Microtubules are polar cytoskeleton filaments that extend via growth at their plus ends. Microtubule plus-end-tracking proteins (+TIPs) accumulate at these growing plus ends to control microtubule dynamics and attachment. The +TIP end-binding protein 1 (EB1) and its homologs possess an autonomous plusend- tracking mechanism and interact with other known +TIPs, which then recruit those +TIPs to the growing plus ends. A major +TIP class contains the SXIP (Ser-X-Ile-Pro, with X denoting any amino acid residue) motif, known to interact with EB1 and its homologs for plus-end tracking, but the role of SXIP in regulating EB1 activities is unclear. We show here that an interaction of EB1 with the SXIP-containing +TIP CDK5 regulatory subunit-associated protein 2 (CDK5RAP2) regulates several EB1 activities, including microtubule plus-end tracking, dynamics at microtubule plus ends, microtubule and α/β-tubulin binding, and microtubule polymerization. The SXIP motif fused with a dimerization domain from CDK5RAP2 significantly enhanced EB1 plus-end-tracking and microtubule-polymerizing and bundling activities, but the SXIP motif alone failed to do so. An SXIP-binding-deficient EB1 mutant displayed significantly lower microtubule plus-end tracking than the wild-type protein in transfected cells. These results suggest that EB1 cooperates with CDK5RAP2 and perhaps other SXIPcontaining +TIPs in tracking growing microtubule tips.Wealso generated plus-end-tracking chimeras of CDK5RAP2 and the adenomatous polyposis coli protein (APC) and found that overexpression of the dimerization domains interfered with microtubule plus-end tracking of their respective SXIP-containing chimeras. Our results suggest that disruption of SXIP dimerization enables detailed investigations of microtubule plus-endassociated functions of individual SXIP-containing +TIPs.
|Number of pages||13|
|Journal||Journal of Biological Chemistry|
|State||Published - May 5 2017|
Bibliographical noteFunding Information:
This work was supported by grants from the Research Grants Council (General Research Fund and Theme-based Research Scheme) of Hong Kong, the National Key Basic Research Program of China (2013CB530900), the University Grants Committee (Area of Excellence Scheme) of Hong Kong, the Innovation and Technology Commission (ITCPD/17-9) of Hong Kong, and the TUYF Charitable Trust.
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology