Affinage

ARL15

ADP-ribosylation factor-like protein 15 · UniProt Q9NXU5

Length
204 aa
Mass
22.9 kDa
Annotated
2026-06-09
22 papers in source corpus 12 papers cited in narrative 11 extracted findings
Cross-family judge faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

ARL15 is a small Arf-like GTPase that regulates membrane trafficking, divalent cation homeostasis, and TGFβ signaling from the Golgi and endomembrane compartments (PMID:34089346, PMID:35834310, PMID:40241309). It is a bona fide nucleotide-binding enzyme: it possesses intrinsic GTPase activity, binds GTP and GDP with distinct affinities, and undergoes an N-terminal conformational change upon nucleotide loading (PMID:37939768). Membrane targeting is achieved through triple S-acylation at N-terminal cysteines (Cys17, Cys22, Cys23) catalyzed redundantly by the Golgi S-acyltransferases ZDHHC7 and ZDHHC3; loss of acylation redistributes ARL15 to the cytosol (PMID:41999893). From the Golgi, ARL15 directs trafficking of selective cargoes including caveolin-2 and STX6, and its depletion alters cell adhesion, spreading, and traction force generation (PMID:40241309). In its GTP-bound state ARL15 binds the CBS-pair domain of CNNM magnesium transporters—a structurally defined interaction (R95 critical)—to inhibit both CNNM-mediated Mg2+ efflux and TRPM7-mediated divalent cation influx, in competition with PRL phosphatases (PMID:34089346, PMID:37449820, PMID:36711628). Active ARL15 also binds the MH2 domain of Smad4 to relieve its autoinhibition and promote Smad complex assembly, with Smad4 in turn acting as a GAP that dissociates ARL15, positioning ARL15 as a positive effector of TGFβ family signaling (PMID:35834310). Physiologically, ARL15 supports adiponectin secretion and adipogenesis (PMID:29242557), and germline knockout in mice is postnatally lethal with complete cleft palate (PMID:37773757).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2017 Medium

    Established the first cellular role for ARL15 by showing it is required for a specific secretory and differentiation program rather than general secretion.

    Evidence siRNA knockdown in 3T3-L1 adipocytes/preadipocytes with GFP-localization microscopy

    PMID:29242557

    Open questions at the time
    • No molecular partner or biochemical mechanism for the secretion defect identified
    • Golgi localization shown by overexpressed GFP fusion only
  2. 2019 Low

    Linked ARL15 to endothelial insulin signaling, raising the possibility of a metabolic signaling role.

    Evidence ARL15 overexpression in HUVECs with NO, ROS, and pathway western blot readouts

    PMID:30682341

    Open questions at the time
    • Overexpression-only with no direct binding or mechanism
    • No loss-of-function confirmation
    • Cannot distinguish direct from indirect effects on the IR/IRS1/AKT/eNOS axis
  3. 2021 High

    Identified ARL15 as a direct negative regulator of magnesium transport through binding the CBS domains of CNNM transporters, defining its first molecular partner and function.

    Evidence Co-IP/pulldown, co-localization, and 25Mg2+ uptake assays in kidney cells

    PMID:34089346

    Open questions at the time
    • Nucleotide-state dependence of binding not resolved here
    • Mechanism by which ARL15 affects CNNM N-glycosylation unclear
  4. 2021 Medium

    Showed ARL15 membrane targeting depends on palmitoylation and identified ARL6IP5 as an interactor, beginning to define how ARL15 is anchored.

    Evidence Palmitoylation assay, Golgi-marker microscopy, palmitoylation-deficient mutant, and Co-IP/MS in mouse liver/adipocyte models

    PMID:34779483

    Open questions at the time
    • Acyltransferase responsible not identified
    • Functional role of ARL6IP5 interaction not established
  5. 2022 High

    Defined a GTPase cycle coupling ARL15 to TGFβ signaling, showing active ARL15 relieves Smad4 autoinhibition while Smad4 serves as its GAP.

    Evidence Reciprocal Co-IP, dominant-active/negative mutants, domain mapping, and GAP activity assay

    PMID:35834310

    Open questions at the time
    • GEF that activates ARL15 not identified
    • Connection between Smad4 effector role and trafficking/Mg2+ functions unresolved
  6. 2023 High

    Provided the structural and biophysical basis for ARL15–CNNM inhibition and revealed competition with PRL phosphatases and cross-regulation of TRPM7.

    Evidence X-ray crystallography of ARL15–CNNM2 CBS complex, in vitro transport assays, R95A mutagenesis, and competition binding

    PMID:36711628 PMID:37449820

    Open questions at the time
    • How a single ARL15 simultaneously controls efflux and influx channels mechanistically unclear
    • In vivo relevance of PRL competition not tested
  7. 2023 Medium

    Characterized ARL15 as an enzymatically active GTPase that changes conformation upon nucleotide binding.

