Cellular & Molecular Biology Letters最新文献

The skin is a barrier that protects the human body against environmental factors (physical, including solar radiation, chemicals, and pathogens). The integrity and, consequently, the effective metabolic activity of skin cells is ensured by the cell membrane, the important structural and metabolic elements of which are phospholipids. Phospholipids are subject to continuous transformation, including enzymatic hydrolysis (with the participation of phospholipases A, C, and D) to free polyunsaturated fatty acids (PUFAs), which under the influence of cyclooxygenases (COX1/2), lipoxygenases (LOXs), and cytochrome P450 (CYPs P450) are metabolized to various classes of oxylipins, depending on the type of PUFA being metabolized and the enzyme acting. The most frequently analyzed oxylipins, especially in skin cells, are eicosanoids, which are derivatives of arachidonic acid (AA). Their level depends on both environmental factors and endogenous metabolic disorders. However, they play an important role in homeostasis mechanisms related to the structural and functional integrity of the skin, including maintaining redox balance, as well as regulating inflammatory processes arising in response to endogenous and exogenous factors reaching skin cells. Therefore, it is believed that dysregulation of eicosanoid levels may contribute to the development of skin diseases, such as psoriasis or atopic dermatitis, which in turn suggests that targeted control of the generation of specific eicosanoids may have diagnostic significance and beneficial therapeutic effects. This review is the first systemic and very detailed approach presenting both the causes and consequences of changes in phospholipid metabolism leading to the generation of eicosanoids, changes in the level of which result in specific metabolic disorders in skin cells leading to the development of various diseases. At the same time, existing literature data indicate that further detailed research is necessary to understand a clear relationship between changes in the level of specific eicosanoids and the pathomechanisms of specific skin diseases, as well as to develop an effective diagnostic and therapeutic approach.

Background: Regulation of messenger RNA (mRNA) transport and translation in neurons is essential for dendritic plasticity and learning/memory development. The trafficking of mRNAs along the hippocampal neuron dendrites remains translationally silent until they are selectively transported into the spines upon glutamate-induced receptor activation. However, the molecular mechanism(s) behind the spine entry of dendritic mRNAs under metabotropic glutamate receptor (mGluR)-mediated neuroactivation and long-term depression (LTD) as well as the fate of these mRNAs inside the spines are still elusive.

Method: Different molecular and imaging techniques, e.g., immunoprecipitation (IP), RNA-IP, Immunofluorescence (IF)/fluorescence in situ hybridization (FISH), live cell imaging, live cell tracking of RNA using beacon, and mouse model study are used to elucidate a novel mechanism regulating dendritic spine transport of mRNAs in mammalian neurons.

Results: We demonstrate here that brief mGluR1 activation-mediated dephosphorylation of pFMRP (S499) results in the dissociation of FMRP from TDP-43 and handover of TDP-43/Rac1 mRNA complex from the dendritic transport track on microtubules to myosin V track on the spine actin filaments. Rac1 mRNA thus enters the spines for translational reactivation and increases the mature spine density. In contrast, during mGluR1-mediated neuronal LTD, FMRP (S499) remains phosphorylated and the TDP-43/Rac1 mRNA complex, being associated with kinesin 1-FMRP/cortactin/drebrin, enters the spines owing to Ca²⁺-dependent microtubule invasion into spines, but without translational reactivation. In a VPA-ASD mouse model, this regulation become anomalous.

Conclusions: This study, for the first time, highlights the importance of posttranslational modification of RBPs, such as the neurodevelopmental disease-related protein FMRP, as the molecular switch regulating the dendrite-to-spine transport of specific mRNAs under mGluR1-mediated neurotransmissions. The misregulation of this switch could contribute to the pathogenesis of FMRP-related neurodisorders including the autism spectrum disorder (ASD). It also could indicate a molecular connection between ASD and neurodegenerative disease-related protein TDP-43 and opens up a new perspective of research to elucidate TDP-43 proteinopathy among patients with ASD.

