Molecular basis of clathrin-mediated stabilization of microtubules for chromosome segregation
Final Report Abstract
Clathrin is required for accurate chromosome segregation and mitosis, and surprisingly operates in this capacity via a mechanism that is independent of its classical endocytosis and vesicle trafficking functions. During mitosis clathrin localizes to the microtubule spindle and promotes microtubule stability and chromosome alignment. The mechanisms by which clathrin stabilizes microtubules, however, have been unclear. In this work, we have shown that clathrin adaptor interaction sites on clathrin heavy chain (CHC), required for clathrinmediated endocytosis, are repurposed during mitosis to directly recruit the microtubulestabilizing protein GTSE1 to the spindle. Structural analyses revealed these sites interact directly with “clathrin-box” motifs, usually found in clathrin adaptor proteins, on GTSE1. Disrupting this interaction via point mutations released GTSE1 from mitotic spindles, causing defects in chromosome alignment. Surprisingly, this disruption destabilized a specific microtubule population, astral microtubules, and not others (e.g. kinetochore-microtubles). The resulting loss of astral microtubules caused a specific failure of chromosome congression, and led to the defining of an important mechanism by which clathrin promotes chromosome congression. We have thus uncovered for the first time a repurposing of this endocytic clathrin-adaptor interaction mechanism during mitosis. In contrast to clathrin adaptor proteins that utilize this interaction to recruit clathrin to sites of coat formation, clathrin on the spindle utilizes it to recruit GTSE1, which in turn stabilizes microtubules via GTSE1’s ability to inhibit a potent microtubule destabilizing (depolymerizing) enzyme, MCAK. Thus, a major mechanism by which clathrin stabilizes MTs is ultimately inhibition of MCAK. We have shown that this is ultimately required for efficient chromosome alignment, which is essential to the faithful transmission of the genome at each cell division and to avoid the chromosomal instability common to cancers.
Publications
- Clathrin’s adaptor interaction sites are repurposed to stabilize microtubules during mitosis. J Cell Biol. 2020 Jan 13;219(2)
Rondelet A, Lin Y-C, Singh D, Porfetye AT, Hecker A, Brinkert P, Schmidt N, Bendre S, Müller F, Widlund PO, Bange T, Hiller M, Vetter IR, Bird AW
(See online at https://dx.doi.org/10.1083/jcb.201907083)
