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TACC3 is a microtubule plus end-tracking protein that promotes axon elongation and also regulates microtubule plus end dynamics in multiple embryonic cell types.

Nwagbara BU, Faris AE, Bearce EA, Erdogan B, Ebbert PT, Evans MF, Rutherford EL, Enzenbacher TB, Lowery LA - Mol. Biol. Cell (2014)

Bottom Line: Using high-resolution live-imaging data on tagged +TIPs, we show that TACC3 localizes to the extreme microtubule plus end, where it lies distal to the microtubule polymerization marker EB1 and directly overlaps with the microtubule polymerase XMAP215.TACC3 also plays a role in regulating XMAP215 stability and localizing XMAP215 to microtubule plus ends.Taken together, our results implicate TACC3 as a +TIP that functions with XMAP215 to regulate microtubule plus end dynamics.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.

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TACC3 can act as a +TIP in nonneuronal embryonic cells. (A–C) Expression of mKate2-tubulin (A), GFP-TACC3 (B), and merge (C) in cultured fibroblasts derived from embryonic somitic mesoderm. See Figure 4 Supplemental Movie 1. (A′–C′) Magnified views of the boxed regions in A–C. See Figure 4 Supplemental Movie 2. (A′′–C′′) Magnified time-lapse montages of the boxed regions in A′–C′. (D) Time-lapse montage of another MT in the process of undergoing catastrophe, with GFP-TACC3 localizing. (E) Fluorescence intensity profile of line-scan average from 43 MT plus ends. (F) Histogram depicting the distribution of lengths of detectable GFP-TACC3 localization on the plus ends of MTs. (G) Percentage of MT plus ends with GFP-TACC3 localization for different MT dynamics instability states. (H) Quantification of mean fluorescence intensity of 4 × 4 pixel square of GFP-TACC3 accumulation on the ends of MTs, when visible. Box-and-whisker plots indicate the mean (diamond), median, extrema, and quartiles. Bar, 1 μm.
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Figure 4: TACC3 can act as a +TIP in nonneuronal embryonic cells. (A–C) Expression of mKate2-tubulin (A), GFP-TACC3 (B), and merge (C) in cultured fibroblasts derived from embryonic somitic mesoderm. See Figure 4 Supplemental Movie 1. (A′–C′) Magnified views of the boxed regions in A–C. See Figure 4 Supplemental Movie 2. (A′′–C′′) Magnified time-lapse montages of the boxed regions in A′–C′. (D) Time-lapse montage of another MT in the process of undergoing catastrophe, with GFP-TACC3 localizing. (E) Fluorescence intensity profile of line-scan average from 43 MT plus ends. (F) Histogram depicting the distribution of lengths of detectable GFP-TACC3 localization on the plus ends of MTs. (G) Percentage of MT plus ends with GFP-TACC3 localization for different MT dynamics instability states. (H) Quantification of mean fluorescence intensity of 4 × 4 pixel square of GFP-TACC3 accumulation on the ends of MTs, when visible. Box-and-whisker plots indicate the mean (diamond), median, extrema, and quartiles. Bar, 1 μm.

Mentions: Plus end tracking of GFP-TACC3 was not restricted to neural-derived cells, as fibroblasts isolated from mesodermal somite tissue also showed clear plus end tracking (Figure 4, A–C, and Figure 4 Supplemental Movies 1 and 2). We also observed on several occasions that shrinking MTs paused concurrently with obvious accumulation of GFP-TACC3 (Figure 4D). This was most apparent in the mesodermal and neural crest cells, as these had greater numbers of MTs to examine. The plot profiles and distribution of GFP-TACC3 on MT plus ends in fibroblasts were similar to that of the neural cell types, with mean length of GFP-TACC3 plus end accumulation being 0.67 μm (Figure 4, E and F, data measured from 55 MTs). GFP-TACC3 accumulation was detectable on 100% of growing MTs, 70% of paused MTs, and 25% of shrinking MTs (Figure 4G; see also Figure 4 Supplement for an example of GFP-TACC3 on shrinking MT). Measuring fluorescence intensity values of GFP-TACC3 localized at the tips of MTs demonstrated that whereas GFP-TACC3 was observable on one-fourth of shrinking MTs (Figure 4G), mean GFP intensities were ∼40% less on shrinking MTs than on growing MTs. In addition, the maximum intensity of GFP-TACC3 fluorescence on shrinking MTs (106 fluorescence units; top whisker in Figure 4H, box plot) was close to half that of the maximum intensity of fluorescence on growing MTs (172 fluorescence units; Figure 4H), demonstrating that the maximum number of GFP-TACC3 molecules that localize to shrinking MTs is not as great as those that can bind to growing MT plus ends. Thus our results demonstrate that TACC3 can act as a +TIP in multiple vertebrate embryonic cell types and also support the notion that TACC3 may either promote MT polymerization or reduce MT catastrophe.


