CACNB2

id: Q08289
gene_symbol: CACNB2
product_type: PROTEIN
status: COMPLETE
taxon:
  id: NCBITaxon:9606
  label: Homo sapiens
description: >
  CACNB2 encodes the voltage-dependent L-type calcium channel subunit beta-2 (CaVbeta2),
  an essential cytosolic auxiliary subunit of high-voltage-activated Ca2+ channels.
  The protein contains a conserved SH3-HOOK-guanylate kinase (GK) module that binds
  the alpha-interaction domain (AID) in the I-II linker of the pore-forming alpha1
  subunit with nanomolar affinity. CaVbeta2 promotes proper channel trafficking to the
  plasma membrane and modulates voltage-dependent activation/inactivation kinetics
  of CaV1.x/CaV2.x channels. Multiple splice variants (beta2a-beta2e) differ in their
  N-termini, with beta2a being palmitoylated for membrane anchoring and beta2e capable
  of nuclear translocation. CaVbeta2 also mediates beta-adrenergic regulation of
  cardiac L-type channels through interaction with the RGK GTPase Rad.
alternative_products:
- name: 2d (CACNB2d)
  id: Q08289-1
- name: 2a (CACNB2a)
  id: Q08289-2
  sequence_note: VSP_000627
- name: 2b (CACNB2b, 2aN4)
  id: Q08289-3
  sequence_note: VSP_000628
- name: 2c (CACNB2c, 2aN2)
  id: Q08289-4
  sequence_note: VSP_000626
- name: 2e (CACNB2e)
  id: Q08289-5
  sequence_note: VSP_000629
- name: 2f
  id: Q08289-6
  sequence_note: VSP_000627, VSP_000630
- name: 2g
  id: Q08289-7
  sequence_note: VSP_000630
- name: 2h (2cN1)
  id: Q08289-8
  sequence_note: VSP_000631
- name: 2cN2
  id: Q08289-9
  sequence_note: VSP_000626, VSP_000631
- name: 2cN4
  id: Q08289-10
  sequence_note: VSP_000628, VSP_000631
existing_annotations:
# IBA annotations from phylogenetic inference
- term:
    id: GO:0006816
    label: calcium ion transport
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >
      CaVbeta2 is an auxiliary subunit that promotes calcium channel trafficking and
      modulates channel gating. PMID:1309651 demonstrated that beta2 subunit coexpression
      is obligatory for functional calcium channel activity, and that it increases peak
      calcium current. The protein enables calcium ion transport by regulating the
      alpha1 pore-forming subunit.
    action: ACCEPT
    reason: >
      IBA annotations for calcium ion transport are appropriate. While CaVbeta2 is not
      itself the ion pore, it is essential for functional calcium channel expression
      and directly contributes to calcium transport by enabling channel trafficking
      to the membrane and modulating channel gating properties [PMID:1309651].
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "the beta 2 subunit appears to serve an obligatory function"

- term:
    id: GO:0005891
    label: voltage-gated calcium channel complex
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >
      CaVbeta2 is a core component of the voltage-gated calcium channel complex,
      binding the alpha1 subunit AID with nanomolar affinity (6-20 nM) via its
      GK domain. Structural studies confirm the SH3-GK architecture positions
      CaVbeta between the AID and VSD-II of the alpha1 subunit.
    action: ACCEPT
    reason: >
      This is a well-established core function. CaVbeta2 is part of the calcium
      channel complex in 1:1:1:1 stoichiometry with alpha1, alpha2delta, and gamma
      subunits [UniProt CC, PMID:1309651]. ComplexPortal entries (CPX-3195 and others)
      document CACNB2 in multiple CaV1.x channel complexes.
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "coexpressed with the beta (beta 2) and the alpha 2 (alpha 2b) subunits"

- term:
    id: GO:0007268
    label: chemical synaptic transmission
  evidence_type: IBA
  original_reference_id: GO_REF:0000033
  review:
    summary: >
      Calcium channels play essential roles in neurotransmitter release at presynaptic
      terminals. CaVbeta2 is expressed in neurons and contributes to calcium channel
      function that underlies synaptic transmission.
    action: KEEP_AS_NON_CORE
    reason: >
      While L-type calcium channels contribute to synaptic transmission, this is more
      of a downstream physiological consequence rather than a direct molecular function
      of CaVbeta2. The primary role of CaVbeta2 is channel assembly and modulation;
      synaptic transmission is a higher-level process. This annotation is acceptable
      but represents a non-core function.
    supported_by:
      - reference_id: PMID:8494331
        supporting_text: "The predicted amino acid sequence of this clone shows a high degree of homology to the beta subunit of calcium channel complexes"

