Host cell proteases can process viral capsid proteins

Enteroviruses are the most common viruses infecting humans. Although most of the diseases that enteroviruses cause are symptomless or mild, enteroviruses can also cause more severe diseases.

Calpains are common host cell proteases, ubiquitous in the cell cytoplasm. The group of Docent Varpu Marjomäki has shown earlier that inhibition of calpain proteases very efficiently stops enterovirus infection. The work done now sheds light to the mechanism of the inhibitory effect. The work suggests that enteroviruses have learnt through evolution to take advantage of the cellular resources for their own benefit.

"We showed that calpain proteases can cut out viral capsid proteins from the larger polyprotein, and thus have the potential to contribute to the assembly of new viruses," says Docent Varpu Marjomäki.

The work done is very interesting as suggested by the eminent virologist Dr. Marco Vignuzzi from Pasteur-Institute, Paris.

"I consider this an outstanding observation and very significant first demonstration that will lead to significant advances in the field. It may very likely be that this mechanism of cleavage is also used by viruses in other viral families," Vignuzzi says.

According to Vignuzzi the work is to be considered to be one of the most interesting things that will be published this year in picornavirus research. This work was part of Mira Laajala´s dissertation at 22.11.2019 in Marjomäki´s group. Laajala showed further that calpain proteases have cross-reactivity against viral proteases as well. Inhibition of calpain proteases thus offers a future possibility to develop anti-viral therapies based on calpains.