Ionic strength alters crosslinker-driven self-organization of microtubules

Prashali Chauhan, Hong Beom Lee, Niaz Goodbee, Sophia Martin, Ruell Branch, Sumon Sahu, Jennifer M. Schwarz, Jennifer L. Ross

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The microtubule cytoskeleton is a major structural element inside cells that directs self-organization using microtubule-associated proteins and motors. It has been shown that finite-sized, spindle-like microtubule organizations, called “tactoids,” can form in vitro spontaneously from mixtures of tubulin and the antiparallel crosslinker, MAP65, from the MAP65/PRC1/Ase family. Here, we probe the ability of MAP65 to form tactoids as a function of the ionic strength of the buffer to attempt to break the electrostatic interactions binding MAP65 to microtubules and inter-MAP65 binding. We observe that, with increasing monovalent salts, the organizations change from finite tactoids to unbounded length bundles, yet the MAP65 binding and crosslinking appear to stay intact. We further explore the effects of ionic strength on the dissociation constant of MAP65 using both microtubule pelleting and single-molecule binding assays. We find that salt can reduce the binding, yet salt never negates it. Instead, we believe that the salt is affecting the ability of the MAP65 to form phase-separated droplets, which cause the nucleation and growth of tactoids, as recently demonstrated.

Original languageEnglish (US)
Pages (from-to)328-338
Number of pages11
JournalCytoskeleton
Volume81
Issue number8
DOIs
StatePublished - Aug 2024

Keywords

  • MAP65
  • PRC1
  • antiparallel crosslinker
  • electrostatics
  • ionic strength
  • microtubule
  • self-assembly
  • self-organization
  • spindle
  • tactoid

ASJC Scopus subject areas

  • Structural Biology
  • Cell Biology

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