Microtubule Plus‐End‐Tracking Proteins


Microtubules are dynamic cytoskeletal components necessary for several intracellular processes, including cell division, differentiation, migration and intracellular transport. Microtubule plus‐end‐tracking proteins (+TIPs) consist of a highly diversified group of evolutionary conserved families of proteins that preferentially accumulate at the plus‐ends of microtubules. Importantly, +TIPs are capable of interacting with each other, which allows the establishment of complex protein networks greatly implicated in the regulation of microtubule behaviour. These networks play an important role mediating the interactions between microtubules and several cellular structures, such as membranes, kinetochores and the actin cytoskeleton, thereby influencing cellular architecture and coordinating diverse biological processes. For these reasons, +TIPs have been extensively studied, including the peculiar structural features allowing for the generation of networks, the mechanisms behind microtubule plus‐end‐tracking and their respective roles in the cell.

Key Concepts

  • +TIPs consist of an evolutionarily conserved, yet highly diversified group of proteins that preferentially accumulate at the plus‐end of microtubules regulating their dynamics.
  • In their structure +TIPs can comprise specialized domains fit to directly interact with tubulin, or able to bind proteins capable of autonomously associating with tubulin.
  • The establishment of +TIPs networks responsible for the regulation of microtubule dynamics is important for numerous biological processes in interphase and mitosis.

Keywords: microtubule; microtubule dynamics; microtubule‐associated proteins; mitosis; plus‐end‐tracking; cytoskeleton

Figure 1. +TIP distribution in interphase mammalian cells. (a) Schematic drawing of a cell with distinct MT populations emerging from the microtubule organising centre (MTOC). The growing MTs (green) hold +TIPs (purple) at their end that promote MT polymerisation, whereas MTs undergoing catastrophe (red) comprise a different +TIP composition. (b and c) Immunofluorescence of fixed HeLa cells stably expressing EB1‐EGFP (in b) or EGFP‐CLASP1 (in c) (green) and stained for α‐tubulin (red in b), EB1 (red in c) and counterstained with 4,6‐diamino‐2‐phenylindole (DAPI) to reveal the DNA (blue). Higher magnifications of selected region‐of‐interest (ROI) shows the distribution of these +TIPs at the distal ends of MTs. (d and e) Dynamic behaviour of +TIPs in the intracellular space at the distal ends of microtubules. (d) Colour‐coded time projection of a sequence of 15 frames, corresponding to 30 s. A red‐green‐blue (RGB) gradient filter was applied to each frame, consequently leading to early frames being red‐coloured, whereas latter frames are blue labelled. As a result, moving features (microtubule tips) are seen as coloured tracks. Scale: 10 µm. (e) Kymograph (plot of distance vs time) of an ROI of live‐cell imaging of a HeLa cell transfected with EB1‐EGFP. Each row is obtained by maximum‐intensity projection along the small axis of the selected ROI. Vertical tracks represent static features and diagonal tracks are observed for moving particles. Horizontal scale: 10 µm; Vertical: 10 s.
Figure 2. Mechanisms of +TIPs delivery to microtubule ends. Schematic illustration picturing the various mechanisms used by +TIPs to locate to plus‐ends. Plus‐end‐tracking proteins can reach MT ends by diffusion from the cytoplasm or along the MT lattice. Autonomous +TIPs, such as EBs, can recognise and directly bind to MT plus‐ends through their calponin homology (CH) domain. They are also capable of carrying other +TIPs to that region through hitchhiking. Particularly, +TIPs with an SxIP domain can bind to the end‐binding homology region (EBH), whereas some CAP‐Gly proteins identify and attach to composite binding sites of EBs C‐terminus (EEY). Alternatively, +TIPs can also be brought to the plus‐ends through a kinesin‐mediated transport. Some +TIPs could also be able to co‐polymerise with soluble tubulin dimers and then move to the MT plus‐end.
Figure 3. Localization of CLASP1 in mitosis. Mitotic HeLa cells stably expressing EGFP‐CLASP1 (green) were fixed, stained for α‐tubulin (red) and DNA was counterstained with DAPi (blue). EGFP‐CLASP1 can be found at the spindle, centrosomes, midzone and midbody, as indicated by arrows in the second and third panel, respectively. Higher magnification on the first image of selected ROI show EGFP‐CLASP1 at kinetochores bound to MTs (k‐fibres).


