Yoshida Tomoyuki, Uchida Satoshi, Mishina Masayoshi
Department of Molecular Neurobiology and Pharmacology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
J Neurochem. 2009 Oct;111(1):160-70. doi: 10.1111/j.1471-4159.2009.06309.x. Epub 2009 Jul 27.
The synaptic vesicle accumulation and subsequent morphological remodeling of axon terminals are characteristic features of presynaptic differentiation of zebrafish olfactory sensory neurons. The synaptic vesicle accumulation and axon terminal remodeling are regulated by protein kinase A and calcineurin signaling, respectively. To investigate upstream signals of presynaptic differentiation, we focused on Ca(2+) signaling as Ca(2+)/calmodulin is required for the activation of both calcineurin and some adenylyl cyclases. We here showed that application of Ca(2+)/calmodulin inhibitor or olfactory sensory neuron-specific expression of calmodulin inhibitory peptide suppressed both synaptic vesicle accumulation and axon terminal remodeling. Thus, the trigger of presynaptic differentiation could be Ca(2+) release from intracellular stores or Ca(2+) influx. Application of a phospholipase C inhibitor or olfactory sensory neuron-specific expression of inositol 1,4,5-trisphosphate (IP(3)) 5-phosphatase suppressed synaptic vesicle accumulation, but not morphological remodeling. In contrast, application of a voltage-gated Ca(2+) channel blocker or expression of Kir2.1 inward rectifying potassium channel prevented the morphological remodeling. We also provided evidence that IP(3) signaling acted upstream of protein kinase A signaling. Our results suggest that IP(3)-mediated Ca(2+)/calmodulin signaling stimulates synaptic vesicle accumulation and subsequent neuronal activity-dependent Ca(2+)/calmodulin signaling induces the morphological remodeling of axon terminals.
突触小泡的积累以及轴突终末随后的形态重塑是斑马鱼嗅觉感觉神经元突触前分化的特征性表现。突触小泡的积累和轴突终末的重塑分别受蛋白激酶A和钙调神经磷酸酶信号通路的调控。为了研究突触前分化的上游信号，我们聚焦于Ca(2+)信号，因为Ca(2+)/钙调蛋白是激活钙调神经磷酸酶和某些腺苷酸环化酶所必需的。我们在此表明，应用Ca(2+)/钙调蛋白抑制剂或在嗅觉感觉神经元中特异性表达钙调蛋白抑制肽可同时抑制突触小泡的积累和轴突终末的重塑。因此，突触前分化的触发因素可能是细胞内储存的Ca(2+)释放或Ca(2+)内流。应用磷脂酶C抑制剂或在嗅觉感觉神经元中特异性表达肌醇1,4,5-三磷酸（IP(3)）5-磷酸酶可抑制突触小泡的积累，但不影响形态重塑。相反，应用电压门控Ca(2+)通道阻滞剂或表达内向整流钾通道Kir2.1可阻止形态重塑。我们还提供了证据表明IP(3)信号通路作用于蛋白激酶A信号通路的上游。我们的结果表明，IP(3)介导的Ca(2+)/钙调蛋白信号通路刺激突触小泡的积累，随后神经元活动依赖性的Ca(2+)/钙调蛋白信号通路诱导轴突终末的形态重塑。
