So after lab meeting, I’m going to grab a drink at the plus end of a microtubule. I hear it’s a swingin’ place, with lots of cool things going on. I also hear a kinesin-8 is a real mover and shaker at the plus end, but you’ll have to check out today’s image to see for yourself.
The structure and function of the mitotic spindle depends on the amazing qualities of microtubules. Microtubules grow and shorten from their plus ends (mostly), which are the ends that reach out towards the periphery of the cell or chromosomes during mitosis. The plus ends of microtubules are hotspots of activity—plus-tip-tracking proteins bind to the plus ends of microtubules and can regulate the dynamics of each microtubule individually. A group recently found that a microtubule motor called KIF18B plays an important role in regulating microtubule dynamics at the plus end. According to Stout and colleagues, KIF18B controls the length of astral microtubules, which are those that extend towards the cell periphery, and does so by interacting with another well-studied plus-tip-tracking protein called EB1. Without KIF18B, cells have an increased number and length of microtubules. As seen in the images above, KIF18B (green) is on the ends of astral microtubules during different stages of mitosis, and EB1 (orange) is found on the ends of all microtubules. Microtubules are gray, and chromosomes are blue.
Stout, J., Yount, A., Powers, J., LeBlanc, C., Ems-McClung, S., & Walczak, C. (2011). Kif18B interacts with EB1 and controls astral microtubule length during mitosis Molecular Biology of the Cell, 22 (17), 3070-3080 DOI: 10.1091/mbc.E11-04-0363