IRBIT controls apoptosis by interacting with the Bcl-2 homolog, Bcl2l10, and by promoting ER-mitochondria contact

A computational perception of BBOX1-IP3R3 interaction uncovers inhibitors for dysregulated calcium signalling in triple negative breast cancer

Triple Negative Breast Cancer (TNBC) is the most aggressive type of breast cancer unveiling negative expression on oestrogen receptors, progesterone receptors, and HER2. The anomalous activation of signalling pathways and specific types of mutations characterize the progression of TNBC. Protein-protein interaction in the tumour microenvironment plays a crucial role in tumour aggressiveness. Disrupting the signalling pathways that promote cell progression, migration, and survival opens up a promising avenue for targeting the aggressive form of TNBC. The present study emphasizes the molecular interaction mechanism driving the aggressive and recalcitrant TNBC between BBOX1-IP3R3. The BBOX1-IP3R3 complex destabilization was accomplished using compounds obtained from various databases through virtual screening, molecular, and essential dynamics. The interaction study revealed that the four hits bound at the interface and facilitated better binding affinity with the highest docking score and optimal binding free energy. In addition, the molecular dynamics simulation, PCA/FEL, and MM/PBSA analysis conclusively evaluate the binding potential of the compounds and unequivocally stabilize specific conformations or deception of the complexes in high-energy states. Thus, the identified compounds lead to the disruption of BBOX1-IP3R3 interaction, which aids in the therapeutic option of TNBC.

Mitochondria-membranous organelle contacts at a glance

Mitochondrial contact sites are specialized interfaces where mitochondria physically interact with other organelles. Stabilized by molecular tethers and defined by unique proteomic and lipidomic profiles, these sites enable direct interorganellar communication and functional coordination, playing crucial roles in cellular physiology and homeostasis. Recent advances have expanded our knowledge of contact site-resident proteins, illuminated the dynamic and adaptive nature of these interfaces, and clarified their contribution to pathophysiology. In this Cell Science at a Glance article and the accompanying poster, we summarize the mitochondrial contacts that have been characterized in mammals, the molecular mechanisms underlying their formation, and their principal functions.

Redox state of NAD modulates the activation of Na-bicarbonate cotransporter NBCe1-B via IRBIT and L-IRBIT

Nicotinamide adenine dinucleotide (NAD) is well known as a coenzyme involved in many redox reactions in cellular energy metabolism, or as a substrate for many NAD+-consuming enzymes, including those that generate the second messenger cyclic ADP-ribose or deacetylate proteins (e.g., histones). The role of NAD in non-catalytic proteins is poorly understood. IRBIT and L-IRBIT (the IRBITs) are two cytosolic proteins that are structurally related to dehydrogenases but lack catalytic activity. Instead, by interacting directly with their targets, the IRBITs modulate the function of numerous proteins with important roles, ranging from Ca2+ signaling and intracellular pH (pHi) regulation to DNA metabolism to autophagy. Among the targets of the IRBITs is the Na+-HCO3- cotransporter NBCe1-B, which plays a central role in intracellular pH (pHi) regulation and epithelial electrolyte transport. Here, we demonstrate that NAD modulates NBCe1-B activation by serving as a cofactor of IRBIT or L-IRBIT. Blocking NAD salvage pathway greatly decreases NBCe1-B activation by the IRBITs. Administration of the oxidized form NAD+ enhances, whereas the reduced form NADH decreases NBCe1-B activity. Our study represents the first example in which the redox state of NAD, via IRBIT or L-IRBIT, modulates the function of a membrane transport protein. Our findings reveal a new role of NAD and greatly expand our understanding of NAD biology. Because the NAD redox state fluctuates greatly with metabolic status, our work provides insight into how, via the IRBITs, energy metabolism could affect pHi regulation and many other IRBIT-dependent processes.

The BCL2 family: from apoptosis mechanisms to new advances in targeted therapy

The B cell lymphoma 2 (BCL2) protein family critically controls apoptosis by regulating the release of cytochrome c from mitochondria. In this cutting-edge review, we summarize the basic biology regulating the BCL2 family including canonical and non-canonical functions, and highlight milestones from basic research to clinical applications in cancer and other pathophysiological conditions. We review laboratory and clinical development of BH3-mimetics as well as more recent approaches including proteolysis targeting chimeras (PROTACs), antibody-drug conjugates (ADCs) and tools targeting the BH4 domain of BCL2. The first BCL2-selective BH3-mimetic, venetoclax, showed remarkable efficacy with manageable toxicities and has transformed the treatment of several hematologic malignancies. Following its success, several chemically similar BCL2 inhibitors such as sonrotoclax and lisaftoclax are currently under clinical evaluation, alone and in combination. Genetic analysis highlights the importance of BCL-XL and MCL1 across different cancer types and the possible utility of BH3-mimetics targeting these proteins. However, the development of BH3-mimetics targeting BCL-XL or MCL1 has been more challenging, with on-target toxicities including thrombocytopenia for BCL-XL and cardiac toxicities for MCL1 inhibitors precluding clinical development. Tumor-specific BCL-XL or MCL1 inhibition may be achieved by novel targeting approaches using PROTACs or selective drug delivery strategies and would be transformational in many subtypes of malignancy. Taken together, we envision that the targeting of BCL2 proteins, while already a success story of translational research, may in the foreseeable future have broader clinical applicability and improve the treatment of multiple diseases.

Phosphorylation of Bok at Ser-8 blocks its ability to suppress IP3R-mediated calcium mobilization

BACKGROUND

Bok is a poorly characterized Bcl-2 protein family member with roles yet to be clearly defined. It is clear, however, that Bok binds strongly to inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs), which govern the mobilization of Ca2+ from the endoplasmic reticulum, a signaling pathway required for many cellular processes. Also known is that Bok has a highly conserved phosphorylation site for cAMP-dependent protein kinase at serine-8 (Ser-8). Whether Bok, or phosphorylated Bok, has any direct impact on the Ca2+ mobilizing function of IP3Rs remains to be established.

METHODS

Bok Ser-8 phosphorylation was characterized using purified proteins, G-protein coupled receptor agonists that increase cAMP levels in intact cells, mass spectrometry, and immunoreactivity changes. Also, using mammalian cells that exclusively or predominately express IP3R1, to which Bok binds strongly, and a fluorescent Ca2+-sensitive dye or a genetically-encoded Ca2+ sensor, we explored how endogenous and exogenous Bok controls the Ca2+ mobilizing function of IP3R1, and whether Bok phosphorylation at Ser-8, or replacement of Ser-8 with a phosphomimetic amino acid, is regulatory.

RESULTS

Our results confirm that Ser-8 of Bok is phosphorylated by cAMP-dependent protein kinase, and remarkably that phosphorylation can be detected with Bok specific antibodies. Also, we find that Bok has suppressive effects on IP3R-mediated Ca2+ mobilization in a variety of cell types. Specifically, Bok accelerated the post-maximal decline in G-protein coupled receptor-induced cytosolic Ca2+ concentration, via a mechanism that involves suppression of IP3R-dependent Ca2+ release from the endoplasmic reticulum. These effects were dependent on the Bok-IP3R interaction, as they are only seen with IP3Rs that can bind Bok (e.g., IP3R1). Surprisingly, Bok phosphorylation at Ser-8 weakened the interaction between Bok and IP3R1 and reversed the ability of Bok to suppress IP3R1-mediated Ca2+ mobilization.

