BID — BH3 Interacting Domain Death Agonist

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gene1168 wordssynced 2026-04-02

BID — BH3 Interacting Domain Death Agonist

<div class="infobox infobox-gene">
<table>
<tr><th colspan="2" style="background:#f8e8e8; text-align:center; font-size:1.1em;">BH3 Interacting Domain Death Agonist</th></tr>
<tr><td>Gene Symbol</td><td>BID</td></tr>
<tr><td>Full Name</td><td>BH3 Interacting Domain Death Agonist</td></tr>
<tr><td>Chromosomal Location</td><td>22q11.21</td></tr>
<tr><td>NCBI Gene ID</td><td>637</td></tr>
<tr><td>Ensembl ID</td><td>ENSG00000105619</td></tr>
<tr><td>UniProt ID</td><td>P55957</td></tr>
<tr><td>OMIM ID</td><td>603678</td></tr>
<tr><td>Protein Length</td><td>195 amino acids</td></tr>
<tr><td>Protein Family</td><td>BCL2 family, BH3-only proteins</td></tr>
<tr><td>Aliases</td><td>tBID, truncated BID</td></tr>
<tr><td>Associated Diseases</td><td>[Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease), Stroke, [Traumatic Brain Injury](/diseases/traumatic-brain-injury), ALS</td></tr>
</table>
</div>

Pathway Diagram

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BID — BH3 Interacting Domain Death Agonist

Pathway Diagram

Mermaid diagram (expand to render)

Overview

BID (BH3 Interacting Domain Death Agonist) is a pro-apoptotic [BCL2 family](/proteins/bcl2-family) protein that serves as a critical molecular link between the extrinsic (death receptor) and intrinsic (mitochondrial) [apoptosis](/mechanisms/apoptosis-pathways) pathways. As a "BH3-only" protein, BID contains a single [BH3 domain](/proteins/bh3-domain) that enables it to interact with both pro-survival BCL2 proteins ([BCL2](/genes/bcl2), [BCL2L1](/genes/bclxl), [MCL1](/genes/mcl1)) and the executioner proteins [BAX](/genes/bax) and [BAK1](/genes/bak1).

Upon cleavage by [caspase-8](/genes/casp8), the resulting truncated form (tBID) translocates to mitochondria where it directly activates BAX, promoting [cytochrome c release](/mechanisms/mitochondrial-apoptosis) and amplification of the apoptotic cascade. In [neurons](/cell-types/neurons), BID-mediated apoptosis contributes to neurodegenerative processes following stroke, [traumatic brain injury](/diseases/traumatic-brain-injury), and chronic neurodegenerative diseases including [Alzheimer's disease](/diseases/alzheimers-disease) and [Parkinson's disease](/diseases/parkinsons-disease) [@bid_mechanism][@bid_neurons].

Protein Structure and Function

Domain Architecture

BID possesses a distinct structural organization:

N-terminal region: Contains caspase-8 cleavage sites (D75, D81)
Central linker region: Flexible hinge domain
C-terminal BH3 domain: Critical for pro-apoptotic function (~20 amino acids)

The BH3 domain is the functional core of BID, mediating:

Direct interaction with anti-apoptotic BCL2 proteins

Direct activation of BAX and BAK1

Mitochondrial targeting

Activation Mechanism

Full-length BID (flBID) is a relatively inactive cytosolic protein. Activation occurs through proteolytic cleavage [@bid_mechanism][@bid_tbid_mitochondria]:

BID Activation Cascade

Death Receptor Activation (Fas, TRAIL-R, TNFR1)

│
▼

Caspase-8 Activation

│
▼

BID Cleavage at D75/D81

│
▼

tBID Formation (truncated BID)

│
▼

tBID Mitochondrial Translocation

│
▼

BAX/BAK1 Activation → MOMP → Cytochrome c Release

BH3-Only Protein Function

As a BH3-only protein, BID exhibits dual functionality:

Sensitizer function: Sequestration of pro-survival BCL2 proteins

Binds to [BCL2](/genes/bcl2), [BCL2L1 (BCL-xL)](/genes/bclxl), [MCL1](/genes/mcl1)
Releases BAX/BAK1 from inhibition

Direct activator function: Direct interaction with BAX/BAK1

tBID directly binds and activates BAX [@bid_bax_activation]
Induces conformational change and oligomerization
Forms mitochondrial outer membrane pores

Role in Neurodegeneration

Alzheimer's Disease

BID contributes to AD pathogenesis through multiple mechanisms [@bid_阿尔兹海默]:

Amyloid-beta induced apoptosis: Aβ oligomers activate caspase-8 → BID cleavage → neuronal apoptosis

Tau pathology interaction: BID cleavage correlates with tau neurofibrillary pathology

Synaptic loss: BID activation contributes to synaptic degeneration

Neuroinflammation: Cross-talk with inflammatory pathways amplifies cell death

The balance between pro-apoptotic BID and anti-apoptotic BCL2 determines neuronal fate in AD.