# IEA annotations from automated pipelines
- term:
    id: GO:0098793
    label: presynapse
  evidence_type: IEA
  original_reference_id: GO_REF:0000108
  review:
    summary: >
      Automated inference based on inter-ontology links. CaVbeta2 would be present
      at presynaptic terminals as part of calcium channel complexes that regulate
      neurotransmitter release.
    action: KEEP_AS_NON_CORE
    reason: >
      Presynaptic localization is consistent with calcium channel function in neurons,
      but this is based on logical inference rather than direct experimental evidence
      for CACNB2 specifically. The broader cellular component annotation
      (voltage-gated calcium channel complex) is more directly supported.
    supported_by:
      - reference_id: file:human/CACNB2/CACNB2-uniprot.txt
        supporting_text: "Expressed in all tissues"

- term:
    id: GO:0099509
    label: regulation of presynaptic cytosolic calcium ion concentration
  evidence_type: IEA
  original_reference_id: GO_REF:0000108
  review:
    summary: >
      Automated inference suggesting CaVbeta2 regulates presynaptic calcium levels
      through its role in calcium channel function.
    action: KEEP_AS_NON_CORE
    reason: >
      This is a reasonable inference but represents a tissue-specific downstream
      effect rather than a core function. The annotation to GO:0051928 (positive
      regulation of calcium ion transport) from PMID:1309651 is more directly
      supported experimentally.
    supported_by:
      - reference_id: GO_REF:0000108
        supporting_text: "logical inference based on inter-ontology links"

- term:
    id: GO:0005245
    label: voltage-gated calcium channel activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000002
  review:
    summary: >
      InterPro-based inference. CaVbeta2 does not itself have ion channel activity
      but is essential for functional channel activity when coexpressed with alpha1.
    action: MODIFY
    reason: >
      CaVbeta2 is an auxiliary subunit, not the pore-forming subunit. It does not
      have intrinsic channel activity. The annotation should reflect its role as a
      regulator/auxiliary rather than having the activity itself. However, there is
      an IDA annotation to the same term from PMID:1309651 which is more nuanced.
    proposed_replacement_terms:
      - id: GO:0005891
        label: voltage-gated calcium channel complex

- term:
    id: GO:0005262
    label: calcium channel activity
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >
      UniProt keyword-based inference. Similar issue as GO:0005245 - CaVbeta2 enables
      but does not itself possess calcium channel activity.
    action: MODIFY
    reason: >
      This annotation conflates the auxiliary subunit with the pore. CaVbeta2 is
      essential for channel function but the channel activity resides in the alpha1
      subunit. A more appropriate annotation would be to the channel complex or
      a regulatory function.
    proposed_replacement_terms:
      - id: GO:0005891
        label: voltage-gated calcium channel complex

- term:
    id: GO:0005891
    label: voltage-gated calcium channel complex
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: >
      Combined automated annotation confirming CaVbeta2 is part of the voltage-gated
      calcium channel complex.
    action: ACCEPT
    reason: >
      This correctly annotates CaVbeta2 as a component of the channel complex,
      which is well-supported by multiple lines of evidence including structural
      data and biochemical studies [PMID:1309651, UniProt].
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "coexpression with the alpha 2b subunit"

- term:
    id: GO:0006811
    label: monoatomic ion transport
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >
      General ion transport term from UniProt keyword mapping.
    action: ACCEPT
    reason: >
      This is a parent term of calcium ion transport (GO:0006816) and is acceptable
      as a broader annotation. It correctly reflects CaVbeta2's role in enabling
      calcium channel function.
    supported_by:
      - reference_id: file:human/CACNB2/CACNB2-uniprot.txt
        supporting_text: "Calcium transport keyword"

- term:
    id: GO:0006816
    label: calcium ion transport
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >
      UniProt keyword-based inference for calcium ion transport, consistent with
      the IBA annotation to the same term.
    action: ACCEPT
    reason: >
      Consistent with the IBA annotation and well-supported by the role of CaVbeta2
      in enabling functional calcium channel expression [PMID:1309651].
    supported_by:
      - reference_id: file:human/CACNB2/CACNB2-uniprot.txt
        supporting_text: "Calcium channel; Calcium transport keywords"

- term:
    id: GO:0034220
    label: monoatomic ion transmembrane transport
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >
      UniProt keyword-based inference for ion transmembrane transport.
    action: ACCEPT
    reason: >
      Appropriate parent term reflecting CaVbeta2's role in enabling calcium flux
      across the plasma membrane through the channel complex.
    supported_by:
      - reference_id: file:human/CACNB2/CACNB2-uniprot.txt
        supporting_text: "Ion transport keyword"

- term:
    id: GO:0034702
    label: monoatomic ion channel complex
  evidence_type: IEA
  original_reference_id: GO_REF:0000043
  review:
    summary: >
      UniProt keyword-based inference for ion channel complex membership.
    action: ACCEPT
    reason: >
      Correct parent term of GO:0005891 (voltage-gated calcium channel complex).
      CaVbeta2 is indeed part of an ion channel complex.
    supported_by:
      - reference_id: file:human/CACNB2/CACNB2-uniprot.txt
        supporting_text: "Ion channel keyword"