CONCLUSIONS

For the first time, Bok was shown to directly suppress IP3R1 activity, which was reversed by Ser-8 phosphorylation. We hypothesize that this suppression of IP3R1 activity is due to Bok regulation of the conformational changes in IP3R1 that mediate channel opening. This study provides new insights on the role of Bok, its interaction with IP3Rs, and the impact it has on IP3R-mediated Ca2+ mobilization.

CISD2 counteracts the inhibition of ER-mitochondrial calcium transfer by anti-apoptotic BCL-2

CISD2, a 2Fe2S cluster domain-containing protein, is implicated in Wolfram syndrome type 2, longevity and cancer. CISD2 is part of a ternary complex with IP3 receptors (IP3Rs) and anti-apoptotic BCL-2 proteins and enhances BCL-2's anti-autophagic function. Here, we examined how CISD2 impacted the function of BCL-2 in apoptosis and in controlling IP3R-mediated Ca2+ signaling. Using purified proteins, we found a direct interaction between the cytosolic region of CISD2 and BCL-2's BH4 domain with a submicromolar affinity. At the functional level, the cytosolic region of CISD2, as a purified protein, did not affect the ability of BCL-2 to inhibit BAX-pore formation. In a cellular context, loss of CISD2 did not impede the suppression of apoptosis by BCL-2. Also, in Ca2+-signaling assays, absence of CISD2 did not affect the inhibition of IP3R-mediated Ca2+ release by BCL-2. Combined, these experiments indicate that CISD2 is not essential for BCL-2 function in apoptosis and cytosolic Ca2+ signaling. Instead, CISD2 overexpression enhanced BCL-2-mediated suppression of cytosolic IP3R-mediated Ca2+ release. However, consistent with the presence of CISD2 and BCL-2 at mitochondria-associated ER membranes (MAMs), the most striking effect was observed at the level of ER-mitochondrial Ca2+ transfer. While BCL-2 overexpression inhibited ER-mitochondrial Ca2+ transfer, overexpression of CISD2 together with BCL-2 abrogated the effect of BCL-2. The underlying mechanism is linked to ER-mitochondrial contact sites, since BCL-2 reduced ER-mitochondrial contact sites while co-expression of CISD2 together with BCL-2 abolished this effect. These findings reveal a unique interplay between BCL-2 and CISD2 at Ca2+-signaling nanodomains between ER and mitochondria.

The role of S-adenosylhomocysteine hydrolase-like 1 in cancer

This integrative review aims to highlight the importance of investigating the functional role of AHCYL1, also known as IRBIT, in cancer cells. It has recently been suggested that AHCYL1 regulates cell survival/death, stemness capacity, and the host adaptive response to the tumor microenvironment. Despite this knowledge, the role of AHCYL1 in cancer is still controversial, probably due to its ability to interact with multiple factors in a tissue-specific manner. Understanding the mechanisms regulating the functional interplay between the tumor and the tumor microenvironment that controls the expression of AHCYL1 could provide a deeper comprehension of the regulation of tumor development. Addressing how AHCYL1 modulates cellular plasticity processes in a tumoral context is potentially relevant to developing translational approaches in cancer biology.

Single-Cell Analysis of Elemental Contents by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry

Elemental analysis at the single-cell level is an emerging technique in the field of inductively coupled plasma mass spectrometry (ICP-MS). In comparison to the analysis of cell suspensions by fast time-resolved analysis, single-cell sampling by laser ablation (LA) allows the discriminatory analysis of single cells according to their size and morphology. In this study, we evaluated the changes in elemental contents in a single cell through differentiation of rat adrenal pheochromocytoma into neuron-like cells by LA-ICP-MS. The contents of seven essential minerals were increased about 2-3 times after the differentiation. In addition, we evaluated the degree of differentiation at the single-cell level by means of imaging cytometry after immunofluorescence staining of microtubule-associated protein 2 (Map2), a neuron-specific protein. The fluorescence intensities of Alexa Fluor 488-conjugated secondary antibody against the anti-Map2 primary antibody showed large variations among the cells after the onset of differentiation. Although the average fluorescence intensity was increased through the differentiation, there were still less-matured neuron-like cells that exhibited a lower fluorescence intensity after 5 days of differentiation. Since a positive correlation between the fluorescence intensity and the cell size in area was found, we separately measured the elemental contents in the less-matured smaller cells and well-matured larger cells by LA-ICP-MS. The larger cells had higher elemental contents than the smaller cells, indicating that the essential minerals are highly required at a later stage of differentiation.

The functional roles of S-adenosyl-methionine and S-adenosyl-homocysteine and their involvement in trisomy 21

The one-carbon metabolism pathway is involved in critical human cellular functions such as cell proliferation, mitochondrial respiration, and epigenetic regulation. In the homocysteine-methionine cycle S-adenosyl-methionine (SAM) and S-adenosyl-homocysteine (SAH) are synthetized, and their levels are finely regulated to ensure proper functioning of key enzymes which control cellular growth and differentiation. Here we review the main biological mechanisms involving SAM and SAH and the known related human diseases. It was recently demonstrated that SAM and SAH levels are altered in plasma of subjects with trisomy 21 (T21) but how this metabolic dysregulation influences the clinical manifestation of T21 phenotype has not been previously described. This review aims at providing an overview of the biological mechanisms which are altered in response to changes in the levels of SAM and SAH observed in DS.

Bcl-B: an "unknown" protein of the Bcl-2 family

Bcl-B is a poorly understood protein of the Bcl-2 family that is highly expressed in many healthy tissues and tumor types. Bcl-B is considered an antiapoptotic protein, but many reports have revealed its contradictory roles in different cancer types. In this mini-review, we elucidate the functions of Bcl-B in normal conditions and various pathologies, its regulation of programmed cell death, its oncogene/oncosuppressor activity in tumorigenesis, its impact on drug-acquired resistance, and possible approaches to inhibit Bcl-B.

The ER-mitochondria interface, where Ca2+ and cell death meet

Endoplasmic reticulum (ER)-mitochondria contact sites are crucial to allow Ca²⁺ flux between them and a plethora of proteins participate in tethering both organelles together. Inositol 1,4,5-trisphosphate receptors (IP₃Rs) play a pivotal role at such contact sites, participating in both ER-mitochondria tethering and as Ca²⁺-transport system that delivers Ca²⁺ from the ER towards mitochondria. At the ER-mitochondria contact sites, the IP₃Rs function as a multi-protein complex linked to the voltage-dependent anion channel 1 (VDAC1) in the outer mitochondrial membrane, via the chaperone glucose-regulated protein 75 (GRP75). This IP₃R-GRP75-VDAC1 complex supports the efficient transfer of Ca²⁺ from the ER into the mitochondrial intermembrane space, from which the Ca²⁺ ions can reach the mitochondrial matrix through the mitochondrial calcium uniporter. Under physiological conditions, basal Ca²⁺ oscillations deliver Ca²⁺ to the mitochondrial matrix, thereby stimulating mitochondrial oxidative metabolism. However, when mitochondrial Ca²⁺ overload occurs, the increase in [Ca²⁺] will induce the opening of the mitochondrial permeability transition pore, thereby provoking cell death. The IP₃R-GRP75-VDAC1 complex forms a hub for several other proteins that stabilize the complex and/or regulate the complex's ability to channel Ca²⁺ into the mitochondria. These proteins and their mechanisms of action are discussed in the present review with special attention for their role in pathological conditions and potential implication for therapeutic strategies.

