SPTBN2 Antibody

What is SPTBN2 and what is its biological function?

SPTBN2 (Spectrin Beta Non-Erythrocytic 2), also known as beta-III spectrin or SCA5, is a member of the spectrin family that functions as an important component of the neuronal membrane cytoskeleton. Spectrins are composed of two alpha and two beta spectrin subunits that form dimers, tetramers, and higher polymers, serving as membrane organizers and stabilizers .

SPTBN2 plays a critical role in:

• Maintaining neuronal membrane integrity

• Regulating the glutamate signaling pathway by stabilizing the glutamate transporter EAAT4 at the plasma membrane surface

• Supporting Purkinje cell structure and function in the cerebellum

Mutations in SPTBN2 cause spinocerebellar ataxia type 5 (SCA5), characterized by neurodegeneration, progressive locomotor incoordination, dysarthria, and uncoordinated eye movements .

What are the common applications for SPTBN2 antibodies in laboratory research?

SPTBN2 antibodies are versatile tools used in multiple laboratory techniques:

Different antibodies have varying specificities and applications, so researchers should verify each antibody's validation data for their specific application .

What is the molecular weight of SPTBN2 and how is it detected?

SPTBN2 is a large protein with:

• Calculated molecular weight: 271 kDa

• Observed molecular weight: 270-271 kDa in experimental conditions

When performing Western blot analysis, the high molecular weight of SPTBN2 requires:

• Lower percentage gels (6-8%)

• Extended transfer times

• Specialized transfer conditions for large proteins

• Appropriate molecular weight markers with range up to 300 kDa

The expected band should appear at approximately 271 kDa when using validated antibodies .

In which tissues is SPTBN2 primarily expressed?

SPTBN2 exhibits a tissue-specific expression pattern:

Within the nervous system, SPTBN2 shows highest expression in the cerebellum, specifically in Purkinje cell soma and dendrites. This expression pattern correlates with the neurological symptoms observed in spinocerebellar ataxia type 5 (SCA5) caused by SPTBN2 mutations .

What distinguishes SPTBN2 from other spectrin family members?

SPTBN2 (beta-III spectrin) is one of several beta-spectrin variants that can be differentiated from other family members:

Use antibodies targeting unique epitopes (such as aa 350-500 or aa 2150-2200 regions of SPTBN2) to ensure specificity and minimize cross-reactivity with other spectrin family members .

How does SPTBN2 expression differ in lung adenocarcinoma compared to normal tissue?

Research has identified SPTBN2 as a potential biomarker for lung adenocarcinoma (LUAD), with significant expression differences:

Analysis of the Cancer Cell Line Encyclopedia (CCLE) database showed that SPTBN2 expression in non-small cell lung cancer (NSCLC) ranked 13th among all examined cancer cell lines. This upregulation at both mRNA and protein levels suggests SPTBN2 plays a significant role in LUAD pathogenesis .

What methods are recommended for validating SPTBN2 antibody specificity?

To ensure research reproducibility, comprehensive validation of SPTBN2 antibody specificity is essential:

• Western Blot Analysis:

  • Confirm single band at expected molecular weight (271 kDa)

  • Test in tissues with known SPTBN2 expression (e.g., cerebellum)

  • Include positive and negative control lysates

• siRNA Knockdown Controls:

  • Transfect cells with SPTBN2 siRNA and confirm signal reduction

  • Compare with non-targeting siRNA controls

  • Use RT-qPCR to quantify knockdown efficiency

• Immunoprecipitation Validation:

  • Perform IP followed by Western blot with a different SPTBN2 antibody

  • Example: Immunoprecipitate SPTBN2 from HeLa cells using ab264177 (3 μg/mg lysate), then detect with a different antibody recognizing a distinct epitope

• Peptide Competition:

  • Pre-incubate antibody with immunizing peptide

  • Confirm signal elimination in presence of blocking peptide

• Cross-Reactivity Testing:

  • Test antibody against recombinant spectrin family proteins

  • Perform protein array analysis to check specificity

These validation approaches ensure reliable results in experimental applications and minimize false-positive findings .

What are the recommended protocols for SPTBN2 immunohistochemistry?

