The parasite that causes malaria requires precise control of gene expression to progress through the various stages of its complex life cycle. A new study, by a multinational team of researchers, including Penn State scientists, has gained critical insights into these regulatory control mechanisms in Plasmodium falciparum, the deadliest of the malaria parasites. The findings provide new opportunities for the development of therapeutic approaches against a disease that affects millions of people worldwide every year, according to the research team.
A paper describing the research appears today (Feb. 19) in the journal Nature.
Malaria is caused by parasites of the genus Plasmodium, which are transmitted to humans through the bite of infected mosquitoes.
"To survive, replicate and transition between their mosquito and human hosts, the parasites undergo developmental transitions controlled by changes in their gene expression," said Manuel Llinás, Ernest C. Pollard Professor in Biotechnology, professor of biochemistry and molecular biology and of chemistry in the Eberly College of Science at Penn State and a member of the research team. "Understanding the molecular processes that regulate these gene expression changes during the parasite's complex life cycle is therefore crucial to specifically combatting the pathogen at different stages of its development."
The new study reveals a protein that modulates the structure of the Plasmodium genome, allowing precise control of the timing of gene expression in the parasite. Genes are encoded in the DNA that makes up chromosomes, which consist of DNA wrapped around proteins, forming a complex structure called chromatin. To be functional, the genes must be expressed. Proteins that regulate how and when gene are expressed must be able to access the DNA through the chromatin to produce RNA, which can be functional itself, or be used as a template to make biologically active proteins.
"The structure of chromatin can be open, allowing access of regulatory proteins to the DNA, or closed, preventing access," Llinás said. "At different stages of the Plasmodium life cycle, different regions of the chromosomes may be open or closed, and the remodeling of chromatin between stages helps ensure that the right genes are expressed at the right stages."
This type of gene expression control does not change the DNA itself, but rather operates a level above -a phenomenon broadly called epigenetics. The team found that a protein functioning as a chromatin remodeler, called PfSnf2L, is essential to regulate the "just-in-time" expression of genes so that they are turned on or off in a stage-specific manner in Plasmodium falciparum. Using the unique DNA sequence and functional properties of PfSnf2L, the team were then able to identify a highly specific small molecule inhibitor that blocks PfSnf2L function and also kills the parasite. The team found that the inhibitor also prevents the development of sexual-stage parasites, meaning they cannot be transmitted by mosquitoes.
"Our research shows that PfSnf2L is essential for P. falciparum to dynamically adjust gene expression," said Maria Theresia Watzlowik of the University of Regensburg in Germany, the first author of the study. "This insight offers us the development of therapies that inhibit life cycle progression of the parasite and block transmission."
The researchers used a multidisciplinary approach, involving a screening platform for potential inhibitors, genetic manipulation of malaria parasites and genome-wide characterization to uncover the role of the anti-plasmodial molecule NH125. This inhibitor represents a new class of antimalarials, the researchers said, potentially targeting all life cycle stages.
"Many antimalarial drugs target only the asexual blood stages of the parasite, leaving the sexual stages unaffected and ready for transmission by the mosquito." said Ritwik Singhal, doctoral candidate in the Penn State Molecular, Cellular, and Integrative Biosciences Graduate Program. "This makes NH125's ability to target both the asexual and sexual stages even more remarkable, especially in multiple strains of the parasite."
The researchers emphasized that the new findings not only advance the basic understanding of gene regulation during the Plasmodium life cycle but could also offer practical applications. Targeted interventions in gene regulation could increase the effectiveness of existing drugs or prevent the development of drug-resistance, by killing the parasites before they can adapt.
"Malaria is one of the most adaptive diseases we face," said Gernot Längst of the University of Regensburg and an author of the paper. "By targeting its epigenetic regulation, we have an opportunity to directly disrupt the parasite's capacity to modulate gene expression, reducing the likelihood of resistance development."
Malaria remains one of the greatest global health threats. In 2022, there were an estimated 247 million infections and over 600,000 deaths, mostly in sub-Saharan Africa. Targeting developmental regulation offers a promising potential solution for new treatment options, according to the team.
"The study underscores the importance of integrating epigenetics into malaria research," said Markus Meissner of the Ludwig-Maximilians-University in Munich, Germany, one of the leaders of the research team. "Future work will focus on testing small molecules that inhibit the parasite's epigenetic machinery and exploring their effectiveness in preclinical models."
In addition to Llinás, Watzlowik, Singhal, Längst and Meissner, the research team includes graduate student Victoria A. Bonnell at Penn State; Elisabeth Silberhorn and Simon Holzinger at the University of Regensburg; Sujaan Das, Ella Schadt, Matthew Gow and Andreas Klingl at Ludwig-Maximilians University; and Kannan Venugopal, Barbara Stokes, Lauriane Sollelis, and Matthias Marti at University of Zurich in Switzerland. The German Research Foundation, the U.S. National Institutes of Health and the Wellcome Trust funded the research. Additional support was provided by the Penn State Huck Institutes of the Life Sciences, where Llinás, Singhal, and Bonnell are members of the Huck Center for Malaria Research.