S-adenosylhomocysteine hydrolase-like protein 1 (AHCYL1) inhibits lung cancer tumorigenesis by regulating cell plasticity

BACKGROUND

Lung cancer is one of the most frequently diagnosed cancers characterized by high mortality, metastatic potential, and recurrence. Deregulated gene expression of lung cancer, likewise in many other solid tumors, accounts for their cell heterogeneity and plasticity. S-adenosylhomocysteine hydrolase-like protein 1 (AHCYL1), also known as Inositol triphosphate (IP(3)) receptor-binding protein released with IP(3) (IRBIT), plays roles in many cellular functions, including autophagy and apoptosis but AHCYL1 role in lung cancer is largely unknown.

RESULTS

Here, we analyzed the expression of AHCYL1 in Non-Small Cell Lung Cancer (NSCLC) cells from RNA-seq public data and surgical specimens, which revealed that AHCYL1 expression is downregulated in tumors and inverse correlated to proliferation marker Ki67 and the stemness signature expression. AHCYL1-silenced NSCLC cells showed enhanced stem-like properties in vitro, which correlated with higher expression levels of stem markers POU5F1 and CD133. Also, the lack of AHCYL1 enhanced tumorigenicity and angiogenesis in mouse xenograft models highlighting stemness features.

CONCLUSIONS

These findings indicate that AHCYL1 is a negative regulator in NSCLC tumorigenesis by modulating cell differentiation state and highlighting AHCYL1 as a potential prognostic biomarker for lung cancer.

Mitochondria-associated endoplasmic reticulum membranes: A promising toxicity regulation target

Mitochondria-associated endoplasmic reticulum membranes (MAMs) are dynamic suborganelle membranes that physically couple endoplasmic reticulum (ER) and mitochondria to provide a platform for exchange of intracellular molecules and crosstalk between the two organelles. Dysfunctions of mitochondria and ER and imbalance of intracellular homeostasis have been discovered in the research of toxics. Cellular activities such as oxidative stress, ER stress, Ca²⁺ transport, autophagy, mitochondrial fusion and fission, and apoptosis mediated by MAMs are closely related to the toxicological effects of various toxicants. These cellular activities mediated by MAMs crosstalk with each other. Regulating the structure and function of MAMs can alleviate the damage caused by toxicants to some extent. In this review, we discuss the relationships between MAMs and the mechanisms of toxicological effects, and highlight MAMs as a potential target for protection against toxicants.

Mitochondria-endoplasmic reticulum contacts in sepsis-induced myocardial dysfunction

Mitochondrial and endoplasmic reticulum (ER) are important intracellular organelles. The sites that mitochondrial and ER are closely related in structure and function are called Mitochondria-ER contacts (MERCs). MERCs are involved in a variety of biological processes, including calcium signaling, lipid synthesis and transport, autophagy, mitochondrial dynamics, ER stress, and inflammation. Sepsis-induced myocardial dysfunction (SIMD) is a vital organ damage caused by sepsis, which is closely associated with mitochondrial and ER dysfunction. Growing evidence strongly supports the role of MERCs in the pathogenesis of SIMD. In this review, we summarize the biological functions of MERCs and the roles of MERCs proteins in SIMD.

Balancing life and death: BCL-2 family members at diverse ER-mitochondrial contact sites

The outer mitochondrial membrane is a busy place. One essential activity for cellular survival is the regulation of membrane integrity by the BCL-2 family of proteins. Another critical facet of the outer mitochondrial membrane is its close approximation with the endoplasmic reticulum. These mitochondrial-associated membranes (MAMs) occupy a significant fraction of the mitochondrial surface and serve as key signaling hubs for multiple cellular processes. Each of these pathways may be considered as forming their own specialized MAM subtype. Interestingly, like membrane permeabilization, most of these pathways play critical roles in regulating cellular survival and death. Recently, the pro-apoptotic BCL-2 family member BOK has been found within MAMs where it plays important roles in their structure and function. This has led to a greater appreciation that multiple BCL-2 family proteins, which are known to participate in numerous functions throughout the cell, also have roles within MAMs. In this review, we evaluate several MAM subsets, their role in cellular homeostasis, and the contribution of BCL-2 family members to their functions.

Endoplasmic Reticulum-Mitochondria Contacts Modulate Reactive Oxygen Species-Mediated Signaling and Oxidative Stress in Brain Disorders: The Key Role of Sigma-1 Receptor

Significance: Mitochondria-Associated Membranes (MAMs) are highly dynamic endoplasmic reticulum (ER)-mitochondria contact sites that, due to the transfer of lipids and Ca2+ between these organelles, modulate several physiologic processes, such as ER stress response, mitochondrial bioenergetics and fission/fusion events, autophagy, and inflammation. In addition, these contacts are implicated in the modulation of the cellular redox status since several MAMs-resident proteins are involved in the generation of reactive oxygen species (ROS), which can act as both signaling mediators and deleterious molecules, depending on their intracellular levels. Recent Advances: In the past few years, structural and functional alterations of MAMs have been associated with the pathophysiology of several neurodegenerative diseases that are closely associated with the impairment of several MAMs-associated events, including perturbation of the redox state on the accumulation of high ROS levels. Critical Issues: Inter-organelle contacts must be tightly regulated to preserve cellular functioning by maintaining Ca2+ and protein homeostasis, lipid metabolism, mitochondrial dynamics and energy production, as well as ROS signaling. Simultaneously, these contacts should avoid mitochondrial Ca2+ overload, which might lead to energetic deficits and deleterious ROS accumulation, culminating in oxidative stress-induced activation of apoptotic cell death pathways, which are common features of many neurodegenerative diseases. Future Directions: Given that Sig-1R is an ER resident chaperone that is highly enriched at the MAMs and that controls ER to mitochondria Ca2+ flux, as well as oxidative and ER stress responses, its potential as a therapeutic target for neurodegenerative diseases such as Amyotrophic Lateral Sclerosis, Alzheimer, Parkinson, and Huntington diseases should be further explored. Antioxid. Redox Signal. 37, 758-780.