Akhmanova A, Hoogenraad CC, Drabek K, et al. (2001) Clasps are CLIP‐115 and −170 associating proteins involved in the regional regulation of microtubule dynamics in motile fibroblasts. Cell 104 (6): 923–935.

Akhmanova A and Steinmetz MO (2008) Tracking the ends: a dynamic protein network controls the fate of microtubule tips. Nature Reviews Molecular Cell Biology 9 (4): 309–322.

Akhmanova A and Steinmetz MO (2010) Microtubule +TIPs at a glance. Journal of Cell Science 123 (Pt 20): 3415–3419.

Al‐Bassam J and Chang F (2011) Regulation of microtubule dynamics by TOG‐domain proteins XMAP215/Dis1 and CLASP. Trends in Cell Biology 21 (10): 604–614.

Al‐Bassam J, Kim H, Brouhard G, et al. (2010) CLASP promotes microtubule rescue by recruiting tubulin dimers to the microtubule. Developmental Cell 19 (2): 245–258.

Bieling P, Kandels‐Lewis S, Telley IA, et al. (2008) CLIP‐170 tracks growing microtubule ends by dynamically recognizing composite EB1/tubulin‐binding sites. The Journal of Cell Biology 183 (7): 1223–1233.

Bieling P, Laan L, Schek H, et al. (2007) Reconstitution of a microtubule plus‐end tracking system in vitro. Nature 450 (7172): 1100–1105.

Cassimeris L and Morabito J (2004) TOGp, the human homolog of XMAP215/Dis1, is required for centrosome integrity, spindle pole organization, and bipolar spindle assembly. Molecular Biology of the Cell 15 (4): 1580–1590.

Dixit R, Barnett B, Lazarus JE, et al. (2009) Microtubule plus‐end tracking by CLIP‐170 requires EB1. Proceedings of the National Academy of Sciences of the United States of America 106 (2): 492–497.

Domnitz SB, Wagenbach M, Decarreau J and Wordeman L (2012) MCAK activity at microtubule tips regulates spindle microtubule length to promote robust kinetochore attachment. The Journal of Cell Biology 197 (2): 231–237.

Drabek K, van Ham M, Stepanova T, et al. (2006) Role of CLASP2 in microtubule stabilization and the regulation of persistent motility. Current Biology: CB 16 (22): 2259–2264.

Efimov A, Kharitonov A, Efimova N, et al. (2007) Asymmetric CLASP‐dependent nucleation of noncentrosomal microtubules at the trans‐Golgi network. Developmental Cell 12 (6): 917–930.

Ferreira JG, Pereira AJ, Akhmanova A and Maiato H (2013) Aurora B spatially regulates EB3 phosphorylation to coordinate daughter cell adhesion with cytokinesis. The Journal of Cell Biology 201 (5): 709–724.

Ferreira JG, Pereira AL and Maiato H (2014) Microtubule plus‐end tracking proteins and their roles in cell division. International Review of Cell and Molecular Biology 309: 59–140.

Fukata M, Watanabe T, Noritake J, et al. (2002) Rac1 and Cdc42 capture microtubules through IQGAP1 and CLIP‐170. Cell 109 (7): 873–885.

Galjart N (2005) CLIPs and CLASPs and cellular dynamics. Nature Reviews Molecular Cell Biology 6 (6): 487–498.

Galjart N (2010) Plus‐end‐tracking proteins and their interactions at microtubule ends. Current Biology: CB 20 (12): R528–R537.

Galjart N and Perez F (2003) A plus‐end raft to control microtubule dynamics and function. Current Opinion in Cell Biology 15 (1): 48–53.

