A Plasmodium Calcium-Dependent Protein Kinase Controls Zygote Development and Transmission by Translationally Activating Repressed mRNAs

Abstract

SummaryCalcium-dependent protein kinases (CDPKs) play key regulatory roles in the life cycle of the malaria parasite, but in many cases their precise molecular functions are unknown. Using the rodent malaria parasite Plasmodium berghei, we show that CDPK1, which is known to be essential in the asexual blood stage of the parasite, is expressed in all life stages and is indispensable during the sexual mosquito life-cycle stages. Knockdown of CDPK1 in sexual stages resulted in developmentally arrested parasites and prevented mosquito transmission, and these effects were independent of the previously proposed function for CDPK1 in regulating parasite motility. In-depth translational and transcriptional profiling of arrested parasites revealed that CDPK1 translationally activates mRNA species in the developing zygote that in macrogametes remain repressed via their 3′ and 5′UTRs. These findings indicate that CDPK1 is a multifunctional protein that translationally regulates mRNAs to ensure timely and stage-specific protein expression.

The development of malaria parasites in the mosquito midgut

“…In female macrogametocytes, CDPK1 initiates the release of the translational repression of messenger RNAs (mRNAs) (Sebastian et al ., 2012). Translational repression in macrogametocytes has been linked to components of regulatory ribonucleoprotein complexes.…”

“…A de novo synthesis study in zygotes identified 91 proteins synthesized only after fertilization, most of which are involved in motility and invasion (Sebastian et al ., 2012). A recent cross‐fertilization study further showed that the zygote/ookinete stage exhibits a maternal phenotype either from maternal mRNA inheritance or transcription of the maternal alleles, while the respective paternal alleles are silenced in these stages (Ukegbu et al ., 2015).…”

“…berghei , these arrest in the zygote stage and lack IMC components and microneme proteins like SOAP and the thrombospondin‐related adhesive protein‐related protein CTRP. Similarly, downregulation of GAP45 expression in the midgut stages resulted in zygotes unable to transform into ookinetes (Sebastian et al ., 2012). Two IMC sub‐compartment proteins, ISP1 and 3, associate with the forming apical complex in P .…”

Translational repression of the cpw-wpc gene family in the malaria parasite Plasmodium

“…The DEAD-box RNA helicase DOZI (Development of Zygote Inhibited) [18] and the LSm protein CITH (CAR-I and Trailer Hitch homolog) [17] are core components of cytoplasmic messenger ribonucleoprotein particles (mRNPs) that function in the storage and stabilization of known repressed mRNAs in the female gametocyte, but are ready for rapid translation during ookinete formation after transmission of the parasite to the mosquito vector [17,18,[38][39][40]43]. Several P. berghei cpw-wpc transcripts were present in the pool of genes affected in cells depleted of DOZI and CITH (Table 4) [17,18].…”

Phospholipases during membrane dynamics in malaria parasites

“…At the same time, PI-PLC is stimulated, which hydrolyses PIP 2 to generate DAG and IP 3 (Martin et al, 1994;Raabe et al, 2011b), resulting in the release of calcium from internal stores (Billker et al, 2004). Downstream of this signaling cascade, the increased calcium levels are sensed by specific calcium-dependent protein kinases, which in turn control DNA replication and protein biosynthesis (Billker et al, 2004;Ojo et al, 2014Ojo et al, , 2012Sebastian et al, 2012).…”