- term:
    id: GO:0042383
    label: sarcolemma
  evidence_type: IEA
  original_reference_id: GO_REF:0000044
  review:
    summary: >
      UniProt subcellular location-based inference for sarcolemma localization.
      UniProt explicitly states CaVbeta2 localizes to sarcolemma in cardiac muscle.
    action: ACCEPT
    reason: >
      This is directly supported by UniProt subcellular location annotation stating
      "Cell membrane, sarcolemma; Peripheral membrane protein; Cytoplasmic side."
      CaVbeta2 associates with L-type channels in cardiac T-tubule/sarcolemma.
    supported_by:
      - reference_id: file:human/CACNB2/CACNB2-uniprot.txt
        supporting_text: "Cell membrane, sarcolemma; Peripheral membrane protein; Cytoplasmic side"

- term:
    id: GO:0070588
    label: calcium ion transmembrane transport
  evidence_type: IEA
  original_reference_id: GO_REF:0000120
  review:
    summary: >
      Combined automated inference for calcium ion transmembrane transport.
    action: ACCEPT
    reason: >
      Consistent with CaVbeta2's essential role in enabling functional calcium
      channel activity that mediates transmembrane calcium flux.
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "directs the recombinant expression of a dihydropyridine-sensitive L-type Ca2+ channel"

# IPI annotations from protein-protein interaction studies
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:32296183
  review:
    summary: >
      High-throughput protein interactome study (HuRI) identified binary protein
      interactions involving CACNB2.
    action: MARK_AS_OVER_ANNOTATED
    reason: >
      While technically correct, "protein binding" is uninformative. CaVbeta2 binds
      specific proteins including the alpha1 subunit AID, RRAD, CAMK2A, and others.
      More specific binding annotations would be more informative.
    supported_by:
      - reference_id: PMID:32296183
        supporting_text: "With approximately 53,000 protein-protein interactions, HuRI has approximately four times as many such interactions as there are high-quality curated interactions from small-scale studies"

- term:
    id: GO:0051015
    label: actin filament binding
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: >
      Ensembl Compara ortholog transfer suggesting actin filament binding.
      PMID:25533460 demonstrated direct CaVbeta-actin interaction.
    action: ACCEPT
    reason: >
      PMID:25533460 provides experimental evidence for direct CaVbeta-actin interaction
      using co-sedimentation and FRET experiments. The study showed CaVbeta2 distributes
      along actin filaments in cardiomyocytes.
    supported_by:
      - reference_id: PMID:25533460
        supporting_text: "we uncover a direct interaction between CaVbeta and actin filaments"

- term:
    id: GO:0098684
    label: photoreceptor ribbon synapse
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: >
      Ensembl Compara ortholog transfer suggesting localization to photoreceptor
      ribbon synapse. The beta2e isoform is known to predominate in retina.
    action: KEEP_AS_NON_CORE
    reason: >
      The beta2e isoform is specifically expressed in retina, making this a plausible
      but tissue-specific localization. The deep research file notes "beta2e predominates
      in retina." However, this is based on ortholog transfer rather than direct
      experimental evidence in human.
    supported_by:
      - reference_id: file:human/CACNB2/CACNB2-deep-research-falcon.md
        supporting_text: "beta2e predominates in retina"

- term:
    id: GO:0099626
    label: voltage-gated calcium channel activity involved in regulation of presynaptic cytosolic calcium levels
  evidence_type: IEA
  original_reference_id: GO_REF:0000107
  review:
    summary: >
      Ensembl Compara ortholog transfer for presynaptic calcium channel activity.
    action: MODIFY
    reason: >
      CaVbeta2 is not the pore and does not have intrinsic channel activity. This
      annotation conflates the auxiliary subunit with the functional activity.
      The annotation should be to the complex or a regulatory function.
    proposed_replacement_terms:
      - id: GO:0005891
        label: voltage-gated calcium channel complex

# NAS annotations
- term:
    id: GO:0070588
    label: calcium ion transmembrane transport
  evidence_type: NAS
  original_reference_id: PMID:22982493
  review:
    summary: >
      Non-traceable author statement from a review about CaV1.1 channels noting
      the general role of beta subunits in calcium channel function.
    action: ACCEPT
    reason: >
      While NAS is a weaker evidence code, the annotation is consistent with
      the established role of CaVbeta2. PMID:22982493 is a review discussing
      calcium channel function.
    supported_by:
      - reference_id: PMID:22982493
        supporting_text: "Ca(V)1.1 is the prototype for the other nine known Ca(V) channel isoforms"

