Fig. 5. Arr-2 is required for rhabdomeric localization of TRPL channels. (A) Shown are representative cross-sections of single ommatidia from wild-type, arr1¹, arr2⁵, and arr2¹ mutants that were either dark-adapted (Dark), or light-exposed for 2 hours (Stage 1) or 12 hours (Stage 2), and then immunostained for TRPL. Whereas wild-type flies, arr1¹ and arr2¹ mutants displayed rhabdomeric localization of TRPL in the dark, arr2⁵ mutants exhibited a mislocalization of TRPL channels in a pattern similar to TRPL channels in wild-type photoreceptors after a 2-hour light-exposure. All arrestin mutants displayed TRPL staining in the stalk membrane after a 2-hour light-exposure and TRPL staining in the basolateral membrane after a 12-hour light-exposure. For stage 1, arr2⁵ mutants were light-exposed using a 50.7x10³ lux white-light source. Shown for each genotype and light condition are representative ommatidia from multiple retinal tissue sections; wild-type: see Fig. 1; arr1¹: five eyes of four flies (Dark), six eyes of five flies (Stage 1), four eyes of three flies (Stage 2); arr2⁵: 19 eyes of 13 flies (Dark), five eyes of five flies (Stage 1), eight eyes of seven flies (Stage 2); arr2¹: 11 eyes of ten flies (Dark), eight eyes of six flies (Stage 1), eight eyes of six flies (Stage 2). (B) Representative immunoblot showing the presence of wild-type Arr-2 protein and the C-terminal truncated Arr-2 (39 kD), expressed in wild type and arr2¹ mutants, respectively. The immunoblot was probed with a polyclonal antibody against the Nterminal sequence of Arr-2 (see Materials and Methods). Anti-INAD was used as a loading control.