THADA

THADA is a multifunctional scaffolding protein that participates in tRNA modification, ER calcium homeostasis, and intracellular protein trafficking. THADA forms a complex with the methyltransferase FTSJ1 to mediate 2'-O-methylation at position 32 of tRNA anticodon loops, with a conserved DUF2428-domain motif essential for this activity and the tRNA substrate anchored within THADA itself (PMID:35559166, PMID:40483304). THADA binds and uncouples the sarco/ER Ca²⁺ ATPase SERCA, dissociating ATP hydrolysis from Ca²⁺ transport; in pancreatic β-cells this depletes ER Ca²⁺ stores through combined SERCA2 inhibition and RyR2-mediated leakage, and under persistent ER stress THADA assembles a DR5/FADD/caspase-8 pro-apoptotic complex that drives β-cell apoptosis (PMID:28399403, PMID:36823211). THADA also functions as a cargo adaptor in COPII-dependent ER-to-Golgi trafficking by bridging PD-L1 to the SEC24A coat subunit; loss of THADA causes ER retention and ERAD-mediated degradation of PD-L1, reducing its surface expression and enhancing T cell cytotoxicity against cancer cells (PMID:34341130).

1. 2007 Medium

   Initial characterization revealed that THADA contains ARM repeat-like domains and that its most conserved C-terminal region is disrupted by thyroid adenoma translocations, implicating loss of this domain in neoplasia and suggesting a protein-interaction scaffolding function.

   Evidence Comparative vertebrate genomic sequencing and mapping of translocation breakpoints in thyroid adenomas

   PMID:17889454

   Open questions at the time

   • No biochemical validation of ARM repeat-mediated interactions
   • Mechanism linking domain disruption to thyroid neoplasia not established
2. 2009 Medium

   A common THADA variant (rs7578597) was linked to reduced β-cell secretory response in humans, providing the first physiological evidence connecting THADA to pancreatic β-cell function.

   Evidence Hyperglycemic clamp with GLP-1 and arginine stimulation in a genotyped human cohort (n=336)

   PMID:19833888

   Open questions at the time

   • No direct molecular mechanism demonstrated for the variant's effect on β-cell function
   • Whether the variant alters THADA expression or protein function was unknown
3. 2017 High

   Two breakthroughs established distinct THADA functions: binding and uncoupling SERCA to control ER Ca²⁺ and energy balance (with Drosophila THADA KO causing obesity rescued by SERCA reduction), and participation in gene fusions that drive IGF2BP3 overexpression and IGF1R/PI3K/MAPK oncogenic signaling in thyroid tumors.

   Evidence Drosophila knockout with genetic epistasis for SERCA function; whole-genome/transcriptome analysis with xenograft validation for gene fusion

   PMID:28193878 PMID:28399403

   Open questions at the time

   • Structural basis of THADA-SERCA interaction not determined
   • Whether the SERCA-uncoupling and gene-fusion mechanisms are relevant in the same tissue contexts was unclear
   • THADA gene fusions drive IGF2BP3 overexpression without producing a chimeric THADA protein, so the normal THADA protein is not directly implicated in this oncogenic pathway
4. 2021 High

   THADA was identified as a cargo adaptor required for ER-to-Golgi trafficking of PD-L1, bridging PD-L1 to the COPII component SEC24A; this explained how THADA loss causes ER retention and degradation of PD-L1, enhancing anti-tumor immunity.

   Evidence THADA knockdown in human colorectal cancer cells, co-immunoprecipitation of PD-L1/SEC24A, ER retention and ERAD assays, T cell killing assay, MC38 mouse tumor model

   PMID:34341130

   Open questions at the time

   • Whether THADA mediates trafficking of other ER-to-Golgi cargoes beyond PD-L1 was not tested
   • Structural basis of the THADA-SEC24A-PD-L1 ternary interaction was not resolved
5. 2022 High

   THADA (human ortholog of yeast Trm732) was shown to be required for FTSJ1-mediated 2'-O-methylation at tRNA position 32, with a conserved RRSAGLP motif in its DUF2428 domain essential for this catalytic function.

   Evidence Yeast complementation with Trm732/THADA variants, in vivo tRNA modification assays, mutagenesis of conserved motif

   PMID:35559166

   Open questions at the time

   • Structural basis of THADA-FTSJ1-tRNA interaction not yet visualized
   • Physiological consequences of loss of Nm32 modification in mammalian cells not assessed
6. 2023 High

   In mammalian β-cells, THADA was shown to deplete ER Ca²⁺ via dual mechanisms — SERCA2 inhibition and RyR2-mediated leakage — and to assemble a DR5/FADD/caspase-8 pro-apoptotic complex under ER stress, with β-cell-specific Thada knockout improving glycemic control in mice.

   Evidence Global and β-cell-specific Thada knockout mice, Ca²⁺ imaging, co-immunoprecipitation of DR5/FADD/caspase-8, in vivo metabolic phenotyping

   PMID:36823211

   Open questions at the time

   • How THADA is regulated or activated to switch between its Ca²⁺-uncoupling and apoptotic-complex-assembly roles is unknown
   • Whether the DR5/FADD/caspase-8 complex forms in non-β-cell contexts was not tested
7. 2024 Medium

   THADA was placed upstream of LAT1 (amino acid transporter) expression in cancer cell proliferation and linked to PI3K/AKT/mTOR-mediated autophagy inhibition, broadening its roles in cancer cell signaling.

   Evidence THADA knockdown/rescue in HepG2 and KB cells with LAT1 readout; NGS and western blot in gastric cancer cells with mTOR pathway analysis

   PMID:38234670 PMID:38561668

   Open questions at the time

   • Direct mechanism linking THADA to LAT1 transcription or stability not elucidated
   • mTOR pathway activation data are correlative without epistasis or reconstitution
   • Whether these cancer proliferation roles reflect the known SERCA or tRNA modification functions is unclear
8. 2025 High

   Cryo-EM structure of the THADA-FTSJ1-tRNA ternary complex revealed that tRNA is anchored inside THADA and that FTSJ1 engages THADA via a unique C-terminal interaction mode distinct from the FTSJ1-WDR6 complex, completing the structural picture of THADA's role in tRNA modification.

   Evidence Cryo-EM structure determination, biochemical binding and methylation assays, mutagenesis of THADA-tRNA contact residues

   PMID:40483304

   Open questions at the time

   • How THADA's tRNA modification function relates to its SERCA and trafficking functions — whether these are context-dependent or simultaneous — is unresolved
   • Physiological consequences of disrupting THADA-tRNA contacts in mammalian models not yet tested

• It remains unknown how THADA coordinates its multiple functions (tRNA modification, SERCA uncoupling, COPII trafficking, apoptotic complex assembly), whether these are regulated by distinct domains or cellular states, and whether a unifying structural or regulatory principle governs its multifunctionality.
• No structural model of THADA in complex with SERCA or the DR5/FADD/caspase-8 complex
• Tissue-specific regulation of THADA's distinct functions is not characterized
• Whether ARM-repeat domains mediate all protein-protein interactions or only a subset is untested