Recent work from dif­fer­ent lab­o­ra­to­ries has shown that a fam­ily of pro­teins is recruited to the tips of micro­tubules (reviewed in Akhmanova and Stein­metz, 2008). In par­tic­u­lar, most of these pro­teins are recruited specif­i­cally to micro­tubule tips under­go­ing poly­meri­sa­tion. Exam­ples of cells trans­fected with some of these micro­tubule tip-proteins (con­ju­gated with EGFP) are shown in the fol­low­ing four videos:

A B16 melanoma cell express­ing GFP-CLIP-170.

A gold­fish fibrob­last express­ing GFP-EB1, that was injected with Cy-3 tubu­lin.

A gold­fish fibrob­last express­ing GFP-EB3.

An MRC5 cell trans­fected with RFP-tubulin and EB3-GFP show­ing the local­iza­tion of EB3 at grow­ing micro­tubule tips. Video was kindly pro­vided by Ilya Grig­oriev and Anna Akhmanova (Rot­ter­dam)

Dual label microscopy shows that micro­tubule tip com­plexes track into focal adhe­sions:

Video of a fish fibrob­last express­ing GFP-CLIP-170 and DsRed-zyxin recorded on a laser scan­ning con­fo­cal micro­scope. Note the repeated pen­e­tra­tion of micro­tubule tips into the periph­eral focal adhe­sions. (From Krylyshk­ina et al., 2003)

By using evanes­cent wave microscopy it can be demon­strated that the tracks are very close to the ven­tral cell sur­face (Krylyshk­ina et al., 2003). These tracks bring micro­tubule tip com­plexes close enough to focal adhe­sions for mol­e­c­u­lar exchanges to occur:

Evanes­cent wave microscopy of a fish fibrob­last trans­fected with GFP-CLIP-170 and DsRed zyxin. The micro­tubule tips enter the layer of excit­ing radi­a­tion within 100200nm above the sub­strate and track close to the ven­tral sur­face into focal adhe­sions. (From Krylyshk­ina et al., 2003)

Related Pub­li­ca­tions

  • Akhmanova, A. and Stein­metz, M., O. (2008). Track­ing the ends: a dynamic pro­tein net­work con­trols the fate of micro­tubule tips. Nat. Rev. Mol. Cell. Biol. 9, 309322. NCBI PubMed
  • Krylyshk­ina, O., Ander­son, K. I., Kave­rina, I., Upmann, I., Manstein, D. J., Small, J. V., Toomre, D. K. (2003). Nanome­ter tar­get­ing of micro­tubules to focal adhe­sions. J. Cell Biol. 161, 853859. PDF

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