ENKD1

ENKD1 is a centrosome- and microtubule-associated protein that couples microtubule organization to ciliogenesis, mitotic spindle control, and innate immune regulation (PMID:35301795, PMID:35197565, PMID:35072334). At the mother centriole it initiates ciliogenesis by competing with CEP97 for binding to CP110, promoting CP110 removal; its loss detains CP110 and blocks cilium formation, a defect reversed by concurrent CP110 knockdown (PMID:35301795). As a microtubule-binding protein localizing to the centriole wall and ciliary axoneme, it increases tubulin polymerization and microtubule stability, regulating ciliary length and Hedgehog responsiveness (PMID:35072334), and stabilizes astral microtubules through EB1 to orient the mitotic spindle, supporting asymmetric division and epidermal architecture (PMID:35197565, PMID:40879264). ENKD1 activity is governed by post-translational modification: HDAC6 deacetylates it at K98 to disrupt its γ-tubulin interaction and centrosomal localization (PMID:40155750), while CYLD deubiquitinates it at K141/K242 to enable an ENKD1–Ezrin interaction required for RPE phagocytosis (PMID:39373352). Beyond the cytoskeleton, ENKD1 restrains innate immunity, binding GGPS1 to lower geranylgeranyl diphosphate production and inactivate RAC1 (PMID:40048432), and acting with the E3 ligase TRIM21 to drive K48-linked ubiquitination and degradation of RUBCN, thereby dampening LC3-associated phagocytosis and bacterial clearance (PMID:41187080).

1. 2022 High

   Established ENKD1 as a centrosomal initiator of ciliogenesis acting through the CP110/CEP97 cap, answering how it controls cilium assembly.

   Evidence Co-IP, super-resolution microscopy, double-knockdown epistasis rescue and Enkd1 knockout mice

   PMID:35301795

   Open questions at the time

   • Structural basis of ENKD1-CP110 competition with CEP97 not resolved
   • Whether ENKD1 acts catalytically or stoichiometrically at the centriole unclear
2. 2022 High

   Defined ENKD1 as a microtubule-binding protein that stabilizes astral microtubules to orient the spindle, linking it to asymmetric division and epidermal thickness.

   Evidence Microtubule co-sedimentation, domain rescue, live spindle imaging in Enkd1 knockout mice

   PMID:35197565

   Open questions at the time

   • Molecular determinants of microtubule binding within the domain not mapped at residue level
   • How spindle orientation cues are transmitted to ENKD1 unknown
3. 2022 High

   Showed ENKD1 directly promotes tubulin polymerization and microtubule stability at the centriole wall and axoneme, tying its MAP activity to ciliary content and Hedgehog signaling.

   Evidence In vitro tubulin polymerization, cellular stability assays, BioID proximity proteomics, Hedgehog reporter assays

   PMID:35072334

   Open questions at the time

   • Direct effectors downstream of ciliary length defects not identified
   • Mechanism by which ENKD1 senses or regulates ciliary content unclear
4. 2024 High

   Identified a CYLD-dependent deubiquitination switch (K141/K242) that licenses ENKD1-Ezrin interaction for RPE phagocytosis, revealing post-translational control of an ENKD1 function outside the cilium.

   Evidence Co-IP, ubiquitination site mapping, deubiquitinase assay, Cyld knockout mice, phagocytosis assays

   PMID:39373352

   Open questions at the time

   • The E3 ligase that ubiquitinates ENKD1 at K141/K242 not identified
   • How Ezrin engagement is structurally coupled to ENKD1 deubiquitination unclear
5. 2025 High

   Defined a HDAC6-mediated deacetylation event at K98 that disrupts ENKD1-γ-tubulin binding and centrosomal targeting, providing a second layer of PTM control over spindle positioning.

   Evidence Deacetylation and site-specific mutagenesis assays, Co-IP, centrosomal localization imaging, HDAC6 overexpression in mouse cornea

   PMID:40155750

   Open questions at the time

   • The acetyltransferase opposing HDAC6 at K98 not identified
   • Whether acetylation state interacts with the CYLD ubiquitination switch unknown
6. 2025 Medium

   Revealed an immune-suppressive role: ENKD1 binds GGPS1 to reduce geranylgeranyl diphosphate and inactivate RAC1, dampening pro-inflammatory signaling.

   Evidence Co-IP, GGPS1 enzymatic activity assays, RAC1 activation assays, TLR stimulation, ENKD1 knockout mice

   PMID:40048432

   Open questions at the time

   • Abstract-level detail limits full mechanistic confidence
   • How ENKD1 modulates GGPS1 catalysis biochemically not defined
   • Relationship between cytoskeletal and immune functions unclear
7. 2025 High

   Showed ENKD1 acts with TRIM21 to drive K48-ubiquitination and degradation of RUBCN, suppressing LC3-associated phagocytosis and bacterial clearance.

   Evidence Reciprocal Co-IP, K48-linkage ubiquitination assay, RUBCN degradation, LC3 lipidation and phagosome-lysosome fusion assays, ENKD1 knockout infection model

   PMID:41187080

   Open questions at the time

   • Whether ENKD1 is a substrate adaptor or activator of TRIM21 not resolved
   • How this LAP role relates to ENKD1's centrosomal functions unknown
8. 2025 Medium

   Extended the microtubule-stabilizing role to keratinocyte migration and epidermal elasticity, implicating EB1 as a functional partner.

   Evidence Enkd1 knockout mice, localization imaging, microtubule stability and migration assays, EB1 interaction studies

   PMID:40879264

   Open questions at the time

   • EB1 mechanistic link not fully elaborated
   • Direct vs indirect ENKD1-EB1 interaction not established

• How ENKD1's cytoskeletal/ciliary roles mechanistically integrate with its immune-regulatory functions, and what governs partitioning between these activities, remains unresolved.
• No unifying model linking centrosomal localization to GGPS1/TRIM21 immune signaling
• No structural data on ENKD1 or its binding interfaces
• Coordination between the K98 acetylation and K141/K242 ubiquitination switches unexplored