- term:
    id: GO:0030315
    label: T-tubule
  evidence_type: NAS
  original_reference_id: PMID:27273705
  review:
    summary: >
      Non-traceable author statement from Dolphin review on voltage-gated calcium
      channels and their auxiliary subunits, indicating T-tubule localization.
    action: ACCEPT
    reason: >
      T-tubule localization is consistent with the role of L-type calcium channels
      in excitation-contraction coupling in cardiac and skeletal muscle. The review
      discusses calcium channel physiology and pathophysiology.
    supported_by:
      - reference_id: PMID:27273705
        supporting_text: "Voltage-gated calcium channels and their auxiliary subunits"

- term:
    id: GO:0045933
    label: positive regulation of muscle contraction
  evidence_type: NAS
  original_reference_id: PMID:22982493
  review:
    summary: >
      CaVbeta2 contributes to calcium influx that triggers muscle contraction.
    action: KEEP_AS_NON_CORE
    reason: >
      This is a downstream physiological effect. CaVbeta2 enables calcium channel
      function, and calcium influx is required for muscle contraction, but this
      is an indirect effect rather than a direct molecular function.
    supported_by:
      - reference_id: PMID:22982493
        supporting_text: "Ca(V)1.1 is the prototype for the other nine known Ca(V) channel isoforms"

- term:
    id: GO:0045933
    label: positive regulation of muscle contraction
  evidence_type: NAS
  original_reference_id: PMID:34072954
  review:
    summary: >
      Review on CaV1.2 trafficking mechanisms discussing the role of beta subunits
      in cardiac calcium channel function.
    action: KEEP_AS_NON_CORE
    reason: >
      Consistent with the other NAS annotation to this term. CaVbeta2 contributes
      to cardiac calcium channel function which underlies muscle contraction, but
      this is an indirect downstream effect.
    supported_by:
      - reference_id: PMID:34072954
        supporting_text: "The number and activity of functional CaV1.2 channels at the t-tubule dyads dictates the amplitude of the Ca2+ influx"

- term:
    id: GO:0070588
    label: calcium ion transmembrane transport
  evidence_type: NAS
  original_reference_id: PMID:27273705
  review:
    summary: >
      Non-traceable author statement from Dolphin review on voltage-gated calcium channels.
    action: ACCEPT
    reason: >
      Consistent with other annotations and the established role of CaVbeta2 in
      enabling functional calcium channel activity.
    supported_by:
      - reference_id: PMID:27273705
        supporting_text: "For the CaV 1 and CaV 2 channels, their ability to reach their required destinations in the cell membrane"

# More IPI annotations
- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:28130356
  review:
    summary: >
      Study on CAMK2A mutations and ASD-related behaviors identified interaction
      between CaMKIIalpha and CACNB2. The E183V mutation reduced CaMKIIalpha binding
      to calcium channel subunits.
    action: MARK_AS_OVER_ANNOTATED
    reason: >
      The study identifies specific interaction with CAMK2A but the annotation is
      to generic "protein binding." UniProt confirms CACNB2 interacts with CAMK2A.
      A more specific annotation would be preferable.
    supported_by:
      - reference_id: PMID:28130356
        supporting_text: "The E183V mutation also reduces CaMKIIalpha binding to established ASD-linked proteins, such as Shank3 and subunits of l-type calcium channels"

# IDA annotations - experimental evidence
- term:
    id: GO:0005891
    label: voltage-gated calcium channel complex
  evidence_type: IDA
  original_reference_id: PMID:17224476
  review:
    summary: >
      Antzelevitch et al. studied loss-of-function mutations in cardiac calcium
      channels including CACNB2 (S481L mutation). CHO-K1 cells were cotransfected
      with CACNB2b and other channel subunits for electrophysiology studies.
    action: ACCEPT
    reason: >
      The study directly demonstrates CaVbeta2b is part of the cardiac L-type
      calcium channel complex through heterologous expression and electrophysiology.
      Mutations in CACNB2 affect channel function.
    supported_by:
      - reference_id: PMID:17224476
        supporting_text: "CHO-K1 cells were cotransfected with cDNAs encoding wild-type or mutant CACNB2b"

- term:
    id: GO:0051015
    label: actin filament binding
  evidence_type: ISS
  original_reference_id: PMID:25533460
  review:
    summary: >
      Study demonstrated direct CaVbeta-actin interaction using co-sedimentation
      assays and FRET experiments in HL-1 cardiomyocytes. Single-molecule localization
      showed CaVbeta2 distributing along actin filaments.
    action: ACCEPT
    reason: >
      This is strong experimental evidence for actin filament binding. The study
      used multiple methods to demonstrate the interaction and showed functional
      relevance for channel trafficking.
    supported_by:
      - reference_id: PMID:25533460
        supporting_text: "using co-sedimentation assays and FRET experiments, we uncover a direct interaction between CaVbeta and actin filaments"

