Microtubule minus-end aster organization is driven by processive HSET-tubulin clusters

Nat Commun. 2018 Jul 9;9(1):2659. doi: 10.1038/s41467-018-04991-2.

Abstract

Higher-order structures of the microtubule (MT) cytoskeleton are comprised of two architectures: bundles and asters. Although both architectures are critical for cellular function, the molecular pathways that drive aster formation are poorly understood. Here, we study aster formation by human minus-end-directed kinesin-14 (HSET/KIFC1). We show that HSET is incapable of forming asters from preformed, nongrowing MTs, but rapidly forms MT asters in the presence of soluble (non-MT) tubulin. HSET binds soluble (non-MT) tubulin via its N-terminal tail domain to form heterogeneous HSET-tubulin clusters containing multiple motors. Cluster formation induces motor processivity and rescues the formation of asters from nongrowing MTs. We then show that excess soluble (non-MT) tubulin stimulates aster formation in HeLa cells overexpressing HSET during mitosis. We propose a model where HSET can toggle between MT bundle and aster formation in a manner governed by the availability of soluble (non-MT) tubulin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Tracking / methods
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Kinesin / genetics
  • Kinesin / metabolism*
  • Microscopy, Fluorescence / methods
  • Microtubules / metabolism*
  • Molecular Motor Proteins / metabolism*
  • Protein Binding
  • Time-Lapse Imaging / methods
  • Tubulin / metabolism*

Substances

  • KIFC1 protein, human
  • Molecular Motor Proteins
  • Tubulin
  • Green Fluorescent Proteins
  • Kinesin