The role of plasma membrane calcium ATPase 4 (PMCA4) in modulating Plasmodium infection and malaria severity

Malaria is a major public health problem in many parts of the world including Indonesia, causing an estimated 150-300 million clinical cases and killing more than 430 thousand people annually (WHO Report, 2015). Strategies to control malaria that have demonstrated some success include anti-malaria treatment for infected individuals, application of insecticide to reduce mosquito populations, and reduction of human contact with infected mosquitoes via bednets. However, the rapid spread of parasite resistance to the currently available anti-malarial drugs has hampered large-scale efforts at malaria control within the last few years. Development of new anti-malarial drugs that target novel biochemical pathways is needed to avoid cross resistance.

Recent genetic studies in human populations have identified a calcium pump called PMCA4 that is present in human red blood cells and in cells lining the blood vessels (endothelium) to have a very strong association with resistance against malaria infection and the occurrence of brain malaria. These findings imply that PMCA4 can be used as a possible target for anti-malaria treatment and for the reduction of cerebral malaria, the most deadly complication of this disease.

Pilot observations conducted through a collaboration between scientists at The University of Manchester and Eijkman Institute Indonesia have demonstrated that treatment with drugs that inhibit PMCA4 activity might reduce malaria infection in a mouse model as well as in a cell culture system. Based on this promising preliminary result, in this project we will further investigate whether: 1) Inhibition of PMCA4 genetically in mice will inhibit the growth of malaria parasite (Plasmodium) and reduce the occurrence of experimental brain malaria 2) Inhibition of PMCA4 using a potent and specific pharmacological inhibitor will inhibit the growth of malaria parasite (Plasmodium) in mice and reduce the occurrence of experimental brain malaria 3) In the Indonesian population genetic variations in the PMCA4 gene are associated with resistance against malaria and severity of the disease.

It is expected that this study will provide new information on how malaria infection is regulated at the molecular level. If our hypothesis is correct this project may identify a novel pharmacological target for malaria treatment.

Background: Malaria is one of the biggest killers in developing countries worldwide. The rapid growth of parasite resistance to available anti-malarial drugs has become a major problem in controlling the disease. Therefore, development of new anti-malarial drugs that target novel biochemical pathways is needed.

Scientific rationale: Recent genome wide analysis studies (GWAS) have identified the plasma membrane calcium ATPase 4 (PMCA4) as a powerful determinant of the susceptibility to malaria infection and the development of cerebral malaria in human patients. Consistently, our preliminary data has also shown that pharmacological inhibition of PMCA4 reduces Plasmodium infection in a mouse model of malaria as well as in human parasite P. falciparum in vitro culture.

Plan of research: To further study the role of PMCA4 in mediating resistance and severity of malaria we will use mice with genetic ablation of the Pmca4 gene. We will examine if Pmca4 deletion in mice will result in the reduction of parasite burden as well as prevention of the development of experimental cerebral malaria (ECM). In addition, we will also test if treatment with novel PMCA4 inhibitors, which were identified in our laboratory, will reduce parasite infection and the occurrence of ECM in mice. Lastly, we will also study the association between human PMCA4 gene polymorphisms with malaria severity in an Indonesian population and analyse the functional implications of the polymorphisms at molecular level.

Outcomes: This study will provide information on the mechanisms through which PMCA4 interferes with the dynamics of malaria infection and its severity. It may also identify PMCA4 as a novel target for malaria treatment.

This project will benefit scientists, academics and clinicians working in the field of infectious disease and malaria. It will yield new information on the role of the plasma membrane calcium ATPase 4 (PMCA4) in determining malaria resistance and severity. It will also provide a mechanistic explanation on how human PMCA4 genetic polymorphisms are associated with malaria. This will impact academics by providing a new biological concept in the understanding of malaria resistance and severity and by stimulating future studies in elucidating the role of calcium signalling during malaria infection.

The research will also provide information as to whether pharmacological inhibition of PMCA4 will reduce malaria infection and/or severity. This will impact pharmacological and drug development companies by providing a new concept in malaria therapy, i.e. by targeting the host's cells as opposed to targeting the parasite.

The existing strong collaboration between the University of Manchester and Eijkman Institute provides opportunities for knowledge and technology transfer between these two institutions. This will impact on both young scientists as well as established researchers in these institutions to share knowledge and ideas and develop further collaborations in the future.

Finally, in the long-term future the success of this research may also impact on the global effort in eradicating malaria by providing a new way to control malaria infection. This will benefit malaria patients and all of the people living in the malaria endemic areas worldwide.