Hsp72 is targeted to the mitotic spindle by Nek6 to promote K-fiber assembly and mitotic progression.
Hsp70 proteins represent a family of chaperones that regulate cellular homeostasis and are required for cancer cell survival. However, their function and regulation in mitosis remain unknown. In this paper, we show that the major inducible cytoplasmic Hsp70 isoform, Hsp72, is required for assembly of a robust bipolar spindle capable of efficient chromosome congression. Mechanistically, Hsp72 associates with the K-fiber-stabilizing proteins, ch-TOG and TACC3, and promotes their interaction with each other and recruitment to spindle microtubules (MTs). Targeting of Hsp72 to the mitotic spindle is dependent on phosphorylation at Thr-66 within its nucleotide-binding domain by the Nek6 kinase. Phosphorylated Hsp72 concentrates on spindle poles and sites of MT-kinetochore attachment. A phosphomimetic Hsp72 mutant rescued defects in K-fiber assembly, ch-TOG/TACC3 recruitment and mitotic progression that also resulted from Nek6 depletion. We therefore propose that Nek6 facilitates association of Hsp72 with the mitotic spindle, where it promotes stable K-fiber assembly through recruitment of the ch-TOG-TACC3 complex.
Department of Biochemistry, University of Leicester, Leicester LE1 9HN, England, UK.
Laura
L
O'Regan
Department of Biochemistry, University of Leicester, Leicester LE1 9HN, England, UK.
Josephina
J
Sampson
Department of Biochemistry, University of Leicester, Leicester LE1 9HN, England, UK.
Mark W
MW
Richards
Kinasource Ltd, The Sir James Black Center, Dundee DD1 5EH, Scotland, UK.
Axel
A
Knebel
Centre for Mechanochemical Cell Biology, Warwick Medical School, Coventry CV4 7AL, England, UK.
Daniel
D
Roth
Department of Cellular and Molecular Physiology, University of Liverpool, Liverpool L69 3BX, England, UK.
Fiona E
FE
Hood
Centre for Mechanochemical Cell Biology, Warwick Medical School, Coventry CV4 7AL, England, UK.
Anne
A
Straube
Centre for Mechanochemical Cell Biology, Warwick Medical School, Coventry CV4 7AL, England, UK Department of Cellular and Molecular Physiology, University of Liverpool, Liverpool L69 3BX, England, UK.
Stephen J
SJ
Royle
Department of Biochemistry, University of Leicester, Leicester LE1 9HN, England, UK.
Richard
R
Bayliss
Department of Biochemistry, University of Leicester, Leicester LE1 9HN, England, UK amf5@le.ac.uk.
Andrew M
AM
Fry
D057809:HEK293 Cells; D050884:HSP72 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000502:physiology*; D009154:Mutation; D000072379:NIMA-Related Kinases; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*
C454180:CKAP5 protein, human; D050884:HSP72 Heat-Shock Proteins; D008869:Microtubule-Associated Proteins; C120551:TACC3 protein, human; C459456:NEK6 protein, human; D000072379:NIMA-Related Kinases; D017346:Protein Serine-Threonine Kinases