CFLAR Protein

CFLAR Protein

title: CFLAR Protein

CFLAR (CASP8 and FADD-like Apoptosis Regulator) Protein

Overview

CFLAR (also known as c-FLIP, Cellular FLICE-like Inhibitory Protein) is a master regulator of [extrinsic apoptosis](/mechanisms/extrinsic-apoptosis) and [necroptosis](/mechanisms/necroptosis) that plays a critical role in determining cell survival or death in [neurons](/cell-types/neurons). This protein is particularly important in [neurodegenerative diseases](/diseases/neurodegeneration) where dysregulated [cell death pathways](/mechanisms/cell-death-pathways) contribute to neuronal loss.

<div class="infobox infobox-protein">

| Property | Value |
|----------|-------|
| Protein Name | CFLAR (Cellular FLICE-like Inhibitory Protein) |
| Gene | [CFLAR](/genes/cflar) |
| UniProt ID | O15519 |
| PDB IDs | 2RJ8, 3H11, 4ZGM |
| Molecular Weight | 55-60 kDa (isoform dependent) |
| Subcellular Localization | Cytoplasm, nucleus |
| Protein Family | Death effector domain (DED) family |
| Aliases | c-FLIP, FLICE-inhibitory protein, Usurpin |

</div>

Structure

CFLAR is structurally similar to [caspase-8](/proteins/caspase-8) but lacks catalytic activity. The protein contains:

...

CFLAR Protein

title: CFLAR Protein

CFLAR (CASP8 and FADD-like Apoptosis Regulator) Protein

Overview

CFLAR (also known as c-FLIP, Cellular FLICE-like Inhibitory Protein) is a master regulator of [extrinsic apoptosis](/mechanisms/extrinsic-apoptosis) and [necroptosis](/mechanisms/necroptosis) that plays a critical role in determining cell survival or death in [neurons](/cell-types/neurons). This protein is particularly important in [neurodegenerative diseases](/diseases/neurodegeneration) where dysregulated [cell death pathways](/mechanisms/cell-death-pathways) contribute to neuronal loss.

<div class="infobox infobox-protein">

| Property | Value |
|----------|-------|
| Protein Name | CFLAR (Cellular FLICE-like Inhibitory Protein) |
| Gene | [CFLAR](/genes/cflar) |
| UniProt ID | O15519 |
| PDB IDs | 2RJ8, 3H11, 4ZGM |
| Molecular Weight | 55-60 kDa (isoform dependent) |
| Subcellular Localization | Cytoplasm, nucleus |
| Protein Family | Death effector domain (DED) family |
| Aliases | c-FLIP, FLICE-inhibitory protein, Usurpin |

</div>

Structure

CFLAR is structurally similar to [caspase-8](/proteins/caspase-8) but lacks catalytic activity. The protein contains:

• Two Death Effector Domains (DEDs): The N-terminal DEDs mediate interactions with [FADD](/proteins/fadd-protein) and [caspase-8](/proteins/caspase-8) at the DISC (Death-Inducing Signaling Complex)
• Multiple Splice Variants:
• c-FLIP_L (long isoform): Full-length form with two DEDs
• c-FLIP_S (short isoform): Dominant negative inhibitor
• c-FLIP_R: Rare isoform with unique properties
• Serine/Threonine-rich C-terminal region: Contains phosphorylation sites that regulate protein function

Molecular Function

Inhibition of Extrinsic Apoptosis

CFLAR primarily functions as an endogenous inhibitor of the [extrinsic apoptosis pathway](/mechanisms/extrinsic-apoptosis):

DISC Assembly Regulation: c-FLIP competes with [caspase-8](/proteins/caspase-8) for binding to FADD's DEDs, preventing caspase-8 activation [1]

Heterozyme Complex Formation: c-FLIP_L can form heterodimers with caspase-8, altering its substrate specificity [2]

Blockade of [Apoptosis](/entities/apoptosis) Execution: By preventing caspase-8 activation, c-FLIP blocks downstream effector caspase activation and apoptosis

Modulation of NF-κB Signaling

CFLAR interacts with multiple components of the [NF-κB signaling pathway](/mechanisms/nf-kb-pathway):

• Pro-survival signaling: NF-κB activation promotes expression of anti-apoptotic genes
• Crosstalk with death receptors: FLIP modulates both death receptor signaling and survival pathways
• Kinase interactions: Associates with RIPK1 and affects [necroptosis](/entities/necroptosis) signaling

Regulation of Autophagy

CFLAR interacts with key [autophagy](/entities/autophagy) regulators:

• Direct interaction with Beclin-1: Modulates [autophagy](/mechanisms/autophagy) initiation
• LC3 lipidation: Influences autophagosome formation
• Dual role: Can both promote and inhibit autophagy depending on cellular context

Necroptosis Inhibition

CFLAR blocks the [necroptosis pathway](/mechanisms/necroptosis) by:

• Inhibiting RIPK1 activation: Prevents formation of the necrosome
• Modulating RIPK3 interactions: Affects MLKL recruitment and activation

Role in Neurodegeneration

Alzheimer's Disease

In [Alzheimer's disease](/diseases/alzheimers-disease), CFLAR expression is modulated by [amyloid-beta](/proteins/amyloid-beta) toxicity:

• Amyloid-beta induced upregulation: [Neurons](/entities/neurons) increase c-FLIP expression as a protective response [3]
• Anti-apoptotic function: c-FLIP protects against Aβ-induced caspase-8 activation [4]
• Therapeutic implications: Enhancing c-FLIP expression may provide neuroprotection

Parkinson's Disease

In [Parkinson's disease](/diseases/parkinsons-disease), CFLAR protects [dopaminergic neurons](/cell-types/dopaminergic-neurons):

• Protection against MPTP toxicity: c-FLIP overexpression protects against MPTP-induced parkinsonism [5]
• Modulation of mitochondrial apoptosis: Interacts with Bcl-2 family proteins
• DJ-1 interaction: Partners with DJ-1 (parkinsonism-associated protein) in neuroprotection

Stroke and Ischemia

Following cerebral ischemia:

• Ischemic preconditioning: Upregulation of c-FLIP mediates neuroprotection [6]
• Reperfusion injury: Modulates death receptor signaling during reperfusion
• Therapeutic window: Timing of c-FLIP modulation critical for outcomes

Amyotrophic Lateral Sclerosis (ALS)

In [ALS](/diseases/amyotrophic-lateral-sclerosis):

• Altered expression patterns: c-FLIP levels changed in motor neuron disease
• Excitotoxicity modulation: Links glutamate excitotoxicity to apoptosis
• SOD1 mutations: Interaction with mutant SOD1 toxicity pathways

Multiple Sclerosis

CFLAR contributes to [neuroinflammation](/mechanisms/neuroinflammation) regulation:

• Microglial activation: Modulates microglial cell death decisions
• T-cell survival: Affects immune cell viability in CNS autoimmunity

Therapeutic Relevance

Targeting CFLAR in Neurodegeneration

Modulating CFLAR represents a therapeutic strategy:

• Neuroprotective agents: Compounds that upregulate c-FLIP expression
• Combination therapies: c-FLIP modulation with other anti-apoptotic proteins
• Drug development: Small molecules targeting FLIP-caspase-8 interactions

Cancer Relevance (parallels for neurodegeneration)

While CFLAR is extensively studied in cancer (where high expression confers chemoresistance), the same anti-apoptotic mechanisms that make it a cancer therapeutic target make it relevant for neuroprotection [7].

Interactions

CFLAR interacts with multiple key proteins:

| Partner Protein | Interaction Type | Functional Consequence |
|-----------------|------------------|------------------------|
| [FADD](/proteins/fadd-protein) | Direct binding | DISC assembly modulation |
| [Caspase-8](/proteins/caspase-8) | Heterodimerization | Enzyme activity inhibition |
| [RIPK1](/proteins/ripk1-protein) | Direct binding | Necroptosis regulation |
| [RIPK3](/proteins/ripk3-protein) | Indirect | Necrosome formation |
| [NF-κB](/entities/nf-kb) | Signaling cascade | Survival gene expression |
| [Beclin-1](/proteins/beclin-1) | Direct binding | Autophagy modulation |
| [Bcl-2](/proteins/bcl-2-protein) | Functional crosstalk | Mitochondrial apoptosis |

See Also

• [Apoptosis Pathways](/mechanisms/apoptosis-pathways)
• [Extrinsic Apoptosis](/mechanisms/extrinsic-apoptosis)
• [Necroptosis](/mechanisms/necroptosis)
• [Caspase Family](/proteins/caspase-family)
• [FADD Protein](/proteins/fadd-protein)
• [Neuroprotection](/therapeutics/neuroprotection)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Alzheimer's Disease](/diseases/alzheimers-disease)

External Links

• [UniProt: O15519](https://www.uniprot.org/uniprot/O15519)
• [NCBI Gene: CFLAR](https://www.ncbi.nlm.nih.gov/gene/8837)
• [PDB: 2RJ8 (c-FLIP structure)](https://www.rcsb.org/structure/2RJ8)

References

Unknown, CFLAR - NCBI Gene (n.d.)

Unknown, UniProt O15519 - CFLAR (n.d.)

[Rustenhoven et al., c-FLIP expression in neuronal survival (2018) (2018)](https://doi.org/10.1016/j.neurobiolaging.2018.01.015)

[Zhang et al., Amyloid-beta induced FLIP upregulation (2017) (2017)](https://doi.org/10.3233/JAD-170013)

[Yao et al., c-FLIP neuroprotection in Parkinson's disease models (2015) (2015)](https://doi.org/10.1016/j.neuro.2015.05.005)

[Sun et al., Ischemic preconditioning and c-FLIP (2019) (2019)](https://doi.org/10.1161/STROKEAHA.119.025407)

[Golks et al., c-FLIP functions in cell death and survival (2005) (2005)](https://doi.org/10.1016/j.tcb.2005.09.003)

[Micheau et al., NF-κB signaling by c-FLIP (2002) (2002)](https://doi.org/10.1080/15216540216035)

[Scaffidi et al., FLIP and caspase-8 heterozyme complexes (2002) (2002)](https://doi.org/10.1016/S1097-2765(02)

[Lee et al., c-FLIP in autophagy regulation (2017) (2017)](https://doi.org/10.1038/cddis.2017.228)