- term:
    id: GO:0072659
    label: protein localization to plasma membrane
  evidence_type: ISS
  original_reference_id: PMID:25533460
  review:
    summary: >
      The study demonstrated that CaVbeta promotes anterograde trafficking of L-type
      channels by anchoring them to actin filaments en route to the plasma membrane.
    action: ACCEPT
    reason: >
      The study provides a model where CaVbeta promotes channel trafficking to the
      membrane via actin interaction. This is consistent with the known role of
      CaVbeta2 in channel trafficking.
    supported_by:
      - reference_id: PMID:25533460
        supporting_text: "CaVbeta promotes anterograde trafficking of the L-type channels by anchoring them to actin filaments in their itinerary to the plasma membrane"

- term:
    id: GO:0086007
    label: voltage-gated calcium channel activity involved in cardiac muscle cell action potential
  evidence_type: IMP
  original_reference_id: PMID:17224476
  review:
    summary: >
      Study identified CACNB2 mutations in Brugada syndrome patients with cardiac
      arrhythmias. The S481L mutation caused loss-of-function affecting cardiac
      action potentials.
    action: MODIFY
    reason: >
      CaVbeta2 does not have intrinsic channel activity - it is an auxiliary subunit.
      The annotation should reflect its role in modulating channel function. The
      correct annotation would be to a regulatory function or the channel complex.
    proposed_replacement_terms:
      - id: GO:0005891
        label: voltage-gated calcium channel complex
    supported_by:
      - reference_id: PMID:17224476
        supporting_text: "loss-of-function missense mutations in CACNA1C (A39V and G490R) and CACNB2 (S481L) encoding the alpha1- and beta2b-subunits"

- term:
    id: GO:0086045
    label: membrane depolarization during AV node cell action potential
  evidence_type: IMP
  original_reference_id: PMID:17224476
  review:
    summary: >
      Study on Brugada syndrome with CACNB2 mutations affecting cardiac conduction.
    action: KEEP_AS_NON_CORE
    reason: >
      This is a specific cardiac electrophysiology phenotype associated with
      CACNB2 mutations. While the annotation captures the disease phenotype,
      membrane depolarization is a downstream effect of calcium channel function
      rather than a direct function of CaVbeta2.
    supported_by:
      - reference_id: PMID:17224476
        supporting_text: "Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST-segment elevation"

- term:
    id: GO:0086056
    label: voltage-gated calcium channel activity involved in AV node cell action potential
  evidence_type: IMP
  original_reference_id: PMID:17224476
  review:
    summary: >
      Study linking CACNB2 mutations to cardiac arrhythmias affecting AV node function.
    action: MODIFY
    reason: >
      Same issue as GO:0086007 - CaVbeta2 is not the channel pore and does not have
      intrinsic channel activity. It modulates channel function as an auxiliary subunit.
    proposed_replacement_terms:
      - id: GO:0005891
        label: voltage-gated calcium channel complex
    supported_by:
      - reference_id: PMID:17224476
        supporting_text: "ST-segment elevation, short QT intervals, and sudden cardiac death"

- term:
    id: GO:0086091
    label: regulation of heart rate by cardiac conduction
  evidence_type: IMP
  original_reference_id: PMID:17224476
  review:
    summary: >
      CACNB2 mutations cause cardiac arrhythmias affecting heart rate and conduction.
    action: KEEP_AS_NON_CORE
    reason: >
      This is a downstream physiological effect of calcium channel dysfunction.
      CaVbeta2 contributes to cardiac calcium channel function which is essential
      for proper conduction and heart rate, but this is an indirect effect.
    supported_by:
      - reference_id: PMID:17224476
        supporting_text: "Brugada syndrome phenotype is combined with shorter-than-normal QT intervals"

- term:
    id: GO:0098912
    label: membrane depolarization during atrial cardiac muscle cell action potential
  evidence_type: IMP
  original_reference_id: PMID:17224476
  review:
    summary: >
      Brugada syndrome study showing effects of CACNB2 mutations on atrial action potentials.
    action: KEEP_AS_NON_CORE
    reason: >
      Similar to other cardiac electrophysiology annotations - this is a downstream
      consequence of calcium channel function rather than a direct molecular function.
    supported_by:
      - reference_id: PMID:17224476
        supporting_text: "cardiac calcium channel underlie a new clinical entity"

- term:
    id: GO:1904879
    label: positive regulation of calcium ion transmembrane transport via high voltage-gated calcium channel
  evidence_type: ISS
  original_reference_id: PMID:25533460
  review:
    summary: >
      Study demonstrated that CaVbeta2 overexpression increases L-type current
      by increasing channels in the plasma membrane.
    action: ACCEPT
    reason: >
      This accurately reflects the role of CaVbeta2 in promoting calcium channel
      trafficking and increasing calcium current. The study showed CaVbeta2-N3
      overexpression induced an increase in L-type current.
    supported_by:
      - reference_id: PMID:25533460
        supporting_text: "Overexpression of CaVbeta2-N3 in HL-1 cells induces an increase in L-type current without altering voltage-dependent activation, thus reflecting an increased number of channels in the plasma membrane"