Background: Glioblastoma multiforme (GBM) is a highly aggressive brain tumor, characterized by its poor prognosis. Glycolipid metabolism is strongly associated with GBM development and malignant behavior. However, the precise functions of snoRNAs and ADARs in glycolipid metabolism within GBM cells remain elusive. The objective of the present study is to delve into the underlying mechanisms through which snoRNAs and ADARs exert regulatory effects on glycolipid metabolism in GBM cells.

Methods: RNA immunoprecipitation and RNA pull-down experiments were conducted to verify the homodimerization of ADAR2 by SNORD113-3, and Sanger sequencing and Western blot experiments were used to detect the A-to-I RNA editing of PHKA2 mRNA by ADAR2. Furthermore, the phosphorylation of EBF1 was measured by in vitro kinase assay. Finally, in vivo studies using nude mice confirmed that SNORD113-3 and ADAR2 overexpression, along with PHKA2 knockdown, could suppress the formation of subcutaneous xenograft tumors and improve the outcome of tumor-bearing nude mice.

Results: We found that PHKA2 in GBM significantly promoted glycolipid metabolism, while SNORD113-3, ADAR2, and EBF1 significantly inhibited glycolipid metabolism. SNORD113-3 promotes ADAR2 protein expression by promoting ADAR2 homodimer formation. ADAR2 mediates the A-to-I RNA editing of PHKA2 mRNA. Mass spectrometry analysis and in vitro kinase testing revealed that PHKA2 phosphorylates EBF1 on Y256, reducing the stability and expression of EBF1. Furthermore, direct binding of EBF1 to PKM2 and ACLY promoters was observed, suggesting the inhibition of their expression by EBF1. These findings suggest the existence of a SNORD113-3/ADAR2/PHKA2/EBF1 pathway that collectively regulates the metabolism of glycolipid and the growth of GBM cells. Finally, in vivo studies using nude mice confirmed that knockdown of PHKA2, along with overexpression of SNORD113-3 and ADAR2, could obviously suppress GBM subcutaneous xenograft tumor formation and improve the outcome of those tumor-bearing nude mice.

Conclusions: Herein, we clarified the underlying mechanism involving the SNORD113-3/ADAR2/PHKA2/EBF1 pathway in the regulation of GBM cell growth and glycolipid metabolism. Our results provide a framework for the development of innovative therapeutic interventions to improve the prognosis of patients with GBM.

Proper adhesion of cells to their environment is essential for the normal functioning of single cells and multicellular organisms. To attach to the extracellular matrix (ECM), mammalian cells form integrin adhesion complexes consisting of many proteins that together link the ECM and the actin cytoskeleton. Similar to mammalian cells, the amoeboid cells of the protist Dictyostelium discoideum also use multiprotein adhesion complexes to control their attachment to the underlying surface. However, the exact composition of the multiprotein complexes and the signaling pathways involved in the regulation of adhesion in D. discoideum have not yet been elucidated. Here, we show that the IQGAP-related protein IqgC is important for normal attachment of D. discoideum cells to the substratum. Mutant iqgC-null cells have impaired adhesion, whereas overexpression of IqgC promotes directional migration. A RasGAP C-terminal (RGCt) domain of IqgC is sufficient for its localization in the ventral adhesion focal complexes, while RasGAP activity of a GAP-related domain (GRD) is additionally required for the proper function of IqgC in adhesion. We identify the small GTPase RapA as a novel direct IqgC interactor and show that IqgC participates in a RapA-regulated signaling pathway targeting the adhesion complexes that include talin A, myosin VII, and paxillin B. On the basis of our results, we propose that IqgC is a positive regulator of adhesion, responsible for the strengthening of ventral adhesion structures and for the temporal control of their subsequent degradation.

Background: Metabolism is error prone. For instance, the reduced forms of the central metabolic cofactors nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH), can be converted into redox-inactive products, NADHX and NADPHX, through enzymatically catalyzed or spontaneous hydration. The metabolite repair enzymes NAXD and NAXE convert these damaged compounds back to the functional NAD(P)H cofactors. Pathogenic loss-of-function variants in NAXE and NAXD lead to development of the neurometabolic disorders progressive, early-onset encephalopathy with brain edema and/or leukoencephalopathy (PEBEL)1 and PEBEL2, respectively.

