Mutations in apl-1 and ppk-3 or vacl-14 lead to defective processing of late endosomes and lysosomes in young adults.

<p>(A) In control animals and single apl-1(yn5), vacl-14(ok1877) and ppk-3(n2835) mutants late endosomes stained using GFP::RAB-7 as a marker were visible as vesicles or small vacuoles. Combination of the mutations in apl-1(yn5); vacl-14(ok1877) or apl-1(yn-5) ppk-3(n2835) double mutants led to a drastic alteration of the morphology of the late endosomal compartment, e.g. late endosomes became tubular and clustered in the hypoderm and intestine when comparing double with single mutants. While in single mutants individual compartments were abundant, they appeared 'squashed' and tubular in the double mutants (indicated by arrows). (B) Analysis of the lysosomal marker GFP::LMP-1 showed that in single apl-1(yn5), vacl-14(ok1877) and ppk-3(n2835) mutants distinct, LMP-1 positive vacuoles of variable sizes were apparent. However, in apl-1(yn5); vacl-14(ok1877) and apl-1(yn5) ppk-3(n2835) double mutants the LMP-1 positive structures appeared aggregated, mimicking the defect observed in GFP::RAB-7 worms, suggesting a defect in late endosomal and lysosomal trafficking. These data showed that APL-1 and the PPK-3 complex are required for late endosomal processing. Bar, 100μm.