Centrioles generate a local pulse of Polo/PLK1 activity to initiate mitotic centrosome assembly

Abstract

Mitotic centrosomes are formed when centrioles start to recruit large amounts of pericentriolar material (PCM) around themselves in preparation for mitosis. This centrosome “maturation” requires the centrioles and also Polo/PLK1 protein kinase. The PCM comprises several hundred proteins and, in Drosophila, Polo cooperates with the conserved centrosome proteins Spd‐2/CEP192 and Cnn/CDK5RAP2 to assemble a PCM scaffold around the mother centriole that then recruits other PCM client proteins. We show here that in Drosophila syncytial blastoderm embryos, centrosomal Polo levels rise and fall during the assembly process—peaking, and then starting to decline, even as levels of the PCM scaffold continue to rise and plateau. Experiments and mathematical modelling indicate that a centriolar pulse of Polo activity, potentially generated by the interaction between Polo and its centriole receptor Ana1 (CEP295 in humans), could explain these unexpected scaffold assembly dynamics. We propose that centrioles generate a local pulse of Polo activity prior to mitotic entry to initiate centrosome maturation, explaining why centrioles and Polo/PLK1 are normally essential for this process.

Pericentriolar matrix (PCM) integrity relies on cenexin and polo-like kinase (PLK)1

“…Interestingly, our analyses reveal that the PLK1 scaffold Cep192 ( Joukov et al. , 2014 ; Wong et al. , 2021 ) is detected in arthropods where the cenexin C-terminal extension is lacking.…”

SH2D4A promotes centrosome maturation to support spindle microtubule formation and mitotic progression

“…The centrosome is a fundamental membraneless organelle that supports cell division by forming bipolar spindles 3 , 4 . Centrosome maturation occurs during mitotic entry, with pericentriolar material (PCM) such as Cep192/SPD-2 and pericentrin accumulating around the centrioles 5 , 6 . The recruitment of γ-tubulin ring complex (γTuRC), one of the PCMs, is especially important for the nucleation of centrosomal microtubules.…”

Centriole distal-end proteins CP110 and Cep97 influence centriole cartwheel growth at the proximal end

“…We wondered whether CP110 and Cep97 might influence Plk4 abundance in the cytoplasm. As described previously, in our hands the cytosolic concentration of Plk4-monomeric NeonGreen expressed from its own promoter was too low to be measured by conventional Fluorescence Correlation Spectroscopy (FCS), so we used Peak Counting Spectroscopy (PeCoS) instead ( Aydogan et al, 2020 ; Wong et al, 2022 ). Varying the cytoplasmic dosage of CP110 or Cep97 did not detectably alter cytoplasmic Plk4 levels ( Fig.…”