| 2010 |
Cbln1 forms a trans-synaptic tripartite complex bridging presynaptic neurexins (NRXNs) on granule cells to the N-terminal domain (NTD) of postsynaptic GluRδ2 (GluD2) on Purkinje cells, mediating cerebellar synapse formation. Synaptogenic activity of GluD2 is abolished in cbln1-null cultures and restored by recombinant Cbln1; knockdown of NRXNs in granule cells also abolishes the synaptogenic activity. Soluble NTD of GluD2 and extracellular domain of NRXN1β each suppress Cbln1 synaptogenic activity in vitro and in vivo. |
Cerebellar primary cultures from cbln1-null mice, recombinant Cbln1 rescue, NRXN knockdown, competitive inhibition with soluble domain fragments, in vivo injection |
Cell |
High |
20537373
|
| 2010 |
Cbln1 directly binds the N-terminal domain of GluD2 (the orphan glutamate receptor). The Cbln1–GluD2 complex acts as a bidirectional synapse organizer: Cbln1-coated beads directly induce presynaptic differentiation and indirectly cause postsynaptic molecule clustering via GluD2. GluD2 postsynaptic expression combined with exogenous Cbln1 is necessary and sufficient to induce new synapses in vitro and in adult cerebellum in vivo. |
Direct binding assays, bead-coated recombinant Cbln1 synaptogenesis assay, in vitro and in vivo synapse induction experiments |
Science |
High |
20395510
|
| 2005 |
Cbln1 is a glycoprotein secreted from cerebellar granule cells that is essential for (1) maintaining pre- and postsynaptic elements at parallel fiber–Purkinje cell synapses, (2) establishing proper climbing fiber–Purkinje cell innervation, and (3) induction of long-term depression at parallel fiber–Purkinje cell synapses. cbln1-null mice phenocopy GluRδ2-null mice, establishing Cbln1 in the same signaling pathway as GluRδ2. |
cbln1 knockout mice, genetic epistasis (phenocopy of GluRδ2-null), electrophysiology (LTD), morphological analysis |
Nature Neuroscience |
High |
16234806
|
| 2000 |
Cbln1 forms homomeric hexameric complexes and also interacts specifically with Cbln3 to form heteromeric complexes, mediated by conserved N-terminal cysteine residues (for higher-order oligomerization) and the C-terminal C1q domain (for trimerization). C1qB binds to neither Cbln1 nor Cbln3, demonstrating specificity. Cbln3 cannot form stable homomers. |
Yeast two-hybrid screen using Cbln1 as bait, mammalian co-expression, binding specificity assays |
The Journal of Neuroscience |
Medium |
10964938
|
| 2005 |
Cbln1 undergoes proteolytic processing in the synaptic compartment. Only uncleaved Cbln1 (containing the cerebellin motif) is released and assembles into hexameric complexes. Cleavage at the N-terminus of the cerebellin sequence yields trimeric complexes by separating the C-terminal C1q domain from N-terminal cysteine residues. Cleavage at the C-terminus of the cerebellin motif disrupts the C1q domain and abolishes subunit interactions. |
Biochemical analysis of cerebellar lysates, yeast two-hybrid, mammalian expression systems, protease cleavage mapping |
Journal of Neurochemistry |
Medium |
16135095
|
| 2006 |
Cbln1 is secreted from cerebellar granule cells in complex with Cbln3. Cbln1 and Cbln3 reciprocally regulate each other's degradation and secretion: cbln1-null mice lack both Cbln1 and Cbln3, whereas cbln3-null mice lack Cbln3 but have ~6-fold increased Cbln1. Cbln3 cannot form homomers and is secreted only when bound to Cbln1. A single arginine residue in Cbln3 causes ER retention via steric clash that is masked upon Cbln1 binding ('hide-and-run' mechanism). |
cbln1 and cbln3 knockout mice and double knockouts, structural modeling, mutation analysis, biochemical secretion assays |
Molecular and Cellular Biology |
High |
17030622
|
| 2008 |
