed fluorogenic SLE substrates enable imaging in the presence of excess dye. To exploit this feature for reversible labeling, we engineered two variants of HaloTag7 with restored dehalogenase activity.

The Important Role of Membrane Fluidity on the Lytic Mechanism of the α-Pore-Forming Toxin Sticholysin I.

Actinoporins have emerged as archetypal α-pore-forming toxins (PFTs) that promote the formation of pores in membranes upon oligomerization and insertion of an α-helix pore-forming domain in the bilayer. These proteins have been used as active components of immunotoxins, therefore, understanding their lytic mechanism is crucial for developing this and other applications. However, the mechanism of how the biophysical properties of the membrane modulate the properties of pores generated by actinoporins remains unclear.

Visualization of BOK pores independent of BAX and BAK reveals a similar mechanism with differing regulation.

BOK is a poorly understood member of the BCL-2 family of proteins that has been proposed to function as a pro-apoptotic, BAX-like effector. However, the molecular mechanism and structural properties of BOK pores remain enigmatic. Here, we show that the thermal stability and pore activity of BOK depends on the presence of its C-terminus as well as on the mitochondrial lipid cardiolipin.

MERLIN: A BRET-Based Proximity Biosensor for Studying Mitochondria-ER Contact Sites.

The contacts between the endoplasmic reticulum (ER) and mitochondria play a fundamental role in a wide variety of cellular processes, like the exchange of calcium and lipids between both organelles, as well as in apoptosis and in autophagy signaling. Despite their importance, due to their dynamic and heterogeneous nature, we still lack understanding of the molecular composition, structure, and regulation of these structures. In this chapter, we introduce a new bioluminescence resonance energy transfer (BRET)-based biosensor for the quantitative analysis of mitochondria-ER interorganellar distances without perturbing their natural environment, which we call MERLIN (mitochondria ER length indicator nanosensor).

Curcumin and NCLX inhibitors share anti-tumoral mechanisms in microsatellite-instability-driven colorectal cancer.

Background And Aims: Recent evidences highlight a role of the mitochondria calcium homeostasis in the development of colorectal cancer (CRC). To overcome treatment resistance, we aimed to evaluate the role of the mitochondrial sodium-calcium-lithium exchanger (NCLX) and its targeting in CRC. We also identified curcumin as a new inhibitor of NCLX.