PLK1 controls centriole distal appendage formation and centrobin removal via independent pathways

 

Background

The centrosome is the main microtubule organizing organelle in most animal cells. The two centrioles in its core are duplicated in S-phase, giving rise to two additional “daughter” centrioles. Each new centriole remains associated with the respective older template, such that after mitosis a cell inherits two centrioles of different ages – the daughter made in the cycle just before, and a “mother” made two or more cycles ago. Once this cell reaches the S-phase, these centrioles become the mother and “grandmother”, respectively, upon duplication.

The three generations of centrioles can be distinguished based on specific identifiers: the youngest centrioles are enriched in daughter proteins (e.g. centrobin), whereas the oldest will have distal and subdistal appendages comprising several proteins. It was recently reported that asymmetric localization of centrobin at the daughter centriole is necessary for distal appendage recruitment in ciliated RPE cells¹. Centrobin removal from mother centrioles in Drosophila neuroblasts is controlled by Polo kinase² (PLK1),  which has also been reported to regulate and be regulated by appendage proteins^3–6.

These results suggest an interplay between PLK1 and mother-daughter centriole identity establishment, and this is what Le Roux-Bordieu and colleagues investigated further in this preprint.

 

Key findings

The authors used an RPE eGFP-centrin1 cell line, which allowed them to precisely resolve centriole numbers throughout the cell cycle⁷. During G1, centrobin localization was limited to the daughter centriole (soon-to-be mother). From S-phase onward, centrobin was present in all the newly formed daughters and was kept in the mother centriole of most cells. Interestingly, centrobin was even detected in the grandmother centriole of some cells, suggesting a more dynamic localization than previously thought. Only by metaphase was centrobin removed from most mothers and became restricted to daughter centrioles.

To understand the influence of daughter centriole formation in centrobin removal, centriole duplication was inhibited with centrinone. The resulting mitotic cells – with one centriole on each pole (1:1) – kept centrobin on the youngest centriole. This maintenance of centrobin could be due to 1) the lack of duplication of the soon-to-be mother centriole or 2) the absence of any newer daughter centrioles competing for centrobin affinity.

To test this, the authors depleted a biogenesis protein (SAS6) to obtain cells with an intermediate configuration, in which only the grandmother centriole was duplicated (2:1). These cells only had centrobin in the metaphase pole containing the new daughter centriole (associated with the grandmother). The mother centriole lost centrobin despite not having duplicated, suggesting that centrobin removal depends on the presence of newer centrioles with a higher affinity for the protein. Inhibition of PLK1 for 2h with BI2536 resulted in metaphase cells with centrobin in daughters and most mother centrioles, confirming that PLK1 is necessary for centrobin removal.

The centrinone assay also demonstrated that centrobin removal is not required for the recruitment of distal appendage proteins (OFD1 and CEP164). Inhibition of PLK1 for 24h impaired the recruitment of CEP164 (but not OFD1), indicating that PLK1 independently regulates centrobin and CEP164 localization. Strikingly, centrobin was present in all 4 centrioles in metaphase cells lacking the subdistal appendage proteins Cenexin/ODF2, Cep128, and Centriolin. These results suggest that PLK1 activity might be regulated by subdistal appendages, and indirectly affect centrobin localization.

 

Figure 1 – Control metaphase cells (DMSO) have centrobin only in the daughter centrioles and CEP164 only in the mother and grandmother centrioles. PLK1 inhibition impedes CEP164 recruitment to the mother centriole, and the removal of centrobin. Source: Le Roux-Bourdieu et al., Figure 5.

 

What I like about this work

Ever since I started working with centrioles, I have been fascinated by the mother-daughter identity topic. There is something about a centriole being age-tagged at birth and maturing over the cell cycle. The authors of this work address this complex topic (usually hard to conceptualize) very clearly with an elegant experimental design.

 

Questions to the authors

It is interesting to see such a dynamic localization of centrobin after S-phase. Would you also expect to see centrobin localization in the mother centriole upon PLK1 inhibition in G1?

Would you imagine that fusing G1 cells with different “centriolar ages” would also lead to centrobin recruitment by the youngest?

 

References

1. Wang, L., Failler, M., Fu, W. & Dynlacht, B. D. A distal centriolar protein network controls organelle maturation and asymmetry. Nature Communications 9, 3938 (2018).
2. Gallaud, E. et al. Dynamic centriolar localization of Polo and Centrobin in early mitosis primes centrosome asymmetry. PLOS Biology 18, e3000762 (2020).
3. Colicino, E. G. et al. Chromosome misalignment is associated with PLK1 activity at cenexin-positive mitotic centrosomes. MBoC 30, 1598–1609 (2019).
4. Chong, W. M. et al. Super-resolution microscopy reveals coupling between mammalian centriole subdistal appendages and distal appendages. eLife 9, e53580 (2020).
5. Tateishi, K. et al. Two appendages homologous between basal bodies and centrioles are formed using distinct Odf2 domains. J Cell Biol 203, 417–425 (2013).
6. Ishikawa, H., Kubo, A., Tsukita, S. & Tsukita, S. Odf2-deficient mother centrioles lack distal/subdistal appendages and the ability to generate primary cilia. Nat Cell Biol 7, 517–524 (2005).
7. Piel, M., Meyer, P., Khodjakov, A., Rieder, C. L. & Bornens, M. The Respective Contributions of the Mother and Daughter Centrioles to Centrosome Activity and Behavior in Vertebrate Cells. J Cell Biol 149, 317–330 (2000).

Tags: centriole appendages, centrioles, centrobin, centrosome, mitosis, plk1

doi: https://doi.org/10.1242/prelights.30734

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