Scientists from Japan reveal the crystal structure of a cell cycle motor protein, which could be a potential anticancer drug candidate.
Medical lab – illustrative photo. Image credit: NCI
Many anticancer drugs have serious side effects in clinical practice. Kinesin inhibitors block kinesin motor proteins required for cancer cell division and are, thus, promising anticancer drug candidates with minimal side effects. However, their association with kinesin proteins remains unclear.
Researchers from Japan have now addressed this gap by solving the crystal structure of the complex formed by the kinesin protein CENP-E and the non-hydrolyzable ATP analog AMP-PNP, paving the way for the development of cancer therapies with lesser toxicities.
Crystal structure of human CENP-E motor domain – AMPPNP complex. Researchers from Tokyo University of Science unraveled the structure of a complex formed by centromere-associated protein E (CENP-E) motor domain and adenylyl-imidodiphosphate (AMPPNP), a non-hydrolyzable ATP analogue. Understanding this crystal structure could help develop promising anticancer drugs with fewer side effects. Image credit: Hideshi Yokoyama from Tokyo University of Science, Japan
Anticancer drugs are pivotal to cancer treatment, but their toxicity may not always be limited to cancer cells, resulting in harmful side-effects. To develop anticancer therapies that have fewer adverse effects on patients, scientists are now focusing on less toxic molecules to cells.
One such group of drugs is the “kinesin inhibitors.” These inhibitors prevent cancer progression by explicitly targeting kinesin motor proteins required to divide cancer cells. Centromere-associated protein E (CENP-E), a member of the kinesin motor protein, is a promising target for inhibitor therapy, as it is essential for tumor cell replication.
However, determining the structure of CENP-E is crucial to identify inhibitor molecules that can bind to CENP-E and arrest the function.
Interestingly, binding the energy molecule-adenosine triphosphate (ATP) to the motor domain of CENP-E changes its structure or configuration. This also occurs when CENP-E binds to an inhibitor. So far, very few CENP-E inhibitors have been reported and none approved for clinical use. It is, therefore, important to acquire structural information on the CENP-E motor domain.
To this end, a research team from Tokyo University of Science (TUS) in Japan used X-ray crystallography to elucidate the crystal structure of the complex formed by the CENP-E motor domain and a kinesin inhibitor.
The study led by Professor Hideshi Yokoyama from TUS, along with co-authors Ms. Asuka Shibuya from TUS, and Assistant Professor Naohisa Ogo, Associate Professor Jun-ichi Sawada, and Professor Akira Asai from the University of Shizuoka, was published in FEBS Letters on February 23, 2023.
“CENP-E selectively acts on dividing cells, making it a potential new target for anticancer drugs with fewer side-effects”, says Dr. Yokoyama while discussing the motivation underlying this study.
First, the team expressed the CENP-E motor domain in bacterial cells, following which they purified and mixed it with adenylyl-imidodiphosphate (AMPPNP)-a non-hydrolyzable ATP analogue. The mix was crystallized to obtain exhaustive X-ray data.
Using this data, the team obtained the structure of CENP-E motor domain-AMPPNP complex. Next, they compared the structure with CENP-E-bound adenosine diphosphate (CENP-E-MgADP) and other previously known kinesin motor protein-AMPPNP complexes.
From these comparisons, the team speculated that the helix alpha 4 in the motor domain was likely responsible for the loose binding of CENP-E to microtubules, i.e., cell structures crucial to cell division.
“Compared to the α4 helices of other kinesins, the α4 of CENP-E binds slowly and with lesser strength to microtubules than other kinesins, throughout the ATP hydrolysis cycle”, adds Dr.Yokoyama.
The discovery of the crystal structure of the complex is expected to facilitate additional structure-activity relationship studies, which will bring scientists a step closer to developing anticancer drugs targeting CENP-E. The research team is optimistic about the future applications of their research and are confident that it will be possible to design drugs based on the methods employed in this study.
“The ultimate goal is to use the preparation and crystallization methods described in our study for future drug design studies that aim at developing anticancer drugs with fewer side-effects,” concludes a hopeful Dr. Yokoyama.
We, too, believe that this study will bring cancer patients new hope and alleviate the side-effects they experience during treatment.
Source: Tokyo University of Science