TACC3 is a microtubule plus end-tracking protein that promotes axon elongation and also regulates microtubule plus end dynamics in multiple embryonic cell types.

Nwagbara BU, Faris AE, Bearce EA, Erdogan B, Ebbert PT, Evans MF, Rutherford EL, Enzenbacher TB, Lowery LA - Mol. Biol. Cell (2014)

TACC3 can act as a +TIP in nonneuronal embryonic cells. (A–C) Expression of mKate2-tubulin (A), GFP-TACC3 (B), and merge (C) in cultured fibroblasts derived from embryonic somitic mesoderm. See Figure 4 Supplemental Movie 1. (A′–C′) Magnified views of the boxed regions in A–C. See Figure 4 Supplemental Movie 2. (A′′–C′′) Magnified time-lapse montages of the boxed regions in A′–C′. (D) Time-lapse montage of another MT in the process of undergoing catastrophe, with GFP-TACC3 localizing. (E) Fluorescence intensity profile of line-scan average from 43 MT plus ends. (F) Histogram depicting the distribution of lengths of detectable GFP-TACC3 localization on the plus ends of MTs. (G) Percentage of MT plus ends with GFP-TACC3 localization for different MT dynamics instability states. (H) Quantification of mean fluorescence intensity of 4 × 4 pixel square of GFP-TACC3 accumulation on the ends of MTs, when visible. Box-and-whisker plots indicate the mean (diamond), median, extrema, and quartiles. Bar, 1 μm.
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Related In: Results  -  Collection

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Figure 4: TACC3 can act as a +TIP in nonneuronal embryonic cells. (A–C) Expression of mKate2-tubulin (A), GFP-TACC3 (B), and merge (C) in cultured fibroblasts derived from embryonic somitic mesoderm. See Figure 4 Supplemental Movie 1. (A′–C′) Magnified views of the boxed regions in A–C. See Figure 4 Supplemental Movie 2. (A′′–C′′) Magnified time-lapse montages of the boxed regions in A′–C′. (D) Time-lapse montage of another MT in the process of undergoing catastrophe, with GFP-TACC3 localizing. (E) Fluorescence intensity profile of line-scan average from 43 MT plus ends. (F) Histogram depicting the distribution of lengths of detectable GFP-TACC3 localization on the plus ends of MTs. (G) Percentage of MT plus ends with GFP-TACC3 localization for different MT dynamics instability states. (H) Quantification of mean fluorescence intensity of 4 × 4 pixel square of GFP-TACC3 accumulation on the ends of MTs, when visible. Box-and-whisker plots indicate the mean (diamond), median, extrema, and quartiles. Bar, 1 μm.
Mentions: Plus end tracking of GFP-TACC3 was not restricted to neural-derived cells, as fibroblasts isolated from mesodermal somite tissue also showed clear plus end tracking (Figure 4, A–C, and Figure 4 Supplemental Movies 1 and 2). We also observed on several occasions that shrinking MTs paused concurrently with obvious accumulation of GFP-TACC3 (Figure 4D). This was most apparent in the mesodermal and neural crest cells, as these had greater numbers of MTs to examine. The plot profiles and distribution of GFP-TACC3 on MT plus ends in fibroblasts were similar to that of the neural cell types, with mean length of GFP-TACC3 plus end accumulation being 0.67 μm (Figure 4, E and F, data measured from 55 MTs). GFP-TACC3 accumulation was detectable on 100% of growing MTs, 70% of paused MTs, and 25% of shrinking MTs (Figure 4G; see also Figure 4 Supplement for an example of GFP-TACC3 on shrinking MT). Measuring fluorescence intensity values of GFP-TACC3 localized at the tips of MTs demonstrated that whereas GFP-TACC3 was observable on one-fourth of shrinking MTs (Figure 4G), mean GFP intensities were ∼40% less on shrinking MTs than on growing MTs. In addition, the maximum intensity of GFP-TACC3 fluorescence on shrinking MTs (106 fluorescence units; top whisker in Figure 4H, box plot) was close to half that of the maximum intensity of fluorescence on growing MTs (172 fluorescence units; Figure 4H), demonstrating that the maximum number of GFP-TACC3 molecules that localize to shrinking MTs is not as great as those that can bind to growing MT plus ends. Thus our results demonstrate that TACC3 can act as a +TIP in multiple vertebrate embryonic cell types and also support the notion that TACC3 may either promote MT polymerization or reduce MT catastrophe.

Bottom Line: Using high-resolution live-imaging data on tagged +TIPs, we show that TACC3 localizes to the extreme microtubule plus end, where it lies distal to the microtubule polymerization marker EB1 and directly overlaps with the microtubule polymerase XMAP215.TACC3 also plays a role in regulating XMAP215 stability and localizing XMAP215 to microtubule plus ends.Taken together, our results implicate TACC3 as a +TIP that functions with XMAP215 to regulate microtubule plus end dynamics.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.

Show MeSH
Related in: MedlinePlus