Mitotic functions of kinesin-5

Abstract

In all eukaryotic cells, molecular motor proteins play essential roles in spindle assembly and function. The homotetrameric kinesin-5 motors in particular generate outward forces that establish and maintain spindle bipolarity and contribute to microtubule flux. Cell-cycle dependent phosphorylation of kinesin-5 motors regulates their localization to the mitotic spindle. Analysis of live cells further shows that kinesin-5 motors are highly dynamic in the spindle. Understanding the interactions of kinesin-5 motors with microtubules and other spindle proteins is likely to broaden the documented roles of kinesin-5 motors during cell division.

Figure1

Localization and activity of Eg5 in mammalian cells. (A) Indirect immunofluorescence of an LLC-Pk1 cell stained with antibodies to tubulin (MTs) and Eg5. Notice that Eg5 is enriched near spindle poles and excluded from astral microtubules. (B) Image of a living LLC-Pk1 cell expressing Eg5-EGFP. Bars = 10 um. (C) Model showing Eg5 activity in the mitotic spindle. Static Eg5 at the spindle equator (yellow) crosslinks antiparallel microtubules and generates a force that opposes dynein/dynactin (blue). In the half spindle, interactions with TPX2 (purple) may target Eg5 (yellow) to parallel microtubules and interactions with dynein may promote poleward motion.