Autophagy is a lysosome-dependent degradation and recycling pathway essential for cellular homeostasis. Late-stage autophagy depends on lysosomal fusion machinery. Rab GTPases are master regulators of intracellular vesicle traffic, and many Rabs participate in the regulation of autophagy. This thesis combines compound screening, tissue-level Rab24 analysis, and mechanistic studies to investigate pharmacological autophagy modulation, Rab24 protein levels in tissues, and the role of Rab24 in lysosome-directed fusion events. Candidate autophagy modulators were evaluated in A549 cells by confocal microscopy for effects on autophagic flux, using the autophagy markers LC3 and p62. The tested compounds showed distinct, condition-dependent effects: famciclovir reduced autophagy flux under basal (fed) but not starvation conditions, while vioprolides suppressed the flux under both fed and starvation conditions. In a canine fibroblast model of neuronal vacuolation and spinocerebellar degeneration, slightly elevated basal LC3 flux and a blunted starvation response were observed. None of the tested compounds normalized flux to wild-type levels. Rab24 protein abundance was mapped across mouse tissues during postnatal development and adulthood and assessed across human cancers using tissue microarrays. Rab24 levels were tissue- and age-dependent, with enrichment in brain and several epithelial cell types. Rab24 protein levels also varied across tumor entities: elevated levels were detected in breast and skin cancers and in cancers of neuronal origin, while pancreatic neuroendocrine tumors showed reduced Rab24 levels. Finally, mechanistic studies in Neuro-2a cells linked Rab24 to lysosomal delivery: Rab24 knockout altered the balance of autophagic and degradative compartments without detectable defects in lysosomal activity. APEX2 proximity proteomics and co-immunoprecipitation identified the homotypic fusion and vacuolar protein sorting (HOPS) tethering complex and Rab7a as Rab24 interactors. The ataxia-associated Rab24-Q38P mutation weakened these interactions without loss of GTP binding. Together, the results support a model in which Rab24 promotes autophagic clearance by facilitating HOPS-dependent fusion events. The thesis places Rab24 function into tissue contexts relevant for neurodegeneration and cancer.