- term:
    id: GO:1990454
    label: L-type voltage-gated calcium channel complex
  evidence_type: IDA
  original_reference_id: PMID:1309651
  review:
    summary: >
      Williams et al. demonstrated functional expression of L-type calcium channels
      requiring coexpression of beta2 with alpha1D and alpha2b subunits in Xenopus oocytes.
    action: ACCEPT
    reason: >
      This is a core annotation strongly supported by the paper. The study showed
      beta2 is required for functional L-type channel expression and is part of
      the channel complex.
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "directs the recombinant expression of a dihydropyridine-sensitive L-type Ca2+ channel when coexpressed with the beta (beta 2) and the alpha 2 (alpha 2b) subunits"

- term:
    id: GO:0008331
    label: high voltage-gated calcium channel activity
  evidence_type: IDA
  original_reference_id: PMID:1309651
  review:
    summary: >
      The study expressed a human neuronal high-voltage-activated calcium channel
      requiring beta2 for function.
    action: MODIFY
    reason: >
      CaVbeta2 enables high-voltage-gated calcium channel function but does not
      itself have channel activity. The alpha1 subunit forms the pore. The annotation
      should reflect the auxiliary/regulatory role.
    proposed_replacement_terms:
      - id: GO:1990454
        label: L-type voltage-gated calcium channel complex
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "the beta 2 subunit appears to serve an obligatory function"

# TAS annotations from Reactome
- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-5577213
  review:
    summary: >
      Reactome pathway entry for LTCC multimer transporting calcium from extracellular
      region to cytosol places CaVbeta2 at the plasma membrane.
    action: ACCEPT
    reason: >
      CaVbeta2 localizes to the plasma membrane as part of the L-type calcium channel
      complex. UniProt also states sarcolemma/plasma membrane localization.
    supported_by:
      - reference_id: file:human/CACNB2/CACNB2-uniprot.txt
        supporting_text: "Cell membrane, sarcolemma; Peripheral membrane protein; Cytoplasmic side"

- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: TAS
  original_reference_id: Reactome:R-HSA-9614031
  review:
    summary: >
      Reactome pathway for Class IV antihypertensives binding LTCC multimer.
    action: ACCEPT
    reason: >
      Same as above - plasma membrane localization is well-established for CaVbeta2.
    supported_by:
      - reference_id: Reactome:R-HSA-9614031
        supporting_text: "Class IV antihypertensives bind LTCC multimer"

- term:
    id: GO:0051928
    label: positive regulation of calcium ion transport
  evidence_type: IDA
  original_reference_id: PMID:1309651
  review:
    summary: >
      Williams et al. showed that beta2 coexpression is required for functional
      calcium channel expression and increases peak calcium current.
    action: ACCEPT
    reason: >
      This is a core function. The study demonstrated that "the beta 2 subunit
      appears to serve an obligatory function" and that channels with beta2 have
      enhanced calcium current compared to alpha1 alone (which showed no current).
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "Expression of the alpha 1D subunit alone, or coexpression with the alpha 2b subunit, did not elicit functional Ca2+ channel activity. Thus, the beta 2 subunit appears to serve an obligatory function"

- term:
    id: GO:0005245
    label: voltage-gated calcium channel activity
  evidence_type: IDA
  original_reference_id: PMID:1309651
  review:
    summary: >
      Study demonstrated voltage-gated calcium channel activity requires beta2.
    action: MODIFY
    reason: >
      While the study demonstrates CaVbeta2 is essential for channel function,
      CaVbeta2 itself does not have ion channel activity - the alpha1 subunit
      forms the pore. The annotation should reflect the regulatory role.
    proposed_replacement_terms:
      - id: GO:0005891
        label: voltage-gated calcium channel complex
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "the beta 2 subunit appears to serve an obligatory function"

- term:
    id: GO:0070509
    label: calcium ion import
  evidence_type: IDA
  original_reference_id: PMID:1309651
  review:
    summary: >
      Study demonstrated functional calcium influx through channels containing beta2.
    action: ACCEPT
    reason: >
      CaVbeta2 enables calcium ion import by being essential for functional channel
      expression. The term correctly reflects the biological process.
    supported_by:
      - reference_id: PMID:1309651
        supporting_text: "dihydropyridine-sensitive L-type Ca2+ channel"

- term:
    id: GO:0005515
    label: protein binding
  evidence_type: IPI
  original_reference_id: PMID:17525370
  review:
    summary: >
      Study demonstrated CACNB2 interaction with RRAD (Ras associated with diabetes),
      an RGK GTPase that regulates L-type calcium channel function.
    action: MODIFY
    reason: >
      The study identifies a specific interaction with RRAD that is functionally
      important for channel trafficking. "Protein binding" is too generic; a more
      specific annotation would be preferable.
    proposed_replacement_terms:
      - id: GO:0005515
        label: protein binding
    additional_reference_ids:
      - PMID:36424916
    supported_by:
      - reference_id: PMID:17525370
        supporting_text: "upregulation of L-type Ca2+ channel expression in the plasma membrane"
      - reference_id: file:human/CACNB2/CACNB2-uniprot.txt
        supporting_text: "Interacts with RRAD; interaction may be involved in beta-adrenergic regulation of heart rate and contractile force"

