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Viral entry via endocytosis. Viruses with no viral envelope enter the cell generally through endocytosis; they “trick” the host cell to ingest the virions through the cell membrane. Cells can take in resources from the environment outside of the cell, and these mechanisms may be exploited by viruses to enter a cell in the same manner as ...
Entry, or penetration, is the second step in viral replication. This step is characterized by the virus passing through the plasma membrane of the host cell. The most common way a virus gains entry to the host cell is by receptor-mediated endocytosis, which comes at no energy cost to the virus, only the host cell. Receptor-mediated endocytosis ...
Endocytosis is a cellular process in which substances are brought into the cell. The material to be internalized is surrounded by an area of cell membrane, which then buds off inside the cell to form a vesicle containing the ingested materials. Endocytosis includes pinocytosis (cell drinking) and phagocytosis (cell eating). It is a form of ...
To enter the cells, proteins on the surface of the virus interact with proteins of the cell. Attachment, or adsorption, occurs between the viral particle and the host cell membrane. A hole forms in the cell membrane, then the virus particle or its genetic contents are released into the host cell, where replication of the viral genome may commence.
Exocytosis and its counterpart, endocytosis, are used by all cells because most chemical substances important to them are large polar molecules that cannot pass through the hydrophobic portion of the cell membrane by passive means. Exocytosis is the process by which a large amount of molecules are released; thus it is a form of bulk transport.
However, receptor-mediated endocytosis is also actively implicated in transducing signals from the cell periphery to the nucleus. This became apparent when it was found that the association and formation of specific signaling complexes via clathrin-mediated endocytosis is required for the effective signaling of hormones (e.g. EGF).
Figure 3: Examples of endocytosis. The process is similar in animal cells. In most cases, rather than viral DNA being injected into an animal cell, a section of the membrane encases the virus and the cell then absorbs both the virus and the encasing section of the membrane into the cell. This process, called endocytosis, is shown in Figure 3. [5]
Firstly, there must be sufficient quantity of virus available to initiate infection. Cells at the site of infection must be accessible, in that their cell membranes display host-encoded receptors that the virus can exploit for entry into the cell, and the host anti-viral defense systems must be ineffective or absent. [3] [5]