Affinage

ARL5A

ADP-ribosylation factor-like protein 5A · UniProt Q9Y689

Length
179 aa
Mass
20.7 kDa
Annotated
2026-06-09
15 papers in source corpus 9 papers cited in narrative 9 extracted findings
Cross-family judge faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

ARL5A is an ARF-family small GTPase that governs endosome-to-trans-Golgi-network (TGN) retrograde trafficking through a nucleotide-state-dependent effector cascade (PMID:22245584, PMID:31575603). It is recruited to the TGN downstream of the master regulator ARFRP1, which coordinates a bifurcated GTPase cascade in which ARL1 recruits golgin tethers while ARL5 recruits the GARP tethering complex (PMID:31575603); ARL5 binds GARP directly and is required to keep GARP membrane-associated, with loss of ARL5 displacing GARP to the cytosol, enlarging late endosomes, and impairing retrograde delivery of cargo such as TGN38, Shiga toxin, and the mannose-6-phosphate receptor without affecting anterograde transport (PMID:25795912, PMID:22245584). In its active GTP-bound state ARL5 also engages the armadillo-repeat effector ARMH3 and recruits/stimulates PI4KB at the TGN, generating the principal TGN pool of PI4P that supports protein secretion and glycan modification; this lipid-kinase arm is genetically separable from the GARP-dependent retrograde arm (PMID:35844135, PMID:39580461). ARL5 activity is coupled to nutrient state: amino acids stimulate retrograde trafficking through SLC38A9, v-ATPase, and Ragulator, with Ragulator acting on ARL5 to promote GARP-dependent transport independently of Rag GTPases and mTORC1 (PMID:30478271). ARL5A additionally localizes to nuclei and nucleoli and binds heterochromatin protein 1α (HP1α) in a GTP-dependent manner, with nuclear import mediated by a C-terminal bipartite NLS interacting with importin-α (PMID:12414990). ARL5A is downregulated by miR-202-3p, and its knockdown inhibits colorectal cancer cell proliferation (PMID:24327274).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 1996 Low

    Established ARL5 as a distinct ARF-family GTPase, defining the molecular class within which all later mechanism would be interpreted.

    Evidence Degenerate-primer PCR cloning, sequence analysis of GTP-binding motifs, and Northern blot tissue survey in rat

    PMID:8765741

    Open questions at the time
    • No functional mechanism established beyond family membership
    • Subcellular localization and effectors unknown at this stage
  2. 2002 High

    First functional characterization placed ARL5A in the nucleus/nucleolus and identified a nucleotide-state-dependent HP1α interaction, raising a chromatin-associated role distinct from later Golgi findings.

    Evidence Yeast two-hybrid, in vitro pulldown and Co-IP in COS cells, T35N/Q80L mutant localization, myristoylation and NLS/importin-α analysis

    PMID:12414990

    Open questions at the time
    • Functional consequence of HP1α binding for heterochromatin or gene expression not defined
    • Relationship between nuclear and Golgi pools of ARL5A unresolved
  3. 2012 High

    Localized ARL5 to the TGN and demonstrated a cargo-selective requirement in retrograde, but not anterograde, transport, defining its core trafficking function.

    Evidence Constitutively active/dominant-negative mutant expression, RNAi, and retrograde (TGN38, Shiga toxin) versus anterograde (E-cadherin) transport assays

    PMID:22245584

    Open questions at the time
    • Molecular effector mediating retrograde transport not yet identified
    • Mechanism of TGN recruitment unknown
  4. 2015 High

    Identified the GARP tethering complex as a direct ARL5 effector, providing the molecular basis for ARL5-dependent retrograde delivery and showing conservation from Drosophila to human.

    Evidence Liposome and affinity-chromatography binding assays, Drosophila Arl5 knockout, and ARL5B RNAi in HeLa with GARP localization readouts

    PMID:25795912

    Open questions at the time
    • How ARL5 is itself activated/recruited to the TGN not addressed
    • Functional distinction between ARL5A and ARL5B paralogs not resolved
  5. 2018 Medium

    Linked nutrient sensing to retrograde trafficking by showing amino acids activate ARL5 via a SLC38A9/v-ATPase/Ragulator module independent of Rag GTPases and mTORC1.

    Evidence Co-IP, RNAi of pathway components, and amino acid stimulation/starvation retrograde trafficking assays

    PMID:30478271

    Open questions at the time
    • GEF activity of Ragulator toward ARL5 proposed but not demonstrated in vitro
    • Structural basis of the Ragulator-ARL5 interaction unknown
  6. 2019 High

    Placed ARL5 in an ARFRP1-governed bifurcated GTPase cascade, clarifying how a single upstream regulator coordinates parallel ARL1-golgin and ARL5-GARP tethering arms at the TGN.

