The multiple functions of cysteine-string protein analyzed at Drosophila nerve terminals
The multiple functions of cysteine-string protein analyzed at Drosophila nerve terminals
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DOI：
10.1523/jneurosci.3610-04.2005
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发表时间：
2005-03-02
影响因子：
5.3
通讯作者：
Zinsmaier, KE
中科院分区：
文献类型：
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作者：
Bronk, P;Nie, ZP;Zinsmaier, KE
突触囊泡相关半胱氨酸串蛋白（CSP）在突触传递中起重要作用.先前的研究揭示了csp无效突变果蝇的神经肌肉接头（NMJ）处的多个缺陷，但这些缺陷是彼此独立的还是通过J结构域介导的与热休克同源蛋白70（Hsc 70）的相互作用而机制性地联系在一起尚未确定。为了解决这个问题，我们在体内结构/功能分析的CSP的遗传解剖的个人功能。缺乏J结构域的突变型CSP在csp空突变型NMJ中的表达完全恢复了诱发递质释放的正常热耐受性，但在室温下并未完全恢复诱发释放，并且未能逆转异常的末端内Ca（2+）水平。这表明J结构域介导的功能对于调节终末内Ca（2+）水平是必需的，但对于调节诱发释放仅部分需要，而对于保护诱发释放对抗热应激不需要。因此，CSP也可以作为一个Hsc 70独立的伴侣保护诱发释放热应力。缺乏L结构域的突变CSP的表达恢复了神经传递，并部分逆转了异常的终末内Ca（2+）水平，这表明L结构域对于CSP调节终末内Ca（2+）水平的作用是重要的，尽管不是必需的。我们检测到csp突变对动作电位触发的单个突触前Ca（2+）信号没有影响，表明突触前Ca（2+）内流并不主要受损。J和L结构域也是CSP在突触生长中发挥作用所必需的。总之，这些结果表明，CSP有几个独立的突触功能，影响突触生长，诱发释放，诱发释放的热保护，以及在休息和刺激过程中的终末内Ca（2+）水平。
The synaptic vesicle- associated cysteine- string protein ( CSP) is important for synaptic transmission. Previous studies revealed multiple defects at neuromuscular junctions (NMJs) of csp null- mutant Drosophila, but whether these defects are independent of each other or mechanistically linked through J domain mediated- interactions with heat- shock cognate protein 70 ( Hsc70) has not been established. To resolve this issue, we genetically dissected the individual functions of CSP by an in vivo structure/ function analysis. Expression of mutant CSP lacking the J domain at csp null- mutant NMJs fully restored normal thermo- tolerance of evoked transmitter release but did not completely restore evoked release at room temperature and failed to reverse the abnormal intraterminal Ca (2+) levels. This suggests that J domain- mediated functions are essential for the regulation of intraterminal Ca (2+) levels but only partially required for regulating evoked release and not required for protecting evoked release against thermal stress. Hence, CSP can also act as an Hsc70- independent chaperone protecting evoked release from thermal stress. Expression of mutant CSP lacking the L domain restored neurotransmission and partially reversed the abnormal intraterminal Ca (2+) levels, suggesting that the L domain is important, although not essential, for the role of CSP in regulating intraterminal Ca2+ levels. We detected no effects of csp mutations on individual presynaptic Ca (2+) signals triggered by action potentials, suggesting that presynaptic Ca (2+) entry is not primarily impaired. Both the J and L domains were also required for the role of CSP in synaptic growth. Together, these results suggest that CSP has several independent synaptic functions, affecting synaptic growth, evoked release, thermal protection of evoked release, and intraterminal Ca (2+) levels at rest and during stimulation.