| Aspect | Key findings (1-2 sentences) | Evidence type (review/primary; cell line/animal/human cohort) | Key molecules/complexes | Representative sources with year+DOI/URL | Notes on ARL8A vs ARL8B specificity |
|---|---|---|---|---|---|
| Definition | ARL8A is the human ADP-ribosylation factor-like protein 8A, a small Arf-family GTPase and one of two vertebrate ARL8 paralogs; ARL8A and ARL8B are ~91% identical and share the core role of regulating lysosome dynamics. Family reviews place ARL8 proteins at the center of lysosomal positioning, trafficking, and fusion control. (pqac-00000000, pqac-00000002, pqac-00000011) | Review plus family-level experimental summary; mammalian cell biology | ARL8A/ARL8B, Arf family small GTPases | Khatter et al., 2015, doi:10.1080/21592799.2015.1086501, https://doi.org/10.1080/21592799.2015.1086501; Rizalar, 2022, doi:10.17169/refubium-36173, https://doi.org/10.17169/refubium-36173 | Much of the direct mechanistic literature is stronger for ARL8B, but family sources explicitly include ARL8A as the closely related human paralog. |
| Localization | ARL8A/ARL8B localize predominantly to lysosomes, showing high co-localization with lysosomal markers such as CD63 and LAMP2 rather than early endosome marker EEA1. Membrane association depends on an N-terminal amphipathic helix and N-terminal acetylation rather than canonical Arf myristoylation. (pqac-00000000, pqac-00000002, pqac-00000013) | Review and experimental localization studies; mammalian cells | Lysosome, CD63, LAMP2, amphipathic helix, NatC-mediated acetylation | Khatter et al., 2015, doi:10.1080/21592799.2015.1086501, https://doi.org/10.1080/21592799.2015.1086501; Rizalar, 2022, doi:10.17169/refubium-36173, https://doi.org/10.17169/refubium-36173 | Evidence explicitly names both ARL8A and ARL8B for lysosomal localization; acetylation data are best established for ARL8B but are generally discussed at the ARL8-family level. |
| Upstream recruitment to lysosomes | BORC acts upstream of ARL8 proteins and is required for ARL8A/ARL8B recruitment to lysosomes; BORC loss causes juxtanuclear lysosome clustering and prevents normal centrifugal dispersal. Forced kinesin attachment can bypass BORC deficiency, supporting a motor-recruitment role upstream of transport. (pqac-00000009, pqac-00000023, pqac-00000024, pqac-00000029) | Primary mechanistic studies in HeLa cells; review support | BORC, myrlysin/BORCS5, diaskedin, ARL8A/ARL8B | Guardia et al., 2016, doi:10.1016/j.celrep.2016.10.062, https://doi.org/10.1016/j.celrep.2016.10.062; Khatter et al., 2015, doi:10.1080/21592799.2015.1086501, https://doi.org/10.1080/21592799.2015.1086501 | Guardia et al. directly tested Arl8a/Arl8b together in motor-dependence experiments; older reviews often emphasize ARL8B as the best-characterized paralog. |
| Anterograde lysosome motility | In the GTP-bound state, ARL8 recruits SKIP/PLEKHM2, which binds kinesin light chain KLC2 and enables kinesin-1-dependent plus-end transport of lysosomes toward the cell periphery. Overexpression of ARL8 proteins or SKIP promotes peripheral lysosome redistribution, whereas depletion causes perinuclear clustering. (pqac-00000000, pqac-00000006, pqac-00000013, pqac-00000024, pqac-00000028) | Primary cell-line studies plus reviews; mammalian cells | SKIP/PLEKHM2, KLC2, kinesin-1/KIF5B | Guardia et al., 2016, doi:10.1016/j.celrep.2016.10.062, https://doi.org/10.1016/j.celrep.2016.10.062; Khatter et al., 2015, doi:10.1080/21592799.2015.1086501, https://doi.org/10.1080/21592799.2015.1086501 | Core mechanism is usually demonstrated with ARL8B, but family evidence and knockdown/KO logic indicate ARL8A contributes and can overlap functionally with ARL8B. |
| Kinesin-3 and track-specific transport | BORC-ARL8 functions upstream of kinesin-3 as well as kinesin-1; KIF1A/KIF1Bβ drive lysosome movement on more peripheral, tyrosinated microtubules, whereas KIF5B favors more central, acetylated microtubules. This establishes regional routing of lysosomes along different microtubule tracks. (pqac-00000008, pqac-00000023, pqac-00000025, pqac-00000027) | Primary mechanistic cell-line studies | KIF1A, KIF1Bβ, KIF5B, acetylated vs tyrosinated microtubules, BORC-ARL8 | Guardia et al., 2016, doi:10.1016/j.celrep.2016.10.062, https://doi.org/10.1016/j.celrep.2016.10.062; Shelke et al., 2023, doi:10.1083/jcb.202209084, https://doi.org/10.1083/jcb.202209084 | Direct kinesin-3 binding is commonly described for ARL8 family members; the literature usually does not isolate ARL8A-specific biochemistry from ARL8B here. |