    Evidence Genetic epistasis with ARFRP1/ARL1/ARL5 knockdown/knockout, fluorescence localization, and retrograde transport assays in mammalian cells

    PMID:31575603

    Open questions at the time
    • Direct nucleotide-exchange relationships within the cascade not biochemically reconstituted
    • Quantitative contribution of each arm to specific cargo not parsed
  7. 2022 Medium

    Extended ARL5 function beyond tethering by identifying PI4KB as an interactor recruited to the TGN to support PI4P synthesis and secretion.

    Evidence miniTurboID proximity biotinylation with TMT mass spectrometry, interaction assays, and secretion assays

    PMID:35844135

    Open questions at the time
    • Whether PI4KB binding is direct or bridged by another effector not fully resolved
    • Single-lab interactome
  8. 2024 High

    Defined the complete TGN recruitment axis (SYS1-ARFRP1-ARL5) and identified ARMH3 as a GTP-dependent effector that activates PI4KB for PI4P/GOLPH3-dependent glycosylation, separating the lipid-kinase arm from the GARP retrograde arm.

    Evidence Proximity biotinylation, direct binding assays, RNAi/KO, PI4P lipid measurements, transport assays, and active/dominant-negative mutant analysis

    PMID:39580461

    Open questions at the time
    • Structural basis of ARMH3-ARL5 recognition not solved
    • How ARL5 partitions between GARP and ARMH3 effector arms not quantified

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the nuclear/HP1α-associated pool of ARL5A relates mechanistically to its TGN trafficking functions, and whether nucleotide cycling is shared or compartment-specific, remains unresolved.
  • No reconciliation of nuclear and Golgi ARL5A roles in the corpus
  • GEF that activates ARL5 not biochemically defined
  • Distinct in vivo roles of ARL5A versus ARL5B paralogs not delineated

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003924 GTPase activity 3 GO:0098772 molecular function regulator activity 3
Localization
GO:0005794 Golgi apparatus 4 GO:0005634 nucleus 1 GO:0005730 nucleolus 1
Pathway
R-HSA-5653656 Vesicle-mediated transport 3 R-HSA-9609507 Protein localization 2
Partners
ARFRP1ARMH3GARPHP1API4KBRAGULATORSYS1

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2002 Human ARL5 (ARL5A) localizes to nuclei and nucleoli; the GDP-bound mutant T35N concentrates in nucleoli, while the GTP-bound mutant Q80L interacts with heterochromatin protein 1α (HP1α) in a nucleotide-state-dependent manner requiring the MIR-like motif. The N-terminus is myristoylated, and nuclear import depends on a C-terminal bipartite nuclear localization signal that interacts with importin-α. Yeast two-hybrid screen, in vitro protein-interaction assay, co-immunoprecipitation in COS cells, mutant expression (T35N/Q80L), co-localization imaging, N-terminal myristoylation analysis Journal of cell science High 12414990
2015 Drosophila Arl5 (ortholog of human ARL5A/ARL5B) localizes to the trans-Golgi and directly interacts with the GARP (Golgi-associated retrograde protein) tethering complex; loss of Arl5 causes partial displacement of GARP from the Golgi and enlargement of the late endosomal compartment, indicating Arl5 recruits GARP to the TGN to facilitate endosome-to-Golgi retrograde trafficking. Depletion of human ARL5B in HeLa cells also makes GARP cytosolic, confirming functional conservation. Liposome and column-based affinity chromatography (binding assay), genetic knockout in Drosophila, RNAi depletion in HeLa cells, fluorescence co-localization, retrograde transport assays Biology open High 25795912
2012 ARL5A and ARL5B both localize to the trans-Golgi in mammalian cells; constitutively active ARL5B (Q70L) enhances endosome-to-TGN transport of TGN38, whereas dominant-negative ARL5B (T30N) disperses to cytoplasm and perturbs the Golgi. ARL5B depletion by RNAi reduces retrograde transport of TGN38 and Shiga toxin and alters mannose-6-phosphate receptor distribution, with no effect on anterograde E-cadherin transport. GFP-tagged constitutively active and dominant-negative mutant expression, RNAi knockdown, retrograde transport assays (TGN38, Shiga toxin), anterograde transport assay (E-cadherin), fluorescence microscopy Experimental cell research High 22245584
2019 ARFRP1 acts upstream of both ARL1 and ARL5 at the TGN; ARL1 recruits golgin tethering factors while ARL5 recruits the GARP complex, with ARFRP1 acting as a master regulator coordinating this bifurcated GTPase cascade required for retrograde cargo delivery to the TGN. Genetic epistasis analysis in mammalian cells, RNAi/KO of ARFRP1/ARL1/ARL5, localization studies by fluorescence microscopy, retrograde transport assays The Journal of cell biology High 31575603
2018 Amino acids stimulate endosome-to-Golgi retrograde trafficking through a pathway requiring SLC38A9, v-ATPase, and Ragulator (but not Rag GTPases or mTORC1). ARL5 interacts with Ragulator in an amino acid-regulated manner, and Ragulator may function as a guanine nucleotide exchange factor (GEF) to activate ARL5; active ARL5 together with its effector GARP is required for amino acid-stimulated retrograde trafficking. Co-immunoprecipitation, RNAi knockdown of pathway components, retrograde trafficking assays, amino acid stimulation/starvation experiments Nature communications Medium 30478271
2022 ARL5A and ARL5B interact with and recruit phosphatidylinositol 4-kinase beta (PI4KB) to the trans-Golgi network, promoting PI4KB's function in PI4P synthesis and protein secretion. Proximity biotinylation (miniTurboID) combined with TMT-based quantitative mass spectrometry, protein interaction assays, functional secretion assays The EMBO journal Medium 35844135
2024 ARL5 (ARL5A/B) is recruited to the TGN by ARFRP1 in complex with the transmembrane protein SYS1. The armadillo-repeat protein ARMH3 (C10orf76) is a novel ARL5 effector that binds active (GTP-bound) but not inactive ARL5, and is recruited to the TGN via the SYS1-ARFRP1-ARL5 axis. ARMH3 activates PI4KB at the TGN, accounting for the main pool of PI4P there, which in turn recruits GOLPH3 and supports glycan modifications at the TGN. ARMH3 is not required for retrograde transport of cargo proteins (unlike GARP). Proximity biotinylation, protein interaction assays, RNAi/KO, PI4P lipid measurements, retrograde transport assays, fluorescence co-localization, dominant-negative/active mutant analysis Nature communications High 39580461
1996 ARL5 was cloned as a novel ARF-family GTPase containing all six conserved GTP-binding motifs; its closest relative is ARL1 (49% amino acid identity). Low-level mRNA expression was detected across multiple rat tissues with highest levels in brain, intestine, and thymus. PCR cloning with degenerate primers, cDNA library screening, sequence analysis, Northern blot tissue expression Biochimica et biophysica acta Low 8765741
2013 ARL5A protein level is downregulated by miR-202-3p through binding to the 3′ UTR of ARL5A mRNA; knockdown of ARL5A phenocopies the cell-proliferation inhibition caused by miR-202-3p overexpression in colorectal cancer cells. Luciferase reporter assay (3′ UTR binding), Western blot, RNAi knockdown of ARL5A, cell proliferation and colony formation assays, xenograft mouse model Clinical cancer research Medium 24327274

