KIAA0319L

KIAA0319L (AAVR) is a multi-domain cell-surface receptor that serves as the essential entry receptor for adeno-associated virus (AAV) across multiple serotypes, with its PKD domains directly engaging the viral capsid to determine transduction efficiency (PMID:30742069, PMID:31434885). Receptor engagement follows two divergent structural rules: the PKD2 domain binds at a conserved plateau region adjacent to the icosahedral three-fold axis for AAV1, AAV2, and most serotypes (via strands B/C/E and the BC loop), whereas the PKD1 domain uniquely binds AAV5 and the related goat AAVGo.1 at a structurally distinct site on the opposite side of the spike (via strands F/G and the CD loop) (PMID:30742069, PMID:31434885, PMID:33218165, PMID:36453885). The AAVR footprint overlaps epitopes of several neutralizing antibodies, marking the receptor-binding surface as an immunodominant capsid site (PMID:31115336, PMID:33218165). Beyond surface attachment, AAVR functions in intracellular trafficking: its cytosolic tail engages the SNX3-retromer complex to drive membrane tubulation and direct internalized AAV2 to the trans-Golgi network for productive transduction, a route that proceeds without endosomal membrane rupture [PMID:bio_10.1101_2025.11.22.689972]. AAVR expression levels directly determine transduction in physiologically relevant cells, including basolaterally polarized airway epithelia and cochlear/vestibular sensory hair cells, where knockout abolishes and overexpression restores AAV transduction (PMID:30962536, PMID:39776318). Human KIAA0319L sequence variants modulate AAV gene-transfer efficacy in a serotype-specific manner, and PKD2 sequence differences between human and mouse AAVR govern species tropism of engineered capsids (PMID:42137583, PMID:41377965). Independent of its viral-receptor role, mouse knockout links Kiaa0319L to auditory brainstem function rather than to cortical neuronal migration (PMID:29045729).

1. 2017 Medium

   Established whether KIAA0319L contributes to neurodevelopment as had been hypothesized, distinguishing a neuronal-migration role from an auditory one.

   Evidence Knockout mouse cortical histology, auditory brainstem response recordings, and gap-in-noise behavior

   PMID:29045729

   Open questions at the time

   • Molecular mechanism underlying the auditory deficit not defined
   • No link drawn to AAVR's receptor or trafficking activities
   • Single lab; effect partly emerges only in double KO with Kiaa0319
2. 2019 High

   Resolved the atomic basis of AAV-receptor engagement, showing the PKD2 domain binds the AAV2 capsid spike and that interface residues are required for infectivity.

   Evidence Cryo-EM at 2.8 Å with site-directed mutagenesis and infectivity assays; independently replicated by cryo-ET/cryo-EM/XL-MS at 2.4 Å

   PMID:30742069 PMID:31115336

   Open questions at the time

   • Did not address serotypes engaging a different PKD domain
   • Post-binding internalization and trafficking steps not resolved structurally
3. 2019 Medium

   Demonstrated that AAVR expression and basolateral localization control AAV2 entry in a physiological epithelium and that AAVR-independent entry routes exist.

   Evidence Immunocytochemistry, anti-AAVR antibody blockade, and CRISPR knockout with transduction assays in polarized airway epithelia

   PMID:30962536

   Open questions at the time

   • Molecular basis of AAVR-independent AAV2.5T entry not identified
   • Mechanism of basolateral targeting unknown
4. 2019 High

   Defined divergent receptor-engagement rules, revealing PKD1 as the exclusive binding domain for AAV5 versus PKD2 for AAV1/AAV2.

   Evidence Cryo-EM structures of AAV1-AAVR and AAV5-AAVR complexes

   PMID:31434885

   Open questions at the time

   • Functional consequence of two-site binding for trafficking not addressed
   • Did not establish why some serotypes select PKD1 over PKD2
5. 2020 High

   Confirmed AAV5's exclusive PKD1 engagement at high resolution and mapped overlap with neutralizing-antibody epitopes.