Recombinant Cbln1 specifically and reversibly induces parallel fiber (PF) synapse formation in dissociated cbln1-null Purkinje cells in culture and rapidly induces functional, ultrastructurally normal PF synapses in acute cbln1-null cerebellar slices. A single injection of recombinant Cbln1 in adult cbln1-null mice in vivo completely but transiently restores PF synapses and rescues ataxia. |
Dissociated cbln1-null Purkinje cell cultures, acute slice preparations, in vivo injection of recombinant Cbln1, electrophysiology, electron microscopy |
The Journal of Neuroscience |
High |
18524896
|
| 2007 |
Cbln1 is localized to the endolysosomal compartment of neurons (co-localizing with cathepsin D, a lysosomal marker) but not to ER or Golgi. In cbln3-null cerebellum, Cbln1 immunoreactivity increases dramatically, while it is unchanged in extracerebellar neurons, indicating that Cbln3 regulates Cbln1 levels specifically in the cerebellum via the endolysosomal pathway. |
Immunohistochemistry with organelle markers, cbln1-lacZ transgenic mice, cbln3-null mice, subcellular fractionation |
European Journal of Neuroscience |
Medium |
18001291
|
| 2009 |
Cbln1 accumulates specifically in the synaptic cleft of parallel fiber–Purkinje cell synapses (not other PC synapses), co-localizing with Cbln3 and GluRδ2 at these synapses. Intact hexameric Cbln1 specifically binds to postsynaptic sites; neither N-terminal nor C-terminal fragments alone, nor trimeric mutant Cbln1, support specific binding. Cbln1 binding site is located on postsynaptic (Purkinje cell) rather than presynaptic elements. |
Postembedding immunogold electron microscopy, pepsin antigen retrieval, binding assays with recombinant Cbln1 in weaver and pcd mutant cerebellum, subcellular fractionation |
European Journal of Neuroscience |
High |
19200061 19250438
|
| 2009 |
Cbln1 undergoes anterograde trans-neuronal transport from granule cells to Purkinje cells and Bergmann glia, entering the endolysosomal trafficking system. Cbln1 is absent in Purkinje cells and Bergmann glia of GluRδ2-null mice, suggesting GluRδ2 is required for Cbln1 trafficking into postsynaptic cells. Ectopic Cbln1 expression in Purkinje cells (L7-cbln1 transgene) partially rescues locomotor deficits of cbln1-null mice. |
Immunohistochemistry in transgenic and GluRδ2-null mice, L7-cbln1 transgenic mice, behavioral analysis |
Molecular and Cellular Neurosciences |
Medium |
19344768
|
| 2009 |
Neuronal activity (elevated K+ or kainate) decreases cbln1 mRNA expression in mature granule cells within hours, in a manner dependent on L-type voltage-dependent Ca2+ channels and calcineurin. Chronic activity also reduces Cbln1 protein levels, accompanied by reduction of excitatory synapses on Purkinje cell dendrites; this activity-induced synapse reduction is prevented by exogenous Cbln1. |
Granule cell cultures with pharmacological manipulation (K+, kainate, L-type Ca2+ channel blockers, calcineurin inhibitors), qRT-PCR, immunohistochemistry, synapse counting |
The Journal of Neuroscience |
Medium |
19403810
|
| 2012 |
Cbln1 released from parallel fibers induces dynamic structural changes (protrusions forming circular structures that encapsulate Purkinje cell spines) in presynaptic parallel fibers through a mechanism requiring postsynaptic GluD2 and presynaptic neurexin (Nrx). Nrx–Cbln1–GluD2 signaling induces accumulation of synaptic vesicles and GluD2, leading to mature synapse formation via a positive feedback mechanism. |
Time-lapse imaging in organotypic culture, ultrastructural analysis in vivo, genetic manipulation (GluD2/Nrx ablation) |
Neuron |
High |
23141067
|
| 2012 |
Cbln1 and Cbln2 have similar binding activities to β-neurexins and Grid2 (GluD2). Ectopic Cbln2 expression in Purkinje cells of transgenic mice rescues cerebellar deficits in cbln1-null mice, demonstrating functional redundancy mediated by common receptor binding properties. However, Cbln2 does not substitute for Cbln1 in thalamic neurons affecting striatal synapses, implying region-specific receptor/mechanism differences. |
Binding assays, Cbln2 transgenic rescue of cbln1-null mice, cbln2 knockout mice, synaptic analysis |
Journal of Neurochemistry |
Medium |
22117778
|
| 2014 |
Cbln1–GluD2 signaling downregulates the formation and function of inhibitory synapses between Purkinje cells and interneurons. cbln1-null cerebellum shows increased density of interneuron–Purkinje cell inhibitory synapses and increased amplitude and frequency of miniature IPSCs. Recombinant Cbln1 reverses increased inhibitory currents and synapse density; this effect is absent in cbln1/GluD2 double-null mice. Tyrosine phosphorylation is upregulated in cbln1-null cerebellum, and Src-family kinase inhibition suppresses increased IPSCs. |
Immunohistochemistry (vGAT antibody), whole-cell patch-clamp in cerebellar slices, recombinant Cbln1 rescue, double-knockout epistasis, Src kinase inhibitors |
European Journal of Neuroscience |
High |
24467251
|
| 2017 |
Crystal structures of the homotrimeric C1q domains of Cbln1 and Cbln4 resolved at 2.2 Å and 2.3 Å, respectively, reveal that divergence in loop CD accounts for the difference in GluD2 binding between Cbln1 and Cbln4. Negative-stain EM reconstruction of hexameric full-length Cbln1 at 13 Å and Cbln4/Nrxn1β complex at 19 Å shows that Nrxn1β binds to the N-terminal region of Cbln4 (through strand β10 of S4 insert). Cbln4 binds Nrxn1β and forms a stable complex with the LNS domain of Nrxn1β despite not binding GluD2. |
X-ray crystallography, negative-stain electron microscopy, binding assays |
Cell Reports |
High |
28877468
|
| 2019 |
Cbln1 is released from lysosomes in axons (but not dendrites) of cerebellar granule cells in an activity- and Ca2+-dependent manner. Released Cbln1 is retained on axonal surfaces by binding to presynaptic neurexin, then diffuses laterally and accumulates at boutons by binding postsynaptic δ2 glutamate receptors. Cbln1 exocytosis is insensitive to tetanus neurotoxin, is accompanied by cathepsin B release, and is decreased by lysosome disruption. Overexpression of lysosomal sialidase Neu1 inhibits Cbln1 and cathepsin B exocytosis and reduces axonal bouton formation in vivo. |
Live-cell imaging of Cbln1 exocytosis, pharmacological manipulation (tetanus neurotoxin, lysosome disruptors), Neu1 overexpression, in vivo bouton analysis |
Neuron |
High |
31072786
|
| 2017 |
UBE3A (a ubiquitin ligase with transcriptional co-regulatory functions), when overexpressed in the nucleus in VTA glutamatergic neurons, downregulates Cbln1 expression. Cbln1 deletion in VTA glutamatergic neurons impairs sociability and weakens glutamatergic transmission. Viral vector-based restoration of Cbln1 in VTA glutamatergic neurons reverses sociability deficits induced by Ube3a overexpression and/or seizures. |
In vivo mouse genetics, conditional gene deletion/overexpression, viral vector-based Cbln1 restoration, chemogenetic activation, behavioral testing, electrophysiology |
Nature |
High |
28297715
|
| 2010 |
The flap loop (Arg321–Trp339) in the N-terminal domain of GluD2 is the critical region for binding to Cbln1 and induction of presynaptic differentiation. Mutations in flap loop residues, including single amino acid substitutions of Arg321 or Trp323 to alanine, abolish both Cbln1 binding and presynaptic differentiation induction in HEK cells expressing GluD2. |
HEK cell expression, mutagenesis of GluD2 NTD, Cbln1 binding assay, presynaptic differentiation assay, homology modeling |
