Figure 5.

Rho_Q344ter-Dend2 induces internalization of NKAα. A, Rho_Q344ter-Dend2 (green) was expressed together with NKAα fused to PSmOrange fluorescent protein (magenta) in rod photoreceptors. These transgenic tadpoles aged 9 DPF were treated for 24 h with either DMSO (Control) or 100 nm BA1 (BA1). BA1-treated rods exhibited vesicles containing both Rho_Q344ter-Dend2 and PSmOrange-NKAα in the ISs. B, Comparative quantification of intracellular fluorescence from PSmOrange-NKAα in either the presence (+) or absence (−) of 100 nm BA1 and either with (+Q344ter) or without coexpression of Rho_Q344ter-Dend2. Nearly equal amounts of PSmOrange-NKAα were observed among untreated and BA1-treated cells expressing only PSmOrange-NKAα (NS, p = 0.35; based on 80 untreated cells and 140 BA1-treated cells from n = 4 animals each). Conversely, BA1-treated cells expressing both PSmOrange-NKAα and Rho_Q344ter-Dend2 had significantly increased amounts of PSmOrange-NKAα in the ISs compared with untreated cells expressing both PSmOrange-NKAα and Rho_Q344ter-Dend2 (p < 0.001; based on 160 untreated cells and 173 BA1-treated cells from n = 4 animals each). This difference suggests that the presence of Rho_Q344ter-Dend2 was required to bring PSmOrange-NKAα to the IS lysosomes for degradation. C, Cells expressing only the PSmOrange-NKAα fusion protein without Rho_Q344ter-Dend2 did not significantly accumulate PSmOrange-NKAα upon treatment with BA1. Scale bars, 10 μm. ***p < 0.001, NS, not significant.