Gap Junction Protein Connexin 43 as a Target Is Internalized in Astrocyte Neurotoxicity Caused by Di-(2-ethylhexyl) Phthalate

Di-(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in plastic products, consumer products, and packaging materials. It is of great health concern in both animals and humans as it released into the environment and entered into the body from plastic products over time, thereby resulting in neurotoxicity. As a pivotal regulator of the central nervous system (CNS), astrocytes, are crucial for maintaining brain homeostasis. Nevertheless, the underlying reason for astrocyte neurotoxicity due to DEHP exposure remains incompletely understood. Here, using an in vivo model of neurotoxicity in quail, this study summarizes that Cx43 is internalized by phosphorylation and translocated to the nucleus as a consequence of DEHP exposure in astrocytes. This study further demonstrated that astrocytes transformed to pro-inflammatory status and induced the formation of autophagosomes. Of note, integrated immunofluorescent codetection approaches revealed an overexpression of the glial fibrillary acidic protein (GFAP) and down-expression of Cx43 in astrocytes. Therefore, in terms of neurotoxicity, this experiment in vivo models directly linked Cx43 internalization to autophagy and neuroinflammation and ultimately locked these changes to the astrocytes of the brain. These findings unveil a potential approach targeting Cx43 internalization for the treatment of neurodegeneration caused by DEHP exposure in astrocytes.

RyR2/IRBIT regulates insulin gene transcript, insulin content, and secretion in the insulinoma cell line INS-1

The role of ER Ca2+ release via ryanodine receptors (RyR) in pancreatic β-cell function is not well defined. Deletion of RyR2 from the rat insulinoma INS-1 (RyR2KO) enhanced IP3 receptor activity stimulated by 7.5 mM glucose, coincident with reduced levels of the protein IP3 Receptor Binding protein released with Inositol 1,4,5 Trisphosphate (IRBIT). Insulin content, basal (2.5 mM glucose) and 7.5 mM glucose-stimulated insulin secretion were reduced in RyR2KO and IRBITKO cells compared to controls. INS2 mRNA levels were reduced in both RyR2KO and IRBITKO cells, but INS1 mRNA levels were specifically decreased in RyR2KO cells. Nuclear localization of S-adenosylhomocysteinase (AHCY) was increased in RyR2KO and IRBITKO cells. DNA methylation of the INS1 and INS2 gene promotor regions was very low, and not different among RyR2KO, IRBITKO, and controls, but exon 2 of the INS1 and INS2 genes was more extensively methylated in RyR2KO and IRBITKO cells. Exploratory proteomic analysis revealed that deletion of RyR2 or IRBIT resulted in differential regulation of 314 and 137 proteins, respectively, with 41 in common. These results suggest that RyR2 regulates IRBIT levels and activity in INS-1 cells, and together maintain insulin content and secretion, and regulate the proteome, perhaps via DNA methylation.

Functions and Clinical Significance of CACNA2D1 in Gastric Cancer

BACKGROUND

Voltage-gated calcium channels form as a complex of several subunits, among which the function of CACNA2D1, one of the genes encoding the α2δ subunit, remains unclear. The aim of our study was to investigate the role of CACNA2D1 and evaluate the efficacy of amlodipine, a blocker of CACNA2D1, in the treatment of gastric cancer (GC).

METHODS

Knockdown experiments were performed on the human GC cell lines MKN7 and HGC27 using CACNA2D1 small interfering RNA (siRNA), and changes in cell proliferation, the cell cycle, apoptosis, migration, and invasion were assessed. The gene expression profiles of cells were examined using a microarray analysis. An immunohistochemical (IHC) analysis was conducted on samples obtained from 196 GC patients who underwent curative gastrectomy. In addition, the antitumor effects of amlodipine were investigated using a xenograft model.

RESULTS

Cell proliferation, migration, and invasion were suppressed in CACNA2D1-depleted cells, and apoptosis was induced. The results of the microarray analysis showed that the apoptosis signaling pathway was enhanced via p53, BAX, and caspase 3 in CACNA2D1-depleted cells. A multivariate analysis identified high CACNA2D1 expression levels, confirmed by IHC, as an independent poor prognostic factor in GC patients. Moreover, subcutaneous tumor volumes were significantly smaller in a xenograft nude mouse model treated with a combination of amlodipine and cisplatin than in a model treated with cisplatin alone.

CONCLUSIONS

The present study indicates that CACNA2D1 regulates the apoptosis signaling pathway and may have potential as a biomarker for cancer growth and as a therapeutic target for GC.

Unbiased proteomic profiling reveals the IP3R modulator AHCYL1/IRBIT as a novel interactor of microtubule-associated protein tau

Microtubule-associated protein tau is a naturally unfolded protein that can modulate a vast array of physiological processes through direct or indirect binding with molecular partners. Aberrant tau homeostasis has been implicated in the pathogenesis of several neurodegenerative disorders, including Alzheimer's disease. In this study, we performed an unbiased high-content protein profiling assay by incubating recombinant human tau on microarrays containing thousands of human polypeptides. Among the putative tau-binding partners, we identify SAH hydrolase-like protein 1/inositol 1,4,5-trisphosphate receptor (IP3R)-binding protein (AHCYL1/IRBIT), a member of the SAH hydrolase family and a previously described modulator of IP3R activity. Using coimmunoprecipitation assays, we show that endogenous as well as overexpressed tau can physically interact with AHCYL1/IRBIT in brain tissues and cultured cells. Proximity ligation assay experiments demonstrate that tau overexpression may modify the close localization of AHCYL1/IRBIT to IP3R at the endoplasmic reticulum. Together, our experimental evidence indicates that tau interacts with AHCYL1/IRBIT and potentially modulates AHCYL1/IRBIT function.

Endoplasmic reticulum-mitochondria signaling in neurons and neurodegenerative diseases

Recent advances have revealed common pathological changes in neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis with related frontotemporal dementia (ALS/FTD). Many of these changes can be linked to alterations in endoplasmic reticulum (ER)-mitochondria signaling, including dysregulation of Ca2+ signaling, autophagy, lipid metabolism, ATP production, axonal transport, ER stress responses and synaptic dysfunction. ER-mitochondria signaling involves specialized regions of ER, called mitochondria-associated membranes (MAMs). Owing to their role in neurodegenerative processes, MAMs have gained attention as they appear to be associated with all the major neurodegenerative diseases. Furthermore, their specific role within neuronal maintenance is being revealed as mutant genes linked to major neurodegenerative diseases have been associated with damage to these specialized contacts. Several studies have now demonstrated that these specialized contacts regulate neuronal health and synaptic transmission, and that MAMs are damaged in patients with neurodegenerative diseases. This Review will focus on the role of MAMs and ER-mitochondria signaling within neurons and how damage of the ER-mitochondria axis leads to a disruption of vital processes causing eventual neurodegeneration.

Still no Rest for the Reductases: Ribonucleotide Reductase (RNR) Structure and Function: An Update

Herein we present a multidisciplinary discussion of ribonucleotide reductase (RNR), the essential enzyme uniquely responsible for conversion of ribonucleotides to deoxyribonucleotides. This chapter primarily presents an overview of this multifaceted and complex enzyme, covering RNR's role in enzymology, biochemistry, medicinal chemistry, and cell biology. It further focuses on RNR from mammals, whose interesting and often conflicting roles in health and disease are coming more into focus. We present pitfalls that we think have not always been dealt with by researchers in each area and further seek to unite some of the field-specific observations surrounding this enzyme. Our work is thus not intended to cover any one topic in extreme detail, but rather give what we consider to be the necessary broad grounding to understand this critical enzyme holistically. Although this is an approach we have advocated in many different areas of scientific research, there is arguably no other single enzyme that embodies the need for such broad study than RNR. Thus, we submit that RNR itself is a paradigm of interdisciplinary research that is of interest from the perspective of the generalist and the specialist alike. We hope that the discussions herein will thus be helpful to not only those wanting to tackle RNR-specific problems, but also those working on similar interdisciplinary projects centering around other enzymes.