Biochemical and Biophysical Research Communications |
Medium |
20599760
|
| 2020 |
Cbln1/GluD2-dependent competitive interactions shape Purkinje cell dendritic arbor morphogenesis. Sparse but not global GluD2 knockout causes under-elaboration of Purkinje cell dendrites in the deep molecular layer and overelaboration in the superficial molecular layer, demonstrating that competition between granule cell inputs via Cbln1/GluD2 is required for normal dendritic development. Developmental and genetic epistasis analyses confirm this is a synaptotrophic mechanism. |
Sparse and global GluD2 conditional knockout, developmental analysis, GluD2 overexpression, structure-function analysis, genetic epistasis, computational modeling |
Neuron |
High |
33352118
|
| 2022 |
Cbln1 functions as an axon growth and guidance cue during early neural development (distinct from its later synaptogenic role), acting in an autocrine manner on commissural neuron axons to promote axon growth. Cbln1 also acts as an attractive guidance cue from intermediate target tissues. These functions are mediated by neurexin-2 (Nrxn2) as the Cbln1 receptor for axon growth and guidance. Cbln1 also regulates cerebellar parallel fiber growth and retinal ganglion cell axon guidance. |
Mouse and chick embryo experiments, loss-of-function and gain-of-function in developing spinal cord, identification of Nrxn2 as receptor by genetic epistasis and binding assays |
PLoS Biology |
Medium |
36395107
|
| 2023 |
UBE3A impairs excitatory VMHvl-to-arcuate synapse formation by decreasing Cbln1 gene expression. This synapse is organized by an NRXN1–CBLN1–GluD1 transsynaptic complex. Targeted deletion of Grid1 (GluD1) in arcuate AgRP neurons impairs VMHvl-to-AgRP/NPY excitatory synapses. Chemogenetic/optogenetic activation of arcuate AgRP/NPY neurons inhibits VMHvl neurons and represses aggression, placing the NRXN1–CBLN1–GluD1 complex in a hypothalamic circuit regulating aggression. |
Conditional gene deletion, chemogenetic and optogenetic manipulation, behavioral testing, synapse analysis in mouse brain |
bioRxivpreprint |
Medium |
36909588
|
| 2025 |
D-serine inhibits the interaction between Cbln1 and GluD1 in a concentration-dependent manner (IC50 ~300 µM) in an in vitro cell-binding assay. In ex vivo central amygdala slices, recombinant Cbln1 increases excitatory neurotransmission and GluD1 expression; this effect is partially blocked by D-serine pre-treatment. The pro-nociceptive behavioral effect of intra-CeA Cbln1 injection is inhibited by D-serine. |
In vitro cell-binding assay, ex vivo CeA slice electrophysiology, in vivo intra-CeA injection with behavioral readout |
Cellular and Molecular Life Sciences |
Medium |
39890638
|
| 2023 |
YTHDF3 interacts with BTG2 and is involved in the decay of Cbln1 mRNA in the hippocampus, leading to downregulation of Cbln1 protein expression. This identifies YTHDF3/BTG2 as an m6A-dependent post-transcriptional regulatory mechanism controlling Cbln1 levels. |
Co-immunoprecipitation (YTHDF3-BTG2 interaction), mRNA decay assays, hippocampal gene expression analysis in prenatal hypoxia model |
iScience |
Low |
38205248
|
| 2023 |
Cbln1 expressed by CSN subpopulations is sufficient to direct axon extension toward thoraco-lumbar spinal segments. Gain-of-function misexpression of Cbln1 in CSNBC-lat neurons (which normally project only to bulbar-cervical segments) redirects their axons past normal targets toward thoracic segments, demonstrating that Cbln1 is a molecular determinant of segmentally specific corticospinal axon projection targeting. |
In utero electroporation, AAV-mediated postmitotic gene delivery, axon tracing in mouse brain, gain-of-function experiments |
The Journal of Neuroscience |
Medium |
36823038
|