BID — BH3 Interacting Domain Death Agonist

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><strong>Gene Symbol</strong></td><td>BID</td></tr>
<tr><td><strong>Full Name</strong></td><td>BH3 Interacting Domain Death Agonist</td></tr>
<tr><td><strong>Chromosomal Location</strong></td><td>22q11.21</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>637</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000105619</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>P55957</td></tr>
<tr><td><strong>OMIM ID</strong></td><td>603678</td></tr>
<tr><td><strong>Protein Length</strong></td><td>195 amino acids</td></tr>
<tr><td><strong>Protein Family</strong></td><td>BCL2 family, BH3-only proteins</td></tr>
<tr><td><strong>Aliases</strong></td><td>tBID, truncated BID</td></tr>
<tr><td><strong>Associated Diseases</strong></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

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><strong>Gene Symbol</strong></td><td>BID</td></tr>
<tr><td><strong>Full Name</strong></td><td>BH3 Interacting Domain Death Agonist</td></tr>
<tr><td><strong>Chromosomal Location</strong></td><td>22q11.21</td></tr>
<tr><td><strong>NCBI Gene ID</strong></td><td>637</td></tr>
<tr><td><strong>Ensembl ID</strong></td><td>ENSG00000105619</td></tr>
<tr><td><strong>UniProt ID</strong></td><td>P55957</td></tr>
<tr><td><strong>OMIM ID</strong></td><td>603678</td></tr>
<tr><td><strong>Protein Length</strong></td><td>195 amino acids</td></tr>
<tr><td><strong>Protein Family</strong></td><td>BCL2 family, BH3-only proteins</td></tr>
<tr><td><strong>Aliases</strong></td><td>tBID, truncated BID</td></tr>
<tr><td><strong>Associated Diseases</strong></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

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)

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

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

• 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]:

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]:

Stroke and Ischemia

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

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)

• [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

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

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

• 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

See Also

• [Apoptosis Pathways](/mechanisms/apoptosis-pathways)
• [Mitochondrial Apoptosis](/mechanisms/mitochondrial-apoptosis)
• [BAX](/genes/bax)
• [BAK1](/genes/bak1)
• [BCL2](/genes/bcl2)
• [Caspase-8](/genes/casp8)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Stroke](/diseases/stroke)
• [Traumatic Brain Injury](/diseases/traumatic-brain-injury)
• [BCL2 Family Proteins](/proteins/bcl2-family)

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

• [Is disrupted sleep a cause or consequence of neurodegeneration? Analyze the bidirectional relationsh](/analysis/SDA-2026-04-02-gap-20260402-003058) &#x1f504;
• [Is disrupted sleep a cause or consequence of neurodegeneration? Analyze the bidirectional relationsh](/analysis/SDA-2026-04-02-gap-20260402-003115) &#x1f504;

Pathway Diagram

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