Figure 2

STIM1-dependent SOCE operates and mediates netrin-1-induced Ca²⁺elevation in Xenopus neuronal growth cones. (A) A schematic diagram of full-length wild-type (WT) and mutant constructs of XSTIM1. (B) Bright field and pseudocolor images of fluo-4 fluorescence of growth cones of Xenopus spinal neurons from the uninjected or mcherry-XSTIM1-DN injected embryos in the presence of CPA in Ca²⁺-free media, before and after the re-addition of 1.5 mM Ca²⁺ bath solution. Pseudocolors indicate Ca²⁺ levels, with white as the highest and black as the lowest. Scale bar: 10 μm. (C) Summary of internal Ca²⁺ store depletion-induced Ca²⁺ entry in growth cones at different time points before and after re-addition of 1.5 mM Ca²⁺. The fluorescence intensity was normalized to the average fluorescence intensity of 2 min baseline levels prior to Ca²⁺ re-addition. Values represent mean ± s.e.m. (n = 25 for control, n = 10 for XSTIM1-DN and n = 19 for hSTIM1-DN; * indicates P < 0.01; Bootstrap-test). (D) XTRPC1 is required for store depletion-evoked Ca²⁺ entry in neuronal growth cones. Summary of internal Ca²⁺ store depletion-induced Ca²⁺ entry in growth cones from the control-MO or XTRPC1-MO injected embryos at different time points before and after the re-addition of 1.5 mM Ca²⁺. Values represent mean ± s.e.m. (n = 12 for control, and n = 13 for XTRPC1-MO; * indicates P < 0.01; Bootstrap-test). (E) XSTIM1 is required for netrin-1-induced Ca²⁺ elevation in growth cone. Summary of time course of Ca²⁺ changes in neuronal growth cones from uninjected or mCherry-XSTIM1-DN mRNA injected embryos. The fluorescence intensity was normalized to the average fluorescence intensity of 2 min baseline levels prior to the netrin-1 application (10 ng/ml). Values represent mean ± s.e.m. (n = 6 for control and n = 9 for XSTIM1-DN; * indicates P < 0.05; Bootstrap-test).