Dissection of Mechanisms Involved in the Regulation of Plasmodium falciparum Calcium-dependent Protein Kinase 4

Abstract

Recent studies have demonstrated that calcium-dependent protein kinases (CDPKs) are used by calcium to regulate a variety of biological processes in the malaria parasite Plasmodium. CDPK4 has emerged as an important enzyme for parasite development, because its gene disruption in rodent parasite Plasmodium berghei causes major defects in sexual differentiation of the parasite (Billker, O., Dechamps, S., Tewari, R., Wenig, G., Franke-Fayard, B., and Brinkmann, V. (2004) Cell 117, 503-514). Despite these findings, it is not very clear how PfCDPK4 or any other PfCDPK is regulated by calcium at the molecular level. We report the biochemical characterization and elucidation of molecular mechanisms involved in the regulation of PfCDPK4. PfCDPK4 was detected on gametocyte periphery, and its activity in the parasite was regulated by phospholipase C. Even though the Junction Domain (JD) of PfCDPK4 shares moderate sequence homology with that of the plant CDPKs, it plays a pivotal role in PfCDPK4 regulation as previously reported for some plant CDPKs. The regions of the J-domain involved in interaction with both the kinase domain and the calmodulinlike domain were mapped. We propose a model for PfCDPK regulation by calcium, which may also prove useful for design of inhibitors against PfCDPK4 and other members of the PfCDPK family.

Analysis of Noncanonical Calcium-Dependent Protein Kinases in Toxoplasma gondii by Targeted Gene Deletion Using CRISPR/Cas9

“…In the absence of calcium, CDPKs are autoinhibited due to the fact that the CAD occludes the active face of the kinase domain. Peptides from the junctional domain are capable of inhibiting kinase activity of several CDPKs in vitro (13,14), consistent with the finding that the junctional domain interacts with the kinase domain in the autoinhibited structure (11,12). Upon binding to calcium, the CAD domain completely reorganizes and flips to the backside of the kinase domain, opening the nucleotide and substrate binding pockets to activate the enzyme (11,12).…”

Characterization of Plasmodium falciparum Calcium-dependent Protein Kinase 1 (PfCDPK1) and Its Role in Microneme Secretion during Erythrocyte Invasion

“…Studies on CDPKs from plants as well as Plasmodium show that the JD plays a crucial role in the calcium-dependent regulation of these enzymes (18,19). Peptides based on JD sequences inhibit PfCDPK4 activity, confirming their role in regulation of PfCDPK4 activity (15).…”

“…These proteins are present in the motor complex at the parasite inner membrane complex and are likely to play critical roles in parasite motility. PfCDPK4 is expressed in the sexual stages of P. falciparum and may play a role in development of sexual stages similar to PbCDPK4 (15). PfCDPK5 plays a critical role in egress of P. falciparum merozoites from mature schizonts (16).…”

Allosteric activation of apicomplexan calcium-dependent protein kinases

“…Peptide mimetics of this region inhibit both plant (7,8) and parasite kinases (6,21). Based on observations of plant CDPK truncations that appeared constitutively active and Ca 2+ -independent, CDPK KDs-like those of CaMKs-were thought to be intrinsically active (7,21). These truncations consisted of N-terminal fusions with GST, which can dimerize and stabilize the conformation of its fusion partners.…”