Pinosomes help a virus escape

Many virus species are taken into their host via receptor-mediated endocytosis, after which the virus particle is temporarily contained within endosomes. For genome propagation, most viruses must escape into the cytosol. New results from Meier et al. (page 1119) explain how Adenovirus type 2 (Ad2), one of the most rapidly escaping viruses known, tricks the cell into helping it break free.

Meier et al. first show that Ad2 enters in clathrin- dependent endosomes. But subsequent escape from the endosomes is dependent on pinocytosis, a process by which extracellular material is taken in within enclosed lamellipodia at ruffling membranes. Ad2 initiates integrin signaling and thus pinocytosis at the plasma membrane. It also triggers pinosomal lysis, again apparently from the cell surface, as internalized viral particles were not required.

The virus is not taken in by pinocytosis, so what...