Endoplasmic Reticulum-Mitochondria Contacts: A Potential Therapy Target for Cardiovascular Remodeling-Associated Diseases

Cardiovascular remodeling occurs in cardiomyocytes, collagen meshes, and vascular beds in the progress of cardiac insufficiency caused by a variety of cardiac diseases such as chronic ischemic heart disease, chronic overload heart disease, myocarditis, and myocardial infarction. The morphological changes that occur as a result of remodeling are the critical pathological basis for the occurrence and development of serious diseases and also determine morbidity and mortality. Therefore, the inhibition of remodeling is an important approach to prevent and treat heart failure and other related diseases. The endoplasmic reticulum (ER) and mitochondria are tightly linked by ER-mitochondria contacts (ERMCs). ERMCs play a vital role in different signaling pathways and provide a satisfactory structural platform for the ER and mitochondria to interact and maintain the normal function of cells, mainly by involving various cellular life processes such as lipid metabolism, calcium homeostasis, mitochondrial function, ER stress, and autophagy. Studies have shown that abnormal ERMCs may promote the occurrence and development of remodeling and participate in the formation of a variety of cardiovascular remodeling-associated diseases. This review focuses on the structure and function of the ERMCs, and the potential mechanism of ERMCs involved in cardiovascular remodeling, indicating that ERMCs may be a potential target for new therapeutic strategies against cardiovascular remodeling-induced diseases.

Bcl-xL and IP3R interaction: Intimate relationship with an uncertain outcome

Bcl-2 family proteins are major apoptosis regulators. They control a key step in apoptosis execution referred to as the mitochondrial outer membrane permeabilization. Several Bcl-2 homologs were also reported to act at the level of the endoplasmic reticulum (ER) where they control intracellular Ca²⁺ trafficking. There is an increasing body of evidence that, in addition to their conventional role as MOMP regulators, several Bcl-2 family members, including Bcl-xL, are linked to Ca²⁺ -dependent processes, independent of cell death. Among them Bcl-xL has been proposed to promote IP₃R1 channel opening and sustain mitochondrial bioenergetics. A recent article by Rosa and colleagues in Cell Death & Differentiation challenges this model and support the notion that Bcl-xL acts more as a repressor than as a sensitizer of IP3R1 opening. They suggest the existence of intrafamilial competition among the Bcl-2 family of protein with respect to their effect on IP3R Ca²⁺ permeability, which might be important regarding their respective non-canonical functions. In this regard, the results by Rosa and colleagues open exciting avenues regarding the biological process by which Bcl-xL affects Ca²⁺ trafficking through IP 3 R channels.

Communications between Mitochondria and Endoplasmic Reticulum in the Regulation of Metabolic Homeostasis

Mitochondria associated membranes (MAM), which are the contact sites between endoplasmic reticulum (ER) and mitochondria, have emerged as an important hub for signaling molecules to integrate the cellular and organelle homeostasis, thus facilitating the adaptation of energy metabolism to nutrient status. This review explores the dynamic structural and functional features of the MAM and summarizes the various abnormalities leading to the impaired insulin sensitivity and metabolic diseases.

Sodium bicarbonate transporter NBCe1 regulates proliferation and viability of human prostate cancer cells LNCaP and PC3

Studies on cultured cancer cells or cell lines have revealed multiple acid extrusion mechanisms and their involvement in cancer cell growth and progression. In the present study, the role of the sodium bicarbonate transporters (NBCs) in prostate cancer cell proliferation and viability was examined. qPCR revealed heterogeneous expression of five NBC isoforms in human prostate cancer cell lines LNCaP, PC3, 22RV1, C4-2, DU145, and the prostate cell line RWPE-1. In fluorescence pH measurement of LNCaP cells, which predominantly express NBCe1, Na⁺ and HCO₃^–-mediated acid extrusion was identified by bath ion replacement and sensitivity to the NBC inhibitor S0859. NBCe1 knockdown using siRNA oligonucleotides decreased the number of viable cells, and pharmacological inhibition with S0859 (50 µM) resulted in a similar decrease. NBCe1 knockdown and inhibition also increased cell death, but this effect was small and slow. In PC3 cells, which express all NBC isoforms, NBCe1 knockdown decreased viable cell number and increased cell death. The effects of NBCe1 knockdown were comparable to those by S0859, indicating that NBCe1 among NBCs primarily contributes to PC3 cell proliferation and viability. S0859 inhibition also decreased the formation of cell spheres in 3D cultures. Immunohistochemistry of human prostate cancer tissue microarrays revealed NBCe1 localization to the glandular epithelial cells in prostate tissue and robust expression in acinar and duct adenocarcinoma. In conclusion, our study demonstrates that NBCe1 regulates acid extrusion in prostate cancer cells and inhibiting or abolishing this transporter decreases cancer cell proliferation.

Bcl-2 Family of Proteins in the Control of Mitochondrial Calcium Signalling: An Old Chap with New Roles

Bcl-2 family proteins are considered as one of the major regulators of apoptosis. Indeed, this family is known to control the mitochondrial outer membrane permeabilization (MOMP): a central step in the mitochondrial pathway of apoptosis. However, in recent years Bcl-2 family members began to emerge as a new class of intracellular calcium (Ca²⁺) regulators. At mitochondria-ER contacts (MERCs) these proteins are able to interact with major Ca²⁺ transporters, thus controlling mitochondrial Ca²⁺ homeostasis and downstream Ca²⁺ signalling pathways. Beyond the regulation of cell survival, this Bcl-2-dependent control over the mitochondrial Ca²⁺ dynamics has far-reaching consequences on the physiology of the cell. Here, we review how the Bcl-2 family of proteins mechanistically regulate mitochondrial Ca²⁺ homeostasis and how this regulation orchestrates cell death/survival decisions as well as the non-apoptotic process of cell migration.

Balancing ER-Mitochondrial Ca2+ Fluxes in Health and Disease

Organelles cooperate with each other to control cellular homeostasis and cell functions by forming close connections through membrane contact sites. Important contacts are present between the endoplasmic reticulum (ER), the main intracellular Ca²⁺-storage organelle, and the mitochondria, the organelle responsible not only for the majority of cellular ATP production but also for switching on cell death processes. Several Ca²⁺-transport systems focalize at these contact sites, thereby enabling the efficient transmission of Ca²⁺ signals from the ER toward mitochondria. This provides tight control of mitochondrial functions at the microdomain level. Here, we discuss how ER-mitochondrial Ca²⁺ transfers support cell function and how their dysregulation underlies, drives, or contributes to pathogenesis and pathophysiology, with a major focus on cancer and neurodegeneration but also with attention to other diseases such as diabetes and rare genetic diseases.

