Unconventional COPII-mediated secretory protein trafficking continues in the absence of the Sar1 GTPase

Coat protein complex II (COPII) plays an integral role in the packaging of secretory cargoes within membrane-enclosed transport carriers that leave the endoplasmic reticulum (ER) from discrete membrane subdomains. Lipid bilayer remodeling necessary for this process is driven initially by membrane penetration of the coat subunit Sar1 and further stabilized by assembly of a multi-layer complex of several COPII proteins. However, the relative contributions of these distinct factors to transport carrier formation and protein trafficking remain unclear. Here, we demonstrate that anterograde cargo transport from the ER continues in the absence of Sar1, although the unconventional carriers that form fail to efficiently deliver their contents to subsequent compartments in the secretory pathway. Instead, cargoes accumulate immediately adjacent to the perinuclear Golgi under these conditions, together with components of the COPII coat. Our findings highlight new mechanisms by which COPII promotes transport carrier biogenesis and strongly suggests that the Sar1 GTPase plays a critical role in transport carrier uncoating ahead of membrane fusion and secretory cargo delivery at acceptor compartments.

Identification of Factors to Improve Public Transit Services (A Case Study of Prithvi Chowk to Talchowk Section of Prithivi Highway)

This research presents studies on a segment of highway to determine the quantitative factors that inuence transit services. Travel time and delay study is one of the method to determine quantitative factors. Tour time is described as the average period of time required to journey from one region to some other. Total departure time consists of gadgets which include total working time, places and general delay time. The examine section was done in Prithvi chowk to Tal chowk of Prithvi Highway which is turned to be 12.5 km long. Additionally, it has been found that the principle variables affecting travel time are: postpone time because of forestall selecting and choosing up passengers, bus model and bus size.32 trips public transport carrier and a 10 trips non-public automobile journey have been held during peak hours. Models are developed the use of SPSS software to become aware of the relationship between the causes of delays and the overall-time delays. Travel time and learning delays can help reduce the number of private vehicles operating and increase the number of public vehicles in order to reduce congestion and improve the e efficiency of the public transport system. It turned into determined that there was a full-size distinction in tour time among the use of the public transit services and the car.

Sustainable Transport of Goods Using Combined Transport Solutions: The Case of EU

This paper analyzes the importance of bimodal solutions in the rail-road transport of goods with an emphasis on the aspect of ecology within the geographical region of EU-28. Using the panel regression analysis in the period from 2010 to 2019, we are trying to confirm the dependence between the road and rail transport of goods by applying several freight units’ measures: the freight transport performance in tonne-kilometres, the freight transport performance in tonne-kilometres per thousand of USD, and the amount of goods transported in thousands of tonnes. The application of data to all selected freight units’ measures in the regression models confirms a relationship between road and rail transport. A direct relationship between these two modes of transport confirms the complementarity effect, which means that, in most cases, the goods transport solutions require the combination of road and rail mode, where the railway should be considered as the main transport/carrier, the road transport, however, should have the role of short pre-transport or post-transport. The ecological aspect of such bimodal solutions can also be emphasized since the railway transport is considered as an ecological mode.

Influencing Factors, Energy Consumption, and Carbon Emission of Central Heating in China: A Supply Chain Perspective

The rapid growth of energy demand in China’s central heating sector and the large differences in regions have posed challenges to its energy supply safety, which affected the progress of China’s energy transformation. From a supply chain perspective, this study uses the feasible generalized least squares method to conduct empirical research on the central heating data of 17 provinces in China from 2006 to 2017. The results shows that the main factors of central heating includes energy consumption structure, heat generation method, heat transport carrier, heating degree days and heating area; The main factor that increases the energy consumption of central heating in each province is the same, namely Heating area (HA). However, the main factors that reduce energy consumption in each province are different; using gas instead of coal for clean heating can reduce some greenhouse gas emissions while bringing huge gas supply pressure. According to the results, this study provides some policy suggestions.

The Small GTPase Arf6 Functions as a Membrane Tether in a Chemically-Defined Reconstitution System

