Affinage

CSPG5

Chondroitin sulfate proteoglycan 5 · UniProt O95196

Length
566 aa
Mass
60.0 kDa
Annotated
2026-06-09
15 papers in source corpus 6 papers cited in narrative 6 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CSPG5 (CALEB/NGC/neuroglycan C) is a brain-specific transmembrane EGF-domain chondroitin sulfate proteoglycan that promotes dendritic arborization and dendritic spine formation during neuronal development (PMID:9950058, PMID:17431398). Its EGF-like domain drives both processes, with dendritic branching requiring PI3K-Akt-mTOR and PKC signaling while spine morphogenesis is PI3K-independent but PKC-dependent (PMID:17431398). Mechanistically, CALEB/NGC activates Rac1 at the plasma membrane to drive branching, and RhoG acts upstream to limit its plasma membrane abundance and thereby reduce dendritic complexity (PMID:27412363). Signaling output is tuned by two cytoplasmic-tail interactions: the Golgi protein PIST binds the juxtamembrane segment and regulates intracellular trafficking through Golgi-derived vesicles (PMID:12885772), while the PP2A regulatory subunit B56beta recruits the PP2A trimer to suppress CALEB/NGC-induced Akt phosphorylation and selectively antagonize Akt-dependent dendritic branching (PMID:18385213). In vivo, loss of CALEB/NGC impairs presynaptic maturation of inhibitory GABAergic synapses on cerebellar Purkinje cells and causes premature elimination of supernumerary climbing fiber synapses (PMID:23889129).

Mechanistic history

Synthesis pass · year-by-year structured walk · 6 steps
  1. 1998 Medium

    Defined CSPG5 as a brain-specific transmembrane chondroitin sulfate proteoglycan with a modular domain architecture, establishing the molecular substrate for all later functional work.

    Evidence cDNA cloning from human brain library, Northern blot, and FISH chromosomal mapping

    PMID:9950058

    Open questions at the time
    • No function assigned to any domain at this stage
    • Cytoplasmic-tail binding partners unidentified
    • Tissue distribution within brain not resolved
  2. 2003 High

    Identified the first cytoplasmic-tail partner, linking CALEB/NGC to intracellular trafficking machinery and assigning a function to its conserved juxtamembrane segment.

    Evidence Yeast two-hybrid, reciprocal co-immunoprecipitation, and Golgi co-localization (with brefeldin A/nocodazole) in COS7 cells and primary neurons

    PMID:12885772

    Open questions at the time
    • Functional consequence of PIST binding for trafficking not quantified at the cell-surface level
    • Whether PIST regulates CALEB/NGC signaling output unknown
  3. 2007 High

    Established the core developmental function of CALEB/NGC — driving dendritic branching and spine formation via its EGF-like domain — and dissected the divergent signaling pathways underlying each process.

    Evidence Gain/loss-of-function in primary neurons, in utero electroporation in mouse cortex, and pharmacological inhibition of PI3K/Akt/mTOR/PKC

    PMID:17431398

    Open questions at the time
    • Upstream activator/ligand of the EGF-like domain not identified
    • Direct effector linking signaling to cytoskeletal remodeling not yet defined
  4. 2008 High

    Showed how CALEB/NGC signaling is negatively regulated, identifying PP2A recruitment via B56beta as a brake on Akt-dependent branching but not spine formation.

    Evidence Yeast two-hybrid, Co-IP, affinity chromatography/mass spectrometry, and Akt phosphorylation assays in primary neurons

    PMID:18385213

    Open questions at the time
    • Direct PP2A dephosphorylation target on the Akt axis not pinpointed
    • Whether B56beta recruitment is regulated dynamically during development unknown
  5. 2013 High

    Provided in vivo developmental relevance by showing CALEB/NGC is required for presynaptic GABAergic maturation and proper climbing fiber synapse refinement in the cerebellum.

