LIN7A

LIN7A (Veli-1/MALS-1) is a PDZ-domain scaffold protein that assembles multiprotein complexes at cell-cell contacts and synapses to maintain apico-basal polarity, support neuronal development, and restrain cellular invasion. It directly binds MAGUK family partners such as VAM-1/MPP3 and recruits transmembrane cargo including the α2/β1 nitric oxide-sensitive guanylyl cyclase to nectin-based cell-cell contacts via its PDZ domain (PMID:11311936, PMID:27793718). In the brain, LIN7A localizes to presynaptic fractions and is required for cortical neuronal migration and interhemispheric axon development, with its transcription regulated by Ca²⁺/calcineurin signaling (PMID:24658322, PMID:12393911). Loss of LIN7A promotes glioblastoma invasion by elevating MMP-2/MMP-9 activity and triggering nuclear β-catenin accumulation, while its overexpression in breast epithelial cells disrupts lumen formation, demonstrating that precise LIN7A dosage is critical for polarity and invasion control (PMID:40021783, PMID:26887652).

1. 2001 Medium

   Identifying a direct MAGUK-family binding partner for LIN7A established that Veli-1 participates in scaffolded protein complexes in neuronal and epithelial cells, raising the question of what cargo these complexes recruit.

   Evidence GST pull-down and blot overlay assays demonstrating VAM-1–Veli-1 direct binding

   PMID:11311936

   Open questions at the time

   • No in vivo validation of the VAM-1–Veli-1 interaction
   • Functional consequence of complex formation not tested
   • Other MAGUK partners not compared
2. 2002 Medium

   Demonstrating that LIN7A transcription is controlled by Ca²⁺ influx through the calcineurin pathway in neurons revealed how synaptic activity could dynamically regulate this scaffold, but the downstream transcription factor remained unidentified.

   Evidence Pharmacological activation/inhibition of Ca²⁺/calcineurin signaling in cultured cerebellar granule cells with transcriptional readouts

   PMID:12393911

   Open questions at the time

   • Transcription factor mediating calcineurin-dependent LIN7A expression not identified
   • In vivo relevance of activity-dependent regulation not tested
3. 2014 Medium

   Loss-of-function experiments in vivo showed that LIN7A is required for cortical neuronal migration and axon pathfinding, moving it from a biochemical scaffold to a functionally required neurodevelopmental factor.

   Evidence RNAi knockdown via in utero electroporation in mouse cortex with immunohistochemical analysis of migration and axon tracts

   PMID:24658322

   Open questions at the time

   • Molecular mechanism linking LIN7A to migration machinery not defined
   • Rescue experiment not reported
   • Presynaptic localization shown biochemically but functional role at synapses not tested
4. 2016 Medium

   Two studies expanded LIN7A's role beyond neurons: overexpression in breast epithelial cells disrupted lumen formation and drove invasion, establishing LIN7A as a dosage-sensitive polarity regulator, while PDZ-domain-mediated recruitment of NO-sensitive guanylyl cyclase to nectin-based cell-cell contacts via MPP3 provided a concrete cargo-delivery mechanism.

   Evidence 3D lumen-formation and invasion assays in breast epithelial cells; co-precipitation from brain synaptosomes and domain-mapping in HEK293 cells with truncation mutants

   PMID:26887652 PMID:27793718

   Open questions at the time

   • Whether lumen-formation defect operates through the same β-catenin or MMP pathways identified later is unknown
   • Structural basis of PDZ-dependent heterodimer selectivity not resolved
   • In vivo validation of guanylyl cyclase targeting not performed
5. 2025 Medium

   Silencing LIN7A in glioblastoma cells identified a specific invasion-suppressive mechanism: LIN7A restrains MMP-2/9 activity and prevents nuclear β-catenin accumulation, linking its polarity-scaffold function to Wnt/β-catenin pathway control.

   Evidence Lentiviral knockdown in U87 cells with zymography, β-catenin immunofluorescence, invasion assays, and orthotopic xenograft

   PMID:40021783

   Open questions at the time

   • Direct physical link between LIN7A and β-catenin retention at junctions not shown
   • Whether MMP upregulation is a direct or indirect consequence of polarity loss is unresolved
   • Single cell line (U87) limits generalizability

• The direct molecular mechanism by which LIN7A restrains β-catenin nuclear translocation and MMP expression, and whether its neurodevelopmental and tumor-suppressive roles share a common polarity-dependent signaling axis, remain unresolved.
• No structural model of LIN7A in complex with its partners
• No genetic knockout mouse phenotype reported
• Relationship between calcineurin-dependent transcriptional regulation and polarity/invasion functions not connected