Scientists study enzyme involved in autoimmune diseases – 02/03/2023 – Science

Involved in a series of biological processes, phosphatase enzymes are directly related to several diseases. A protein of this class, known as PTPN2 (non-receptor protein tyrosine phosphatase type 2), is highly expressed in T cells (lymphocytes) of the immune system (hence it is also known as T cell protein tyrosine phosphatase or, simply, TCPTP) and its deficiency stimulates inflammatory responses such as those that occur in cases of type 1 diabetes, rheumatoid arthritis, osteoarthritis, lupus and certain types of cancer.

Understanding its molecular mechanism in the laboratory, however, was a complex task, since its behavior was different in the organism.

Researchers from the Universities of São Paulo and the Universities of California in San Diego (United States) were able to reproduce the in vivo performance of the enzyme in the laboratory and understand its functioning, opening doors for the investigation of drugs that are effective against it. The results of the study were published in the Journal of Biological Chemistry.

Supported by Fapesp, the investigation began with an extensive search in the scientific literature so that the authors could think of strategies to be applied in in vitro assays in order to mimic the intracellular environment. This was achieved after numerous unsuccessful experimental trials.

“We discovered that, inside different human cells, PTPN2 aggregates naturally, reducing its enzymatic action, and then, in the laboratory, we made use of drugs called crowding agents, which promote this aggregation without affecting the activity of the enzyme”, explains Fábio Luis Forti, professor at the Department of Biochemistry at the Institute of Chemistry at USP (IQ-USP) and co-author of the study.

The researchers believe that this factor may explain why such a relevant enzyme is still poorly understood at the molecular level in vivo, despite being much investigated. From now on, they believe, new studies should emerge. “We were able to reproduce the same results of PTPN2 activity, including targets that are directly involved in immune responses.”

The enzyme acts directly, for example, in the JAK-STAT signaling pathway, the main one involved in gene expression aimed at immune responses. “Any chemical, physical or biological mechanism that triggers an immune response in our cells is normally mediated through this pathway”, explains Forti.

Differentiated drugs

Unlike many enzymes involved in cancer and other pathologies, which are very present or have mutations that make them very active, requiring the action of drugs that block their functioning (most drugs act in this sense), the PTPN2 gene presents polymorphisms (alternative forms of the gene) that lead to the loss of their protein function —and this is linked to the fact that they cluster naturally. That is, it is its enzymatic deficiency or ineffectiveness that causes the patient to have exacerbated inflammation and autoimmune reaction.

“Knowing this, we can better research existing oral, nasal or injectable drugs that can act directly on the activation of this enzyme in cases where it is naturally inactive, which is what happens in lupus, rheumatoid arthritis, type 1 diabetes , in certain lymphomas, in breast cancer and in glioblastoma [tumor maligno que afeta o cérebro e a coluna]”, says Fort.

“Furthermore, our work opens an interesting window of exploration for the development of new drugs that have these functions, which is what we intend to do next through screenings of libraries of synthetic and/or natural compounds by appropriate technologies based on the assays that we developed with this study”, he adds.

To contribute to the mission, the group of researchers from the United States maintains collaborations with biotechnology startups and other pharmaceutical companies that are aware of the latest discoveries related to phosphatases, which are still poorly explored pharmacological targets.

The article “Macromolecular crowding amplifies allosteric regulation of T-cell protein tyrosine phosphatase” can be read at: www.sciencedirect.com/science/article/pii /S0021925822010985?via%3Dihub.