PRICKLE2

PRICKLE2 is a core planar cell polarity (PCP) protein with a conserved PET domain, three LIM domains, and a C-terminal Prickle-homologous region that functions across neuronal development, epithelial morphogenesis, and ciliated organ formation (PMID:12525887, PMID:23711981, PMID:36176272). In neurons it operates as a postsynaptic scaffold, binding directly to the guanylate kinase domain of PSD-95 and assembling into a complex with NMDA receptor subunits at asymmetric synapses (PMID:21324980); loss of Prickle2 reduces dendrite branching, synapse number, PSD size, and synaptic currents, and autism- and epilepsy-associated PRICKLE2 variants recapitulate these deficits (PMID:23711981). Beyond the synapse, Prickle2 directly binds AnkG480 at the axonal initial segment to modulate microtubule bundling, neuronal polarity, AIS maturation, and action-potential firing (PMID:36083912), and promotes neurite outgrowth by associating with and lowering Dishevelled1 levels (PMID:22218901). During morphogenesis, Prickle2 drives apical-junction remodeling and tissue fluidity in a Rac1-dependent manner through its Ser/Thr-rich region (PMID:39951022), and its LIM-containing region binds strained actin filaments — a recruitment normally restrained by the PET domain and C-terminal region and abolished by epilepsy-associated variants (PMID:41160432). In early embryogenesis, farnesylation-dependent nuclear localization of Prickle2 is required for active RhoA accumulation and apical-basal polarity establishment (PMID:22333836), and the protein is also required for normal motile cilia and ciliated-organ development (PMID:24708399, PMID:24938409, PMID:36176272). Prickle2 protein levels are constrained post-translationally by Vangl2, which promotes its Cullin-1-dependent, Lys48-linked polyubiquitination and proteasomal degradation (PMID:30814664).

1. 2003 Low

   Established the domain architecture defining PRICKLE2 as a vertebrate Prickle homolog, fixing the PET/LIM/PKH module that later structure-function studies would dissect.

   Evidence Bioinformatic sequence and domain comparison of human PRICKLE2 against Drosophila prickle

   PMID:12525887

   Open questions at the time

   • Computational prediction only with no functional validation
   • No cellular role or localization tested
2. 2007 Medium

   Linked PRICKLE2 expression to postmitotic neurons and gave it a first functional readout — neurite outgrowth — defining a neuronal context for later mechanistic work.

   Evidence Immunohistochemistry, in situ hybridization, and siRNA knockdown in Neuro2a cells

   PMID:17868671

   Open questions at the time

   • No molecular mechanism for the outgrowth phenotype
   • Single neuroblastoma line, no primary neurons
3. 2011 High

   Resolved how Prickle2 acts at the synapse by identifying direct binding to the PSD-95 GK domain and complex formation with NMDA receptors, establishing a postsynaptic scaffolding role.

   Evidence Subcellular fractionation, immunoelectron microscopy, reciprocal co-IP, and GST pulldown

   PMID:21324980

   Open questions at the time

   • Functional consequence of the complex for receptor signaling not measured here
   • Stoichiometry and regulation of complex assembly unknown
4. 2012 Medium

   Placed Prickle2 upstream of Dishevelled1 in neurite outgrowth, providing a mechanistic link to PCP/Wnt machinery in neurons.

   Evidence Co-IP, overexpression western blot, and double-overexpression epistasis in C1300 cells

   PMID:22218901

   Open questions at the time

   • Mechanism of Dvl1 level reduction not defined
   • Single cell line, overexpression-based
5. 2012 High

   Demonstrated a farnesylation-dependent nuclear requirement for Prickle2 in early embryos, showing nuclear Pk2 drives active RhoA and apical-basal polarity — an unexpected non-cytoplasmic PCP function.

   Evidence Nuclear vs cytoplasmic rescue constructs, farnesylation inhibitor, RhoA activity assay in Pk2-/- mouse embryos

   PMID:22333836

   Open questions at the time

   • Nuclear targets/effectors of Pk2 unidentified
   • Mechanism linking nuclear Pk2 to RhoA activation unknown
6. 2013 High

   Connected Prickle2 loss to defined synaptic and dendritic deficits and showed human ASD-associated variants are functionally impaired, tying the gene to neurodevelopmental disease.

