Additional remarks phenotype | Mutant/mutation
The mutant expresses a C-terminal HA-tagged version of celTOS.
Protein (function)
CelTOS is localized to the micronemes of ookinetes and (salivary gland) sporozoites and is secreted. It plays a role in migration of ookinetes through cells of the mosquito midgutwall and in hepatocyte traversal of sporozoites.
Phenotype
PbcelTOS-3xHA expression in micronemes of ookinetes
The mutant in this study was generated to screen for genetic interactions among protein kinases. In this study a role of CDPK4 during erythrocytic (asexual blood stage) proliferation has been found, which was dependent on a negative interaction with PKG.
From the paper:
In P. falciparum schizonts and P. berghei sporozoites, PKG controls microneme secretion, a process that is also critical to sustain gliding in ookinetes. The PKG-inhibitor C2 blocks the secretion of the ookinete microneme protein CelTOS-3xHA into the culture supernatant, specifically in the inhibitor-sensitive line, indicating that signalling through PKG is required for microneme secretion also in ookinetes. However, depletion of CDPK1 and chemical inhibition of CDPK4 does not affect secretion of CelTOS-3xHA either individually, or in combination. In marked contrast, deletion of CDPK3, an ookinete-specific CDPK needed for optimal gliding, does reduce secretion of CelTOS-3xHA. Complementation of cdpk3 deletion ascertained that this effect was due to the absence of CDPK3 expression. Furthermore, CDPK3 does not appear to interact functionally with CDPK4, since addition of inhibitor 1294 does not decrease motility further in the CDPK3-KO. Altogether, this suggests that the main function of CDPK3 is to control microneme secretion downstream of PKG but independently of CDPK4, while CDPK1 and CDPK4 perform complementary functions in supporting efficient gliding.
From the Abstract:
Most members of a calcium-dependent protein kinase (CDPK) family show genetic redundancy during erythrocytic proliferation. To identify relationships between phospho-signalling pathways, we here screen 294 genetic interactions among protein kinases in Plasmodium berghei. This reveals a synthetic negative interaction between a hypomorphic allele of the protein kinase G (PKG) and CDPK4 to control erythrocyte invasion which is conserved in P. falciparum. CDPK4 becomes critical when PKG-dependent calcium signals are attenuated to phosphorylate proteins important for the stability of the inner membrane complex, which serves as an anchor for the acto-myosin motor required for motility and invasion. Finally, we show that multiple kinases functionally complement CDPK4 during erythrocytic proliferation and transmission to the mosquito.
Additional information
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