    Evidence GTPase kinetics, Kd determination, and SAXS on apo and nucleotide-bound protein

    PMID:37939768

    Open questions at the time
    • No mutagenesis validating catalytic residues
    • SAXS-level resolution only for conformational change
  8. 2023 Medium

    Demonstrated ARL15 is essential for development, with knockout causing lethality, cleft palate, and impaired migration, linking it to morphogenesis and metabolism in vivo.

    Evidence CRISPR germline knockout mice, metabolic phenotyping, and MEF migration assays

    PMID:37773757

    Open questions at the time
    • Molecular pathway underlying cleft palate not defined
    • Whether phenotypes reflect TGFβ, Mg2+, or trafficking functions unresolved
  9. 2025 Medium

    Defined ARL15's role in selective Golgi cargo trafficking and its consequences for cell adhesion mechanics.

    Evidence GFP-fusion microscopy, siRNA depletion, dominant-negative mutants, and traction force/adhesion assays in HeLa cells

    PMID:40241309

    Open questions at the time
    • Mechanism linking cargo mislocalization to altered adhesion not established
    • Direct cargo-binding versus indirect effects not distinguished
  10. 2026 High

    Resolved the molecular basis of ARL15 membrane anchoring by identifying triple S-acylation sites and the responsible ZDHHC enzymes.

    Evidence APE acylation assay, Cys-to-Ser mutagenesis, fractionation/imaging, and siRNA/CRISPR enzyme identification in HEK293T

    PMID:41999893

    Open questions at the time
    • Whether acylation is dynamically regulated not addressed
    • Impact of acylation on specific downstream functions (CNNM, Smad4) not tested
  11. 2026 Low

    Connected ARL15 to connective tissue and inflammatory gene programs in disease-relevant synovial fibroblasts.

    Evidence siRNA knockdown with differential transcriptomics in RA synovial fibroblasts and MH7A cells

    PMID:42087570

    Open questions at the time
    • Transcriptomic association only with no direct mechanism
    • No functional rescue
    • Causality between ARL15 and COMP/IFN gene changes not established

Open questions

Synthesis pass · forward-looking unresolved questions
  • How ARL15's distinct molecular functions—Golgi cargo trafficking, CNNM/TRPM7 ion transport inhibition, and Smad4-effector signaling—are coordinated within a single GTPase cycle, and which upstream GEF activates it, remains unresolved.
  • No GEF identified
  • Integration of trafficking, ion transport, and TGFβ roles not mapped onto one pathway

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 3 GO:0003924 GTPase activity 2
Localization
GO:0005794 Golgi apparatus 4 GO:0005886 plasma membrane 3 GO:0005783 endoplasmic reticulum 2 GO:0005764 lysosome 1 GO:0005829 cytosol 1
Pathway
R-HSA-382551 Transport of small molecules 2 R-HSA-5653656 Vesicle-mediated transport 2 R-HSA-162582 Signal Transduction 1 R-HSA-392499 Metabolism of proteins 1
Partners
ARL6IP5CNNM1CNNM2CNNM3CNNM4SMAD4STX6