Methods: To gain insights into the molecular disease mechanisms, we investigated the metabolic impact of NAXD deficiency in human cell models. Control and NAXD-deficient cells were cultivated under different conditions, followed by cell viability and mitochondrial function assays as well as metabolomic analyses without or with stable isotope labeling. Enzymatic assays with purified recombinant proteins were performed to confirm molecular mechanisms suggested by the cell culture experiments.

Results: HAP1 NAXD knockout (NAXDko) cells showed growth impairment specifically in a basal medium containing galactose instead of glucose. Surprisingly, the galactose-grown NAXDko cells displayed only subtle signs of mitochondrial impairment, whereas metabolomic analyses revealed a strong inhibition of the cytosolic, de novo serine synthesis pathway in those cells as well as in NAXD patient-derived fibroblasts. We identified inhibition of 3-phosphoglycerate dehydrogenase as the root cause for this metabolic perturbation. The NAD precursor nicotinamide riboside (NR) and inosine exerted beneficial effects on HAP1 cell viability under galactose stress, with more pronounced effects in NAXDko cells. Metabolomic profiling in supplemented cells indicated that NR and inosine act via different mechanisms that at least partially involve the serine synthesis pathway.

Conclusions: Taken together, our study identifies a metabolic vulnerability in NAXD-deficient cells that can be targeted by small molecules such as NR or inosine, opening perspectives in the search for mechanism-based therapeutic interventions in PEBEL disorders.

Hypoxia-inducible factors (HIFs) are essential transcription factors that orchestrate cellular responses to oxygen deprivation. HIF-1α, as an unstable subunit of HIF-1, is usually hydroxylated by prolyl hydroxylase domain enzymes under normoxic conditions, leading to ubiquitination and proteasomal degradation, thereby keeping low levels. Instead of hypoxia, sometimes even in normoxia, HIF-1α translocates into the nucleus, dimerizes with HIF-1β to generate HIF-1, and then activates genes involved in adaptive responses such as angiogenesis, metabolic reprogramming, and cellular survival, which presents new challenges and insights into its role in cellular processes. Thus, the review delves into the mechanisms by which HIF-1 maintains its stability under normoxia including but not limited to giving insights into transcriptional, translational, as well as posttranslational regulation to underscore the pivotal role of HIF-1 in cellular adaptation and malignancy. Moreover, HIF-1 is extensively involved in cancer and cardiovascular diseases and potentially serves as a bridge between them. An overview of HIF-1-related drugs that are approved or in clinical trials is summarized, highlighting their potential capacity for targeting HIF-1 in cancer and cardiovascular toxicity related to cancer treatment. The review provides a comprehensive insight into HIF-1's regulatory mechanism and paves the way for future research and therapeutic development.

Background: Epigenetic modifications have been proved to play important roles in the spinal degenerative diseases. As a type of noncoding RNA, the microRNA (miRNA) is a vital class of regulatory factor in the epigenetic modifications, while the role of miRNAs in the regulation of epigenetic modifications in ligamentum flavum hypertrophy (LFH) has not been fully investigated.

Methods: The miRNA sequencing analysis was used to explore the change of miRNA expression during the fibrosis of ligamentum flavum (LF) cells caused by the TGF-β1 (10 ng/ml). The downregulated miRNA miR-335-3p was selected to investigate its effects on the fibrosis of LF cells and explored the accurate relevant mechanisms.

Results: A total of 21 miRNAs were differently expressed during the fibrosis of LF cells. The downregulated miR-335-3p was selected for further investigation. MiR-335-3p was distinctly downregulated in the LFH tissues compared to non-LFH tissues. Overexpression of miR-335-3p could inhibit the fibrosis of LF cells. Further research showed miR-335-3p prevented the fibrosis of LF cells via binding to the 3'-UTR of SERPINE2 to reduce the expression of SERPINE2. The increased SERPINE2 expression might promote the fibrosis of LF cells via the activation of β-catenin signaling pathway to promote the transcription of fibrosis-related genes (ACTA2 and COL3A1).

Conclusions: Our results revealed that miR-335-3p prevented the fibrosis of LF cells via the epigenetic regulation of SERPINE2/β-catenin signaling pathway. The epigenetic regulator miR-335-3p might be a promising potential target for the treatment of LFH.

