ART1

ART1 (ARTC1) is a GPI-anchored or ER-resident arginine-specific mono-ADP-ribosyltransferase that uses NAD+ as a co-substrate to transfer ADP-ribose onto arginine residues of cell-surface, extracellular, and ER-luminal target proteins, thereby regulating integrin-mediated adhesion, ER stress responses, calcium homeostasis, and immune cell viability. ART1 modifies α7-integrin to enhance laminin binding, ADP-ribosylates the ER chaperone GRP78/BiP during the unfolded protein response, and modifies VAPB at Arg50 to maintain intracellular calcium homeostasis, with its enzymatic activity stabilized by interaction with ARTC3 (PMID:18939989, PMID:25292337, PMID:37381178). Proteome-wide profiling in ARTC1-knockout mice identified hundreds of ADP-ribosylated substrates in skeletal muscle and heart, including hemopexin (PMID:30110646). Tumor-expressed ART1 ADP-ribosylates P2X7R on CD8+ T cells, triggering NAD-induced cell death and enabling immune evasion, and genetic or antibody-mediated ART1 blockade restores anti-tumor immunity in murine cancer models (PMID:35294260).

1. 1998 High

   Establishing that Art1 encodes a functional arginine-specific mono-ADP-ribosyltransferase resolved the molecular identity and enzymatic specificity of the gene product, placing it in the ecto-enzyme family with predominant cardiac and skeletal muscle expression.

   Evidence Molecular cloning, recombinant Art1-Fc fusion protein with in vitro enzymatic assay, Northern blot in mouse tissues

   PMID:9841866

   Open questions at the time

   • Endogenous substrates in muscle not identified
   • Human ortholog localization not determined
   • Catalytic mechanism and NAD+ binding site not structurally resolved
2. 2005 Medium

   Identification of mutant ARTC1 peptides as antigens recognized by CD4+ regulatory T cells in melanoma linked ART1 to tumor immunology for the first time, raising the question of whether ART1 enzymatic activity contributes to immune modulation.

   Evidence Expression cloning and functional T cell assays with 164mel melanoma-derived T cell clones

   PMID:15728473

   Open questions at the time

   • Whether wild-type ARTC1 enzymatic activity (not just mutant peptide) modulates anti-tumor immunity was not tested
   • Generalizability beyond a single melanoma line unknown
3. 2008 High

   Demonstrating that myogenin/E-box and MEF-2/A-T-rich element cooperativity drives ART1 transcription in myotubes, and that ART1 ADP-ribosylates α7-integrin to enhance laminin binding, connected the enzyme's tissue-specific expression to a functional role in muscle cell-matrix adhesion.

   Evidence Promoter mutagenesis with reporter assays, EMSA, biochemical ADP-ribosylation and laminin-binding assays

   PMID:18939989

   Open questions at the time

   • In vivo significance of α7-integrin ADP-ribosylation for muscle function not tested
   • Whether ADP-ribosylation is reversible in this context unknown
4. 2013 Medium

   Loss-of-function studies in colon carcinoma cells revealed that ART1 sustains pro-survival Akt/NF-κB signaling and suppresses cisplatin-induced apoptosis, broadening ART1's role from muscle physiology to cancer cell survival.

   Evidence Lentiviral shRNA knockdown in CT26 cells with Western blot for phospho-Akt, NF-κB p65, Bcl-2 family members

   PMID:24335275

   Open questions at the time

   • Direct ADP-ribosylation substrate linking ART1 to Akt activation not identified
   • Results from a single cell line and single lab
   • Whether this reflects enzymatic activity or scaffold function unclear
5. 2014 High

   Showing that human ARTC1 resides in the ER lumen and ADP-ribosylates GRP78/BiP during ER stress overturned the assumption that ARTC1 acts exclusively as an ecto-enzyme and established a role in the unfolded protein response.

   Evidence Subcellular fractionation, immunofluorescence, macro-domain pull-down for ADP-ribosylated proteins, ER stress induction

   PMID:25292337

   Open questions at the time

   • How ER-localized ARTC1 is activated by ER stress not mechanistically resolved
   • Functional consequence of GRP78 ADP-ribosylation on chaperone activity not determined
   • Reconciliation of GPI-anchored ecto-enzyme versus ER-resident forms across species incomplete
6. 2018 High

   Proteome-wide ADP-ribosylome profiling in ARTC1-KO mice revealed hundreds of substrates in muscle and heart and validated hemopexin as a bona fide target, establishing ART1 as a broad-specificity extracellular/surface ADP-ribosyltransferase.

   Evidence Mass spectrometry-based profiling comparing wild-type and ARTC1-KO mouse tissues

   PMID:30110646

   Open questions at the time

   • Functional consequences of ADP-ribosylation for most identified substrates unknown
   • Whether all identified sites are direct ARTC1 targets or include indirect effects not fully resolved
7. 2022 High

   Demonstrating that tumor-expressed ART1 ADP-ribosylates P2X7R on CD8+ T cells to trigger NAD-induced cell death provided a direct immune-evasion mechanism and validated ART1 as a therapeutic target, with antibody blockade restoring anti-tumor immunity.

   Evidence In vitro ADP-ribosylation assay, ART1-KO mice, anti-ART1 antibody blockade in NSCLC and melanoma tumor models, flow cytometry of CD8+ T cell infiltration

   PMID:35294260

   Open questions at the time

   • Whether ART1-mediated NICD operates in human tumors in situ not demonstrated
   • Structural basis of ART1-P2X7R interaction not resolved
   • Contribution of other ARTC family members to NICD not excluded
8. 2024 High

   Identification of VAPB Arg50 as an ARTC1 substrate and ARTC3 as a stabilizing partner linked ART1 enzymatic activity to intracellular calcium homeostasis, revealing a regulatory circuit within the ARTC family.

   Evidence Co-immunoprecipitation of ARTC1-ARTC3, site-directed mutagenesis of VAPB Arg50, calcium imaging after ARTC1 knockdown

   PMID:37381178

   Open questions at the time

   • Structural basis of ARTC3-ARTC1 stabilization not determined
   • Whether VAPB ADP-ribosylation affects ER-mitochondria contact sites not tested
   • Tissue contexts beyond cell lines not explored

• Key unresolved questions include the structural basis of ARTC1 catalysis and substrate selectivity, how the enzyme is partitioned between ER-luminal and GPI-anchored pools across tissues, and whether ART1-targeted therapies can be translated to human cancer immunotherapy.
• No crystal or cryo-EM structure of ARTC1
• No systematic comparison of ER versus cell-surface pools in human tissues
• Human clinical relevance of anti-ART1 immunotherapy not established