Three-dimensional model may lead to the formulation of a drug against the disease.
Article by Maria Guimarães – Pesquisa FAPESP Magazine – March 27, 2017 (see link below)
The three-dimensional structure of NS5 is described as a hand, with palm, thumb and three fingers.
With its diminutive size, a mosquito can cause considerable fear. Especially if, after a bite crushed with a slap it display striped legs. And even more so if who took the sting are pregnant. The mosquito Aedes aegypti, transmitter of viruses causing zika, dengue and chikungunya, is indeed a fearsome enemy. For this reason, physicist Glaucius Oliva, a professor at the Institute of Physics of São Carlos campus of the University of São Paulo (IFSC-USP) and coordinator of the Center for Research and Innovation in Biodiversity and Drug Discoverys (CIBFar), dreams of a drug that can be used after the bite or as soon as symptoms appear, in order to block the proliferation of viruses and accelerate healing. His group has just taken the first step in this search: it unraveled the three-dimensional structure of the protein most crucial to the replication of the genetic material of the virus, as described in an article published (27/3) in the journal Nature Communications.
“We seek the development of drugs through the modeling of molecules that interact with specific receptors,” says Oliva. CIBFar is one of the Research, Innovation and Dissemination Centers (Cepids) financed by FAPESP. “But we had never worked with viruses until the formation of the Zika Network (see Pesquisa FAPESP nº 239).
The urgency of the research caught the attention of the researcher, who began to coordinate the molecular modeling of the proteins encoded by the genome of the zika virus. It is a rather short molecule of RNA that carries the code for 10 proteins: three structural, responsible for the physical structure that surrounds the genetic material, and seven non-structural, associated with the replication of viral RNA. “The heart of the replication complex is the NS5 protein, a polymerase enzyme that uses RNA itself as a template to produce copies,” explains Oliva. It is this protein that his group has characterized, and is intended to target as a drug development.
To reach the structure, it was necessary to clone the RNA, a step made in partnership with Cellco, a company created and incubated at USP in São Carlos by three former IFSC doctoral students with the objective of offering solutions for biotechnology research laboratories. After synthesizing the gene, in order to work not directly with the virus, and to produce the protein, it was necessary to form crystals with the molecule, a way to enable the investigation of its configuration through X-ray crystallography. With this, it was possible to get to the detail on the smallest possible scale, with the location of each of the thousands of atoms that make up the protein.
With this model, it remains a way to interfere with the functioning of the polymerase and prevent genetic replication. Researchers in São Carlos are not the first to adopt this strategy. “Pharmaceuticals Novartis has been trying for years to produce a drug against dengue by focusing on the virus’s NS5,” says Oliva. Although the company has another scale in terms of financial resources and facilities, if compared to the university, it does not feel at a disadvantage. “What they do, we also do in the search for a molecule that blocks the active site of the protein,” he says. He already knows, in the comparison between the protein of the zika virus and that of the dengue virus, that the respective active sites present important differences. The drug that the CIBFar group seeks, therefore, would be specific to zika. With the publication of the crystallized structure, he hopes to contribute to a race in which different laboratories will seek new inhibitors for the NS5 enzyme, candidates for treatment for the disease.
The widespread interest in this type of approach, and this specifically protein, is in the list of articles published in the same day by Nature Communications: in addition to the work of the USP group, two others run in US universities (see there e there) they also bring the structure of NS5. “The conclusions of the three articles are very similar,” Oliva compares. But he points out that the analysis done in São Carlos has better resolution, an accuracy that may be important in modeling drugs based on receptor structure.
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