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2017 ARL15 knockdown in differentiated murine 3T3-L1 adipocytes impaired adiponectin secretion (but not adipsin secretion or insulin action), and knockdown in preadipocytes impaired adipogenesis. GFP-tagged ARL15 localized predominantly to the Golgi with lower levels at the plasma membrane and intracellular vesicles, suggesting involvement in intracellular trafficking. Conditional siRNA knockdown in 3T3-L1 adipocytes/preadipocytes; GFP-tagging and fluorescence microscopy for subcellular localization Scientific reports Medium 29242557
2021 ARL15 directly interacts with CNNM family magnesium transporters (CNNM1-4) at their carboxyl-terminal CBS domains, co-localizes with CNNM2 in kidney cells at the ER, Golgi, and plasma membrane, and is required for complex N-glycosylation of CNNMs. ARL15 knockdown significantly increased 25Mg2+ uptake in kidney cancer cell lines, establishing ARL15 as a negative regulator of Mg2+ transport. Biochemical pulldown/co-immunoprecipitation; immunocytochemistry co-localization; in silico modeling; stable isotope 25Mg2+ uptake assay; siRNA knockdown; ARL15 overexpression Cellular and molecular life sciences : CMLS High 34089346
2022 Active (GTP-bound) ARL15 specifically binds the MH2 domain of Smad4 and co-localizes with Smad4 at the endolysosome. This binding relieves Smad4 autoinhibition (imposed by intramolecular MH1-MH2 interaction), enabling Smad4 to interact with phosphorylated receptor-regulated Smads to form the Smad complex. Assembly of the Smad complex enhances Smad4's GAP activity toward ARL15, leading to ARL15 dissociation before nuclear translocation. ARL15 thus positively regulates TGFβ family signaling and functions as a Smad4 effector while Smad4 acts as its GAP. Co-immunoprecipitation; fluorescence co-localization; dominant-active and dominant-negative ARL15 mutants; GAP activity assay; domain mapping eLife High 35834310
2021 Endogenous ARL15 is palmitoylated and localizes to the Golgi of mouse liver. Expression of palmitoylation-deficient ARL15 resulted in redistribution to the cytoplasm and mild reduction in adipogenesis-related gene expression. ARL15 undergoes Golgi translocation during adipocyte differentiation (from cis-Golgi in preadipocytes to other Golgi compartments after differentiation). Co-immunoprecipitation and mass spectrometry identified ARL6IP5 (an ER-localized protein) as an interacting partner. Palmitoylation assay; fluorescence microscopy with Golgi markers; palmitoylation-deficient mutant overexpression; co-immunoprecipitation and mass spectrometry Biology open Medium 34779483
2023 Crystal structure of the ARL15 GTPase domain in complex with the CNNM2 CBS-pair domain was solved, revealing the molecular basis for binding. ARL15 inhibits both CNNM2-mediated Mg2+ efflux and TRPM7-mediated divalent cation influx. An ARL15 binding-deficient mutant (R95A) failed to inhibit CNNM and TRPM7 transport. PRL2 (PTP4A2) competes with ARL15 for binding to CNNM, indicating antagonistic regulation. ARL15 was confirmed as a GTP-binding protein with low micromolar affinity for the CNNM CBS-pair domain. X-ray crystallography; in vitro ion transport assays; site-directed mutagenesis; binding competition assays (SPR/ITC); GTP-binding characterization eLife High 36711628 37449820
2023 ARL15 exhibits GTPase enzymatic activity (Km ~100 μM, Vmax ~1.47 μmole/min/μL). GTP binding affinity (Kd) is ~8-fold lower than GDP binding. SAXS analysis revealed that apo monomeric ARL15 adopts a globular shape (Dmax 6.1 nm) and undergoes conformational change upon GTP or GDP binding (Dmax ~7.6-7.7 nm), with the N-terminal region toggling open upon nucleotide binding. Spectroscopy (GTPase kinetics); equilibrium binding (Kd determination); Small Angle X-ray Scattering (SAXS); structural modeling International journal of biological macromolecules Medium 37939768
2025 ARL15 localizes primarily to the Golgi and cell surface in HeLa cells. Depletion of ARL15 causes mislocalization of selective Golgi cargoes caveolin-2 and STX6. Expression of GTPase-independent dominant-negative ARL15 mutants (V80A,A86L,E122K and C22Y,C23Y) also caused mislocalization of these cargoes. ARL15 Golgi localization is dependent on palmitoylation and Arf1-dependent Golgi integrity. ARL15-depleted cells display enhanced cell spreading, adhesion strength, higher traction forces, and multiple focal adhesion points during initial cell adhesion. Stable GFP-fusion expression; fluorescence microscopy; siRNA depletion; dominant-negative mutant expression; traction force microscopy; cell adhesion assays Traffic (Copenhagen, Denmark) Medium 40241309
2023 Global homozygous Arl15 knockout in mice is lethal postnatally and causes complete cleft palate. Arl15 knockout mouse embryonic fibroblasts show decreased cell migration. Heterozygous females show reduced fat mass and transiently lower adiponectin levels. CRISPR/Cas9 germline knockout; metabolic phenotyping; cell migration assays in MEFs FASEB journal Medium 37773757
2026 ARL15 is triply S-acylated (palmitoylated) at three conserved N-terminal cysteine residues (Cys17, Cys22, Cys23) in HEK293T cells. Single Cys-to-Ser mutations substantially reduced S-acylation; triple mutation abolished it entirely. Loss of S-acylation disrupted membrane association of ARL15 (shown by confocal imaging and subcellular fractionation). The Golgi-localized S-acyltransferases ZDHHC7 and ZDHHC3 mediate ARL15 S-acylation in a partially redundant manner; dual inhibition caused marked reduction in S-acylation and redistribution from membranes to cytosol. Acyl-PEGyl exchange gel-shift (APE) assay; site-directed mutagenesis (Cys-to-Ser); confocal imaging; subcellular fractionation; siRNA knockdown screen; CRISPR/Cas9 gene disruption The Journal of biological chemistry High 41999893
2026 ARL15 knockdown in ex vivo RA synovial fibroblasts (RASF) led to downregulation of COMP (extracellular matrix stabilizer) and upregulation of adiponectin and IFN response genes (IFI6, USP18, NPTX1, MX1), and downregulation of CTGF, CD248, and PTX3, implicating ARL15 in connective tissue architecture and inflammation regulation. siRNA gene knockdown; differential transcriptomics in ex vivo RASF and in vitro MH7A cells International journal of rheumatic diseases Low 42087570
2019 Overexpression of ARL15 in HUVECs under high-glucose conditions increased insulin-stimulated NO production and phosphorylation of the IR/IRS1/AKT/eNOS pathway, decreased ROS and MDA, increased SOD, and reduced ERK1/2 phosphorylation and NOX2/NOX4 expression, indicating ARL15 promotes insulin signaling and reduces oxidative stress in endothelial cells. Overexpression in HUVECs; NO measurement; ROS/MDA/SOD assays; western blot for signaling pathway components Life sciences Low 30682341