Source papers

Stage 0 corpus · 15 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 Identification and characterization of nine novel human small GTPases showing variable expressions in liver cancer tissues. Gene expression 111 12450215
2003 Identification and characterization of LASP2 gene in silico. International journal of molecular medicine 83 12883659
2013 microRNA-202-3p inhibits cell proliferation by targeting ADP-ribosylation factor-like 5A in human colorectal carcinoma. Clinical cancer research : an official journal of the American Association for Cancer Research 69 24327274
2005 Gene profiling involved in immature CD4+ T lymphocyte responsible for systemic lupus erythematosus. Molecular immunology 39 16143398
2002 A developmentally regulated ARF-like 5 protein (ARL5), localized to nuclei and nucleoli, interacts with heterochromatin protein 1. Journal of cell science 38 12414990
2019 ARFRP1 functions upstream of ARL1 and ARL5 to coordinate recruitment of distinct tethering factors to the trans-Golgi network. The Journal of cell biology 32 31575603
2015 The small G protein Arl5 contributes to endosome-to-Golgi traffic by aiding the recruitment of the GARP complex to the Golgi. Biology open 29 25795912
2012 Arl5b is a Golgi-localised small G protein involved in the regulation of retrograde transport. Experimental cell research 29 22245584
2018 Amino acids stimulate the endosome-to-Golgi trafficking through Ragulator and small GTPase Arl5. Nature communications 23 30478271
2022 Defining the proximal interaction networks of Arf GTPases reveals a mechanism for the regulation of PLD1 and PI4KB. The EMBO journal 22 35844135
1996 Cloning of a novel member (ARL5) of the ARF-family of Ras-related GTPases. Biochimica et biophysica acta 13 8765741
2024 ARMH3 is an ARL5 effector that promotes PI4KB-catalyzed PI4P synthesis at the trans-Golgi network. Nature communications 7 39580461
2003 Isolation of a new member of the ADP-ribosylation like factor gene family, ARL8, from a cartilage cDNA library. Gene 5 12853149
2022 ARFs get the BioID treatment: what have we been missing? The EMBO journal 1 35929178
2026 Mechanistic investigation into the differences in growth performance and resistance to spring viremia of carp virus in common carp. Frontiers in immunology 0 41694347

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