Gardner MK, Zanic M and Howard J (2013) Microtubule catastrophe and rescue. Current Opinion in Cell Biology 25 (1): 14–22.

Hirokawa N, Noda Y, Tanaka Y and Niwa S (2009) Kinesin superfamily motor proteins and intracellular transport. Nature Reviews Molecular Cell Biology 10 (10): 682–696.

Holmfeldt P, Stenmark S and Gullberg M (2004) Differential functional interplay of TOGp/XMAP215 and the KinI kinesin MCAK during interphase and mitosis. The EMBO Journal 23 (3): 627–637.

Honnappa S, Gouveia SM, Weisbrich A, et al. (2009) An EB1‐binding motif acts as a microtubule tip localization signal. Cell 138 (2): 366–376.

Honnappa S, John CM, Kostrewa D, Winkler FK and Steinmetz MO (2005) Structural insights into the EB1‐APC interaction. The EMBO Journal 24 (2): 261–269.

Komarova Y, De Groot CO, Grigoriev I, et al. (2009) Mammalian end binding proteins control persistent microtubule growth. The Journal of Cell Biology 184 (5): 691–706.

Komarova Y, Lansbergen G, Galjart N, et al. (2005) EB1 and EB3 control CLIP dissociation from the ends of growing microtubules. Molecular Biology of the Cell 16 (11): 5334–5345.

Kumar P and Wittmann T (2012) +TIPs: SxIPping along microtubule ends. Trends in Cell Biology 22 (8): 418–428.

Lan W, Zhang X, Kline‐Smith SL, et al. (2004) Aurora B phosphorylates centromeric MCAK and regulates its localization and microtubule depolymerization activity. Current Biology: CB 14 (4): 273–286.

Lansbergen G and Akhmanova A (2006) Microtubule plus end: a hub of cellular activities. Traffic 7 (5): 499–507.

Lansbergen G, Grigoriev I, Mimori‐Kiyosue Y, et al. (2006) CLASPs attach microtubule plus ends to the cell cortex through a complex with LL5beta. Developmental Cell 11 (1): 21–32.

Lansbergen G, Komarova Y, Modesti M, et al. (2004) Conformational changes in CLIP‐170 regulate its binding to microtubules and dynactin localization. The Journal of Cell Biology 166 (7): 1003–1014.

Leano JB, Rogers SL and Slep KC (2013) A cryptic TOG domain with a distinct architecture underlies CLASP‐dependent bipolar spindle formation. Structure 21 (6): 939–950.

Liu J, Wang Z, Jiang K, et al. (2009) PRC1 cooperates with CLASP1 to organize central spindle plasticity in mitosis. The Journal of Biological Chemistry 284 (34): 23059–23071.

Logarinho E, Maffini S, Barisic M, et al. (2012) CLASPs prevent irreversible multipolarity by ensuring spindle‐pole resistance to traction forces during chromosome alignment. Nature Cell Biology 14 (3): 295–303.

Lomakin AJ, Semenova I, Zaliapin I, et al. (2009) CLIP‐170‐dependent capture of membrane organelles by microtubules initiates minus‐end directed transport. Developmental Cell 17 (3): 323–333.

Maffini S, Maia AR, Manning AL, et al. (2009) Motor‐independent targeting of CLASPs to kinetochores by CENP‐E promotes microtubule turnover and poleward flux. Current Biology: CB 19 (18): 1566–1572.

Maia AR, Garcia Z, Kabeche L, et al. (2012) Cdk1 and Plk1 mediate a CLASP2 phospho‐switch that stabilizes kinetochore‐microtubule attachments. The Journal of Cell Biology 199 (2): 285–301.

Maiato H, Fairley EA, Rieder CL, et al. (2003) Human CLASP1 is an outer kinetochore component that regulates spindle microtubule dynamics. Cell 113 (7): 891–904.

Maiato H, Khodjakov A and Rieder CL (2005) Drosophila CLASP is required for the incorporation of microtubule subunits into fluxing kinetochore fibres. Nature Cell Biology 7 (1): 42–47.

