FIGURE 7:

Intracellular csA-SibA is localized in early endocytic compartments. Wild-type and phg1A mutant cells expressing csA-SibA were fixed and permeabilized, and intracellular csA-SibA was detected with a rabbit antibody recognizing the SibA cytosolic domain, and a fluorescent secondary antibody (red). In the same cells, p25 (A and B) or p80 (C) were detected with specific mouse antibodies (green). (B) An enlarged portion of (A). In both wild-type and phg1A cells, csA-SibA was present in intracellular compartments positive for p25 (arrowheads) but not for p80. Some p25-positive compartments did not contain csA-SibA (asterisks), suggesting that csA-SibA is sorted differently from p25 in the early endocytic pathway. Note that in these experiments, surface csA-SibA is difficult to detect due to cell permeabilization.