Regulation of cGMP-dependent proteinkinases in Plasmodium falciparum

点击翻译按钮获取中文摘要

Malaria is still one of the most threatening infectious diseases. However, treatment of malaria has been hampered by drug resistance and therefore requires development of innovative therapies based on novel drug targets. Malaria is caused by protozoans of the genus Plasmodium, which are transmitted by Anopheles mosquitoes. cGMP-dependent protein kinase from Plasmodium falciparum (PfPKG) is crucial in both sexual and asexual proliferation in mosquito and human hosts, respectively. Since the primary structure PfPKG and human (h)PKG differ significantly, PfPKG could potentially be addressed by targeted interference. However, the function and the regulation of PfPKG is largely unknown.In this application, we aim to investigate the regulation and activation mechanism of PfPKG on a molecular level by employing high-resolution crystal structures. In particular, we will focus on the cyclic nucleotide binding domains (CNBs), where PfPKG displays four CNBs in contrast to two in its human counterpart. Recent structural data (Kim et al., 2015, Huang et al., 2014, and unpublished structures) provide the rational basis for a cyclic nucleotide screen to select candidates that serve as selective cGMP antagonists. In particular, the CNB-D plays a critical role for kinase activation and kinase activity and appears to be essential for the stability of the catalytic domain. Our initial data demonstrate differences in the activation mechanisms between PfPKG and hPKG. Based on these preliminary findings, we will investigate the role of the conserved autoinhibitory domain. In addition, the catalytic domain will be investigated in detail. Interestingly, we identified variations between PfPKG and hPKG in highly conserved structural motifs within the catalytic core, the so-called spine residues. Regulatory and catalytic spines are found in all protein kinases and are crucial for the control of protein kinase activity. We will define the significance of these differences by site-directed mutagenesis and binding studies.By studying PKG in P. falciparum, we have entered a new research field applying our in-depths expertise with cyclic nucleotides and cNMP-dependent protein kinases. In collaboration with international specialists in structural biology and parasitology, we will apply our knowledge towards novel strategies to fight malaria.