Manning AL, Bakhoum SF, Maffini S, et al. (2010) CLASP1, astrin and Kif2b form a molecular switch that regulates kinetochore‐microtubule dynamics to promote mitotic progression and fidelity. The EMBO Journal 29 (20): 3531–3543.

Mimori‐Kiyosue Y, Grigoriev I, Lansbergen G, et al. (2005) CLASP1 and CLASP2 bind to EB1 and regulate microtubule plus‐end dynamics at the cell cortex. The Journal of Cell Biology 168 (1): 141–153.

Montenegro Gouveia S, Leslie K, Kapitein LC, et al. (2010) In vitro reconstitution of the functional interplay between MCAK and EB3 at microtubule plus ends. Current Biology: CB 20 (19): 1717–1722.

Patel K, Nogales E and Heald R (2012) Multiple domains of human CLASP contribute to microtubule dynamics and organization in vitro and in Xenopus egg extracts. Cytoskeleton 69 (3): 155–165.

Pereira AL, Pereira AJ, Maia AR, et al. (2006) Mammalian CLASP1 and CLASP2 cooperate to ensure mitotic fidelity by regulating spindle and kinetochore function. Molecular Biology of the Cell 17 (10): 4526–4542.

Perez F, Diamantopoulos GS, Stalder R and Kreis TE (1999) CLIP‐170 highlights growing microtubule ends in vivo. Cell 96 (4): 517–527.

Samora CP, Mogessie B, Conway L, et al. (2011) MAP4 and CLASP1 operate as a safety mechanism to maintain a stable spindle position in mitosis. Nature Cell Biology 13 (9): 1040–1050.

Steinmetz MO and Akhmanova A (2008) Capturing protein tails by CAP‐Gly domains. Trends in Biochemical Sciences 33 (11): 535–545.

Tirnauer JS, Grego S, Salmon ED and Mitchison TJ (2002) EB1‐microtubule interactions in Xenopus egg extracts: role of EB1 in microtubule stabilization and mechanisms of targeting to microtubules. Molecular Biology of the Cell 13 (10): 3614–3626.

Tsvetkov AS, Samsonov A, Akhmanova A, Galjart N and Popov SV (2007) Microtubule‐binding proteins CLASP1 and CLASP2 interact with actin filaments. Cell Motility and the Cytoskeleton 64 (7): 519–530.

Wittmann T and Waterman‐Storer CM (2005) Spatial regulation of CLASP affinity for microtubules by Rac1 and GSK3beta in migrating epithelial cells. The Journal of Cell Biology 169 (6): 929–939.

Wordeman L, Wagenbach M and von Dassow G (2007) MCAK facilitates chromosome movement by promoting kinetochore microtubule turnover. The Journal of Cell Biology 179 (5): 869–879.

Further Reading

Gouveia SM and Akhmanova A (2010) Cell and molecular biology of microtubule plus end tracking proteins: end binding proteins and their partners. International Review of Cell and Molecular Biology 309: 59–140.

Gupta KK, Alberico EO, Nathke IS and Goodson HV (2014) Promoting microtubule assembly: a hypothesis for the functional significance of the +TIP network. BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology 36 (9): 818–826.

Hirokawa N, Noda Y, Tanaka Y and Niwa S (2009) Kinesin superfamily motor proteins and intracellular transport. Nature Reviews Molecular Cell Biology 10 (10): 682–696.

Miki H, Okada Y and Hirokawa N (2005) Analysis of the kinesin superfamily: insights into structure and function. Trends in Cell Biology 15 (9): 467–476.

Stehbens S and Wittmann T (2012) Targeting and transport: how microtubules control focal adhesion dynamics. The Journal of Cell Biology 198 (4): 481–489.

Stehbens SJ, Paszek M, Pemble H, et al. (2014) CLASPs link focal‐adhesion‐associated microtubule capture to localized exocytosis and adhesion site turnover. Nature Cell Biology 16 (6): 561–573.

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Pereira, Ana L, and Maiato, Helder(Apr 2015) Microtubule Plus‐End‐Tracking Proteins. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0025979]