Advances in biological regulation最新文献

ATPase family AAA domain containing protein 3, commonly known as ATAD3 is a versatile mitochondrial protein that is involved in a large number of pathways. ATAD3 is a transmembrane protein that spans both the inner mitochondrial membrane and outer mitochondrial membrane. It, therefore, functions as a connecting link between the mitochondrial lumen and endoplasmic reticulum facilitating their cross-talk. ATAD3 contains an N-terminal domain which is amphipathic in nature and is inserted into the membranous space of the mitochondria, while the C-terminal domain is present towards the lumen of the mitochondria and contains the ATPase domain. ATAD3 is known to be involved in mitochondrial biogenesis, cholesterol transport, hormone synthesis, apoptosis and several other pathways. It has also been implicated to be involved in cancer and many neurological disorders making it an interesting target for extensive studies. This review aims to provide an updated comprehensive account of the role of ATAD3 in the mitochondria especially in lipid transport, mitochondrial-endoplasmic reticulum interactions, cancer and inhibition of mitophagy.

Calcium (Ca²⁺) is a highly versatile intracellular messenger that regulates several cellular processes. Although it is unclear how a single-second messenger coordinates various effects within a cell, there is growing evidence that spatial patterns of Ca²⁺ signals play an essential role in determining their specificity. Ca²⁺ signaling patterns can differ in various cell regions, and Ca²⁺ signals in the nuclear and cytoplasmic compartments have been observed to occur independently. The initiation and function of Ca²⁺ signaling within the nucleus are not yet fully understood. Receptor tyrosine kinases (RTKs) induce Ca²⁺ signaling resulting from phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis and inositol 1,4,5-trisphosphate (InsP3) formation within the nucleus. This signaling mechanism may be responsible for the effects of specific growth factors on cell proliferation and gene transcription. This review highlights the recent advances in RTK trafficking to the nucleus and explains how these receptors initiate nuclear calcium signaling.

Hepatocellular carcinoma (HCC) is a common cancer which unfortunately has poor outcomes. Common anti-cancer treatments such as chemotherapy and targeted therapy have not increased patient survival significantly. A common treatment for HCC patients is transplantation, however, it has limitations and complications. Novel approaches are necessary to more effectively treat HCC patients. Berberine (BBR) is a nutraceutical derived from various fruits and trees, which has been used for centuries in traditional medicine to treat various diseases such as diabetes and inflammation. More recently, the anti-proliferation effects of BBR have been investigated in the treatment of patients with various cancers, especially colorectal cancer, and in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). In this review, we will focus on studies with BBR in liver diseases.

Lysophosphatidic acid (LPA) is a simple physiological lipid and structurally consists of a fatty, a phosphate and a glycerol. LPA binds to G protein-coupled LPA receptors (LPA₁ to LPA₆). LPA receptor-mediated signaling mediates a variety of biological responses, such as cell growth, migration, morphogenesis, differentiation and protection from apoptosis. It is considered that LPA receptor-mediated signaling plays an important role in the pathogenesis of human malignancies. So far, genetic and epigenetic alterations of LPA receptors have been found in several cancer cells as well as abnormal LPA production. In addition, LPA receptor-mediated signaling regulates the promotion of malignant behaviors, including chemo- and/or radiation-resistance. Chemotherapy and radiotherapy are the common approaches to the treatments of cancers. However, resistance to anticancer drugs and irradiation is the most critical limitation for chemotherapy and radiotherapy. In this review, we provide the roles of LPA receptor-mediated signaling in the regulation of cellular responses induced by chemotherapeutic agents and irradiation and its biological utility as a possible molecular target for improving cancer cell responses to chemotherapy and radiotherapy.

Diacylglycerol kinases (DGKs) are a family of enzymes that catalyze the ATP-dependent conversion of diacylglycerol (DAG) to phosphatidic acid (PtdOH). A common approach to examine the activity of these enzymes relys on a radiometric assay (Epand and Topham, 2007; Tu-Sekine and Raben, 2017). This assay quantifies the DGK-catalyzed incorporation of ³²P into DAG from AT³²P to generate ³²PtdOH and is perhaps been the most widely used assay. While sensitive, its drawbacks are the expense and the potential negative impacts on health and the environment. In this report, we describe a new assay which utilizes fluorescent labeled NBD-DAG (1-Oleoyl-2-[12-[(7-nitro-2-1,3-benzoxadiazol-4-yl) amino] dodecanoyl]-sn-Glycero-3-diacylglycerol) to quantify the DGK-θ-catalyzed conversion of NBD-DAG to NBD-PtdOH. Furthermore, we show the assay is sufficiently sensitive as the measured specific activity was similar to that previously determined with AT³²P (Tu-Sekine and Raben, 2012) and was able to detect the activation of DGK-θ by synaptotagmin-1 (Barber et al., 2022). Overall, this assay is inexpensive, sensitive, and reproducible making it an attractive alternative to currently established assays.