For optimal SPTBN2 detection in tissue sections, follow this detailed IHC protocol:

• Tissue Preparation:

  • Fix tissues in formalin and embed in paraffin

  • Section at 4-5 μm thickness

  • Mount on positively charged slides

• Antigen Retrieval:

  • Primary method: TE buffer (pH 9.0)

  • Alternative method: Citrate buffer (pH 6.0)

  • Heat in pressure cooker or microwave until boiling, then 20 minutes at sub-boiling temperature

• Peroxidase Blocking:

  • Block with 3% H₂O₂ for 20 minutes

  • Wash thoroughly with PBS (pH 7.4)

• Antibody Incubation:

  • Block with serum at room temperature for 30 minutes

  • Incubate with primary SPTBN2 antibody (1:150-1:600 dilution) overnight at 4°C

  • Apply secondary antibody for 1 hour at room temperature

• Detection and Visualization:

  • Develop with 3,3'-diaminobenzidine (DAB)

  • Counterstain nuclei with hematoxylin

  • Dehydrate through ethanol gradient and clear in xylene

  • Mount with permanent mounting medium

• Quantification:

  • Scan stained sections for panoramic analysis

  • Quantify SPTBN2 expression using histochemistry score (H-score)

  • Compare expression levels between experimental and control tissues

How can SPTBN2 be effectively knocked down in cell culture models?

For successful SPTBN2 knockdown experiments:

• siRNA Design and Selection:

  • Design multiple siRNA sequences targeting different regions of SPTBN2 mRNA

  • Test multiple sequences to identify the most effective option

  • Include scrambled siRNA as negative control (si-SPTBN2 NC)

• Transfection Protocol:

  • Use lipid-based transfection reagents (e.g., Lipofectamine 3000)

  • For lung cancer cell lines (A549, H1299):

    • Culture in DMEM with 10% FBS

    • Transfect at 60-70% confluence

    • Follow manufacturer's protocol for lipofection reagent

• Transfection Conditions:

  • Optimal siRNA concentration: 20-50 nM (validate for specific cell lines)

  • Incubation time: 48 hours post-transfection

  • Serum conditions: Reduced serum during transfection, complete medium after 4-6 hours

• Verification of Knockdown:

  • Assess knockdown efficiency using RT-qPCR

  • Confirm protein reduction via Western blot

  • Document percentage of knockdown achieved

• Functional Analysis:

  • After confirming knockdown, proceed with functional assays:

    • Cell proliferation (e.g., CCK-8 assay)

    • Migration (wound-healing assay, Transwell migration)

    • Invasion (Matrigel invasion assay)

What is the role of SPTBN2 in cancer progression, particularly in lung adenocarcinoma?

Recent research has established SPTBN2 as a novel oncogenic factor in lung adenocarcinoma (LUAD):

• Cellular Mechanisms:

  • Proliferation: SPTBN2 knockdown significantly inhibits cell proliferation in A549 and H1299 lung cancer cell lines as demonstrated by CCK-8 assays

  • Migration: Wound-healing assays show reduced migration 48 hours after SPTBN2 knockdown compared to control groups

  • Invasion: Transwell migration and Matrigel invasion assays reveal significantly decreased invasive capabilities following SPTBN2 silencing

• Clinical Correlations:

  • Expression: Significantly upregulated in LUAD tissues compared to adjacent normal tissues across multiple independent datasets

  • Prognosis: High SPTBN2 expression positively correlates with poor prognosis in LUAD patients

  • Biomarker Potential: May serve as a novel biomarker for LUAD diagnosis and prognosis

• Molecular Regulation:

  • miRNA Regulation: miR-16 has been identified as a negative regulator of SPTBN2 mRNA expression

  • Pathway Involvement: KEGG pathway analysis reveals that proteins related to SPTBN2 are enriched in apoptotic and phagosomal pathways

These findings suggest SPTBN2 as a promising therapeutic target for LUAD treatment, with potential for development of targeted therapies aimed at inhibiting its oncogenic functions .

What considerations are important for co-immunoprecipitation experiments with SPTBN2?