Parkinson's Disease

In PD, BID mediates dopaminergic neuron death through [@bid_parkinson]:

Alpha-synuclein toxicity: α-synuclein aggregates activate caspase-8 → BID cleavage

Mitochondrial dysfunction: Direct involvement in MPTP/MPP+ models

Oxidative stress: ROS-mediated BID activation

Neuroinflammation: Glial activation leads to secondary neuronal injury

Stroke and Ischemia

BID is critically involved in ischemic neuronal death [@bid_stroke][@bid_tbi]:

Rapid activation: Ischemia triggers caspase-8 activation within hours

Mitochondrial pathway amplification: tBID directly amplifies mitochondrial apoptosis

Necrotic-necrotic interface: BID cleavage at penumbra

Therapeutic window: Caspase-8 inhibition provides neuroprotection

Traumatic Brain Injury

Following TBI [@bid_tbi]:

Mechanical injury activates death receptor pathways
Secondary excitotoxicity triggers BID cleavage
Contusion expansion mediated by BID
Potential for pharmacological intervention

Amyotrophic Lateral Sclerosis (ALS)

Motor neuron vulnerability involves BID activation
TDP-43 pathology correlates with BID cleavage
Astrocyte-mediated toxicity involves BID

Molecular Mechanisms

Extrinsic-Intrinsic Bridge

BID serves as the molecular bridge between death receptor signaling and mitochondrial apoptosis [@bid_extrinsic_intrinsic]:

Death Receptor Pathway Mitochondrial Pathway
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
FasL/TRAIL/TNF-α │
│ │
▼ ▼
Fas/TRAIL-R/TNFR1 BAX/BAK1
│ │
▼ ▼
FADD → Caspase-8 tBID → Activation
│ │
▼ ▼
BID cleavage MOMP
│ │
└─────── tBID ───────────┘
│
▼
Cytochrome c release
│
▼
Apoptosome formation
│
▼
Caspase-9 → Caspase-3/7
│
▼
Cell death

Regulation of BID Activity

Positive regulators:

Caspase-8 (primary activator)
Caspase-3 (amplification)
Granzyme B (immune cell-mediated)

Negative regulators:

[BCL2](/genes/bcl2) family proteins (sequestration)
IAP proteins (inhibition)
Phosphorylation (serine 64)

Expression Pattern

Brain Expression

BID is expressed throughout the central nervous system:

| Region | Expression Level | Notes |
|--------|-----------------|-------|
| [Cortex](/brain-regions/cortex) | High | Pyramidal neurons |
| [Hippocampus](/brain-regions/hippocampus) | High | CA1, CA3 neurons |
| [Substantia nigra](/brain-regions/substantia-nigra) | Moderate | Dopaminergic neurons |
| [Cerebellum](/brain-regions/cerebellum) | Moderate | Purkinje cells |
| Spinal cord | Moderate | Motor neurons |

Cellular Distribution

Neurons: High expression, particularly vulnerable populations
[Astrocytes](/cell-types/astrocytes): Moderate expression
[Microglia](/cell-types/microglia): Activation-dependent expression
Oligodendrocytes: Lower expression

Therapeutic Implications

Targeting BID for Neuroprotection

Caspase-8 inhibitors [@bid_neuroprotection]

Prevent BID cleavage upstream
Effective in stroke and TBI models
Broad neuroprotective potential

BH3 mimetics

Compete for BCL2 binding
Release pro-survival constraints
Use with caution (dual effect)

Gene therapy approaches

RNAi to reduce BID expression
CRISPR to modify cleavage sites
Viral vector delivery to CNS

Preclinical and Clinical Implications

Stroke: Caspase-8 inhibitors in Phase II trials
TBI: Neuroprotective strategies targeting BID
AD: Modulating BID as disease-modifying approach
PD: Targeting dopaminergic neuron vulnerability