In the Right Place at the Right Time: Regulation of Cell Metabolism by IP3R-Mediated Inter-Organelle Ca2+ Fluxes

In the last few years, metabolism has been shown to be controlled by cross-organelle communication. The relationship between the endoplasmic reticulum and mitochondria/lysosomes is the most studied; here, inositol 1,4,5-triphosphate (IP3) receptor (IP3R)-mediated calcium (Ca²⁺) release plays a central role. Recent evidence suggests that IP3R isoforms participate in synthesis and degradation pathways. This minireview will summarize the current findings in this area, emphasizing the critical role of Ca²⁺ communication on organelle function as well as catabolism and anabolism, particularly in cancer.

The discovery and development of IP3 receptor modulators: an update

Introduction: Inositol 1,4,5-trisphosphate receptors (IP3Rs) are intracellular calcium (Ca²⁺) release channels located on the endoplasmic/sarcoplasmic reticulum. The availability of the structure of the ligand-binding domain of IP3Rs has enabled the design of compatible ligands, but the limiting step remains their actual effectiveness in a biological context.Areas covered: This article summarizes the compelling literature on both agonists and antagonists targeting IP3Rs, emphasizing their strengths and limitations. The main challenges toward the discovery and development of IP3 receptor modulators are also described.Expert opinion: Despite significant progress in recent years, the pharmacology of IP3R still has major drawbacks, especially concerning the availability of specific antag onists. Moreover, drugs specifically targeting the three different subtypes of IP3R are especially needed.

Molecular machineries and physiological relevance of ER-mediated membrane contacts

Membrane contact sites (MCSs) are defined as regions where two organelles are closely apposed, and most MCSs associated with each other via protein-protein or protein-lipid interactions. A number of key molecular machinery systems participate in mediating substance exchange and signal transduction, both of which are essential processes in terms of cellular physiology and pathophysiology. The endoplasmic reticulum (ER) is the largest reticulum network within the cell and has extensive communication with other cellular organelles, including the plasma membrane (PM), mitochondria, Golgi, endosomes and lipid droplets (LDs). The contacts and reactions between them are largely mediated by various protein tethers and lipids. Ions, lipids and even proteins can be transported between the ER and neighboring organelles or recruited to the contact site to exert their functions. This review focuses on the key molecules involved in the formation of different contact sites as well as their biological functions.

IRBIT activates NBCe1-B by releasing the auto-inhibition module from the transmembrane domain

Key points

The electrogenic Na⁺/HCO₃⁻cotransporter NBCe1‐B is widely expressed in many tissues, including pancreas, submandibular gland, brain, heart, etc. NBCe1‐B has very low activity under basal condition due to auto‐inhibition, but can be fully activated by protein interaction with the IP3R‐binding protein released with inositol 1,4,5‐trisphosphate (IRBIT).

The structural components of the auto‐inhibition domain and the IRBIT‐binding domain of NBCe1‐B are finely characterized based on systematic mutations in the present study and data from previous studies.

Reducing negative charges on the cytosol side of the transmembrane domain greatly decreases the magnitude of the auto‐inhibition of NBCe1‐B.

We propose that the auto‐inhibition domain functions as a brake module that inactivates NBCe1‐B by binding to, via electrostatic attraction, the transmembrane domain; IRBIT activates NBCe1‐B by releasing the brake from the transmembrane domain via competitive binding to the auto‐inhibition domain.

Abstract

The electrogenic Na⁺/HCO₃⁻ cotransporter NBCe1‐B is widely expressed in many tissues in the body. NBCe1‐B exhibits only basal activity due to the action of the auto‐inhibition domain (AID) in its unique amino‐terminus. However, NBCe1‐B can be activated by interaction with the IP3R‐binding protein released with inositol 1,4,5‐trisphosphate (IRBIT). Here, we investigate the molecular mechanism underlying the auto‐inhibition of NBCe1‐B and its activation by IRBIT. The IRBIT‐binding domain (IBD) of NBCe1‐B spans residues 1−52, essentially consisting of two arms, one negatively charged (residues 1−24) and the other positively charged (residues 40−52). The AID mainly spans residues 40−85, overlapping with the IBD in the positively charged arm. The magnitude of auto‐inhibition of NBCe1‐B is greatly decreased by manipulating the positively charged residues in the AID or by replacing a set of negatively charged residues with neutral ones in the transmembrane domain. The interaction between IRBIT and NBCe1‐B is abolished by mutating a set of negatively charged Asp/Glu residues (to Asn/Gln) plus a set of Ser/Thr residues (to Ala) in the PEST domain of IRBIT. However, this interaction is not affected by replacing the same set of Ser/Thr residues in the PEST domain with Asp. We propose that: (1) the AID, acting as a brake, binds to the transmembrane domain via electrostatic interaction to slow down NBCe1‐B; (2) IRBIT activates NBCe1‐B by releasing the brake from the transmembrane domain.

The electrogenic Na⁺/HCO₃⁻cotransporter NBCe1‐B is widely expressed in many tissues, including pancreas, submandibular gland, brain, heart, etc. NBCe1‐B has very low activity under basal condition due to auto‐inhibition, but can be fully activated by protein interaction with the IP3R‐binding protein released with inositol 1,4,5‐trisphosphate (IRBIT).

The structural components of the auto‐inhibition domain and the IRBIT‐binding domain of NBCe1‐B are finely characterized based on systematic mutations in the present study and data from previous studies.

Reducing negative charges on the cytosol side of the transmembrane domain greatly decreases the magnitude of the auto‐inhibition of NBCe1‐B.

We propose that the auto‐inhibition domain functions as a brake module that inactivates NBCe1‐B by binding to, via electrostatic attraction, the transmembrane domain; IRBIT activates NBCe1‐B by releasing the brake from the transmembrane domain via competitive binding to the auto‐inhibition domain.

Neuroprotective Effect of L-carnitine. Focus on Changing Mitochondrial Function

Introduction: In this study, the neuroprotective effect of L-carnitine administeredper osin a dose of 25 mg/kg – 800 mg/kg was evaluated. The effects of L-carnitine on changes in mitochondrial function were also studied.

Materials and Methods: The neuroprotective effect and mitochondrial function were evaluated in a model of permanent focal ischemia in Wistar-line rats. L-carnitine was administered to rats orally for 72 hours from the moment of modeling ischemia. On the 4thday after the ischemia simulation, the change in the respiratory function of the mitochondria, the opening time of the mitochondrial permeability transition pore, the mitochondrial membrane potential, the concentration of intracellular calcium and the size of the cerebral necrosis zone were determined in rats’ brain supernatant.

Results: As a result, it was found that the administration of L-carnitine contributed to the restoration of mitochondrial function and a decrease in the size of the brain necrosis zone. At the same time, the administration of L-carnitine in low doses (25 mg/kg – 100 mg/kg) did not have a significant effect on the change in the concentration of intracellular calcium. It should be noted that an increase in the dose of L-carnitine from 200 mg/kg to 800 mg/kg was not accompanied by a significant increase in the therapeutic effect.

