| Abstract No.: | C-A3013 |
| Country: | Canada |
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| Title: | NCS-1, NEURITE OUTGROWTH, AND GROWTH CONE AND SOMATA CALCIUM CURRENTS |
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| Authors/Affiliations: | 1 Kwokyin Hui*; 1 Bechara Saab; 1 Guang-He Fei; 1 Jiang Su; 1 John Roder; 1 Zhong-Ping Feng;
1 University of Toronto, ON, Canada;
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| Content: | Ca2+ is an important modulator of growth cone guidance, regulating the outgrowth and branching of neurites and gene expression in somata. Therefore, elucidating the mechanisms that regulate the calcium currents in the growth cones and somata of growing neurons is important in understanding neuronal development and regeneration. Neuronal calcium sensor-1 (NCS-1) is a calcium-binding protein known to facilitate synaptic transmission. NCS-1 was recently reported to modulate neurite outgrowth in the PC12 cell line by regulating calcium influx through the transient-receptor potential channel TRPC5. NCS-1 was also shown to facilitate calcium influx through voltage-dependent calcium channels; for example, a peptide of the C-terminus of NCS-1 prevents frequency-dependent facilitation of P/Q-type calcium currents in the calyx of Held synapse. Based on these reports, we hypothesize that NCS-1, via its C-terminus, regulates neurite outgrowth by regulating calcium currents in the growth cones.
Materials and Methods. Taking advantage of the large size of the pedal A (PeA) neurons in Lymnaea stagnalis, we examined the effects of NCS-1 on neurite outgrowth using both a C-terminal peptide (CTN), as well as siRNA knockdown. We then examined the effects of these treatments on calcium influx in the growth cones using fura-2 ratiometric calcium-imaging and whole-cell (ruptured) patch-clamp recording techinques. Lastly, we compared the biophysical properties of somata and growth cone whole-cell calcium channel currents using barium and calcium as current carriers.
Results. We found that knockdown of NCS-1 enhances neurite outgrowth and branching, whereas the CTN peptide only enhanced branching. Moreover, knockdown and CTN both reduced frequency-dependent calcium influx in growth cones, with the latter having a lesser effect. Finally, in contrast to growth cones, the biophysical properties of somata calcium currents were not affected by the CTN peptide.
Conclusion. Our findings suggest that the C-terminus of NCS-1 is involved in specific regulation of growth cone calcium currents, and subsequently neurite outgrowth.
This work was supported by the Canadian Institutes of Health Research (MOP 62738). |
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