Question

give at least 4 examples of viral diseases exemplifying how the surface proteins facilitate gaining entry to target the cell

Answer 1

The vicious pathogens known as viruses are active once inside a living cell. There are various types of virus and their sub-types that gain entry by using the cellular communication pathways and cell surface proteins. These hijackers gain entry to a cell and then captures their host's cellular machinery to make their own lifeboats and build themselves up. Very common examples are HIV, West Nile virus, Influenza virus, Ebola virus etc.

The infectious viral particle called virion is the one that takes gain to the entry site and causes the chain of havoc. Let us then examine some of the entry through the use of host surface proteins.

One of the most popular and common types of entry is discussed through the 'endosymbiotic theory'. In this mechanism, seen in the case of Influenza and HIV virus, the particles attach itself to the cell membrane receptors, fusing (receptor-mediated fusion) through that or being swallowed into an endosome. The virus binds to a protein in the cell membrane and does a conformational change that allows them to go inside.

The endosome fusion is based on the understanding that virus coat proteins, generally the envelope surrounding them is a lipid layer and the host cell membrane is also lipid in nature. The attachment to the cell surface receptor with the protruding viral protein, this is recognition. Then the lipid bilayers are induced through the act of viral protein and once they match they are fuses with the host lipid layer and put their viral protein inside the cell.

1. Influenza (RNA virus) is an enveloped virus, it encodes a unique fusion protein called hemagglutinin (HA),

2. HIV (Retroviruses transcribe RNA) is also an enveloped virus, it encodes a unique fusion protein called glycoproteins for HIV (Env),

3. Ebola has enveloped viruses too, they encode a unique fusion protein called glycoprotein for Ebola (GP).

4. In the case of West Nile virus (is a neurotropic RNA virus)- gain advantage through receptor-mediated endocytosis after virus attachment to the cell surface. Host cell surface mannose receptors are one of the modes for them to gain access.