Calneuron I與CaMKIIβ對於神經訊息傳遞的影響

Abstract

在神經生理中，鈣離子訊號複雜的模式與參與在鈣離子訊號傳遞中的鈣離子結合蛋白 (CaBPs) 有相當大的關聯。CaBP8，又稱為Calneuron I (CalnI)，會參與在鈣離子訊號傳遞中並抑制N型鈣離子通道的電流。CaMKII則是在神經突觸的發育與突觸可塑性中扮演重要的角色。在先前的研究中，CalnI與CaMKIIβ被指出可能有交互作用。為了確認CalnI對神經傳導的影響，將CalnI表現在初級培養的神經細胞中，並使用鈣離子影像技術紀錄其神經傳導的情形。除此之外，也利用Sholl analysis來分析表現CalnI的神經細胞其形態是否有所改變。另外在人類胚腎細胞 293T中同時表現CFP-CalnI及YFP-CaMKIIβ來觀察CalnI是否會影響CaMKIIβ在細胞內的分布情形。在表現CalnI的神經細胞中，神經傳導的功能被明顯的阻斷，而鈣離子誘導鈣釋放以及代謝型麩胺酸受體訊息路徑也會受到影響而使細胞內的鈣離子反應減弱。在神經細胞的形態上，神經元突起在遠端的分支數量也因為表現CalnI而明顯減少或變短。而在同時表現CFP-CalnI及YFP-CaMKIIβ的HEK 293T細胞中則發現CalnI確實會影響CaMKIIβ在細胞內的分布情形。綜合以上可知，CalnI會調控鈣離子通道並影響神經傳導，且很有可能與CaMKIIβ交互作用進一步影響突觸發育或可塑性。

The complex patterns of Calcium (Ca2+) signals in neuronal physiology can be largely attributed to calcium binding proteins (CaBPs) which participates in Ca2+ signaling pathway. CaBP8, also referred to as calneuron I (CalnI), is involved in transduction of Ca2+ signaling and inhibiting N-type Ca2+ channel currents. Ca2+/calmodulin-dependent protein kinase II (CaMKII) plays an important role in regulating synaptic development and plasticity. According to a previous study in our lab, a possible interaction between CalnI and CaMKIIβ was indicated by Yeast Two-Hybrid screening. To verify the effects of CalnI on neurotransmission, CalnI and related mutants were overexpressed in primary cultured neurons, and calcium imaging experiments were applied to characterize neurotransmission. In addition, CalnI overexpressed neurons were analyzed by Sholl analysis to investigate if there were any changes in morphology. In addition, CFP-CalnI and YFP-CaMKIIβ co-expressed HEK293T cells were examined to determine whether CalnI affects the localization of CaMKIIβ. The overexpression of CalnI in neurons caused significant deficits in neurotransmission, also decreased the Ca2+ responses in calcium-induced calcium release (CICR) and metabotropic glutamate receptor (mGluR) signaling pathway. In neuronal morphology, the distal branches of neurites in CalnI overexpressed neurons were obviously decreased. Moreover, the fluorescence imaging of CFP-CalnI and YFP-CaMKIIβ co-expressed HEK293T cells shows that the expression of CalnI does affect the localization of CaMKIIβ. Taken together, CalnI may regulate Ca2+ channels to influence neurotransmission, and possibly interacts with CaMKIIβ to further affect the synaptic development or plasticity.