Fig. 4.

Ceramidase expression does not facilitate Rh1 turnover in flies maintained in the dark. (A) A pulse of 1D4-tagged Rh1 was induced in w1118 control flies by heat shock for 1 h at 37°C, and proteins were extracted from retina 1, 2, 3, 4, 5, 7, and 8 days after heat shock and were analyzed by Western blot for the tagged Rh1. The flies were maintained in dark during the whole procedure until homogenization. Rh1 turned over slowly in flies maintained in the dark and had a longer half-life, and a substantial fraction was seen even on day 8. (B) A pulse of 1D4-tagged Rh1 was induced in flies expressing UAS-ceramidase under GMR-GAL4 and was analyzed as described in A. The rate of turnover was not enhanced as in the case of light, and a significant fraction of Rh1 was seen even on day 8. The blots were probed for IPP as loading controls (Lower).