ESCRT proteins and cell signalling

Subunits of the endosomal sorting complex required for transport (ESCRT) were identified as components of a molecular machinery that sorts ubiquitinated membrane proteins into the intraluminal vesicles (ILVs) of multivesicular endosomes (MVEs) for subsequent delivery to the lumen of lysosomes or related organelles. As many of the membrane proteins that undergo ESCRT-mediated sorting are signalling receptors that are ubiquitinated in response to ligand binding, ESCRT subunits have been hypothesized to play a crucial role in attenuation of cell signalling by mediating ligand-induced receptor degradation. Here we discuss this concept based on the examples from loss-of-function studies in model organisms and cell lines. The emerging picture is that ESCRTs are indeed involved in downregulation of receptor signalling pathways associated with cell survival, proliferation and polarity. In addition, the recent discovery of a positive role for the ESCRT pathway in Wnt signalling through sequestration of an inhibitory cytosolic component into MVEs illustrates that ESCRTs may also control signalling in ways that are independent of degradative receptor sorting.     

Focal adhesion regulation of cell behavior

Focal adhesions lie at the convergence of integrin adhesion, signaling and the actin cytoskeleton. Cells modify focal adhesions in response to changes in the molecular composition, two-dimensional (2D) vs. three-dimensional (3D) structure, and physical forces present in their extracellular matrix environment. We consider here how cells use focal adhesions to regulate signaling complexes and integrin function. Furthermore, we examine how this regulation controls complex cellular behaviors in response to matrices of diverse physical and biochemical properties. One event regulated by the physical structure of the ECM is phosphorylation of focal adhesion kinase (FAK) at Y397, which couples FAK to several signaling pathways that regulate cell proliferation, survival, migration, and invasion.     

Pedunculopontine Nucleus Deep Brain Stimulation Improves Gait Disorder in Parkinson’s Disease: A Systematic Review and Meta-analysis

Neurochemical Research - Deep brain stimulation (DBS) of the pedunculopontine nucleus (PPN) has been proposed as a treatment strategy for gait disorder in patients with Parkinson’s disease...     

Sestrin 2 attenuates sepsis‐associated encephalopathy through the promotion of autophagy in hippocampal neurons

Sepsis‐associated encephalopathy (SAE) has typically been associated with a poor prognosis. Although sestrin 2 (SESN2) plays a crucial role in metabolic regulation and the stress response, its expression and functional roles in SAE are still unclear. In the present study, SAE was established in mice through caecal ligation and puncture (CLP). The adeno‐associated virus 2 (AAV2)‐mediated SESN2 expression (ie overexpression and knockdown) system was injected into the hippocampi of mice with SAE, and subsequently followed by electron microscopic analysis, the Morris water maze task and pathological examination. Our results demonstrated an increase of SESN2 in the hippocampal neurons of mice with SAE, 2‐16 hours following CLP. AAV2‐mediated ectopic expression of SESN2 attenuated brain damage and loss of learning and memory functions in mice with SAE, and these effects were associated with lower pro‐inflammatory cytokines in the hippocampus. Mechanistically, SESN2 promoted unc‐51‐like kinase 1 (ULK1)‐dependent autophagy in hippocampal neurons through the activation of the AMPK/mTOR signalling pathway. Finally, AMPK inhibition by SBI‐0206965 blocked SESN2‐mediated attenuation of SAE in mice. In conclusion, our findings demonstrated that SESN2 might be a novel pharmacological intervention strategy for SAE treatment through promotion of ULK1‐dependent autophagy in hippocampal neurons.     

Highly efficient soluble expression and purification of recombinant human basic fibroblast growth factor (hbFGF) by fusion with a new collagen-like protein (Scl2) in Escherichia coli

Abstract

Human basic fibroblast growth factor (hbFGF) is involved in a wide range of biological activities that affect the growth, differentiation, and migration. Due to its wound healing effects and therapy, hbFGF has the potential as therapeutic agent. Therefore, large-scale production of biologically active recombinant hbFGF with low cost is highly desirable. However, the complex structure of hbFGF hinders its high-level expression as the soluble and functional form. In the present study, an efficient, cost-effective, and scalable method for producing recombinant hbFGF was developed. The modified collagen-like protein (Scl2-M) from Streptococcus pyogenes was used as the fusion tag for producing recombinant hbFGF for the first time. After optimization, the expression level of Scl2-M-hbFGF reached approximately 0.85?g/L in the shake flask and 7.7?g/L in a high cell-density fermenter using glycerol as a carbon source. Then, the recombinant Scl2-M-hbFGF was readily purified using one-step acid precipitation and the purified Scl2-M-hbFGF was digested with enterokinase. The digested mixture was further subject to ion-exchange chromatography, and the final high-purity (96%) hbFGF product was prepared by freeze-drying. The recovery rate of the whole purification process attained 55.0%. In addition, the biological activity of recombinant hbFGF was confirmed by using L929 and BALB/c3T3 fibroblasts. Overall, this method has the potential for large scale production of recombinant hbFGF.     

Flavonoid 3′-hydroxylase of Camellia nitidissima Chi. promotes the synthesis of polyphenols better than flavonoids

Molecular Biology Reports - Camellia nitidissima Chi. is an ornamental plant of the genus Camellia L. Its flowers contain a lot of flavonoids and polyphenols. Flavonoid 3′-hydroxylase...     

The optimum dietary methionine requirement of juvenile humpback grouper (Cromileptes altivelis): effects on growth,micromorphology, protein and lipid metabolism

An 8-week feeding trial was conducted to evaluate optimum dietary methionine (Met) requirement of juvenile humpback grouper (Cromileptes altivelis) and the influence of dietary methionine (Met) supplementations on growth, gut micromorphology, protein and lipid metabolism. Seven isoproteic (48.91%) and isolipidic diets (10%) were made to contain 0.70, 0.88, 1.04, 1.27 1.46, 1.61 and 1.76% of dry matter Met levels. Results showed that lower survival, weight gain (WG%), protein efficiency ratio (PER), protein productive value (PPV) but higher daily feed intake (DFI) and feed conversion ratio (FCR) were observed in the Met deficient groups (0.70 and 0.88%). Optimum dietary Met requirement for humpback grouper was found to be 1.07% through the straight-broken line analysis of WG% against Met. Fish fed Met deficient diets (0.70, 0.88%) exhibited lower mRNA levels of growth hormone (GH), growth hormone receptor (GHR), insulin-like growth factor-I (IGF-1), target of rapamycin (TOR) as well as S6 kinase 1 (S6K1) than other dietary groups. Whereas, expression of genes related to general control nonderepressible (GCN2) kinase i.e., GCN2 and C/EBPβ enhancer-binding protein β was upregulated in fish fed low Met diets (P < 0.05). The mRNA expression of hepatic fatty acid synthase (FAS) and sterol regulatory element-binding protein-1 (SREBP-1) were higher in fish fed 0.70 and 0.88% dietary Met group and the lipolytic genes, hepatic peroxisome proliferator-activated receptor α (PPARα) and carnitine palmitoyl transferase-1 (CPT-1) showed an opposite variation tendency as FAS or SREBP1. Generally, the optimum Met requirement for humpback grouper was predicted to be 1.07% of dry matter.