Translocation of the Drosophila Transient Receptor Potential-like (TRPL) Channel Requires Both the N- and C-terminal Regions Together with Sustained Ca2+ Entry

In Drosophila photoreceptors the transient receptor potential-like (TRPL), but not the TRP channels undergo light-dependent translocation between the rhabdomere and cell body. Here we studied which of the TRPL channel segments are essential for translocation and why the TRP channels are required for inducing TRPL translocation. We generated transgenic flies expressing chimeric TRP and TRPL proteins that formed functional light-activated channels. Translocation was induced only in chimera containing both the N- and C-terminal segments of TRPL. Using an inactive trp mutation and overexpressing the Na+/Ca2+ exchanger revealed that the essential function of the TRP channels in TRPL translocation is to enhance Ca2+-influx. These results indicate that motifs present at both the N and C termini as well as sustained Ca2+ entry are required for proper channel translocation.