LZTS3

LZTS3 (ProSAPiP1) is a postsynaptic density scaffolding protein of the Fezzin family that organizes excitatory synapse signaling by physically linking ProSAP2/Shank3 to SPAR-family RapGAPs (PMID:16522626). It binds the PDZ domain of ProSAP2/Shank3 and, through a central coiled-coil/leucine zipper region, recruits SPAR to synapses while also self-associating and heteromultimerizing with PSD-Zip70 (PMID:16522626); the same family extends to SPAR3/Sipa1l3, which is targeted to the postsynapse via interaction with LZTS3 (PMID:26364583). Functionally, LZTS3 sets SPAR protein levels at the PSD and drives dendritic spine maturation without being required for synapse formation per se (PMID:27252646). In the dorsal hippocampus, neuronal loss of LZTS3 depletes synaptic SPAR, PSD-95, and GluN2B-containing NMDA receptors, impairing NMDAR-mediated transmission, CA1 long-term potentiation, and recognition, social, and spatial memory (PMID:41295083, PMID:38915579). In the nucleus accumbens, mTORC1-dependent upregulation of LZTS3 promotes actin filament formation, spine remodeling, and synaptic insertion of GluA2-lacking AMPA receptors that mediate alcohol reward (PMID:28890345). LZTS3 protein stability is controlled by CK1δ-dependent phosphorylation that licenses recognition by the E3 ligase β-TrCP at two degrons (DSGRNS/DSGRAS), driving ubiquitin-proteasomal degradation (PMID:39956246). In non-neuronal cancer contexts, LZTS3 suppresses proliferation and migration and reorganizes the actin cytoskeleton with TAGLN as a downstream effector (PMID:37806182).

1. 2006 High

   Established LZTS3/ProSAPiP1 as a molecular bridge at the postsynaptic density, answering how SPAR RapGAP activity is coupled to the Shank scaffold.

   Evidence Co-immunoprecipitation, yeast two-hybrid, domain mapping and co-localization identifying ProSAP2/Shank3 (PDZ) and SPAR (coiled-coil/leucine zipper) binding plus self-/PSD-Zip70 multimerization

   PMID:16522626

   Open questions at the time

   • Stoichiometry and structure of the Shank3–LZTS3–SPAR assembly not resolved
   • Functional consequence of multimerization not defined
2. 2015 Medium

   Extended the scaffolding logic by showing a second SPAR-family RapGAP, SPAR3/Sipa1l3, uses LZTS3 as a postsynaptic targeting module.

   Evidence Co-IP, pulldown, neuronal co-localization, and domain truncation mapping the C-terminal Fezzin-interaction module

   PMID:26364583

   Open questions at the time

   • Single lab; reciprocal in vivo validation absent
   • Relative contributions of SPAR vs SPAR3 to LZTS3 function unresolved
3. 2016 Medium

   Defined the cellular role of LZTS3 in synapse biology, distinguishing spine maturation from synapse assembly.

   Evidence Lentiviral overexpression and knockdown in primary hippocampal neurons with quantitative immunofluorescence of SPAR and spine morphology

   PMID:27252646

   Open questions at the time

   • In vitro neuronal system only
   • Mechanism linking SPAR level to spine maturation not dissected
4. 2017 High

   Placed LZTS3 downstream of mTORC1 in a circuit-specific pathway, revealing its role in alcohol-driven synaptic plasticity.

   Evidence RNA-seq, lentiviral knockdown, phalloidin actin imaging, synaptic AMPA receptor immunofluorescence and alcohol self-administration in NAc

   PMID:28890345

   Open questions at the time

   • Direct mechanism connecting LZTS3 to GluA2-lacking AMPAR trafficking not established
   • How mTORC1 selectively engages Prosapip1 translation unclear
5. 2025 High

   Provided in vivo genetic proof that LZTS3 is required for hippocampal NMDAR signaling, LTP, and memory, anchoring its scaffolding role to behavior.

   Evidence Cre-loxP neuronal knockout mouse with biochemical fractionation, CA1 electrophysiology, and behavioral memory tasks (replicated across preprint and peer-reviewed report)

   PMID:38915579 PMID:41295083

   Open questions at the time

   • Whether GluN2B/PSD-95 loss is a direct consequence of SPAR mislocalization not separated
   • Cell-type specificity within hippocampal circuits not resolved
6. 2025 Medium

   Identified the post-translational control of LZTS3 abundance, defining a CK1δ–β-TrCP degron axis governing its stability.

   Evidence Co-IP, ubiquitination assays, degron mutagenesis (DSGRNS/DSGRAS), proteasome inhibition, and proliferation/radioresistance assays in vitro and in vivo

   PMID:39956246

   Open questions at the time

   • Single lab; degron phosphosites not directly mapped by mass spectrometry
   • Whether this degradation operates in neurons not tested
7. 2023 Medium

   Demonstrated a non-neuronal tumor-suppressive function of LZTS3 acting through cytoskeletal regulation.

   Evidence Overexpression/silencing, RTCA proliferation, Transwell migration, actin staining, and nude mouse xenografts in colorectal adenocarcinoma cells identifying TAGLN as a downstream target

   PMID:37806182

   Open questions at the time

   • NOTCH pathway placement partly inferential
   • Direct vs indirect regulation of TAGLN not established

• How LZTS3 mechanistically couples its scaffolding role to AMPA/NMDA receptor trafficking and whether the CK1δ–β-TrCP degradation axis tunes synaptic LZTS3 levels in neurons remain unresolved.
• No structural model of the Shank3–LZTS3–SPAR complex
• Link between protein stability control and neuronal function untested
• Mechanism of receptor insertion downstream of LZTS3 unknown