SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Biochemical and biophysical research communications

142

Macroautophagy is a conserved degradative pathway and its deterioration is linked to disturbances in cellular proteostasis and multiple diseases. Here, we show that the RAB GTPase RAB18 modulates autophagy in primary human fibroblasts. The knockdown of RAB18 results in a decreased autophagic activity, while its overexpression enhances the degradative pathway. Importantly, this function of RAB18 is dependent on RAB3GAP1 and RAB3GAP2, which might act as RAB GEFs and stimulate the activity of the RAB GTPase. Moreover, the knockdown of RAB18 deteriorates proteostasis and results in the intracellular accumulation of ubiquitinated degradation-prone proteins. Thus, the RAB GTPase RAB18 is a positive modulator of autophagy and is relevant for the maintenance of cellular proteostasis.

Concepts: Fibroblast, Modulation, ACT, GTPase, Autophagy

102

The current COVID-19 pandemic requires urgent development of effective therapeutics. 5-amino levulinic acid (5-ALA) is a naturally synthesized amino acid and has been used for multiple purposes including as an anticancer therapy and as a dietary supplement due to its high bioavailability. In this study, we demonstrated that 5-ALA treatment potently inhibited infection of SARS-CoV-2, a causative agent of COVID-19, in cell culture. The antiviral effects could be detected in both human and non-human cells, without significant cytotoxicity. Therefore, 5-ALA is worth to be further investigated as an antiviral drug candidate for COVID-19.

62

Supercentenarians (≥110-year-old, SC) are a uniquely informative population not only because they surpass centenarians in age, but because they appear to age more slowly with fewer incidences of chronic age-related disease than centenarians. We reprogramed donor B-lymphoblastoid cell lines (LCL) derived from a 114-year-old (SC), a 43-year-old healthy disease-free control (HDC) and an 8-year-old with a rapid aging disease (Hutchinson-Gilford progeria syndrome (HGPS)) and compared SC-iPSC to HDC-iPSC and HGPS-iPSCs. Reprogramming to pluripotency was confirmed by pluripotency marker expression and differentiation to 3 germ-layers. Each iPSC clone differentiated efficiently to mesenchymal progenitor cells (MPC) as determined by surface marker expression and RNAseq analysis. We identified supercentenarian and HGPS associated gene expression patterns in the differentiated MPC lines that were not evident in the parental iPSC lines. Importantly, telomere length resetting occurred in iPSC from all donors albeit at a lower incidence in supercentenarian iPSCs. These data indicate the potential to use reprogramming to reset both developmental state and cellular age in the “oldest of the old.” We anticipate that supercentenarian iPSC and their differentiated derivatives will be valuable tools for studying the underlying mechanisms of extreme longevity and disease resistance.

46

Genetic amplification, overexpression, and increased signaling from the epidermal growth factor receptor (EGFR) are often found in oral squamous cell carcinoma (OSCC) and thus EGFR is frequently targeted molecularly by the therapeutic antibody cetuximab. We assessed effects of cetuximab in control of EGF-driven malignant traits of OSCC cells. EGF stimulation promoted progression level of mesenchymal traits in OSCC cells, which were attenuated by cetuximab but incompletely. We pursued a potential mechanism underlying such incomplete attenuation of OSCC malignant traits. Cetuximab promoted secretion of EGFR-EVs by OSCC cells and failed to inhibit EGF-driven secretion of EGFR-EVs. Cetuximab was also found to be robustly secreted with the EGFR-EVs by the OSCC cells. Thus, EGF promotes the level of mesenchymal traits of OSCC cells and secretion of EGFR-EVs, which involve cetuximab resistance.

31

SARS-CoV-2 is a novel coronavirus which has caused the COVID-19 pandemic. Other known coronaviruses show a strong pattern of seasonality, with the infection cases in humans being more prominent in winter. Although several plausible origins of such seasonal variability have been proposed, its mechanism is unclear. SARS-CoV-2 is transmitted via airborne droplets ejected from the upper respiratory tract of the infected individuals. It has been reported that SARS-CoV-2 can remain infectious for hours on surfaces. As such, the stability of viral particles both in liquid droplets as well as dried on surfaces is essential for infectivity. Here we have used atomic force microscopy to examine the structural stability of individual SARS-CoV-2 virus like particles at different temperatures. We demonstrate that even a mild temperature increase, commensurate with what is common for summer warming, leads to dramatic disruption of viral structural stability, especially when the heat is applied in the dry state. This is consistent with other existing non-mechanistic studies of viral infectivity, provides a single particle perspective on viral seasonality, and strengthens the case for a resurgence of COVID-19 in winter.

29

Exercise enhances insulin sensitivity in skeletal muscle, but the underlying mechanism remains obscure. Recent data suggest that alternatively activated M2 macrophages enhance insulin sensitivity in insulin target organs such as adipose tissue and liver. Therefore, the aim of this study was to determine the role of anti-inflammatory M2 macrophages in exercise-induced enhancement of insulin sensitivity in skeletal muscle. C57BL6J mice underwent a single bout of treadmill running (20 m/min, 90 min). Twenty-four hours later, ex vivo insulin-stimulated 2-deoxy glucose uptake was found to be increased in plantaris muscle. This change was associated with increased number of CD163-expressing macrophages (i.e., M2-polarized macrophages) in skeletal muscle. Systemic depletion of macrophages by pretreatment of mice with clodronate-containing liposome abrogated both CD163-positive macrophage accumulation in skeletal muscle as well as the enhancement of insulin sensitivity after exercise, without affecting insulin-induced phosphorylation of Akt and AS160 or exercise-induced GLUT4 expression. These results suggest that accumulation of M2-polarized macrophages is involved in exercise-induced enhancement of insulin sensitivity in mouse skeletal muscle, independently of the phosphorylation of Akt and AS160 and expression of GLUT4.