Our research laboratory has a longstanding interest in developmental disorders and embryonic tumors, and recent efforts have focused on the pathogenesis of pediatric liver tumors. This review focuses on hepatoblastoma (HB), the most common pediatric liver malignancy. Despite advances in treatment, patients with metastatic HB have a poor prognosis, and survivors often have permanent side effects attributable to chemotherapy. In an effort to improve survival and lessen long-term complications of HB, we have searched for novel molecular vulnerabilities using a combination of patient derived cell lines, metabolomics, and RNA sequencing of human samples at diagnosis and follow-up. These studies have shed light on pathogenesis and identified putative targets for future therapies in children with advanced HB.

Acquired myeloid malignancies are a spectrum of clonal disorders known to be caused by sequential acquisition of genetic lesions in hematopoietic stem and progenitor cells, leading to their aberrant self-renewal and differentiation. The increasing use of induced pluripotent stem cell (iPSC) technology to study myeloid malignancies has helped usher a paradigm shift in approaches to disease modeling and drug discovery, especially when combined with gene-editing technology. The process of reprogramming allows for the capture of the diversity of genetic lesions and mutational burden found in primary patient samples into individual stable iPSC lines. Patient-derived iPSC lines, owing to their self-renewal and differentiation capacity, can thus be a homogenous source of disease relevant material that allow for the study of disease pathogenesis using various functional read-outs. Furthermore, genome editing technologies like CRISPR/Cas9 enable the study of the stepwise progression from normal to malignant hematopoiesis through the introduction of specific driver mutations, individually or in combination, to create isogenic lines for comparison. In this review, we survey the current use of iPSCs to model acquired myeloid malignancies including myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), acute myeloid leukemia and MDS/MPN overlap syndromes. The use of iPSCs has enabled the interrogation of the underlying mechanism of initiation and progression driving these diseases. It has also made drug testing, repurposing, and the discovery of novel therapies for these diseases possible in a high throughput setting.

Adipose tissue (AT) comprises distinct fat depots such as white AT and brown AT. White and brown adipocytes exhibit different morphological and physiological properties. White adipocytes containing large single lipid droplet (LD) provide energy on demand whereas brown adipocytes loaded with multilocular LDs consume energy to generate heat or dissipate excess energy. Recent studies have shown that multilocular brown-like cells emerge in white AT under certain conditions. These cells termed beige adipocytes participate in energy expenditure and heat generation. In the process of lipolysis, TG is broken down into free fatty acid and diacylglycerol (DG). In this regard, DG also serves as a signaling molecule activating some proteins such as protein kinase C. Therefore, DG kinase (DGK), an enzyme which phosphorylates DG into phosphatidic acid (PA), plays a pivotal role in integrating energy homeostasis and intracellular signaling. Recently, we described that DGKε-KO mice exhibit increased adiposity in visceral white AT accompanied with impaired glucose tolerance early (40 days) in the course of high fat diet (HFD) feeding, although these mice exhibit “browning or beiging” in visceral white AT associated with improved glucose tolerance after longer term HFD feeding (180 days). This study was conducted to understand the overall features of adipose tissues and investigate changes in subcutaneous (inguinal) white AT and interscapular brown AT of DGKε-KO mice during the course of HFD feeding. Results demonstrated that fat accumulation is promoted in all fat depots under 40 days of HFD feeding conditions. Remarkably, “whitening” of brown adipocytes was identified in DGKε-deficient brown AT during the course of HFD feeding, suggesting brown adipocyte dysfunction. In addition, insulin levels were considerably elevated in DGKε-KO mice under 180 days of HFD feeding conditions. Collectively, these findings suggest that brown adipocytes are dysfunctional in DGKε-KO mice, which promotes browning or beiging in visceral white AT. Beige adipocytes may take over energy disposal and contribute to improving glucose tolerance with the aid of high levels of insulin in DGKε-KO mice upon excess feeding.

Cancer still represents the second leading cause of death right after cardiovascular diseases. According to the World Health Organization (WHO), cancer provoked around 10 million deaths in 2020, with lung and colon tumors accounting for the deadliest forms of cancer. As tumor cells become resistant to traditional therapeutic approaches, immunotherapy has emerged as a novel strategy for tumor control. T lymphocytes are key players in immune responses against tumors. Immunosurveillance allows identification, targeting and later killing of cancerous cells. Nevertheless, tumors evolve through different strategies to evade the immune response and spread in a process called metastasis. The ineffectiveness of traditional strategies to control tumor growth and expansion has led to novel approaches considering modulation of T cell activation and effector functions. Program death receptor 1 (PD-1) and cytotoxic T-lymphocyte antigen 4 (CTLA-4) showed promising results in the early 90s and nowadays are still being exploited together with other drugs for several cancer types. Other negative regulators of T cell activation are diacylglycerol kinases (DGKs) a family of enzymes that catalyze the conversion of diacylglycerol (DAG) into phosphatidic acid (PA). In T cells, DGKα and DGKζ limit the PLCγ/Ras/ERK axis thus attenuating DAG mediated signaling and T cell effector functions. Upregulation of either of both isoforms results in impaired Ras activation and anergy induction, whereas germline knockdown mice showed enhanced antitumor properties and more effective immune responses against pathogens. Here we review the mechanisms used by DGKs to ameliorate T cell activation and how inhibition could be used to reinvigorate T cell functions in cancer context. A better knowledge of the molecular mechanisms involved upon T cell activation will help to improve current therapies with DAG promoting agents.