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| Active transport of photoactivated tubulin molecules in growing axons revealed by a new electron microscopic analysis |
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| Author(s): Funakoshi T, Takeda S, Hirokawa N |
| Source: JOURNAL OF CELL BIOLOGY Volume: 133 Issue: 6 Pages: 1347-1353 Published: JUN 1996 |
| Times Cited: 37 References: 39 |
| Abstract: To determine whether tubulin molecules transported in axons are polymers or oligomers, we carried out electron microscopic analysis of the movement of the tubulin molecules after photoactivation. Although previous optical microscopic analyses after photobleaching or photoactivation had suggested that most of the axonal microtubules were stationary, they were not sufficiently sensitive to allow detection of actively transported tubulin molecules which were expected to be only a small fraction of total tubulin molecules in axons. In addition, some recent studies using indirect approaches suggested active polymer transport as a mechanism for tubulin transport (Baas, P.W., F.J. Ahmad. 1993. J. Cell Biol. 120:1427-1437; Yu, W., V.E. Centonze, F.J. Ahmad, and P.W. Bass. 1993. J. Cell Biol. 122:349-359; Ahmad, F.J., and P.W. Bass. 1995. J. Cell Sci 108:2761-2769). So, whether transported tubulin molecules are polymers or not remain to be determined. To clear up this issue, we made fluorescent marks on the tubulin molecules in the axons using a photoactivation technique and performed electron microscopic immunocytochemistry using anti-fluorescein antibody. Using this new method we achieved high resolution and high sensitivity for detecting the transported tubulin molecules. In cells fixed after permeabilization, we found no translocated microtubules. In those fixed without permeabilization, in which oligomers and heterodimers in addition to polymers were preserved, we found much more label in the regions distal to the photoactivated regions than in the proximal regions. These data indicated that tubulin molecules are transported not as polymers but as heterodimers or oligomers by an active mechanism rather than by diffusion. |
| Document Type: Article |
| Language: English |
Addresses:
1. UNIV TOKYO, FAC MED, DEPT ANAT & CELL BIOL, TOKYO 113, JAPAN |
| Publisher: ROCKEFELLER UNIV PRESS, 222 E 70TH STREET, NEW YORK, NY 10021 |
| Subject Category: Cell Biology |
| IDS Number: UT407 |
| ISSN: 0021-9525 |
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