- term:
    id: GO:0007528
    label: neuromuscular junction development
  evidence_type: TAS
  original_reference_id: PMID:8494331
  review:
    summary: >
      Rosenfeld et al. identified CACNB2 (MysB) as a Lambert-Eaton myasthenic syndrome
      antigen with homology to calcium channel beta subunits. The syndrome affects
      the neuromuscular junction.
    action: KEEP_AS_NON_CORE
    reason: >
      While CaVbeta2 is implicated in Lambert-Eaton syndrome affecting the NMJ,
      this annotation represents disease involvement rather than a normal developmental
      function. The study cloned the antigen but did not directly demonstrate a role
      in NMJ development.
    supported_by:
      - reference_id: PMID:8494331
        supporting_text: "Lambert-Eaton myasthenic syndrome is a paraneoplastic neuromuscular disorder in which an immune response directed against a small-cell lung tumor crossreacts with antigens in the neuromuscular junction"

- term:
    id: GO:0005262
    label: calcium channel activity
  evidence_type: NAS
  original_reference_id: PMID:9594024
  review:
    summary: >
      Allen and Mikala studied temperature effects on L-type cardiac calcium channels
      expressed in Xenopus oocytes using different beta subunit isoforms.
    action: MODIFY
    reason: >
      CaVbeta2 is an auxiliary subunit that modulates channel properties but does
      not itself have channel activity. The alpha1 subunit forms the pore.
    proposed_replacement_terms:
      - id: GO:0005891
        label: voltage-gated calcium channel complex
    supported_by:
      - reference_id: PMID:9594024
        supporting_text: "Using instead a different CaCh beta subunit isoform, beta2c"

- term:
    id: GO:0005886
    label: plasma membrane
  evidence_type: NAS
  original_reference_id: PMID:9594024
  review:
    summary: >
      Study expressed calcium channels at the plasma membrane of Xenopus oocytes
      using various subunit combinations.
    action: ACCEPT
    reason: >
      Plasma membrane localization is well-established and consistent with the
      function of CaVbeta2 as part of the calcium channel complex at the cell surface.
    supported_by:
      - reference_id: PMID:9594024
        supporting_text: "cloned human cardiac CaChs expressed in Xenopus oocytes"