    Evidence Constitutive knockout mice with Purkinje cell patch-clamp electrophysiology, Sholl analysis, and Rota-Rod testing

    PMID:23889129

    Open questions at the time
    • Cell-autonomous versus non-autonomous basis of the presynaptic phenotype not resolved
    • Link between CALEB chondroitin sulfate state and synaptic phenotype not mechanistically established
  6. 2016 High

    Placed Rac1 as the essential effector of CALEB/NGC-driven branching and defined RhoG as an upstream regulator controlling its plasma membrane localization.

    Evidence Gain/loss-of-function of Rac1, Cdc42 isoforms, and RhoG in hippocampal neurons with Rac1 activity assays and subcellular localization analysis

    PMID:27412363

    Open questions at the time
    • Molecular step linking CALEB/NGC to Rac1 GEF activation not identified
    • Mechanism by which RhoG reduces CALEB/NGC surface levels unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • The extracellular ligand or activating partner engaging the CALEB/NGC EGF-like domain to initiate intracellular signaling remains unidentified.
  • No receptor or ligand for the EGF-like domain characterized in the corpus
  • Direct biochemical coupling between the cytoplasmic tail and the Rac1/Akt machinery undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060089 molecular transducer activity 2 GO:0098772 molecular function regulator activity 1
Localization
GO:0005794 Golgi apparatus 1 GO:0005886 plasma membrane 1
Partners
GOPCPPP2R5BRAC1RHOG
Complex memberships
PP2A

Evidence

Reading pass · 6 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1998 Human CSPG5 (NGC/neuroglycan C) encodes a 539-amino acid transmembrane chondroitin sulfate proteoglycan with a domain structure consisting of an N-terminal signal sequence, a chondroitin sulfate-attachment domain, an acidic amino acid cluster, an EGF-like domain, a transmembrane domain, and a cytoplasmic tail; brain-specific expression (2.4 kb transcript) was confirmed by Northern blot, and the gene was mapped to chromosomal band 3p21.3 by FISH. cDNA cloning from human brain library, Northern blot analysis, FISH chromosomal mapping Neuroscience research Medium 9950058
2003 CALEB/NGC interacts with the Golgi-associated protein PIST via its juxtamembrane cytoplasmic peptide segment (highly conserved during evolution); this interaction was confirmed by yeast two-hybrid, co-immunoprecipitation, and co-localization in the Golgi apparatus of transfected COS7 cells and primary hippocampal neurons. CALEB/NGC co-localizes with PIST in Golgi-derived vesicles after brefeldin A or nocodazole treatment, implicating PIST in intracellular transport of CALEB/NGC. Yeast two-hybrid screen, co-immunoprecipitation, co-localization immunofluorescence, brefeldin A/nocodazole treatment in COS7 cells and primary neurons The Journal of biological chemistry High 12885772
2007 CALEB/NGC mediates dendritic tree complexity and spine formation: overexpression enhances dendritic branching and spine/filopodia complexity, while genetic and functional inactivation impairs arborization and spine formation in cortical neurons (confirmed by in utero electroporation). The EGF-like domain drives both processes. PI3K-Akt-mTOR signaling and PKC are required for CALEB/NGC-induced dendritic branching; spine morphogenesis is PI3K-independent but PKC-dependent. Overexpression and loss-of-function (knockdown/knockout) in primary neurons, in utero electroporation in mouse cortex, pharmacological inhibition of PI3K/Akt/mTOR/PKC pathways The EMBO journal High 17431398
2008 B56beta, a regulatory subunit of protein phosphatase 2A (PP2A), interacts with CALEB/NGC and inhibits CALEB/NGC-mediated dendritic branching but not spine formation. The entire PP2A trimer (structural and catalytic subunits) binds to CALEB/NGC via B56beta (confirmed by affinity chromatography and mass spectrometry). CALEB/NGC induces Akt phosphorylation in dendrites; B56beta inhibits this Akt phosphorylation and thereby inhibits Akt-dependent dendritic branching. Yeast two-hybrid screen, co-immunoprecipitation, affinity chromatography, mass spectrometry, immunocytochemistry, Akt phosphorylation assays in primary neurons FASEB journal High 18385213
2013 CALEB/CSPG5-deficient mice show impaired presynaptic maturation of inhibitory GABAergic synapses on cerebellar Purkinje cells (decreased evoked amplitudes, altered paired-pulse facilitation, reduced depression after repetitive stimulation at early postnatal stages) and premature elimination of supernumerary climbing fiber synapses. CALEB expression is dynamically regulated during development from a high chondroitin sulfate-containing form to a non-chondroitin sulfate-containing form in Purkinje cells. CALEB-knockout mice, patch-clamp electrophysiology of Purkinje cells, Rota-Rod motor coordination test, Sholl analysis of dye-injected Purkinje cells The European journal of neuroscience High 23889129
2016 CALEB/NGC activates Rac1 at the plasma membrane to drive dendritic branching; Rac1 is essential for CALEB/NGC-mediated dendritic branching. RhoG reduces dendritic complexity by acting upstream of CALEB/NGC, decreasing the amount of CALEB/NGC at the plasma membrane. The palmitoylated (but not prenylated) isoform of Cdc42 adversely affects dendritic outgrowth independently of CALEB/NGC (they are not directly interconnected). Gain- and loss-of-function of Rac1, Cdc42 isoforms, and RhoG in primary hippocampal neurons; Rac1 activity assays; subcellular localization analysis of CALEB/NGC Journal of neurochemistry High 27412363