   Evidence Prickle2 knockout mouse, hippocampal neuron morphology, patch-clamp electrophysiology, human variant assays

   PMID:23711981

   Open questions at the time

   • Molecular pathway linking Pk2 to spine/synapse maintenance not fully resolved
   • Variant mechanism at the protein level not dissected
7. 2014 Medium

   Extended Prickle2 function to motile cilia and directional intracellular transport, and showed PCP and BBS pathways act independently.

   Evidence Prickle2 KO mouse cilia imaging/EM; zebrafish morpholino knockdown, melanosome transport and Kupffer's vesicle assays, BBS complex IP

   PMID:24708399 PMID:24938409

   Open questions at the time

   • Molecular basis of the transport defect unknown
   • How Pk2 affects ciliary motility mechanistically not defined
8. 2015 Medium

   Integrated Vangl2 into the synaptic Pk2-PSD-95 complex via its PDZ interaction, linking core PCP components at the postsynaptic density.

   Evidence Co-IP in cells and hippocampal neurons with PDZ-binding motif deletion constructs

   PMID:26257100

   Open questions at the time

   • Functional output of the tripartite complex not measured
   • Single lab, no structural detail
9. 2019 High

   Defined how Prickle2 levels are controlled, showing Vangl2 drives Cullin-1-dependent, Lys48-linked polyubiquitination and proteasomal degradation of Pk2.

   Evidence Co-IP, proteasome inhibitor, Cullin-1 dominant-negative/siRNA, ubiquitin K48 mutant, in-cell ubiquitination assay in HEK293T

   PMID:30814664

   Open questions at the time

   • Physiological contexts where Vangl2-driven degradation operates not mapped
   • Substrate recognition adaptor not identified
10. 2022 High

    Identified AnkG480 as a direct Prickle2 partner at the axonal initial segment, mechanistically connecting Pk2 to microtubule bundling, neuronal polarity, and excitability.

    Evidence Colocalization, co-IP binding assay, siRNA knockdown, microtubule bundling assay, patch-clamp in neurons

    PMID:36083912

    Open questions at the time

    • How Pk2 regulates AnkG480 bundling activity biochemically unclear
    • Relationship between AIS and synaptic Pk2 pools unknown
11. 2022 Medium

    Confirmed Prickle2 behaves as an asymmetrically segregating core PCP protein in multiciliated airway cells and genetically interacts with Prickle1, indicating partial functional redundancy.

    Evidence Immunofluorescence localization, Prickle2 mutant phenotyping, double-mutant genetic interaction in mouse airway

    PMID:36176272

    Open questions at the time

    • Modest single-mutant phenotype limits resolution of Pk2-specific role
    • Molecular basis of asymmetric segregation not addressed
12. 2025 High

    Revealed mechanochemical regulation of Prickle2: its LIM-containing region binds strained actin, restrained by the PET and C-terminal domains, with epilepsy-associated variants abolishing actin recruitment.

    Evidence Live imaging in Xenopus mesoderm with domain deletion/fusion constructs and patient-variant assays

    PMID:41160432

    Open questions at the time

    • Functional consequence of strained-actin binding in vivo not fully defined
    • How node vs actin partitioning is switched physiologically unknown
13. 2025 High

    Showed Prickle2 promotes tissue fluidity through Rac1-dependent apical-junction remodeling via its Ser/Thr-rich region, linking molecular activity to cell-shape and convergent-extension behavior.

    Evidence Xenopus loss/gain-of-function, live imaging of junction dynamics, STR domain mapping, Rac1 inhibition

    PMID:39951022

    Open questions at the time

    • How the STR engages Rac1 signaling biochemically not defined
    • Mammalian relevance of the fluidity role untested
14. 2025 Medium

    Implicated Prickle2 in dentinogenesis via Wnt/PCP signaling, broadening its developmental roles.

    Evidence In situ hybridization, siRNA knockdown in tooth organ culture, transplantation, pulp exposure model

    PMID:40916368

    Open questions at the time

    • Direct molecular targets in dentinogenesis not identified
    • Pathway placement inferred rather than directly demonstrated

• How Prickle2's distinct molecular activities — synaptic scaffolding, AIS microtubule regulation, nuclear RhoA control, and mechanosensitive actin binding — are coordinated within a single cell, and which are shared versus context-specific, remains unresolved.
• No unified model linking nuclear, synaptic, AIS, and junctional pools
• Structural basis of LIM-domain partner selection unknown
• Upstream signals switching Pk2 between functions undefined