How non-enveloped viruses overcome host cell membranes is poorly understood. Here, we show that after endocytosis and transport to the endoplasmic reticulum (ER), but before crossing the ER membrane to the cytosol, incoming simian virus 40 particles are structurally remodelled leading to exposure of the amino-terminal sequence of the minor viral protein VP2. These hydrophobic sequences anchor the virus to membranes. A negatively charged residue, Glu 17, in the α-helical, membrane-embedded peptide is essential for infection, most likely by introducing an 'irregularity' recognized by the ER-associated degradation (ERAD) system for membrane proteins. Using a siRNA-mediated screen, the lumenal chaperone BiP and the ER-membrane protein BAP31 (both involved in ERAD) were identified as being essential for infection. They co-localized with the virus in discrete foci and promoted its ER-to-cytosol dislocation. Virus-like particles devoid of VP2 failed to cross the membrane. The results demonstrated that ERAD-factors assist virus transport across the ER membrane.

After binding to its cell surface receptor ganglioside GM1, simian virus 40 (SV40) is endocytosed by lipid raft-mediated endocytosis and slowly transported to the endoplasmic reticulum, where partial uncoating occurs. We analyzed the intracellular pathway taken by the virus in HeLa and CV-1 cells by using a targeted small interfering RNA (siRNA) silencing screen, electron microscopy, and live-cell imaging as well as by testing a variety of cellular inhibitors and other perturbants. We found that the virus entered early endosomes, late endosomes, and probably endolysosomes before reaching the endoplasmic reticulum and that this pathway was part of the infectious route. The virus was especially sensitive to a variety of perturbations that inhibited endosome acidification and maturation. Contrary to our previous models, which postulated the passage of the virus through caveolin-rich organelles that we called caveosomes, we conclude that SV40 depends on the classical endocytic pathway for infectious entry.To enter their host cells, the majority of animal viruses take advantage of endocytic mechanisms offered by the cell (23, 39). Penetration into the cytosol usually occurs from endosomes, often triggered by the low lumenal pH. However, there are viruses that deviate from this standard itinerary. These viruses include members of the polyomavirus family, such as mouse polyomavirus (mPy) and simian virus 40 (SV40). These viruses are nonenveloped DNA viruses that replicate in the nucleus. The interest and importance of this virus family are rapidly growing with the increasing number of human polyomaviruses identified. The most recently discovered human pathogens include KI polyomavirus (KIPyV), WU polyomavirus (WUPyV), and Merkel cell polyomavirus (MCPyV) (1,17,20). MCPyV is associated with the aggressive neuroendocrine skin cancer Merkel cell carcinoma.Most polyomaviruses bind to gangliosides on the cell surface and are internalized into small tight-fitting vesicles devoid of a clathrin coat (26,28,30,34,55,59). Instead of using endosomes for penetration, they travel to the lumen of the endoplasmic reticulum (ER), in which they are activated by lumenal thiol oxidoreductases and chaperones before penetrating into the cytosol or possibly directly into the nucleoplasm (28,37,46,53).In this study, we focus on SV40, a virus that binds to GM1 and is internalized via caveola/lipid raft-dependent endocytic mechanisms (2,11,45,57,59). Some virus particles are endocytosed via caveolae, and others enter through a parallel clathrin-and caveolin-independent mechanism. Uptake is slow and nonsynchronous, with transfer into the ER and penetration through the ER membrane occurring several hours after the initial endocytosis (53).Exactly where SV40 spends the intervening hours is not clear. Unlike ER-targeted bacterial toxins such as cholera toxin and Shiga toxin, the virus particles are not observed in the trans-Golgi network or the cisternae of the Golgi complex. Some of them are seen in early endosomes (EEs) by confocal and electron ...

Elucidating the biology of yeast in its full complexity has major implications for science, medicine and industry. One of the most critical processes determining yeast life and physiology is cellular demise. However, the investigation of yeast cell death is a relatively young field, and a widely accepted set of concepts and terms is still missing. Here, we propose unified criteria for the definition of accidental, regulated, and programmed forms of cell death in yeast based on a series of morphological and biochemical criteria. Specifically, we provide consensus guidelines on the differential definition of terms including apoptosis, regulated necrosis, and autophagic cell death, as we refer to additional cell death routines that are relevant for the biology of (at least some species of) yeast. As this area of investigation advances rapidly, changes and extensions to this set of recommendations will be implemented in the years to come. Nonetheless, we strongly encourage the authors, reviewers and editors of scientific articles to adopt these collective standards in order to establish an accurate framework for yeast cell death research and, ultimately, to accelerate the progress of this vibrant field of research.

A large set of high-content RNAi screens investigating mammalian virus infection and multiple cellular activities is analysed to reveal the impact of population context on phenotypic variability and to identify indirect RNAi effects.

Increasing deforestation affects tropical forests, threatening the livelihoods of local populations who subsist on forest resources. The disappearance of wild plants and animals and the increasing influence of market economies affect local health, well-being, and diet. The impact of these changes on wild meat consumption has been well documented, but little attention has been given to wild edible plants, despite their importance as sources of calories and micronutrients. Furthermore, the relationships among food behavior strategies adopted by local populations, their psycho-cultural representations of food, and their food preferences have been poorly explored. In this study, we investigate food behaviors with an emphasis on the role of wild edible plants among a forager-horticulturalist society from the Congo Basin: the Baka. By combining an ethnobotanical survey with data from interviews (n = 536) related to food behaviors and representations of food, our data show that the Baka valorize both agricultural and marketable foods, and that wild plants represent a minor part of their diet, both in frequency and diversity. Finally, by examining how some wild edible plants have shifted from being eaten to being sold, we explore how market-oriented uses of wild edible plants may affect dietary behaviors and biocultural resilience.