Source papers

Stage 0 corpus · 15 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 The novel Streptomyces olivaceoviridis ABC transporter Ngc mediates uptake of N-acetylglucosamine and N,N'-diacetylchitobiose. Molecular genetics and genomics : MGG 49 12111550
2007 The neural EGF family member CALEB/NGC mediates dendritic tree and spine complexity. The EMBO journal 38 17431398
1998 Cloning and chromosomal mapping of the human gene of neuroglycan C (NGC), a neural transmembrane chondroitin sulfate proteoglycan with an EGF module. Neuroscience research 33 9950058
2004 Mutational analysis of the binding affinity and transport activity for N-acetylglucosamine of the novel ABC transporter Ngc in the chitin-degrader Streptomyces olivaceoviridis. Molecular genetics and genomics : MGG 22 15148605
2003 CALEB/NGC interacts with the Golgi-associated protein PIST. The Journal of biological chemistry 19 12885772
2012 Flavone enhances dengue virus type-2 (NGC strain) infectivity and replication in vero cells. Molecules (Basel, Switzerland) 18 22374315
2018 A fully automated three-step protein purification procedure for up to five samples using the NGC chromatography system. Protein expression and purification 15 30102973
2016 Different roles of the small GTPases Rac1, Cdc42, and RhoG in CALEB/NGC-induced dendritic tree complexity. Journal of neurochemistry 14 27412363
2013 Impaired presynaptic function and elimination of synapses at premature stages during postnatal development of the cerebellum in the absence of CALEB (CSPG5/neuroglycan C). The European journal of neuroscience 14 23889129
2008 Immunization with Toscana virus N-Gc proteins protects mice against virus challenge. Virology 14 18355889
2008 B56beta, a regulatory subunit of protein phosphatase 2A, interacts with CALEB/NGC and inhibits CALEB/NGC-mediated dendritic branching. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 12 18385213
2019 Development of BioRad NGC and GE ÄKTA pure systems for highly automated three column protein purification employing tandem affinity, buffer exchange and size exclusion chromatography. Protein expression and purification 6 31499166
2016 Polycyclic aromatic hydrocarbons and molecular hydrogen in oxygen-rich planetary nebulae: the case of NGC 6720. Monthly notices of the Royal Astronomical Society 3 26924856
1993 Purification and characterisation of the restriction endonuclease ItaI from Ilyobacter tartaricus recognizing 5'-GC decreases NGC-3'. Gene 1 8299969
2006 [Construction and identification of genomic cDNA subclones of dengue 2 virus NGC strain]. Nan fang yi ke da xue xue bao = Journal of Southern Medical University 0 16624755

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