Background: Disorders of lipid metabolism are critical factors in the progression of chronic lymphocytic leukemia (CLL). However, the characteristics of lipid metabolism and related regulatory mechanisms of CLL remain unclear.

Methods: Hence, we identified altered metabolites and aberrant lipid metabolism pathways in patients with CLL by ultra-high-performance liquid chromatography-mass spectrometry-based non-targeted lipidomics. A combination of transcriptomics and lipidomics was used to mine relevant target molecule and downstream signaling pathway. In vitro cellular assays, quantitative real-time polymerase chain reaction (qRT-PCR), western blot, fluorescent staining, RNA sequencing, and coimmunoprecipitation were used to monitor the molecular levels as well as to explore the underlying mechanisms.

Results: Significant differences in the content of 52 lipid species were identified in CLL samples and healthy controls. Functional analysis revealed that alterations in glycerolipid metabolism, glycerophospholipid metabolism, sphingolipid metabolism, and metabolic pathways had the greatest impact on CLL. On the basis of the area under the curve value, a combination of three metabolites (phosphatidylcholine O-24:2_18:2, phosphatidylcholine O-35:3, and lysophosphatidylcholine 34:3) potentially served as a biomarker for the diagnosis of CLL. Furthermore, utilizing integrated lipidomic, transcriptomic, and molecular studies, we reveal that ectonucleotide pyrophosphatase/phosphodiesterase 2 (ENPP2) plays a crucial role in regulating oncogenic lipogenesis. ENPP2 expression was significantly elevated in patients with CLL compared with normal cells and was validated in an independent cohort. Moreover, ENPP2 knockdown and targeted inhibitor PF-8380 treatment exerted an antitumor effect by regulating cell viability, proliferation, apoptosis, cell cycle, and enhanced the drug sensitivity to ibrutinib. Mechanistically, ENPP2 inhibited AMP-activated protein kinase (AMPK) phosphorylation and promoted lipogenesis through the sterol regulatory element-binding transcription factor 1 (SREBP-1)/fatty acid synthase (FAS) signaling pathway to promote lipogenesis.

Conclusions: Taken together, our findings unravel the lipid metabolism characteristics of CLL. Moreover, we demonstrate a previously unidentified role and mechanism of ENPP2 in regulation of lipid metabolism, providing a novel therapeutic target for CLL treatment.

Background: Radiotherapy for pelvic malignant tumors inevitably causes intestinal tissue damage. The regeneration of intestinal epithelium after radiation injury relies mainly on crypt fission. However, little is known about the regulatory mechanisms of crypt fission events.

Methods: The effects of WNT4 on crypt regeneration and the symmetry of crypt fission were examined using a mouse small intestinal organoid culture model. Three-dimensional (3D) reconstructed images of organoids were applied to assess the symmetry of crypt fission and Paneth cell localization upon manipulation of WNT4 expression. The effect of WNT4 on the expression of β-catenin target genes was analyzed by real-time quantitative polymerase chain reaction (RT-qPCR). The in vivo effect of WNT4 overexpression mediated by adeno-associated virus (AAV) on symmetric fission of crypt was investigated using a radiation-injured mouse model.

Results: WNT4 has a special function of promoting symmetric fission of small intestinal crypts, although it inhibits budding, stemness, and cell proliferation on organoids. WNT4 promotes the correct localization of Paneth cells in the crypt base by regulating the expression of EphB3, thereby promoting the symmetric fission of small intestinal crypts. WNT4 negatively regulates the canonical WNT/β-catenin signaling pathway, and it promotes symmetric crypt fission in a ROR2 receptor-dependent manner. Moreover, in patients and animal models of radiation-induced intestinal injury, we found that the regenerated crypts are irregular in size and shape, Paneth cells are mislocalized, and the expression of WNT4 is decreased while EphB3 is increased. Importantly, restoration of WNT4 expression mediated by AAV effectively promotes symmetric crypt fission and thus improves the regularity of regenerating crypts in mice with radiation-induced injury.

Conclusions: Our study highlights the critical role of WNT4 in the regulation of crypt fission and provides WNT4 as a potential therapeutic target for radiation enteritis.