Sha Di, Jin Hong, Kopke Richard D, Wu Jang-Yen
Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, USA.
Neurochem Res. 2004 Jan;29(1):199-207. doi: 10.1023/b:nere.0000010449.05927.f9.
Both the membrane-bound choline acetyltransferase (MChAT) and soluble ChAT (SChAT) were found to be activated by ATP-mediated protein phosphorylation. ATP activation of MChAT but not SChAT was found to depend on the integrity of proton gradient of synaptic vesicles because conditions disrupting the proton gradient also abolished the activation of MChAT by ATP. Among the kinases studied, Ca2+/calmodulin kinase II is most effective in activation of MChAT. Transport of ACh into synaptic vesicles by vesicular acetylcholine transporter (VAChT) is also proton gradient-dependent; therefore we proposed that there is a functional coupling between ACh synthesis and its packaging into synaptic vesicles. This notion is supported by the following findings: first, the newly synthesized [3H]-ACh from [3H]-choline was taken up much more efficiently than the pre-existing ACh; second, ATP-activation of MChAT was abolished when VAChT was inhibited by the specific inhibitor vesamicol; third, the activity of ChAT was found to be markedly increased when neurons are under depolarizing conditions.
膜结合型胆碱乙酰转移酶（MChAT）和可溶性胆碱乙酰转移酶（SChAT）均被发现可被ATP介导的蛋白质磷酸化激活。已发现MChAT而非SChAT的ATP激活依赖于突触小泡质子梯度的完整性，因为破坏质子梯度的条件也会消除ATP对MChAT的激活。在所研究的激酶中，Ca2+/钙调蛋白激酶II在激活MChAT方面最为有效。通过囊泡乙酰胆碱转运体（VAChT）将乙酰胆碱转运到突触小泡中也是质子梯度依赖性的；因此我们提出，乙酰胆碱合成与其包装到突触小泡之间存在功能偶联。这一观点得到以下发现的支持：第一，由[3H] - 胆碱新合成的[3H] - 乙酰胆碱比预先存在的乙酰胆碱摄取效率高得多；第二，当VAChT被特异性抑制剂vesamicol抑制时，MChAT的ATP激活被消除；第三，当神经元处于去极化条件下时，胆碱乙酰转移酶的活性显著增加。