Discussion: L-carnitine is one of the key biomolecules that directly affect metabolic processes. It is known that L-carnitine acts as a ”shuttle” for long-chain fatty acids and thus can affect the alteration of mitochondrial function. However, the detailed nature of the mitochondriotropic action of L-carnitine has not been yet established. This was the focus of this study, which showed that the mitochondrion-oriented effect of L-carnitine is dose-dependent and expressed in the form of restoring the respiratory function of mitochondria, restoring the mitochondrial potential and increasing the latent opening time of the mitochondrial permeability transition pore, reducing the level of intracellular calcium.

Conclusion: The study allowed us to expand our understanding of the L-carnitine neuroprotective effect and the effect of this compound on changes in mitochondrial function.

Graphical abstract

[Effect of enhancer of zeste homolog 2 inhibitor GSK126 on the proliferation and apoptosis of tongue squamous cell carcinoma]

OBJECTIVE

This study aims to study the effect of the enhancer of zeste homolog 2 (EZH2) inhibitor GSK126 on the proliferation and apoptosis of human tongue squamous cell carcinoma cells in vitro and explore its related mechanisms in order to obtain insights into the clinical treatment of tongue squamous cell carcinoma.

METHODS

Different concentrations of GSK126 were applied to CAL-27 cells of tongue squamous cell carcinoma, and the effects of drugs on cell proliferation were detected through methyl thiazolyl tetrazolium (MTT) assay, colony formation assay, and 5-ethynyl-2'-deoxyuridine (EdU) fluorescence staining. Hoechst33342 fluorescence staining and the JC-1 method were used in observing apoptosis. The expression levels of extracellular regulated protein kinases (ERK), phospho-extracellular regulated protein kinases (p-ERK), Bax, Bcl-2, and Cleaved caspase-9 in Cal-27 cells were detected through Western blot.

RESULTS

GSK126 inhibited CAL-27 cell proliferation and promoted apoptosis. GSK126 down-regulated the expression of p-ERK and Bcl-2 and increased the expression of Bax and Cleaved caspase-9 (P<0.05).

CONCLUSIONS

GSK126 can inhibit the proliferation of CAL-27 cells in tongue squamous cell carcinoma and promote its apoptosis, and the related mechanism may be associated with the inhibition of the MEK/ERK signaling pathway and activation of the Bax/Bcl-2 pathway.

New horizons in mitochondrial contact site research

Contact sites, areas where two organelles are held in close proximity through the action of molecular tethers, enable non-vesicular communication between compartments. Mitochondria have been center stage in the contact site field since the discovery of the first contact between mitochondria and the endoplasmic reticulum (ER) over 60 years ago. However, only now, in the last decade, has there been a burst of discoveries regarding contact site biology in general and mitochondrial contacts specifically. The number and types of characterized contacts increased dramatically, new molecular mechanisms enabling contact formation were discovered, additional unexpected functions for contacts were shown, and their roles in cellular and organismal physiology were emphasized. Here, we focus on mitochondria as we highlight the most recent developments, future goals and unresolved questions in the field.

Bcl-2-Protein Family as Modulators of IP3 Receptors and Other Organellar Ca2+ Channels

The pro- and antiapoptotic proteins belonging to the B-cell lymphoma-2 (Bcl-2) family exert a critical control over cell-death processes by enabling or counteracting mitochondrial outer membrane permeabilization. Beyond this mitochondrial function, several Bcl-2 family members have emerged as critical modulators of intracellular Ca²⁺ homeostasis and dynamics, showing proapoptotic and antiapoptotic functions. Bcl-2 family proteins specifically target several intracellular Ca²⁺-transport systems, including organellar Ca²⁺ channels: inositol 1,4,5-trisphosphate receptors (IP₃Rs) and ryanodine receptors (RyRs), Ca²⁺-release channels mediating Ca²⁺ flux from the endoplasmic reticulum, as well as voltage-dependent anion channels (VDACs), which mediate Ca²⁺ flux across the mitochondrial outer membrane into the mitochondria. Although the formation of protein complexes between Bcl-2 proteins and these channels has been extensively studied, a major advance during recent years has been elucidating the complex interaction of Bcl-2 proteins with IP₃Rs. Distinct interaction sites for different Bcl-2 family members were identified in the primary structure of IP₃Rs. The unique molecular profiles of these Bcl-2 proteins may account for their distinct functional outcomes when bound to IP₃Rs. Furthermore, Bcl-2 inhibitors used in cancer therapy may affect IP₃R function as part of their proapoptotic effect and/or as an adverse effect in healthy cells.

New Insights in the IP3 Receptor and Its Regulation

The inositol 1,4,5-trisphosphate (IP₃) receptor (IP₃R) is a Ca²⁺-release channel mainly located in the endoplasmic reticulum (ER). Three IP₃R isoforms are responsible for the generation of intracellular Ca²⁺ signals that may spread across the entire cell or occur locally in so-called microdomains. Because of their ubiquitous expression, these channels are involved in the regulation of a plethora of cellular processes, including cell survival and cell death. To exert their proper function a fine regulation of their activity is of paramount importance. In this review, we will highlight the recent advances in the structural analysis of the IP₃R and try to link these data with the newest information concerning IP₃R activation and regulation. A special focus of this review will be directed towards the regulation of the IP₃R by protein-protein interaction. Especially the protein family formed by calmodulin and related Ca²⁺-binding proteins and the pro- and anti-apoptotic/autophagic Bcl-2-family members will be highlighted. Finally, recently identified and novel IP₃R regulatory proteins will be discussed. A number of these interactions are involved in cancer development, illustrating the potential importance of modulating IP₃R-mediated Ca²⁺ signaling in cancer treatment.

IP3 Receptor Plasticity Underlying Diverse Functions

In the body, extracellular stimuli produce inositol 1,4,5-trisphosphate (IP₃), an intracellular chemical signal that binds to the IP₃ receptor (IP₃R) to release calcium ions (Ca²⁺) from the endoplasmic reticulum. In the past 40 years, the wide-ranging functions mediated by IP₃R and its genetic defects causing a variety of disorders have been unveiled. Recent cryo-electron microscopy and X-ray crystallography have resolved IP₃R structures and begun to integrate with concurrent functional studies, which can explicate IP₃-dependent opening of Ca²⁺-conducting gates placed ∼90 Å away from IP₃-binding sites and its regulation by Ca²⁺. This review highlights recent research progress on the IP₃R structure and function. We also propose how protein plasticity within IP₃R, which involves allosteric gating and assembly transformations accompanied by rapid and chronic structural changes, would enable it to regulate diverse functions at cellular microdomains in pathophysiological states.

ER-mitochondria tethering and Ca2+ crosstalk: The IP3R team takes the field

Inter-organelle communication represents a booming topic in cell biology research, with endoplasmic reticulum (ER)-mitochondria coupling playing the lion's share. In a recent work, Bartok and colleagues found that inositol trisphosphates receptors (IP₃Rs), in addition to their well-known involvement in ER-mitochondria Ca²⁺ transfer, are endowed with structural properties at organelles' interface.