references:
- id: GO_REF:0000002
  title: Gene Ontology annotation through association of InterPro records with GO terms
  findings: []
- id: GO_REF:0000033
  title: Annotation inferences using phylogenetic trees
  findings:
    - statement: IBA annotations for calcium ion transport and channel complex are appropriate
- id: GO_REF:0000043
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot keyword mapping
  findings: []
- id: GO_REF:0000044
  title: Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping
  findings:
    - statement: Sarcolemma localization correctly inferred
- id: GO_REF:0000107
  title: Automatic transfer of experimentally verified manual GO annotation data to orthologs using Ensembl Compara
  findings: []
- id: GO_REF:0000108
  title: Automatic assignment of GO terms using logical inference, based on inter-ontology links
  findings: []
- id: GO_REF:0000120
  title: Combined Automated Annotation using Multiple IEA Methods
  findings: []
- id: PMID:1309651
  title: Structure and functional expression of alpha 1, alpha 2, and beta subunits of a novel human neuronal calcium channel subtype.
  findings:
    - statement: Beta2 subunit is obligatory for functional calcium channel expression
    - statement: Coexpression with alpha1D and alpha2b produces dihydropyridine-sensitive L-type channel
    - statement: Beta2 potentiates channel expression and increases peak calcium current
- id: PMID:17224476
  title: Loss-of-function mutations in the cardiac calcium channel underlie a new clinical entity characterized by ST-segment elevation, short QT intervals, and sudden cardiac death.
  findings:
    - statement: CACNB2 S481L mutation causes Brugada syndrome with shortened QT
    - statement: Beta2b is part of cardiac L-type calcium channel complex
    - statement: Mutations affect channel trafficking and function
- id: PMID:17525370
  title: Dominant negative suppression of Rad leads to QT prolongation and causes ventricular arrhythmias via modulation of L-type Ca2+ channels in the heart.
  findings:
    - statement: CACNB2 interacts with RRAD (Ras associated with diabetes)
    - statement: Rad regulates L-type calcium channel expression via CaVbeta
    - statement: Interaction affects channel trafficking to plasma membrane
- id: PMID:22982493
  title: 'Ca(V)1.1: The atypical prototypical voltage-gated Ca²⁺ channel.'
  findings:
    - statement: Review discussing role of beta subunits in calcium channel function
- id: PMID:25533460
  title: 'Direct interaction of CaVβ with actin up-regulates L-type calcium currents in HL-1 cardiomyocytes.'
  findings:
    - statement: CaVbeta2 directly binds actin filaments
    - statement: Interaction promotes channel trafficking to plasma membrane
    - statement: Overexpression increases L-type current by increasing membrane channels
- id: PMID:27273705
  title: 'Voltage-gated calcium channels and their auxiliary subunits: physiology and pathophysiology and pharmacology.'
  findings:
    - statement: Comprehensive review of CaV channel auxiliary subunits
    - statement: Beta subunits essential for channel trafficking and gating
- id: PMID:28130356
  title: A Novel Human CAMK2A Mutation Disrupts Dendritic Morphology and Synaptic Transmission, and Causes ASD-Related Behaviors.
  findings:
    - statement: CaMKIIalpha interacts with CACNB2
    - statement: E183V mutation reduces binding to calcium channel subunits
- id: PMID:32296183
  title: A reference map of the human binary protein interactome.
  findings:
    - statement: High-throughput identification of CACNB2 protein interactions
- id: PMID:34072954
  title: 'Mechanisms and Regulation of Cardiac Ca(V)1.2 Trafficking.'
  findings:
    - statement: Review of beta subunit role in CaV1.2 trafficking
    - statement: Beta subunits essential for proper channel expression
- id: PMID:8494331
  title: Cloning and characterization of a Lambert-Eaton myasthenic syndrome antigen.
  findings:
    - statement: CACNB2 (MysB) identified as autoantigen in Lambert-Eaton syndrome
    - statement: Alternative splicing produces multiple isoforms
- id: PMID:9594024
  title: Effects of temperature on human L-type cardiac Ca2+ channels expressed in Xenopus oocytes.
  findings:
    - statement: Beta2c isoform used in channel expression studies
- id: Reactome:R-HSA-5577213
  title: LTCC multimer transports Ca2+ from extracellular region to cytosol
  findings:
    - statement: CaVbeta2 is component of L-type calcium channel complex
- id: Reactome:R-HSA-9614031
  title: Class IV antihypertensives bind LTCC multimer
  findings:
    - statement: CaVbeta2 part of pharmacologically relevant channel complex

core_functions:
- molecular_function:
    id: GO:0005246
    label: calcium channel regulator activity
  description: >
    CaVbeta2 is an essential auxiliary subunit of voltage-gated calcium channel complexes.
    It binds the alpha1 subunit AID with nanomolar affinity (6-20 nM) via its GK domain.
    PMID:1309651 demonstrated that beta2 is obligatory for functional channel expression
    and promotes calcium ion transport by enabling channel trafficking to the plasma
    membrane and modulating channel gating.
  in_complex:
    id: GO:1990454
    label: L-type voltage-gated calcium channel complex
  supported_by:
    - reference_id: PMID:1309651
      supporting_text: "the beta 2 subunit appears to serve an obligatory function"
    - reference_id: file:human/CACNB2/CACNB2-deep-research-falcon.md
      supporting_text: "CaVbeta2 is a non-enzymatic, cytosolic auxiliary subunit that binds the alpha1-subunit AID to promote proper channel trafficking to the plasma membrane and to tune voltage-dependent activation/inactivation"
- molecular_function:
    id: GO:0051015
    label: actin filament binding
  description: >
    PMID:25533460 demonstrated direct CaVbeta-actin interaction using co-sedimentation
    and FRET experiments. This interaction promotes channel trafficking to the plasma
    membrane, representing a novel mechanism for beta subunit function.

proposed_new_terms: []

suggested_questions:
- question: >
    What is the relative contribution of different CaVbeta2 isoforms (beta2a-e) to
    channel function in different tissues? The isoforms differ in N-terminal sequences
    affecting membrane association (palmitoylation for beta2a, nuclear translocation
    for beta2e). Understanding tissue-specific isoform functions could clarify disease
    mechanisms.
- question: >
    How does the CaVbeta2-RRAD interaction modulate beta-adrenergic regulation of
    cardiac calcium channels at the molecular level? Recent work (PMID:36424916)
    showed Rad phosphorylation releases CaVbeta-mediated inhibition. The structural
    basis of this regulation is not fully understood.

suggested_experiments:
- description: >
    Cryo-EM structural determination of full L-type calcium channel complex with
    different CaVbeta2 isoforms to understand isoform-specific contributions.
    While structures exist, comparing different beta2 isoforms could reveal how
    N-terminal differences affect channel architecture and gating.
- description: >
    Live-cell imaging of CaVbeta2e nuclear translocation dynamics and identification
    of nuclear target genes. The beta2e isoform can translocate to the nucleus and
    regulate gene expression (Frontiers in Physiology 2025), but the target genes
    are not well characterized.