Biomolecular condensates in membrane receptor signaling

Clustering is a prominent feature of receptors at the plasma membrane (PM). It plays an important role in signaling. Liquid–liquid phase separation (LLPS) of proteins is emerging as a novel mechanism underlying the observed clustering. Receptors/transmembrane signaling proteins can be core components essential for LLPS (such as LAT or nephrin) or clients enriched at the phase-separated condensates (for example, at the postsynaptic density or at tight junctions). Condensate formation has been shown to regulate signaling in multiple ways, including by increasing protein binding avidity and by modulating the local biochemical environment. In moving forward, it is important to study protein LLPS at the PM of living cells, its interplay with other factors underlying receptor clustering, and its signaling and functional consequences.     

Synapsin Condensates Recruit alpha-Synuclein

Neurotransmission relies on the tight spatial and temporal regulation of the synaptic vesicle (SV) cycle. Nerve terminals contain hundreds of SVs that form tight clusters. These clusters represent a distinct liquid phase in which one component of the phase are SVs and the other synapsin 1, a highly abundant synaptic protein. Another major family of disordered proteins at the presynapse includes synucleins, most notably α-synuclein. The precise physiological role of α-synuclein in synaptic physiology remains elusive, albeit its role has been implicated in nearly all steps of the SV cycle. To determine the effect of α-synuclein on the synapsin phase, we employ the reconstitution approach using natively purified SVs from rat brains and the heterologous cell system to generate synapsin condensates. We demonstrate that synapsin condensates recruit α-synuclein, and while enriched into these synapsin condensates, α-synuclein still maintains its high mobility. The presence of SVs enhances the rate of synapsin/α-synuclein condensation, suggesting that SVs act as catalyzers for the formation of synapsin condensates. Notably, at physiological salt and protein concentrations, α-synuclein alone is not able to cluster isolated SVs. Excess of α-synuclein disrupts the kinetics of synapsin/SV condensate formation, indicating that the molar ratio between synapsin and α-synuclein is important in assembling the functional condensates of SVs. Understanding the molecular mechanism of α-synuclein interactions at the nerve terminals is crucial for clarifying the pathogenesis of synucleinopathies, where α-synuclein, synaptic proteins and lipid organelles all accumulate as insoluble intracellular inclusions.     

Inter‐colony foraging area segregation quantified in small colonies of Adélie Penguins

Theoretical models on the movement of colonial animals predict that neighbouring colonies may segregate their foraging areas, and many seabird studies have reported the presence of such segregations. However, these studies have often lacked the appropriate null model to test the effect of neighbouring colonies on foraging areas, especially in small colonies or in short‐ranging species. Here, we examined the foraging areas of Adélie Penguins Pygoscelis adeliae from two neighbouring (2 km apart) colonies by using bird‐borne GPS loggers. The field study was conducted at Hukuro Cove colony (104 pairs) and Mizukuguri Cove colony (338 pairs) in Lützow‐Holm Bay, East Antarctica. We obtained GPS tracks for 504 foraging trips from 48 chick‐rearing Adélie Penguins and quantified the degree of overlap in the foraging areas between two colonies. We also produced simulated movement tracks by using correlated random‐walks assuming no inter‐colony competition and quantified the degree of overlap in the simulated foraging areas. Finally, we compared the results from real GPS tracks with those from simulated tracks to examine the effect of neighbouring colonies on Adélie Penguin movement. The results indicate that the degree of overlap was significantly smaller in real tracks than in simulated tracks. In real tracks, the foraging area of the smaller Hukuro Cove colony extended to the other side of the larger Mizukuguri Cove colony, unlike in simulated tracks. Consequently, we suggest that Adélie Penguins from two neighbouring colonies segregated their foraging areas and that the larger colony appeared to affect the foraging area of the smaller colony.     

宫腔镜下冷刀分离术与电切术治疗宫腔粘连的疗效及对宫腔形态恢复和血清白细胞介素的影响

摘要 目的：对比宫腔镜下冷刀分离术与电切术治疗宫腔粘连（IUA）的疗效及对宫腔形态恢复和血清白细胞介素的影响。方法：回顾性分析2019年4月~2021年2月期间来我院接受治疗的83例IUA患者的临床资料。根据手术方式的不同将患者分为A组（宫腔镜下电切术,40例）和B组（宫腔镜下冷刀分离术,43例）,对比两组手术时间及住院时间、宫腔形态恢复情况和血清白细胞介素变化,观察两组术后并发症发生率、月经改善率和宫腔再粘连发生率。结果：B组手术时间、住院时间短于A组（P<0.05）。B组总有效率、内膜创面上皮化愈合满意率均高于A组（P<0.05）。两组血清白细胞介素-6（IL-6）、白细胞介素-8（IL-8）水平升高,但B组低于A组（P<0.05）。两组血清白细胞介素-4（IL-4）、白细胞介素-10（IL-10）降低,但B组高于A组（P<0.05）。两组术后并发症发生率组间对比无统计学差异（P>0.05）。B组月经改善率高于A组,宫腔再粘连发生率低于A组（P<0.05）。结论：与宫腔镜下电切术治疗IUA相比,宫腔镜下冷刀分离术治疗IUA手术时间、住院时间更短,宫腔形态恢复和月经改善情况更好,机体炎性反应更轻微,同时宫腔再粘连发生率更低,疗效更优。     