Concepts: Insulin, Glucose, Obesity, Muscle, Cardiac muscle, Insulin resistance, Adipose tissue, Glycogen

28

Meteorin and its homologue meteorin-like (metrnl) are two novel proteins regulating glial cell differentiation in central nervous system. However, the roles of meteorin and metrnl in other organs or tissues have never been studied. In this study, we showed that meteorin and metrnl were expressed abundantly in white adipose, including visceral and subcutaneous adipose tissues, but to a much lesser extent in brown adipose tissue. Meteorin and metrnl were found to be secreted by explanted human white fat pads, 3T3-L1 preadipocytes and differentiated 3T3-L1 adipocytes. Moreover, meteorin and metrnl were detected in human blood by immunoblotting assay. The mRNA expression of meteorin and metrnl increased along with the 3T3-L1 cells differentiation. Overexpression of meteorin and metrnl using adenovirus promoted the formation of lipid droplets, increased PPARγ protein expression and enhanced mRNA expression of several other adipogenic genes in 3T3-L1 adipocytes. Injection of adipose-specific aP2-promoter driven adenovirus expressing meteorin and metrnl markedly improved global insulin sensitivity and reversed insulin resistance induced by high fat diet in mice. At last, overexpression of meteorin and metrnl further magnified the phosphorylation of Akt upon insulin stimuli in 3T3-L1 cells. Collectively, our data suggests that meteorin and metrnl are two novel pro-differentiative adipokines participating in adipogenesis and regulation of insulin sensitivity.

Concepts: DNA, Protein, Gene expression, Cellular differentiation, Adipose tissue, Tissues, Tissue, Adipocyte

28

Cells move along surfaces both as single cells and multi-cellular units. Recent research points toward pivotal roles for water flux through aquaporins (AQPs) in single cell migration. Their expression is known to facilitate this process by promoting rapid shape changes. However, little is known about the impact on migrating epithelial sheets during wound healing and epithelial renewal. Here, we investigate and compare the effects of AQP9 on single cell and epithelial sheet migration. To achieve this, MDCK-1 cells stably expressing AQP9 were subjected to migration assessment. We found that AQP9 facilitated cell locomotion at both the single and multi-cellular level. Furthermore, we identified major differences in the monolayer integrity and cell size upon expression of AQP9 during epithelial sheet migration, indicating a rapid volume-regulatory mechanism. We suggest a novel mechanism for epithelial wound healing based on AQP-induced swelling and expansion of the monolayer.

Concepts: DNA, Gene, Cell nucleus, Cell, Organism, Wound healing, Epithelium, Multicellular organism

28

Type VII collagen (Col7) is the major component of anchoring fibrils and very important for skin integrity. This is emphasized by the Col7 related skin blistering diseases dystrophic epidermolysis bullosa and epidermolysis bullosa acquisita. Structural data that provides insights into the interaction network of Col7 and thus providing a basis for a better understanding of the pathogenesis of the diseases is missing. We proved that the von-Willebrand-factor A like domain 2 (vWFA2) of Col7 is responsible for type I collagen binding. The interaction has a K(D) value of 90 μM as determined by SPR and is enthalpy driven as derived from the van’t Hoff equation. Furthermore, a hitherto unknown interaction of this domain with type IV collagen was identified. The interaction of vWFA2 with type I collagen is sensitive to the presence of magnesium ions, however, vWFA2 does not contain a magnesium binding site thus magnesium must bind to type I collagen. A lysine residue has been identified to be crucial for type I collagen binding. This allowed localization of the binding site. Mutational analysis suggests different interaction mechanisms in different species and that these interactions might be of covalent nature.

Concepts: Protein, Collagen, Atom, Epidermolysis bullosa, Structural proteins, Epidermolysis bullosa acquisita, Epidermolysis bullosa dystrophica, Van 't Hoff equation

28

The voltage-dependent anion channel (VDAC) and the adenine nucleotide translocase (ANT) have central roles in mitochondrial functions such as nucleotides transport and cell death. The interaction between VDAC, an outer mitochondrial membrane protein and ANT, an inner membrane protein, was studied in isolated mitochondria and in vitro. Both proteins were isolated from various mitochondrial sources and reconstituted in vitro using a biomimetic system composed of recombinant human VDAC isoform 1 (rhVDAC1) immobilized on a surface plasmon resonance (SPR) sensor chip surface. Two enriched-preparations of (H)ANT (ANT from heart, mainly ANT1) and (L)ANT (ANT from liver, mainly ANT2) isoforms interacted differently with rhVDAC1. Moreover, the pharmacological ANT inhibitors atractyloside and bongkrekic acid modulated this interaction. Thus, ANT-VDAC interaction depends both on ANT isoform identity and on the conformation of ANT.

Concepts: DNA, Cell, Metabolism, Adenosine triphosphate, Mitochondrion, Cytoplasm, Citric acid cycle, Translocase of the outer membrane