Recently, the Anhui Key Laboratory of Cellular Dynamics and Chemical Biology at the University of Science and Technology of China, headed by Professor Xuebiao Yao, has identified a new microtubule plus-end tracking protein DDA3 and fully elucidated its roles in regulation of microtubule dynamics and cell migration by using functional proteomics, structure biology combined with biophotonics at nanoscale. This work was published on Scientific Reports (NPG) on May 8th 2013.
Since the first microtubule plus-end tracking protein was identified in 1997, molecular delineation of microtubule plus-end tracking proteins and its spatiotemporal dynamics has attracted great attention in the field given their unique molecular properties and function specificities in cells. However, the molecular mechanisms underlying microtubule plus-end tracking proteins functions during cellular dynamics remains largely elusive. In their pursuit of molecular delineation of protein interaction networks underlying cell division control, Xuebiao Yao’s group has identified a collection of microtubule plus-end tracking proteins (Jiang et al., EMBO Rep. 2009; Wang et al., JBC. 2012) and illustrated a unique post-translational modification underlying regulation of microtubule plus-end tracking proteins (Xia et al., PNAS. 2012; Ward et al., JBC. 2013). The taskforce of tumor metastasis research group led by Liangyu Zhang in the Yao’s lab recently characterized that DDA3, a p53-binding protein, is a unique EB1-dependent, microtubule plus-end tracking protein. DDA3 interacts with EB1 via its SxIP motif within the C-terminal Pro/Ser-rich region. The EB1-based loading of DDA3 is responsible for MT plus-ends stabilization at cell cortex, which in turn orchestrates directional cell migration in response to extracellular cues. Significantly, they have demonstrated how dynamic EB1 acetylation orchestrates accurate DDA3-EB1 interaction, which provides the first line of evidence linking microtubule plus-end acetylation dynamics in regulating cell migration. Collectively, their studies provide insightful view underlying signaling circuitry dynamics during cell migration.

(Left) DDA3 tracked microtubule plus ends in live cells. Arrows indicate that GFP-DDA3 associates with the growing microtubule plus ends. (Middle) TIRF experiments indicated that DDA3 tracks the growing microtubule plus ends in the presence of EB1, whereas in the absence of EB1, the microtubule plus-end tracking of DDA3 was almost undetectable. The corresponding kymograph at the bottom shows the same microtubule over a period of 2 min. (Right) Proposed model of DDA3 function and its regulation at the leading edge of a migrating cell. DDA3 and other potential +TIPs are recruited by EB1 to the growing microtubule plus ends to modulate microtubule dynamics at cell cortex. EB1 acetylation might be a potential regulation of DDA3 and other potential +TIPs underlying this process to facilitate directional cell migration (solid lines and arrow). Disruption of DDA3 (e.g., DDA3 depletion or abnormal EB1 acetylation) results in abnormal microtubule dynamics and hence defects of directional cell migration (dotted lines and arrow).
During this study, the researchers have established a multi-color total internal reflection fluorescence microscopy (TIRFM)-based microtubule plus-end tracking visualization system at the nanoscale, which establishes a unique high-content platform for systematic investigation of dynamics features of microtubule plus-end tracking proteins.
Mounting evidence demonstrate that aberrant regulation of microtubule plus-end dynamics involves in pathogenesis of various diseases including tumor, non-resolving chronic inflammation and cardiovascular malfunction. Thus, molecular delineation of microtubule plus-end tracking proteins and microtubule dynamics in live cells will enable us to consolidate molecular circuitry into dynamic interaction hubs and a unique system to mine chemical inhibitors for interrogation of relevant diseases.
The joint first authors of this paper are doctoral students Liangyu Zhang and Hengyi Shao in School of Life Sciences, University of Science and Technology of China. This work was supported by grants from Chinese 973 Project, Chinese Academy of Science, Natural Science Foundation of China, Anhui Province Key Project and the National Institutes of Health.
Links to the paper: http://www.nature.com/srep/2013/130508/srep01681/full/srep01681.html

(School of Life Sciences, Department of Science and Technology)