HEATR3

HEATR3 is a multifunctional HEAT-repeat protein that links ribosome biogenesis surveillance to selective autophagy and innate immune signaling. In ribosome biogenesis, HEATR3 acts as a nuclear import chaperone for the ribosomal proteins uL18 (RPL5) and uL5 (RPL11); loss-of-function variants reduce nuclear accumulation of uL18, impair pre-rRNA processing and ribosomal subunit formation, and cause Diamond-Blackfan anemia with defective erythroid maturation independent of p53 activation (PMID:35213692). Consistent with this role at the nucleolar surveillance interface, HEATR3 is required for the nucleolar surveillance pathway that stabilizes p53, such that its disruption abolishes p53 accumulation in response to nuclear-acting stresses including DNA damage (PMID:36323262). Independently, HEATR3 functions as a selective autophagy (xenophagy) receptor: it carries an LC3-interacting region (LIR), localizes to invading Salmonella and chemically damaged lysosomes, and recruits LC3 to damaged membranes to drive their lysosomal delivery, acting upstream of ATG5/FIP200 in a calcium-dependent manner (PMID:40178893). HEATR3 also serves as a host nuclear transport adaptor that physically binds the Legionella effector Ceg10 to mediate its nuclear import (PMID:41468429). The mechanistic basis by which HEATR3 modulates downstream signaling outputs has not been characterized in the available corpus.

1. 2013 Low

   First functional link, addressing whether HEATR3 participates in innate immune signaling, placed it as a positive modulator of NOD2-mediated NF-κB activation and tied a missense variant to Crohn's disease.

   Evidence Expression/reporter studies of NOD2 signaling plus haplotype association and exome sequencing in Ashkenazi Jewish individuals

   PMID:23615072

   Open questions at the time

   • Single lab with unspecified reporter assay details and controls
   • No direct biochemical interaction between HEATR3 and NOD2 demonstrated
   • Disease association not mechanistically connected to the signaling readout
2. 2022 High

   Two 2022 studies established HEATR3's core cellular role: it is a nuclear import chaperone for uL18/uL5 required for ribosome biogenesis, and it is required for the nucleolar surveillance pathway that stabilizes p53.

   Evidence Patient-derived cells with HEATR3 variants, shRNA knockdown, yeast complementation, nuclear uL18 immunofluorescence and rRNA processing assays; separately, genome-wide CRISPR loss-of-function screens with a p53 stabilization readout

   PMID:35213692 PMID:36323262

   Open questions at the time

   • Structural basis of uL18/uL5 recognition not resolved
   • Mechanistic detail of how HEATR3 loss blocks p53 stabilization limited
   • Relationship between the chaperone function and the p53 surveillance role not directly tested in one system
3. 2023 Low

   A cancer-cell study asked whether HEATR3 influences proliferative signaling, finding its knockdown suppresses growth, invasion, and migration and reduces AKT/ERK phosphorylation in bladder cancer cells.

   Evidence siRNA knockdown in bladder cancer lines with proliferation, migration/invasion, cell cycle, apoptosis assays and Western blot for p-AKT/p-ERK

   PMID:37518364

   Open questions at the time

   • No direct biochemical link between HEATR3 and AKT/ERK demonstrated
   • Pathway placement inferred indirectly from phenotypes
   • Single lab without orthogonal validation
4. 2025 High

   HEATR3 was defined as a selective autophagy receptor, answering how damaged membranes and cytosolic bacteria are targeted to lysosomes: it uses a LIR motif to recruit LC3 upstream of ATG5/FIP200.

   Evidence Quantitative mass spectrometry, HEATR3 KO and rescue with wild-type vs LIR-mutant, fluorescence microscopy, Salmonella proliferation assay, lysosome damage model, ATG5/FIP200 epistasis and calcium chelation

   PMID:40178893

   Open questions at the time

   • Upstream sensor coupling HEATR3 to calcium signaling not identified
   • Structural basis of LIR-LC3 interaction not resolved
   • Relationship to HEATR3's ribosomal/nuclear roles unexplored
5. 2025 Medium

   HEATR3 was shown to act as a host nuclear transport adaptor co-opted by a bacterial effector, addressing how Legionella Ceg10 reaches the nucleus to acetylate RPS20.

   Evidence Structural analysis of Ceg10, nuclear import assays, and HEATR3 interaction identification by co-immunoprecipitation/pulldown

   PMID:41468429

   Open questions at the time

   • HEATR3 characterization is secondary to the Ceg10 study
   • Whether HEATR3 functions as a general nuclear import adaptor for host cargo beyond ribosomal proteins not established
   • Interface mapping of the HEATR3-Ceg10 interaction not detailed

• It remains unresolved how HEATR3's distinct roles — ribosomal protein import, nucleolar p53 surveillance, LIR-dependent autophagy, and bacterial effector transport — are mechanistically integrated by a single HEAT-repeat scaffold.
• No structural model unifying its cargo-binding and LIR functions
• Whether the autophagy and ribosome roles share a common surface or are mutually exclusive is unknown
• Direct mechanism connecting HEATR3 to NF-κB and AKT/ERK signaling outputs not established