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bioRxiv · 10.1101/2024.08.29.610374

Phospho-regulated tuning of viscoelastic properties balances centrosome growth and strength

Amato, M.·Hwang, J. H.·Rios, M. U.·Familiari, N. E.·Rosen, M. K.·Woodruff, J. B.
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Abstract

Centrosomes are membranelles organelles containing centrioles encapsulated by pericentriolar material (PCM). PCM nucleates microtubules that help position and segregate chromosomes during mitosis, yet how PCM resists microtubule-mediated forces is poorly understood at the material level. Here, we show that PLK-1 phosphorylation of SPD-5 tunes the dynamics and material properties of the PCM scaffold in C. elegans embryos. Microrheology of reconstituted PCM condensates reveals that PLK-1 phosphorylation decreases SPD-5 dynamics and increases condensate viscoelasticity. Similarly, in embryos, phospho-mimetic SPD-5 is less dynamic than wild-type SPD-5, which itself is less dynamic than phospho-null SPD-5. PCM built with phospho-null SPD-5 is smaller than normal, but its assembly can be partially rescued by reducing microtubule-dependent forces. The same is true for PCM built with phospho-mimetic SPD-5, yet the underlying causes are distinct: under force, phospho-null SPD-5 fails to assemble, while phospho-mimetic SPD-5 forms hyper-stable foci that fail to cohere into a uniform, spherical mass. Both mutants have defects with chromosome segregation and viability. Thus, tuning of SPD-5 phosphorylation optimizes PCM material properties to achieve correct PCM size, integrity, and function. Our results demonstrate how regulated chemical modification of a scaffolding protein modulates the material properties and function of a membraneless organelle.

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Amato, M., Hwang, J. H., Rios, M. U., Familiari, N. E., Rosen, M. K., Woodruff, J. B.. 2024-08-30. Phospho-regulated tuning of viscoelastic properties balances centrosome growth and strength. https://doi.org/10.1101/2024.08.29.610374

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