![]() Alternately, the virus can use non-clathrin, non-caveolin-dependent pathways, both dynamin-dependent or independent (4, 5, 6). Using this pathway, the viral particles are targeted to neutral pH caveosomes or to early endosomes with moderately acid pH. Other viruses penetrate host cells via the formation of vesicles covered by caveola molecule (3). The entry of most pH-dependent viruses is mediated by the use of clathrine-coated endocytic vesicles (2). Recently, macropinocytosis has emerged as an important entry pathway for viruses (1). After binding of the particles to the cell surface entry receptor, genetic material is delivered into the cytoplasm of the cell via a specific endocytosis pathway. These pathways include RhoA- (IL-2 pathway), ARF6-, and CDC42-regulated pathway (GEEC pathway). Though poorly documented, the entry of some viruses can be mediated by numerous cargoes which can be endocytosed by mechanisms that are independent of the clathrin coat protein and the fission GTPase, dynamin. Large particles are taken up by phagocytosis, a process restricted to a few cell types. These include clathrin-mediated, macropinocytosis, caveolar/raft-mediated mechanisms, as well as several novel mechanisms. Multiple mechanisms have been defined as pinocytic, that is, they are involved in the uptake of fluids, solutes, and small particles. ![]() Viruses exploit different endocytosis pathways to enter host cells. These pseudoparticles are suitable for high-throughput screenings that help in the development of natural or artificial inhibitors as new therapeutics of the class of entry inhibitors.Ĭopyright © 2011 Elsevier Inc. Finally, we will illustrate more precisely the recent discoveries that have been made within the field of the entry process, with a focus on the use of pseudoparticles. ![]() We will describe the different entry pathways and cellular proteins that viruses have subverted to allow infection of the cell and the receptors that are used. In this chapter, we will summarize the different envelope glycoprotein structures that viruses develop to achieve membrane fusion and the entry of the virus. The comprehension of these mechanisms is essential to develop medicines of the therapeutic class of entry inhibitor like enfuvirtide (Fuzeon) against human immunodeficiency virus (HIV). Following the activation of the EnvGP either by binding to their receptors and/or sometimes the acid pH of the endosomes, many changes of conformation permit ultimately the action of a specific hydrophobic domain, the fusion peptide, which destabilizes the cell membrane and leads to the opening of the lipidic membrane. ![]() First, they acquired a domain to bind to a specific cellular protein, named "receptor." Second, they developed, with the help of cellular proteins, a function of finely controlled fusion to optimize the replication and preserve the integrity of the cell, specific to the genus of the virus. These envelope glycoproteins (EnvGP) evolved in order to combine two features. This fusion process is catalyzed by one or several viral glycoproteins incorporated on the membrane of the virus. Enveloped viruses penetrate their cell targets following the merging of their membrane with that of the cell.
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