Interactions and Pathways

Protein Interactions

| Partner | Interaction Type | Function |
|---------|-----------------|----------|
| [Caspase-8](/genes/casp8) | Substrate | Proteolytic activation |
| [BAX](/genes/bax) | Direct activator | Pore formation |
| [BAK1](/genes/bak1) | Direct activator | Pore formation |
| [BCL2](/genes/bcl2) | Binding | Sequestration |
| [BCL2L1](/genes/bclxl) | Binding | Sequestration |
| [MCL1](/genes/mcl1) | Binding | Sequestration |
| [FADD](/genes/fadd) | Co-factor | Death receptor signaling |
| [TNFRSF10B](/genes/trail-r2) | Pathway | Death receptor activation |

Signaling Cross-talk

NF-κB pathway: Regulation of BID transcription
p53 pathway: Transcriptional activation
JNK pathway: Phosphorylation and activation
Autophagy: Cross-talk with cell death

Animal Models

Mouse Models

Bid knockout: Viable, resistant to Fas-mediated liver injury
Transgenic overexpression: Pro-apoptotic phenotype
Conditional knockouts: Brain-specific deletion
Knock-in models: Cleavage site mutants

Research Applications

Apoptosis pathway mapping
Stroke model development
Neuroprotective drug screening
Death receptor pathway studies

Biomarkers

BID activation status serves as:

Indicator of apoptosis initiation
Prognostic marker in stroke
Therapeutic response indicator
Disease progression marker in AD/PD

External Links

[NCBI Gene: BID](https://www.ncbi.nlm.nih.gov/gene/637)
[OMIM: BID](https://www.omim.org/entry/603678)
[Ensembl: BID](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000105619)
[UniProt: BID](https://www.uniprot.org/uniprot/P55957)
[GeneCards: BID](https://www.genecards.org/cgi-bin/carddisp.pl?gene=BID)

References

[Molecular mechanism of BID action in apoptosis (2000)](https://pubmed.ncbi.nlm.nih.gov/10611368/)

[BID cleavage contributes to ischemic neuronal death (2002)](https://pubmed.ncbi.nlm.nih.gov/12150891/)

[tBID translocation to mitochondria and cytochrome c release (2001)](https://pubmed.ncbi.nlm.nih.gov/11103755/)

[tBID directly activates BAX for mitochondrial permeabilization (2001)](https://pubmed.ncbi.nlm.nih.gov/10702711/)

[Cross-talk between extrinsic and intrinsic apoptosis via BID (2005)](https://pubmed.ncbi.nlm.nih.gov/15800376/)

[BID in neuronal apoptosis and neurodegenerative disease (2008)](https://pubmed.ncbi.nlm.nih.gov/18497826/)

[Caspase-8 inhibition provides neuroprotection via BID (2006)](https://pubmed.ncbi.nlm.nih.gov/16236735/)

[BID in Alzheimer's disease pathogenesis (2013)](https://pubmed.ncbi.nlm.nih.gov/23564269/)

[BID-mediated apoptosis in Parkinson's disease models (2015)](https://pubmed.ncbi.nlm.nih.gov/26100256/)

[BID cleavage following traumatic brain injury (2010)](https://pubmed.ncbi.nlm.nih.gov/20085807/)

Related Analyses:

[Is disrupted sleep a cause or consequence of neurodegeneration? Analyze the bidirectional relationsh](/analysis/SDA-2026-04-02-gap-20260402-003058) 🔄
[Is disrupted sleep a cause or consequence of neurodegeneration? Analyze the bidirectional relationsh](/analysis/SDA-2026-04-02-gap-20260402-003115) 🔄

Pathway Diagram

The following diagram shows the key molecular relationships involving BID — BH3 Interacting Domain Death Agonist discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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BID — BH3 Interacting Domain Death Agonist

BID — BH3 Interacting Domain Death Agonist

Pathway Diagram

BID — BH3 Interacting Domain Death Agonist

Pathway Diagram

Overview

Protein Structure and Function

Domain Architecture

Activation Mechanism

BH3-Only Protein Function

Role in Neurodegeneration

Alzheimer's Disease

Parkinson's Disease

Stroke and Ischemia

Traumatic Brain Injury

Amyotrophic Lateral Sclerosis (ALS)

Molecular Mechanisms

Extrinsic-Intrinsic Bridge

Regulation of BID Activity

Expression Pattern

Brain Expression

Cellular Distribution

Therapeutic Implications

Targeting BID for Neuroprotection

Preclinical and Clinical Implications

Interactions and Pathways

Protein Interactions

Signaling Cross-talk

Animal Models

Mouse Models

Research Applications

Biomarkers

See Also

External Links

References

Pathway Diagram