Arf-family small GTPases are essential protein components for membrane trafficking in all eukaryotic endomembrane systems, particularly during the formation of membrane-bound, coat protein complex-coated transport carriers. In addition to their roles in the transport carrier formation, a number of Arf-family GTPases have been reported to physically associate with coiled-coil tethering proteins and multisubunit tethering complexes, which are responsible for membrane tethering, a process of the initial contact between transport carriers and their target subcellular compartments. Nevertheless, whether and how indeed Arf GTPases are involved in the tethering process remain unclear. Here, using a chemically-defined reconstitution approach with purified proteins of two representative Arf isoforms in humans (Arf1, Arf6) and synthetic liposomes for model membranes, we discovered that Arf6 can function as a bona fide membrane tether, directly and physically linking two distinct lipid bilayers even in the absence of any other tethering factors, whereas Arf1 retained little potency to trigger membrane tethering under the current experimental conditions. Arf6-mediated membrane tethering reactions require trans-assembly of membrane-anchored Arf6 proteins and can be reversibly controlled by the membrane attachment and detachment cycle of Arf6. The intrinsic membrane tethering activity of Arf6 was further found to be significantly inhibited by the presence of membrane-anchored Arf1, suggesting that the tethering-competent Arf6-Arf6 assembly in trans can be prevented by the heterotypic Arf1-Arf6 association in a cis configuration. Taken together, these findings lead us to postulate that self-assemblies of Arf-family small GTPases on lipid bilayers contribute to driving and regulating the tethering events of intracellular membrane trafficking.

The impact of the COVID-19 pandemic on the business models of regular air carriers

This paper analyzes the changing characteristics of air transportation business models due to the COVID-19 pandemic. These characterics differ with each kind of the air transport carrier. It was possible to observe the changes of the business models characteristics even sooner, during the hybridization. As regards the business models hybridization, it's given that with individual type of carriers it's rather natural activity, resulting from the need of increasing profits, reducting costs or simply the effort to successfully enter the different market. With the business model characteristic changes due to the pandemics it's rather about the forced changes triggered by the need to adapt to the current situation. Each air transport carrier bussiness model characteristics are introduced, followed up by the analysis of their changes. These changes were or are induced by the need to adapt or to completely change their behavior in the pandemic affected time. The analytical part of the paper provides easily understandable results of the air transport carrier’s behavior. It is possible to observe what the carriers are capable and willing to undertake in order to keep the customer. This paper ultimately introduces the forced changes, the air transport carriers had to accede in order to save the business from bankruptcy as well as how it would be possible to adapt their provided services in future.

The small GTPase Arf6 functions as a membrane tether in a chemically-defined reconstitution system

Arf-family small GTPases are essential protein components for membrane trafficking in all eukaryotic endomembrane systems, particularly during the formation of membrane-bound, coat protein complex-coated transport carriers. In addition to their roles in the transport carrier formation, a number of Arf-family GTPases have been reported to physically associate with coiled-coil tethering proteins and multisubunit tethering complexes, which are responsible for membrane tethering, a process of the initial contact between transport carriers and their target subcellular compartments. Nevertheless, whether and how indeed Arf GTPases are involved in the tethering process remain unclear. Here, using a chemically-defined reconstitution approach with purified proteins of two representative Arf isoforms in humans (Arf1, Arf6) and synthetic liposomes for model membranes, we discovered that Arf6 can function as a bona fide membrane tether, directly and physically linking two distinct lipid bilayers even in the absence of any other tethering factors, whereas Arf1 retained little potency to trigger membrane tethering under the current experimental conditions. Arf6-mediated membrane tethering reactions require trans-assembly of membrane-anchored Arf6 proteins and can be reversibly controlled by the membrane attachment and detachment cycle of Arf6. The intrinsic membrane tethering activity of Arf6 was further found to be significantly inhibited by the presence of membrane-anchored Arf1, suggesting that the tethering-competent Arf6-Arf6 assembly in trans can be prevented by the heterotypic Arf1-Arf6 association in a cis configuration. Taken together, these findings lead us to postulate that self-assemblies of Arf-family small GTPases on lipid bilayers contribute to driving and regulating the tethering events of intracellular membrane trafficking.

Retromer forms low order oligomers on supported lipid bilayers

Retromer orchestrates the selection and export of integral membrane proteins from the endosome via retrograde and plasma membrane recycling pathways. Long-standing hypotheses regarding the retromer sorting mechanism posit that oligomeric interactions between retromer and associated accessory factors on the endosome membrane drives clustering of retromer-bound integral membrane cargo prior to its packaging into a nascent transport carrier. To test this idea, we examined interactions between components of the sorting nexin 3 (SNX3)–retromer sorting pathway using quantitative single particle fluorescence microscopy in a reconstituted system. This system includes a supported lipid bilayer, fluorescently labeled retromer, SNX3, and two model cargo proteins, RAB7, and retromer-binding segments of the WASHC2C subunit of the WASH complex. We found that the distribution of membrane-associated retromer is predominantly comprised of monomer (∼18%), dimer (∼35%), trimer (∼24%), and tetramer (∼13%). Unexpectedly, neither the presence of membrane-associated cargo nor accessory factors substantially affected this distribution. The results indicate that retromer has an intrinsic propensity to form low order oligomers on a supported lipid bilayer and that neither membrane association nor accessory factors potentiate oligomerization. The results support a model whereby SNX3-retromer is a minimally concentrative coat protein complex adapted to bulk membrane trafficking from the endosomal system.