An Sfi1-like centrin-interacting centriolar plaque protein affects nuclear microtubule homeostasis

Abstract

Malaria-causing parasites achieve rapid proliferation in human blood through multiple rounds of asynchronous nuclear division followed by daughter cell formation. Nuclear divisions critically depend on the centriolar plaque, which organizes intranuclear spindle microtubules. The centriolar plaque consists of an extranuclear compartment, which is connected via a nuclear pore-like structure to a chromatin-free intranuclear compartment. Composition and function of this non-canonical centrosome remain largely elusive. Centrins, which reside in the extranuclear part, are among the very few centrosomal proteins conserved in Plasmodium falciparum. Here we identify a novel centrin-interacting centriolar plaque protein. Conditional knock down of this Sfi1-like protein (PfSlp) caused a growth delay in blood stages, which correlated with a reduced number of daughter cells. Surprisingly, intranuclear tubulin abundance was significantly increased, which raises the hypothesis that the centriolar plaque might be implicated in regulating tubulin levels. Disruption of tubulin homeostasis caused excess microtubules and aberrant mitotic spindles. Time-lapse microscopy revealed that this prevented or delayed mitotic spindle extension but did not significantly interfere with DNA replication. Our study thereby identifies a novel extranuclear centriolar plaque factor and establishes a functional link to the intranuclear compartment of this divergent eukaryotic centrosome.

Malaria parasite centrins can assemble by Ca2+-inducible condensation

“…Interactions between centrins in malaria parasites have already been demonstrated [ 13 , 43 ] and are supported by our localization data ( Fig 1C ). To test whether different centrins could phase separate together, we determined the saturation concentration c sat for PfCen1 and 3.…”

“…Prewetting can be envisioned as wetting of dewdrops on a spider web and has been described for transcription factors condensing on isolated DNA strands [ 68 ]. We previously described a novel Sfi1-like protein (PfSlp) interacting with centrins at the centriolar plaque [ 43 ]. It is characterized by a large size, likely taking an elongated shape, and the presence of multiple centrin binding motifs along its sequence, which is itself highly disordered.…”

Insights into the Cell Division of Neospora caninum

“…In T. gondii , the centrosome is crucial in coordinating cell division, acting as a linker between the buddying process and nuclear mitosis [ 6 , 9 , 10 , 15 ]. In Plasmodium spp., the centriolar plaque (a structure similar to the centrosome but lacking centrioles) is important in coordinating nuclear mitosis [ 27 ].…”

The molecular mechanisms driving Plasmodium cell division

“…Here, centrin-4 is located at the MTOC ( Figure 2A ) and forms a complex with centrin-1 and -3, but it is not essential for asexual stage development and proliferation, suggesting redundancy with, and possible replacement by, other centrins [ 27 ]. In addition, phosphorylation of centrins and an Sfi1-like centrin-interacting centriolar plaque protein (PfSlp — which has a key role in Plasmodium nuclear microtubule homeostasis [ 28 ]) may play an important role in kinetochore assembly and centrin localisation during schizogony. For example, in human cells, phosphorylation of centrins 1 and 2 by casein kinase 2 (CK2) regulates their binding to Sfi1 [ 29 ], and phosphorylation of Sfi1 by CDK1 is essential for yeast spindle pole body separation in G1/S phase [ 30 ].…”