Calcium/calmodulin-dependent inhibition of microtubule assembly by brain synaptic junction |
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Authors: | Tatsuo Suzuki Toshihiro Fujii Ryo Tanaka |
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Institution: | (1) Department of Biochemistry, Nagoya City University Medical School, Mizuho-ku, 467 Nagoya, Japan;(2) Department of Functional Polymer Science Faculty of Textile Science and Technology, Shinshu University, 386 Ueda, Japan |
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Abstract: | The effect of synaptic junction (SJ) on microtubule assembly was examined. After preincubation with ATP at 37°C, rat SJ decreased the initial velocity and the extent of the porcine brain microtubule assembly (initiated by the addition of GTP) in a Ca2+/calmodulin (CaM)-dependent manner. The degree of the inhibition reached 35% of the control assembly (0-min preincubation) after 20-min preincubation with ATP. There was no inhibition either with heat-treated SJ, at 0°C, or in the presence of EGTA or W-7 (CaM antagonist). The inhibition was due neither to protease(s) nor CaM contaminating the preparations. Free Ca2+ concentration level required for the inhibition of microtubule assembly was 10–6 M. Phosphorylation of microtubule proteins was inhibited by SJ in a Ca2+/CaM-dependent manner, and the inhibition occurred in a physiological increase range of intracellular Ca2+ concentration (10–6M) The heat-treated SJ caused no inhibition. The result suggested that the microtubule assembly in the postsynaptic region was regulated by a Ca2+/CaM-dependent protein kinase associated with SJ; i. e., major postsynaptic density protein.Abbreviations used CaM
calmodulin
- DTT
dithiothreitol
- MAPs
microtubule-associated proteins
- MES
2-(N-morphorino)ethanesulfonic acid
- mPSDp
major postsynaptic density protein
- PSD
postsynaptic density
- SDS PAGE
sodium dodecyl sulfate polyacrylamide gel electrophoresis
- W-7
N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride |
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