TheToxoplasma gondiicalcium-dependent protein kinase 7 is involved in early steps of parasite division and is crucial for parasite survival

Abstract

Apicomplexan parasites express various Calcium-Dependent Protein Kinases (CDPKs), and some of them play essential roles in invasion and egress. Five of the six CDPKs conserved in most Apicomplexa have been studied at the molecular and cellular levels in Plasmodium species and/or in Toxoplasma gondii parasites, but the function of CDPK7 was so far uncharacterized. In T. gondii, during intracellular replication, two parasites are formed within a mother cell through a unique process called endodyogeny. Here we demonstrate that the knock-down of CDPK7 protein in T. gondii results in pronounced defects in parasite division and a major growth deficiency, while it is dispensable for motility, egress and microneme exocytosis. In cdpk7-depleted parasites, the overall DNA content was not impaired, but the polarity of daughter cells budding and the fate of several sub-cellular structures or proteins involved in cell division were affected, such as the centrosomes and the kinetochore. Overall, our data suggest that CDPK7 is crucial for proper maintenance of centrosome integrity required for the initiation of endodyogeny. Our findings provide a first insight into the probable role of calcium-dependent signalling in parasite multiplication, in addition to its more widely explored role in invasion and egress.

Regulation of Plasmodium falciparum Development by Calcium-dependent Protein Kinase 7 (PfCDPK7)

“…Because Plasmodium and Toxoplasma divide via the rather divergent processes of schizogony and endodyogeny, respectively, CDPK7 may regulate the division in these parasites via different mechanisms. TgCDPK7ϪKO parasites (26) do not seem to share any other phenotypic trait with PfCDPK7-KO parasites.…”

“…A recent study reported gene disruption of the PfCDPK7 orthologue in Toxoplasma gondii, TgCDPK7, suggested that it is essential for parasite growth. Using a conditional knock-out strategy, TgCDPK7-KO parasites were obtained that exhibited significant defects in parasite division, asynchronous development, and impaired centrosome duplication (26). Because Plasmodium and Toxoplasma divide via the rather divergent processes of schizogony and endodyogeny, respectively, CDPK7 may regulate the division in these parasites via different mechanisms.…”

<em>Sarcocystis neurona</em> Protein Kinases: Computational Identification, Evolutionary Analysis and Putative Inhibitor Docking

“…Further, we identified 10 putative CDPKs in the S. neurona, including CDPK1 (SRCN_3314), CDPK2 (SRCN_4390), CDPK2A (SRCN_2165), CDPK3 (SRCN_3701), CDPK4 (SRCN_6606), CDPK5 (SRCN_3583), CDPK6 (SRCN_3011), CDPK7 (SRCN_6597), CDPK8 (SRCN_5948) and CDPK9 (SRCN_5812). Compared to the 12 CDPKs reported in T. gondii [21], it appears that S. neurona had all the six well-conserved apicomplexan CDPKs (CDPK1, CDPK3, CDPK4, CDPK5, CDPK6 and CDPK7), which provide a link between Ca 2+ signaling and parasite differentiation, motility, invasion and egress [55]. In T. gondii, down-regulation of CDPK1 interfered with parasite motility, host cell invasion and egress [44] while disruption of CDPK3 caused defective parasite egress [75].…”

“…Sequence analysis revealed that, like in other apicomplexans, all identified S. neurona CDPKs except CDPK7 (SRCN_6597) contained both a kinase domain and a Ca2+-binding domain known as the EF-hand domain [21]. Like its T. gondii ortholog, TGME49_028750 (TgCDPK7), the S. neurona CDPK7 (SRCN_6597) contains a pleckstrin-homology (PH) domain just upstream of its PK domain [55]. The domain architecture in CDPKs is such that kinase activity is stimulated upon Ca2+-binding.…”

“…The possible loss notwithstanding, S. neurona contained the 6 CDPKs that are expressed and are well-conserved in most apicomplexans (i.e. CDPK1, CDPK3, CDPK4, CDPK5, CDPK6, and CDPK7) [55]. Sequence analysis revealed that, like in other apicomplexans, all identified S. neurona CDPKs except CDPK7 (SRCN_6597) contained both a kinase domain and a Ca2+-binding domain known as the EF-hand domain [21].…”