Role of endosomes in simian virus 40 entry and infection.

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.

GM1 structure determines SV40-induced membrane invagination and infection.

Incoming simian virus 40 (SV40) particles enter tight-fitting plasma membrane invaginations after binding to the carbohydrate moiety of GM1 gangliosides in the host cell plasma membrane through pentameric VP1 capsid proteins. This is followed by activation of cellular signalling pathways, endocytic internalization and transport of the virus via the endoplasmic reticulum to the nucleus. Here we show that the association of SV40 (as well as isolated pentameric VP1) with GM1 is itself sufficient to induce dramatic membrane curvature that leads to the formation of deep invaginations and tubules not only in the plasma membrane of cells, but also in giant unilamellar vesicles (GUVs).

Staining patterns of keratins in the human urinary tract.

The keratins, members of the intermediate filament family, are characteristically expressed in epithelial cells. In the various types of epithelia, the keratin expression pattern is characterized by cell-type specific combinations of the keratin isotypes with a plain pattern in monolayered (simple) epithelia and more complex patterns in stratified and pseudostratified epithelia. Here we demonstrate that the transitional epithelium of the human urinary tract holds an exceptional position between the pseudostratified and stratified epithelia.

Adeno-associated virus type 5 exploits two different entry pathways in human embryo fibroblasts.

The helper-dependent adeno-associated viruses (AAVs) have attracted great interest as vectors for gene therapy. Uptake and intracellular trafficking pathways of AAV are of importance, since they are often rate-limiting steps in infection. Here, we have investigated the entry of AAV type 5 (AAV5) in primary human embryo fibroblasts.