| Retrograde positioning / bidirectional control | Although ARL8 is best known for outward movement, newer work shows it also participates in retrograde programs through effectors such as RUFY3/RUFY4 and DENND6A-Rab34-RILP-dynein, helping reposition lysosomes toward the juxtanuclear region under specific conditions. This reframes ARL8 as a bidirectional organizer rather than a purely anterograde factor. (pqac-00000010, pqac-00000008) | Primary mechanistic studies; mammalian cells | RUFY3, RUFY4, DENND6A, Rab34, RILP, dynein-dynactin | Kumar et al., 2024, doi:10.1038/s41467-024-44957-1, https://doi.org/10.1038/s41467-024-44957-1; Shelke et al., 2023, doi:10.1083/jcb.202209084, https://doi.org/10.1083/jcb.202209084 | Recent retrograde work is mostly centered on ARL8B or combined ARL8A/ARL8B depletion; ARL8A-specific contribution remains less resolved. |
| Fusion and degradative trafficking | ARL8 recruits HOPS-related machinery to lysosomes and promotes fusion of lysosomes with late endosomes and autophagic cargo carriers, supporting degradative trafficking. Disrupting ARL8-HOPS function impairs endolysosomal fusion and cargo degradation. (pqac-00000003, pqac-00000006, pqac-00000011, pqac-00000012) | Review plus primary cellular studies | HOPS, VPS41, VPS39, PLEKHM1, late endosomes, autophagosomes | Marwaha et al., 2017, doi:10.1083/jcb.201607085, https://doi.org/10.1083/jcb.201607085; Anderson et al., 2022, doi:10.1091/mbc.e21-11-0595-t, https://doi.org/10.1091/mbc.e21-11-0595-t; Khatter et al., 2015, doi:10.1080/21592799.2015.1086501, https://doi.org/10.1080/21592799.2015.1086501 | Direct binding/fusion studies are largely ARL8B-focused; ARL8A is inferred as a paralog with overlapping lysosomal functions unless otherwise specified. |
| Cholesterol egress pathway | The BORC-ARL8-HOPS ensemble is required for lysosomal cholesterol egress by enabling proper NPC2 delivery/retention in the endolysosomal system and supporting CI-MPR-dependent trafficking. Loss of BORC, ARL8, or HOPS leads to cholesterol accumulation in lysosomes and increased NPC2 secretion. (pqac-00000012) | Primary cell-line study with trafficking assays | BORC, ARL8, HOPS, NPC2, CI-MPR, lysosomal cholesterol | Anderson et al., 2022, doi:10.1091/mbc.e21-11-0595-t, https://doi.org/10.1091/mbc.e21-11-0595-t | Study examines ARL8 in a pathway context rather than isolating ARL8A alone; evidence supports ARL8-family relevance to cholesterol homeostasis. |
| Exosome secretion | Inhibition of BORC-ARL8-HOPS-dependent endolysosome fusion increases exosome secretion because multivesicular endosomes are less able to fuse with lysosomes and instead remain available for extracellular vesicle release. HeLa ARL8A/ARL8B double-KO cells were used in this mechanistic framework. (pqac-00000008) | Primary cell-line study; HeLa KO models | BORC, ARL8A/ARL8B, HOPS, MVEs, exosomes | Shelke et al., 2023, doi:10.1083/jcb.202209084, https://doi.org/10.1083/jcb.202209084 | This is one of the clearer recent settings where ARL8A/ARL8B are explicitly studied together via double knockout rather than ARL8B alone. |
| Autophagy | ARL8-dependent positioning intersects with autophagy: nutrient or pH shifts alter ARL8-associated lysosome localization, and perturbing ARL8-linked pathways can affect autophagic flux and LC3B accumulation. BORCS8 disease alleles that impair the BORC-ARL8 axis also cause lysosome clustering and LC3B accumulation, consistent with defective lysosome-autophagosome fusion. (pqac-00000006, pqac-00000010, pqac-00000016, pqac-00000018) | Reviews plus primary cell-line and disease-model studies | LC3B, BORC, DENND6A, lysosome-autophagosome fusion | Kumar et al., 2024, doi:10.1038/s41467-024-44957-1, https://doi.org/10.1038/s41467-024-44957-1; De Pace et al., 2024, doi:10.1093/brain/awad427, https://doi.org/10.1093/brain/awad427 | ARL8A-specific autophagy evidence is limited; most current evidence supports an ARL8-family role or uses BORC perturbation upstream of ARL8A/ARL8B. |