Source papers

Stage 0 corpus · 22 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2009 A genome-wide association study reveals variants in ARL15 that influence adiponectin levels. PLoS genetics 143 20011104
2013 A genome-wide association study reveals ARL15, a novel non-HLA susceptibility gene for rheumatoid arthritis in North Indians. Arthritis and rheumatism 38 23918589
2017 The metabolic syndrome- associated small G protein ARL15 plays a role in adipocyte differentiation and adiponectin secretion. Scientific reports 28 29242557
2021 ARL15 modulates magnesium homeostasis through N-glycosylation of CNNMs. Cellular and molecular life sciences : CMLS 25 34089346
2022 Arl15 upregulates the TGFβ family signaling by promoting the assembly of the Smad-complex. eLife 16 35834310
2015 Association of the ARL15 rs6450176 SNP and serum lipid levels in the Jing and Han populations. International journal of clinical and experimental pathology 16 26722494
2021 Palmitoylated small GTPase ARL15 is translocated within Golgi network during adipogenesis. Biology open 15 34779483
2023 Structural insights into regulation of CNNM-TRPM7 divalent cation uptake by the small GTPase ARL15. eLife 11 37449820
2019 ARL15 overexpression attenuates high glucose-induced impairment of insulin signaling and oxidative stress in human umbilical vein endothelial cells. Life sciences 11 30682341
2014 Association study of ARL15 and CDH13 with T2DM in a Han Chinese population. International journal of medical sciences 6 24688318
2021 Correlation between an intronic SNP genotype and ARL15 level in rheumatoid arthritis. Journal of genetics 5 34187973
2023 ARL15, a GTPase implicated in rheumatoid arthritis, potentially repositions its truncated N-terminus as a function of guanine nucleotide binding. International journal of biological macromolecules 4 37939768
2017 [Genetic polymorphisms of ARL15 and HLA-DMA are associated with rheumatoid arthritis in Han population from northwest China]. Xi bao yu fen zi mian yi xue za zhi = Chinese journal of cellular and molecular immunology 3 29382430
2023 Structural insights into regulation of TRPM7 divalent cation uptake by the small GTPase ARL15. bioRxiv : the preprint server for biology 2 36711628
2023 Study Protocol for the Interactions between Dietary Patterns and ARL15 and ADIPOQ Genes Polymorphisms on Cardiometabolic Risk Factors. International journal of preventive medicine 2 37351048
2025 Interactions between DASH-style diet and ADIPOQ and ARL15 genes polymorphisms on blood pressure and central obesity in Iranian adults. Scientific reports 1 39865127
2025 ARL15 Gene Variant rs255758 Provides Susceptibility to Rheumatoid Arthritis in Northwest Indian Population. International journal of applied & basic medical research 1 40336772
2024 ARL15 and its Multiple Disease Association: Emerging Functions and Potential Therapeutic Application. Current protein & peptide science 1 37718516
2026 S-acylation and membrane localization of the small GTPase ARL15 are mediated by the Golgi S-acyltransferases ZDHHC7 and ZDHHC3. The Journal of biological chemistry 0 41999893
2026 Dissecting ARL15 Function in Rheumatoid Arthritis: Insights From Ex Vivo and in Vitro Synovial Fibroblast Models. International journal of rheumatic diseases 0 42087570
2025 Golgi Localized Arl15 Regulates Cargo Transport and Cell Adhesion. Traffic (Copenhagen, Denmark) 0 40241309
2023 Cleft palate and minor metabolic disturbances in a mouse global Arl15 gene knockout. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 0 37773757

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