Geometrical optimisation of a biochip microchannel fluidic separator

This article reports on the geometric optimisation of a T-shaped biochip microchannel fluidic separator aiming to maximise the separation efficiency of plasma from blood through the improvement of the unbalanced separation performance among different channel bifurcations. For this purpose, an algebraic analysis is firstly implemented to identify the key parameters affecting fluid separation. A numerical optimisation is then carried out to search the key parameters for improved separation performance of the biochip. Three parameters, the interval length between bifurcations, the main channel length from the outlet to the bifurcation region and the side channel geometry, are identified as the key characteristic sizes and defined as optimisation variables. A balanced flow rate ratio between the main and side channels, which is an indication of separation effectiveness, is defined as the objective. It is found that the degradation of the separation performance is caused by the unbalanced channel resistance ratio between the main and side channel routes from bifurcations to outlets. The effects of the three key parameters can be summarised as follows: (a) shortening the interval length between bifurcations moderately reduces the differences in the flow rate ratios; (b) extending the length of the main channel from the main outlet is effective for achieving a uniformity of flow rate ratio but ineffective in changing the velocity difference of the side channels and (c) decreasing the lengths of side channels from upstream to downstream is effective for both obtaining a uniform flow rate ratio and reducing the differences in the flow velocities between the side branch channels. An optimisation process combining the three parameters is suggested as this integration approach leads to fast convergent process and also offers flexible design options for satisfying different requirements.     

Integration of geometric separation mechanisms by implementing curved constrictions in a biochip microchannel fluidic separator

This paper investigates the effectiveness of using curved constrictions in the bifurcation region of T-type fluid separators for promoting flow development in the intervals between bifurcations. A design of biofluid separator is proposed and a mathematical analysis and a numerical simulation of the blood flow in microchannels are conducted. The design is based on a modification of an existing T-shaped biochip device which consists of a main channel and a series of perpendicularly positioned side channels. By means of bifurcation effect, the blood is separated into plasma concentration flow from the side channels and blood cell concentration flow from the main channel. In this design, curved constrictions are inserted between bifurcations to replace the original straight channel section, so that the constriction and curved channel effects can be induced apart from the existing bifurcation effect. The mathematical analysis is aimed to the flow field and shear stress of the blood fluid in the microchannel geometries employed in the current design, including bifurcation, constriction and curved channel. The numerical simulation and mathematical analysis result in agreed conclusions, giving some insights into the importance of the relevant geometries in promoting biofluid separation. The main results can be summarised as follows: (i) the constrictions can largely increase the shear stress by the ratio of square of the reduction of the sections between the constriction and parent main channel. (ii) The curved channel intervals can induce centrifugal force, smoothly transit the flow field and increase the chances depleting fluid from the cell-free layer. (iii) The thickness of the boundary layer skimmed into the side channels from the main channel is decreased in this design and can be controlled, falling into the cell-free layer region by adjusting the geometry of the side channels.     

Asymmetric biocatalysis of S-3-amino-3-phenylpropionic acid with new isolated Methylobacterium Y1-6

β-amino acids are widely used in drug research, and S-3-amino-3-phenylpropionic acid (S-APA) is an important pharmaceutical intermediate of S-dapoxetine, which has been approved for the treatment of premature ejaculation. Chiral catalysis is an excellent method for the preparation of enantiopure compounds. In this study, we used (±)-ethyl-3-amino-3-phenylpropanoate (EAP) as the sole carbon source. Three hundred thirty one microorganisms were isolated from 30 soil samples, and 17 strains could produce S-APA. After three rounds of cultivation and identification, the strain Y1-6 exhibiting the highest enantioselective activity of S-APA was identified as Methylobacterium oryzae. The optimal medium composition contained methanol (2.5 g/L), 1,2-propanediol (7.5 g/L), soluble starch (2.5 g/L), and peptone (10 g/L); it was shaken at 220 rpm for 4–5 days at 30 °C. The optimum condition for biotransformation of EAP involved cultivation at 37 °C for 48 h with 120 mg of wet cells and 0.64 mg of EAP in 1 ml of transfer solution. Under this condition, substrate ee was 92.1% and yield was 48.6%. We then attempted to use Methylobacterium Y1-6 to catalyze the hydrolytic reaction with substrates containing 3-amino-3-phenyl-propanoate ester, N-substituted-β-ethyl-3-amino-3-phenyl-propanoate, and γ-lactam. It was found that 5 compounds with ester bonds could be stereoselectively hydrolyzed to S-acid, and 2 compounds with γ-lactam bonds could be stereoselectively hydrolyzed to (-)-γ-lactam.     

Protein misfolding in Dictyostelium: Using a freak of nature to gain insight into a universal problem

Abstract

Prion-like proteins can undergo conformational rearrangements from an intrinsically disordered to a highly ordered amyloid state. This ability to change conformation is encoded in distinctive domains, termed prion domains (PrDs). Previous work suggests that PrDs change conformation to affect protein function and create phenotypic diversity. More recent work shows that PrDs can also undergo many weak interactions when disordered, allowing them to organize the intracellular space into dynamic compartments. However, mutations within PrDs and altered aggregation properties have also been linked to age-related diseases in humans. Thus, the physiological role of prion-like proteins, the mechanisms regulating their conformational promiscuity and the links to disease are still unclear. Here, we summarize recent work with prion-like proteins in Dictyostelium discoideum. This work was motivated by the finding that D. discoideum has the highest content of prion-like proteins of all organisms investigated to date. Surprisingly, we find that endogenous and exogenous prion-like proteins remain soluble in D. discoideum and do not misfold and aggregate. We provide evidence that this is due to specific adaptations in the protein quality control machinery, which may allow D. discoideum to tolerate its highly aggregation-prone proteome. We predict that D. discoideum will be an important model to study the function of prion-like proteins and their mechanistic links to disease.