| Immune and specialized cell functions | ARL8-family lysosomal transport influences antigen presentation and specialized lysosome-related organelle positioning, including lysosome tubulation in macrophages/dendritic cells and trafficking relevant to CD1d/MHC II presentation. More recent phagocyte work links ARL8-positive endolysosome positioning to immune activation programs, although that literature is centered on ARL8B-positive compartments. (pqac-00000006, pqac-00000007) | Review and immune-cell primary studies | CD1d, MHC II, lytic granules, macrophage lysosome tubules | Khatter et al., 2015, doi:10.1080/21592799.2015.1086501, https://doi.org/10.1080/21592799.2015.1086501; Sharma et al., 2019, doi:10.16943/ptinsa/2019/49574, https://doi.org/10.16943/ptinsa/2019/49574 | Direct immune-function studies overwhelmingly emphasize ARL8B; ARL8A is usually implicated by paralogy rather than direct assay. |
| Neuronal / axonal relevance | ARL8-family proteins participate in long-range neuronal transport, and BORC-dependent recruitment of ARL8 and kinesins is important for distal axon lysosome transport. Human and zebrafish BORCS8 disease data underscore the importance of this pathway for CNS development and function. (pqac-00000000, pqac-00000015, pqac-00000017, pqac-00000018) | Experimental neurobiology and human genetics; animal models and human families | BORC, ARL8, kinesin-1, kinesin-3, distal axon lysosomes | De Pace et al., 2024, doi:10.1093/brain/awad427, https://doi.org/10.1093/brain/awad427; Rizalar, 2022, doi:10.17169/refubium-36173, https://doi.org/10.17169/refubium-36173 | Pathway-level evidence is strong, but ARL8A-specific neuronal assays in human remain sparse relative to ARL8-family or BORC-level evidence. |
| Human disease association | No monogenic human disease is established here for ARL8A itself, but ARL8 pathway disruption is disease-relevant: biallelic BORCS8 variants in five children caused severe infantile-onset neurodegenerative disease with impaired lysosome dispersal, and prostate cancer datasets showed a non-significant ARL8A survival trend. These data support translational relevance of the pathway more strongly than ARL8A as a standalone disease gene. (pqac-00000014, pqac-00000015, pqac-00000022, pqac-00000031) | Human cohort/genetics plus cell validation | BORCS8, ARL8 pathway, prostate cancer cohorts | De Pace et al., 2024, doi:10.1093/brain/awad427, https://doi.org/10.1093/brain/awad427; Nturubika et al., 2024, doi:10.1038/s41416-024-02829-x, https://doi.org/10.1038/s41416-024-02829-x | ARL8A-specific human association in prostate cancer was not statistically significant: log-rank P=0.1471, HR 1.927 (95% CI 0.6692-5.547); disease evidence is stronger for upstream BORC genes than for ARL8A itself. |
| Applications / real-world implementation | Current applications are mainly mechanistic and translational rather than clinical: ARL8 pathway components are used experimentally to manipulate lysosome positioning, degradative flux, cholesterol handling, and exosome release. In cancer and neurodegeneration research, this pathway is being studied as a systems-level vulnerability rather than as an established ARL8A-targeted therapy. (pqac-00000008, pqac-00000010, pqac-00000012, pqac-00000014) | Primary research applications in cell biology, cancer biology, and neurobiology | Exosomes, cholesterol trafficking, autophagy, lysosome positioning | Shelke et al., 2023, doi:10.1083/jcb.202209084, https://doi.org/10.1083/jcb.202209084; Kumar et al., 2024, doi:10.1038/s41467-024-44957-1, https://doi.org/10.1038/s41467-024-44957-1; Anderson et al., 2022, doi:10.1091/mbc.e21-11-0595-t, https://doi.org/10.1091/mbc.e21-11-0595-t | There is no evidence in the gathered set for an approved ARL8A-directed diagnostic or therapy; implementations are presently research-use and pathway-oriented. |


*Table: This table summarizes the strongest gathered evidence for human ARL8A functional annotation, emphasizing where evidence is direct for ARL8A versus inferred from the closely related paralog ARL8B or shared ARL8-family studies.*