FAIM Antibody
Description
Structure and Isoforms of FAIM
FAIM exists in three isoforms generated by alternative splicing:
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FAIM-S (short isoform): Ubiquitously expressed in various tissues, primarily functioning in apoptosis inhibition and neural differentiation .
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FAIM-L (long isoform): Expressed predominantly in neurons, where it protects against Fas-mediated apoptosis and regulates synaptic plasticity .
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FAIM-L_2a and FAIM-S_2a: Newly identified isoforms containing exon 2a, localized to neuronal tissues and exhibiting nuclear localization, potentially influencing transcriptional regulation .
| Isoform | Expression | Primary Function |
|---|---|---|
| FAIM-S | Ubiquitous | Anti-apoptosis, neural differentiation |
| FAIM-L | Neurons | Apoptosis resistance, synaptic plasticity |
| FAIM-L_2a | Neural tissues | Nuclear localization, transcriptional regulation |
Applications of FAIM Antibody
The antibody is employed in:
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Western blot: To detect FAIM expression levels in tissues or cell lysates .
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Immunohistochemistry: To localize FAIM in tumor or neural tissues .
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Flow cytometry: For analyzing FAIM expression in immune cells .
Role in Apoptosis
FAIM inhibits Fas-mediated apoptosis by binding caspase-8 and stabilizing XIAP, a caspase inhibitor . In neurons, FAIM-L prevents Fas-induced apoptosis via ERK pathway activation .
Stress Response
FAIM binds ubiquitinated proteins under cellular stress (e.g., heat shock, oxidative damage), mitigating protein aggregation and tissue damage .
Cancer Implications
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Lung adenocarcinoma: High FAIM-L expression correlates with poor survival. Knockdown induces autophagy, reducing tumor growth .
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NSCLC: FAIM-S overexpression inhibits proliferation and arrests the cell cycle at G2/M .
Neurological Disorders
FAIM-L protects neurons from Alzheimer’s disease-related apoptosis by stabilizing XIAP and modulating synaptic transmission .
Diagnostic and Therapeutic Potential
FAIM antibodies enable precise quantification of FAIM levels in patient samples. Elevated FAIM-L in tumors suggests its utility as a prognostic biomarker . Targeting FAIM with antibodies may modulate apoptosis in cancer or neurodegenerative diseases .
Product Specs
Target Background
- SRT1720, an anti-apoptotic agent, demonstrated a mitigating effect on FAIM knockdown with small interfering RNA-targeted FAIM. This suggests that pretreatment with SRT1720 enhances the survival of aged hMSCs and improves their therapeutic efficacy for rat myocardial infarction (MI). PMID: 28383554
- Subcellular fractionation experiments revealed that, unlike FAIM-S and FAIM-L, FAIM-S_2a and FAIM-L_2a can localize to the nucleus. This suggests they might have additional functions. These findings indicate the presence of two novel FAIM isoforms with potential roles in the physiology and pathology of the nervous system. PMID: 28981531
- Research indicates that FAIM is a novel regulator of insulin signaling and plays a vital role in energy homeostasis. PMID: 26866272
- FAIM modulates IGF-1-induced Akt activation and IRF4 expression, contributing to multiple myeloma cell survival. PMID: 23138182
- The crystal structure of FAIM (1-90) was determined at 2.5 Å resolution. The crystal belonged to space group P3(1), with unit-cell parameters a=b=58.02, c=71.11 Å, α=β=90, γ=120 degrees. PMID: 20693673
- Human keratinocytes transfected with Flip, Faim, or Lifeguard (LFG) demonstrated that heterotopic expression of anti-apoptotic proteins can induce resistance to a major mechanism of rejection. PMID: 17912957
- Expression of the long form of Fas apoptotic inhibitory molecule (FAIML) protects neurons from the cytotoxic actions of death ligands. PMID: 17942717
- FAIM specifically enhances CD40 signaling for NF-kappaB activation, IRF-4 expression, and BCL-6 down-regulation in vitro, but has no effect on its own. PMID: 19592656
Q&A
Basic Research Questions
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What is FAIM and what are its main biological functions?
FAIM (Fas Apoptotic Inhibitory Molecule) was initially identified as a protein inducibly expressed in B lymphocytes resistant to Fas-mediated apoptosis . It functions as an antagonist of Fas-induced cell death but has several additional biological roles:
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Inhibition of receptor-mediated apoptosis in B cells and other cell types
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Promotion of neurite outgrowth through activation of the Ras-ERK pathway and NF-κB
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Regulation of autophagy through glutaminolysis in lung adenocarcinoma
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Potential neuroprotective roles in neurodegenerative diseases
FAIM is broadly expressed in various tissues including brain, liver, thymus, and ovary . Knockout mice for FAIM show increased sensitivity to Fas-mediated apoptosis within B and T cells as well as hepatocytes .
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What are the different isoforms of FAIM and where are they expressed?
FAIM exists in at least three isoforms with distinct expression patterns and functions:
Research has shown that FAIM-L is the main isoform expressed in lung adenocarcinoma cells . In the nervous system, while FAIM-L inhibits neuronal cell death, FAIM-S promotes neurite outgrowth through activation of Erk and NF-κB pathways .
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What applications are FAIM antibodies commonly used for?
FAIM antibodies are used in multiple research applications:
The specific applications depend on the antibody source and should be optimized by the researcher for specific experimental conditions .
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How should I select the appropriate FAIM antibody for my experiment?
When selecting a FAIM antibody, consider these factors:
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Target isoform specificity: Determine which FAIM isoform you want to detect. Some antibodies recognize all isoforms while others are isoform-specific .
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Species reactivity: Confirm the antibody reacts with your species of interest (common reactivities include human, mouse, and rat) .
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Application compatibility: Ensure the antibody is validated for your intended application (WB, IHC, IP, etc.) .
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Immunogen information: Antibodies raised against C-terminal peptides may not distinguish between FAIM-S and FAIM-L .
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Sensitivity: Some antibodies may only detect overexpressed FAIM and not endogenous levels .
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Advanced Research Questions
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How can I optimize detection of endogenous versus overexpressed FAIM?
Detecting endogenous FAIM can be challenging compared to overexpressed protein. Research indicates:
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Some commercially available antibodies may only detect overexpressed FAIM but lack sensitivity for endogenous protein .
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For endogenous detection:
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Consider using tissues with known high expression (brain for FAIM-L, lymphoid tissues for FAIM-S) .
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Optimize protein extraction methods specifically for membrane-associated proteins.
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Use enrichment techniques like immunoprecipitation before Western blotting.
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Increase antibody concentration and extend incubation times (overnight at 4°C).
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Use enhanced chemiluminescent detection systems with longer exposure times .
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For optimization across different cell types, consider the experimental conditions reported in previous studies. For example, in lung adenocarcinoma research, FAIM antibody was used at 1:1000 dilution with HRP-conjugated secondary antibodies and Pro-Light chemiluminescence detection .
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What methods can I use to study FAIM's role in autophagy regulation?
Based on research studying FAIM's role in autophagy:
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Detection of autophagy markers: Monitor LC3B puncta formation and LC3B-II/LC3B-I ratio by immunofluorescence and Western blot .
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Autophagic flux assessment: Use lysosomal inhibitors like chloroquine (CQ) alongside FAIM knockdown/overexpression to measure flux .
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Mechanistic studies: Examine FAIM's interactions with glutaminase C (GAC), MTOR, and ULK1 using co-immunoprecipitation .
Research has shown that knocking down FAIM induces autophagy through suppressing MTOR pathway activation in lung adenocarcinoma, offering a potential mechanism to monitor experimentally .
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