Kinesin-7 CENP-E in tumorigenesis: Chromosome instability, spindle assembly checkpoint, and applications

Abstract

Kinesin motors are a large family of molecular motors that walk along microtubules to fulfill many roles in intracellular transport, microtubule organization, and chromosome alignment. Kinesin-7 CENP-E (Centromere protein E) is a chromosome scaffold-associated protein that is located in the corona layer of centromeres, which participates in kinetochore-microtubule attachment, chromosome alignment, and spindle assembly checkpoint. Over the past 3 decades, CENP-E has attracted great interest as a promising new mitotic target for cancer therapy and drug development. In this review, we describe expression patterns of CENP-E in multiple tumors and highlight the functions of CENP-E in cancer cell proliferation. We summarize recent advances in structural domains, roles, and functions of CENP-E in cell division. Notably, we describe the dual functions of CENP-E in inhibiting and promoting tumorigenesis. We summarize the mechanisms by which CENP-E affects tumorigenesis through chromosome instability and spindle assembly checkpoints. Finally, we overview and summarize the CENP-E-specific inhibitors, mechanisms of drug resistances and their applications.

Keywords: CENP-E; aneuploidy; cancer; chromosome instability; kinesin; tumorigenesis.

FIGURE 1

Structure and molecular kinetics of kinesin-7 CENP-E. (A) CENP-E is comprised of an N-terminal motor domain, a coiled-coil domain, and a C-terminal tail domain. The motor domain is required for plus-end-directed motility, ATP hydrolysis, microtubule binding, and run length. The coiled-coil domain is required for dimerization, structural flexibility, physical interactions with partner proteins, and processivity. The tail domain is essential for microtubule binding, cargo transport, diffusion along microtubules, motility, and kinetics. (B) Three-dimensional structure of human CENP-E motor domain (PDB database, No. 1T5C). The globular N-terminal motor domain contains the ATP/ADP binding site, which is essential for ATP hydrolysis and movement. (C) Schematic structure of kinesin-7 CENP-E. (D) The coordinated movement of CENP-E’s head domains along a microtubule. CENP-E is a processive motor that takes 8 nm steps along microtubules for each adenosine triphosphate hydrolyzed via a hand-over-hand mechanism.

FIGURE 2

Kinesin-7 CENP-E is essential for kinetochore-microtubule attachment, chromosome alignment, and spindle assembly checkpoint in cell division. (A–C) CENP-E proteins are located at microtubules in prophase and accumulate at the kinetochores in prometaphase. CENP-E plays a key role in kinetochore-microtubule attachment and chromosome alignment during prometaphase and metaphase. (D) CENP-E ablation results in chromosome misalignment, spindle disorganization, and the activation of the spindle assembly checkpoint. (E) In wild-type cells, CENP-E proteins are essential for chromosome alignment, kinetochore-microtubule attachment, and the regulation of spindle assembly checkpoint. In the absence of CENP-E, the chromosomes are mono-oriented and misaligned, which further forms a wait anaphase signal and activates the spindle assembly checkpoint.

FIGURE 3

Functions and mechanisms of kinesin-7 CENP-E in cell division. (A) During mitosis, kinesins and microtubule-associated proteins (MAPs) are involved in microtubule crosslinking, kinetochore fiber assembly, and chromosome alignment. (B) The G₁, S, G₂, and M phases in the cell cycle are regulated by a complex cell cycle control system. (C) CENP-E associates with the plus ends of k-fibers and promotes kinetochore-microtubule attachment. (D) CENP-E interacts with BubR1, NDC80, Mps1, and kinetochore proteins to mediate chromosome alignment during metaphase. (E) CENP-E can transport polar chromosome arms along microtubules during prometaphase. (F) Both the motor and tail domains of CENP-E can bind to antiparallel microtubules and crosslink microtubules during spindle assembly. (G) The spindle assembly checkpoint pathway in mitosis. The unattached kinetochores on misaligned chromosomes can result in the formation of the mitotic checkpoint complex (MCC), including MAD1-MAD2, BUB3, CDC20, and BubR1 proteins, and then trigger the spindle assembly checkpoint. The checkpoint activates APC/C^CDC20, inhibits Securin and separase, and then inhibits chromosome separation and regulates metaphase-to-anaphase transition. (H) CENP-E also mediates the organization of spindle poles and regulates centrosome organization and stabilization.

FIGURE 4

Dual roles of CENP-E in tumorigenesis. Reduction of CENP-E or CENP-E ^+/− can induce the occurrence of aneuploidy, and aneuploidy is highly related to chromosomal instability (CIN). CENP-E ^+/− can induce high or low rates of chromosomal instability, which depends on the cell type and genetic damage. A low rate of chromosomal instability can promote tumorigenesis, while a high rate of chromosomal instability will lead to cell death or tumor cell growth inhibition (but not tumor cell initiation). CENP-E is also involved in mitotic checkpoint, and the loss of mitotic checkpoint can also lead to tumorigenesis, suggesting another pathway for CENP-E-induced tumorigenesis.

FIGURE 5

Chemical structures of multiple CENP-E inhibitors. (A) GSK923295; (B) GSK-1; (C) GSK-2; (D) PF-2771; (E) 5-bromoimidazo [1,2-a]pyridine 7; (F) 5-methoxy imidazo [1,2-a]pyridine derivative (+)-(S)-12; (G) Compound A; (H) Syntelin; (I) U62784; (J) benzo [d]pyrrolo [2,1-b]thiazole derivative.

FIGURE 6

Drug resistance of CENP-E inhibitors. Tumor cells can develop resistance to CENP-E inhibitors through the CENP-E gene mutation, membrane transporter proteins overexpression, or their own CENP-E expression level. For example, the deletion of DNA in KBM7 cells will lead to the deletion of the CENP-E tail domain, which in turn leads to specific resistance to GSK923295. The overexpression of P-glycoprotein (Pgp) can also lead to resistance to GSK923295, but the low expression of the Pgp gene in GSK923295-resistant KBM7 cells suggests that cells may generate different mechanisms of drug resistance. No common characteristics of 25 GSK923295-resistant cell lines indicate that other molecular pathways lead to drug resistance.