Bcl-2 and IP3 compete for the ligand-binding domain of IP3Rs modulating Ca2+ signaling output

Bcl-2 proteins have emerged as critical regulators of intracellular Ca2+ dynamics by directly targeting and inhibiting the IP3 receptor (IP3R), a major intracellular Ca2+-release channel. Here, we demonstrate that such inhibition occurs under conditions of basal, but not high IP3R activity, since overexpressed and purified Bcl-2 (or its BH4 domain) can inhibit IP3R function provoked by low concentration of agonist or IP3, while fails to attenuate against high concentration of agonist or IP3. Surprisingly, Bcl-2 remained capable of inhibiting IP3R1 channels lacking the residues encompassing the previously identified Bcl-2-binding site (a.a. 1380-1408) located in the ARM2 domain, part of the modulatory region. Using a plethora of computational, biochemical and biophysical methods, we demonstrate that Bcl-2 and more particularly its BH4 domain bind to the ligand-binding domain (LBD) of IP3R1. In line with this finding, the interaction between the LBD and Bcl-2 (or its BH4 domain) was sensitive to IP3 and adenophostin A, ligands of the IP3R. Vice versa, the BH4 domain of Bcl-2 counteracted the binding of IP3 to the LBD. Collectively, our work reveals a novel mechanism by which Bcl-2 influences IP3R activity at the level of the LBD. This allows for exquisite modulation of Bcl-2's inhibitory properties on IP3Rs that is tunable to the level of IP3 signaling in cells.

ER-mitochondria interactions: Both strength and weakness within cancer cells

ER-mitochondria contact sites represent hubs for signaling that control mitochondrial biology related to several aspects of cellular survival, metabolism, cell death sensitivity and metastasis, which all contribute to tumorigenesis. Altered ER-mitochondria contacts can deregulate Ca2+ homeostasis, phospholipid metabolism, mitochondrial morphology and dynamics. MAM represent both a hot spot in cancer onset and progression and an Achilles' heel of cancer cells that can be exploited for therapeutic perspectives. Over the past years, an increasing number of cancer-related proteins, including oncogenes and tumor suppressors, have been localized in MAM and exert their pro- or antiapoptotic functions through the regulation of Ca2+ transfer and signaling between the two organelles. In this review, we highlight the central role of ER-mitochondria contact sites in tumorigenesis and focus on chemotherapeutic drugs or potential targets that act on MAM properties for new therapeutic approaches in cancer.

Communication between mitochondria and other organelles: a brand-new perspective on mitochondria in cancer

Mitochondria are energy factories of cells and are important pivots for intracellular interactions with other organelles. They interact with the endoplasmic reticulum, peroxisomes, and nucleus through signal transduction, vesicle transport, and membrane contact sites to regulate energy metabolism, biosynthesis, immune response, and cell turnover. However, when the communication between organelles fails and the mitochondria are dysfunctional, it may induce tumorigenesis. In this review, we elaborate on how mitochondria interact with the endoplasmic reticulum, peroxisomes, and cell nuclei, as well as the relation between organelle communication and tumor development .

Overview of BCL-2 Family Proteins and Therapeutic Potentials

BCL-2 family proteins interact in a network that regulates apoptosis. The BH3 amino acid sequence motif serves to bind together this conglomerate protein family, both literally and figuratively. BH3 motifs are present in antiapoptotic and proapoptotic BCL-2 homologs, and in a separate group of unrelated BH3-only proteins often appended to the BCL-2 family. BH3-containing helices mediate many of their physical interactions to determine cell death versus survival, leading to the development of BH3 mimetics as therapeutics. Here we provide an overview of BCL-2 family interactions, their relevance in health and disease, and the progress toward regulating their interactions therapeutically.

MicroRNA-18a promotes hepatocellular carcinoma proliferation, migration, and invasion by targeting Bcl2L10

BACKGROUND

Hepatocellular carcinoma (HCC) is known to feature several microRNA dysregulations. This study aimed to determine and investigate the prognostic value of microRNA (miRNA/miR)-18a and its role in regulating the progression of HCC.

METHODS

miR-18a expressions in human HCC tissues, pair-matched adjacent normal liver tissues as well as in HCC cell lines were determined by quantitative real-time PCR. The prognostic value of miR-18a was determined using Kaplan-Meier survival analysis and multivariable Cox regression assay. The ability of miR-18a in promoting HCC progression was verified in vitro.

RESULTS

miR-18a expressions in HCC tissues and cells were more than twice those of the normal control group (P<0.05). miR-18a expression was associated with the alpha-fetoprotein (AFP) level, TNM stage, tumor size, and intrahepatic vascular invasion (P<0.05). Kaplan- Meier survival analysis revealed that HCC patients with high expression of miR-18a possessed a more unfavorable prognosis (log-rank P<0.001). Overexpression of miR-18a promoted cell apoptosis and proliferation, induced S phase transition, as well as enhanced the migration and invasion ability of HCC cells. miR-18a was found to directly target the downstream molecule Bcl2L10. Furthermore, overexpressing Bcl2L10 was able to partly reverse the promoting effects of miR-18a on HCC cell progression.

CONCLUSION

miR-18a may serve as a prognostic biomarker of HCC as it is demonstrated to carry out a decisive role in HCC progression by promoting HCC cell invasion, migration, and proliferation through targeting Bcl2L10.

Consensus report of the 8 and 9th Weinman Symposia on Gene x Environment Interaction in carcinogenesis: novel opportunities for precision medicine

The relative contribution of intrinsic genetic factors and extrinsic environmental ones to cancer aetiology and natural history is a lengthy and debated issue. Gene-environment interactions (G x E) arise when the combined presence of both a germline genetic variant and a known environmental factor modulates the risk of disease more than either one alone. A panel of experts discussed our current understanding of cancer aetiology, known examples of G × E interactions in cancer, and the expanded concept of G × E interactions to include somatic cancer mutations and iatrogenic environmental factors such as anti-cancer treatment. Specific genetic polymorphisms and genetic mutations increase susceptibility to certain carcinogens and may be targeted in the near future for prevention and treatment of cancer patients with novel molecularly based therapies. There was general consensus that a better understanding of the complexity and numerosity of G × E interactions, supported by adequate technological, epidemiological, modelling and statistical resources, will further promote our understanding of cancer and lead to novel preventive and therapeutic approaches.

Endoplasmic Reticulum-Mitochondrial Contactology: Structure and Signaling Functions

Interorganellar contacts are increasingly recognized as central to the control of cellular behavior. These contacts, which typically involve a small fraction of the endomembrane surface, are local communication hubs that resemble synapses. We propose the term contactology to denote the analysis of interorganellar contacts. Endoplasmic reticulum (ER) contacts with mitochondria were recognized several decades ago; major roles in ion and lipid transfer, signaling, and membrane dynamics have been established, while others continue to emerge. The functional diversity of ER-mitochondrial (ER-mito) contacts is mirrored in their structural heterogeneity, with subspecialization likely supported by multiple, different linker-forming protein structures. The nanoscale size of the contacts has made studying their structure, function, and dynamics difficult. This review focuses on the structure of the ER-mito contacts, methods for studying them, and the roles of contacts in Ca²⁺ and reactive oxygen species (ROS) signaling.