PLCXD2

PLCXD2 is a constitutively active phospholipase C family member that functions as a postsynaptic effector controlling spine apparatus abundance and dendritic spine maturation in cortical neurons. PLCXD2 forms a signaling complex with the GPCR-like receptor GPR158, which directly restrains PLCXD2 enzymatic activity; loss of GPR158 leads to unrestrained PLCXD2 activity, impeding spine apparatus incorporation into dendritic spines and disrupting both structural and functional spine maturation (PMID:40393451). Extracellular heparan sulfate proteoglycans modulate the GPR158–PLCXD2 interaction, providing spatiotemporal control that bypasses canonical G-protein-mediated PLC regulation (PMID:40393451). In gastric cancer cells, PLCXD2 protein levels are post-transcriptionally suppressed by miR-378a-3p within the ACTA2-AS1 ceRNA axis, and PLCXD2 expression suppresses malignant phenotypes including proliferation, migration, and epithelial-mesenchymal transition (PMID:35274046).

1. 2022 Medium

   Identification of PLCXD2 as a functionally relevant target downstream of a non-coding RNA regulatory axis in cancer cells established that PLCXD2 protein levels are post-transcriptionally controlled by miR-378a-3p and that PLCXD2 expression suppresses proliferative and invasive phenotypes in gastric cancer.

   Evidence Luciferase reporter assays, RNA immunoprecipitation, siRNA knockdown with proliferation/migration/invasion readouts in gastric cancer cell lines

   PMID:35274046

   Open questions at the time

   • No direct measurement of PLCXD2 phospholipase activity in cancer cells
   • Single-lab study without independent replication
   • Whether the tumor-suppressive role depends on catalytic activity versus scaffolding is unknown
2. 2025 High

   Discovery that PLCXD2 is a constitutively active PLC restrained by GPR158 in a postsynaptic complex resolved how neurons control PLCXD2 enzymatic output and linked its unrestrained activity to defective spine apparatus dynamics and impaired dendritic spine maturation.

   Evidence In vivo sparse genetic loss-of-function in mouse cortical neurons, co-immunoprecipitation of GPR158–PLCXD2 complex, spine apparatus imaging and functional spine maturation readouts

   PMID:40393451

   Open questions at the time

   • The lipid substrate specificity and catalytic products of PLCXD2 have not been biochemically defined
   • No structural model of the GPR158–PLCXD2 complex exists
   • Whether PLCXD2 functions in non-neuronal postmitotic cells through a similar GPR158-dependent mechanism is unknown
3. 2025 Medium

   The finding that extracellular HSPGs modulate the GPR158–PLCXD2 interaction revealed a non-canonical GPCR-to-PLC signaling pathway that bypasses classical G-protein intermediates, suggesting spatiotemporal regulation of PLCXD2 by the extracellular matrix.

   Evidence Biochemical binding assays and in vivo functional assays examining HSPG modulation of GPR158–PLCXD2 interaction in mouse cortical neurons

   PMID:40393451

   Open questions at the time

   • The specific HSPG species and binding domains involved are not defined
   • Quantitative biochemistry of HSPG-dependent inhibition kinetics is lacking
   • Whether HSPG modulation is activity-dependent or developmentally programmed is unresolved

• The substrate specificity, catalytic mechanism, and lipid products of PLCXD2 remain undefined, and the structural basis for GPR158-mediated inhibition of its constitutive activity has not been determined.
• No in vitro enzymatic reconstitution with defined substrates has been reported
• No crystal or cryo-EM structure of PLCXD2 alone or in complex with GPR158 exists
• Downstream signaling consequences of PLCXD2 catalytic products at synapses are unknown