   Evidence Cryo-EM at 2.5 Å with molecular modeling of antibody footprints

   PMID:33218165

   Open questions at the time

   • Affinity and stoichiometry of PKD1 binding not quantified
   • Trafficking fate after PKD1 binding not addressed
6. 2022 High

   Showed the PKD1-binding mode generalizes beyond AAV5 to a wider capsid class and quantified differential receptor affinity.

   Evidence Cryo-EM of goat AAVGo.1-AAVR PKD12 complex at 2.4 Å plus ELISA binding comparison

   PMID:36453885

   Open questions at the time

   • Relationship between higher binding affinity and transduction outcome not tested
   • Biological host range of AAVGo.1 via human AAVR unexplored
7. 2023 Medium

   Provided biophysical evidence that AAVR affinity is serotype-specific and pH-dependent, supporting a trafficking role beyond surface attachment.

   Evidence BLI, SEC-MALS, and SV-AUC binding measurements under varying pH

   PMID:37441888

   Open questions at the time

   • Direct demonstration of pH-driven Golgi trafficking not provided here
   • Single lab; cellular relevance of in vitro pH dependence not validated
8. 2025 High

   Established AAVR as a determinant of AAV transduction in sensory hair cells in vivo, linking receptor abundance to gene-therapy-relevant cell targeting.

   Evidence Immunocytochemistry, antibody blockade, AAVR knockout mice, and conditional overexpression with transduction assays in vivo and ex vivo

   PMID:39776318

   Open questions at the time

   • Trafficking mechanism in hair cells not dissected
   • Cause of developmental decline in AAVR expression unknown
9. 2025 Medium

   Defined the intracellular itinerary by showing AAVR's cytosolic tail recruits the SNX3-retromer to route AAV via retrograde trafficking to the TGN without endosomal rupture.

   Evidence In vitro SNX3-retromer tubulation reconstitution, AAVR-KO cell trafficking imaging, Galectin-8 recruitment, and VP1u/PLA2-mutant capsid analysis (preprint)

   PMID:bio_10.1101_2025.11.22.689972

   Open questions at the time

   • Preprint not yet peer-reviewed
   • Post-TGN steps requiring VP1u not mechanistically resolved
   • Whether the same route applies to PKD1-engaging serotypes untested
10. 2025 Medium

    Identified the PKD2 sequence determinants of species tropism, with human-versus-mouse residue differences controlling engineered-capsid transduction.

    Evidence Human/mouse PKD2 domain swaps and human AAVR complementation with in vitro and in vivo transduction (preprint)

    PMID:41377965

    Open questions at the time

    • Preprint; single lab
    • Structural basis of the I426V effect not resolved
11. 2025 Medium

    Demonstrated that engineering capsid motifs to weaken AAVR binding rationally de-targets the liver, validating AAVR affinity as a tropism-tuning lever.

    Evidence Cryo-EM of CAP-B10-AAVR PKD2 complexes with affinity measurements and in vivo transduction (preprint)

    PMID:bio_10.1101_2025.06.02.655683

    Open questions at the time

    • Preprint; not peer-reviewed
    • Off-target effects of reduced AAVR binding on other tissues not fully mapped
12. 2026 Medium

    Systematically linked human KIAA0319L coding variants to serotype-specific changes in AAV transduction, including loss-of-function and gain-of-function alleles affecting trafficking.

    Evidence Transfection of AAVR variant constructs in AAVR-null cells with serotype-specific transduction, expression, binding, and nuclear trafficking assays

    PMID:42137583

    Open questions at the time

    • Population frequency and clinical impact of variants not assessed
    • Mechanism by which Ser1031Phe enhances nuclear trafficking only partly defined

• How AAVR's distinct PKD1- versus PKD2-engagement modes feed into a common or divergent retrograde trafficking pathway, and what its endogenous (non-viral) cellular ligand or function is, remain unresolved.
• No endogenous ligand or native physiological function of AAVR identified
• Whether PKD1-binding serotypes use the SNX3-retromer route is untested
• Connection between auditory brainstem phenotype and AAVR's molecular activity unknown