1996 Fiscal Year Final Research Report Summary
Direct Observation of the Regulation of Microtubule Dynamics by MAP2 Phosporylation
| Project/Area Number |
07680715
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Biophysics
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| Research Institution | Nagoya University |
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Principal Investigator |
ITOH Tomohiko Nagoya University Graduate School of Science Associate Professor, 大学院・理学研究科, 講師 (30183742)
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| Project Period (FY) |
1995 – 1996
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| Keywords | microtubule / dynamic instability / MAP2 / phosphorylation / dark-field microscopy |
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| Research Abstract |
Phosphorylation-dependent regulation of microtubule-stabilizing activities of microtubule-associated protein 2 (MAP2) was examined using optical microscopy. MAP2, purified from mammalian brain, was phosphorylated by either cAMP-dependent protein kinase (PKA) or cyclin B-dependent cdc2 kinase. By PKA,15 mloles of phoshoryl groups was incorporated into one mole of MAP2, but about 70% was distributed to the projection region. By cdc2 kinase, 8-10 moles of phosphoryl groups was incorporated into one mole of MAP2 and more than 60% of the phosphates was distributed to the microtubule-binding region. Both phosphorylations similarly reduced binding activity of MAP2 onto microtubules. Direct observation of individual microtubules under a dark-field microscope showed that interconversion between polymerization phase and depolymerization phase was repeated in both unphosphorylated and PKA-phosphorylated MAP2. In cdc2 kinase-phosphorylated MAP2, however, phase transition from depolymerization to polymerization was difficult to take place, with the result that life-time of individual microtubules was as short as in the absence of MAP2. Examination of spontaneous nucleation of microtubules under a dark-field microscope showed that PKA-phosphorylated MAP2 redued nucleating-activity, while cdc2 kinase-phosphorylated MAP2 completely abolished it. These observations show that cdc2 kinase-dependent phosphorylation inhibited both microtubule-stabilizing activity and microtubule-nucleating activity of MAP2, while PKA-dependent phosphorylation affected only microtubule-nucleating activity of MAP2.
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