Figure 6.

VhaPRR regulates vesicular acidification and lysosomal degradation. (A, B) Prepupal wings (5 h APF) were incubated with Lysotracker (red). In apical sections of VhaPRR clones (within dotted line), vesicular Lysotracker uptake was reduced compared with the wild-type tissue (A). In more basal sections, overall uptake was comparable, although some Lysotracker-positive vesicles within the clones appeared enlarged (B, B′). Nuclei (in blue) are normal in number and appearance inside the clone (B′). A x–z projection of another clone is presented in the inset of (B′). Here, apical is up and basal is down. Note the absence of apical Lysotracker signal. (C, D) Pretreatment with the V-ATPase inhibitor Concanamycin A abolished most of the Lysotracker signal in apical (C) and basal (D, D′) sections of wild-type and mutant cells. (E, E′) The ubiquitously expressed GFP–LAMP1 strongly accumulates in cells mutant for VhaPRR, suggesting impaired endolysosomal maturation in pupal wings at 28 h APF. E-Cadherin staining in (E″) shows cell outlines. (F, F′, F′′, G, G′, G′′) Combined Lysotracker uptake and visualization of GFP–LAMP1 shows compartments that accumulate LAMP1 but lack acidification. Most of these compartments can be found in apical cell sections (F′, F″).