When performing co-immunoprecipitation to study SPTBN2 interactions:

• Starting Material:

  • Use at least 1 mg of total cell/tissue lysate

  • HeLa cells have been successfully used for SPTBN2 IP

  • Brain tissue (particularly cerebellum) provides high endogenous expression

• Antibody Selection:

  • Use antibodies validated for IP applications

  • Example: ab264177 (3 μg/mg lysate) has been validated for SPTBN2 IP

  • Consider using combination of polyclonal for IP and monoclonal for detection

• Protocol Optimization:

  • Lysis buffer: Include protease/phosphatase inhibitors

  • Binding conditions: Overnight incubation at 4°C

  • Bead selection: Protein A for rabbit antibodies, Protein G for mouse

  • Wash conditions: Multiple washes with decreasing salt concentration

• Controls and Validation:

  • Input control: Load 5-10% of pre-IP lysate

  • IgG control: Use same species/amount of non-specific IgG

  • Knockout/knockdown control: Demonstrate specificity

• Detection Strategy:

  • Western blot: Use antibody recognizing different epitope than IP antibody

  • Large protein considerations: Adjust gel percentage and transfer conditions

  • Detection sensitivity: Consider enhanced chemiluminescence with longer exposure (30 seconds has been used successfully)

How does SPTBN2 interact with the glutamate transporter EAAT4 in neuronal function?

SPTBN2's functional interaction with EAAT4 reveals important insights into neuronal glutamate handling:

• Structural Relationship:

  • SPTBN2 is also known as glutamate transporter EAAT4-associated protein 41 (GTRAP41)

  • Functions as a physical anchor for EAAT4 at the plasma membrane

  • Forms part of a protein complex stabilizing EAAT4 localization

• Functional Significance:

  • Maintains proper surface expression of EAAT4

  • Enhances glutamate uptake capacity

  • Prevents glutamate excitotoxicity

  • Protects neurons from excitotoxic damage

• Disease Implications:

  • SPTBN2 mutations in SCA5 lead to:

    • Reduced EAAT4 surface expression

    • Impaired glutamate clearance

    • Excitotoxic Purkinje cell damage

    • Progressive cerebellar degeneration

• Research Techniques to Study Interaction:

  • Co-immunoprecipitation of SPTBN2-EAAT4 complexes

  • Surface biotinylation to measure EAAT4 surface expression

  • Glutamate uptake assays in presence/absence of SPTBN2

  • Fluorescence co-localization in neuronal cultures

  • FRET analysis of protein proximity

This interaction represents a critical mechanism for maintaining proper glutamatergic neurotransmission, particularly in cerebellar Purkinje cells .

What methods can be used to study SPTBN2's role in membrane organization?

To investigate SPTBN2's membrane organization functions:

• Advanced Microscopy Techniques:

  • Super-resolution microscopy: Examine SPTBN2 nanoscale organization at the membrane

  • TIRF microscopy: Visualize SPTBN2 at the plasma membrane interface

  • Live-cell imaging: Track dynamic SPTBN2 rearrangements

  • Fluorescence recovery after photobleaching (FRAP): Measure SPTBN2 mobility

• Biochemical Approaches:

  • Membrane fractionation: Isolate plasma membrane and assess SPTBN2 content

  • Detergent resistance: Evaluate SPTBN2 association with lipid rafts

  • Cross-linking studies: Identify SPTBN2 interaction partners at the membrane

  • Native PAGE analysis: Examine SPTBN2 complex formation

• Functional Studies:

  • Membrane fluidity assays: Measure changes upon SPTBN2 depletion

  • Membrane bending capacity: Evaluate SPTBN2's role in membrane curvature

  • Transporter trafficking assays: Quantify impact on membrane protein mobility

  • Electrophysiology: Measure membrane properties in presence/absence of SPTBN2

• Molecular Engineering Approaches:

  • Domain deletion mutants: Identify functional regions for membrane binding

  • Fluorescent protein fusions: Visualize SPTBN2 membrane dynamics

  • Optogenetic manipulation: Control SPTBN2 localization with light

  • CRISPR-Cas9 genome editing: Generate precise mutations mimicking disease states

What are the optimal storage and handling conditions for SPTBN2 antibodies?

Proper antibody handling ensures optimal performance and extended shelf life:

Follow manufacturer-specific recommendations, as formulations may vary between suppliers. For example, antibody ab264177 can be stored at -20°C, while others may have different requirements .

How can researchers distinguish between normal and pathological SPTBN2 function in experimental systems?

To differentiate normal from pathological SPTBN2 function:

• Expression Analysis Approaches:

  • Quantitative RT-PCR: Compare SPTBN2 mRNA levels in normal vs. disease tissues

  • Western blotting: Assess protein expression and potential degradation products

  • Immunohistochemistry: Evaluate tissue distribution and subcellular localization changes

  • Single-cell RNA-seq: Identify cell-specific expression alterations

• Functional Assessment Methods:

  • Mutant expression studies: Compare WT vs. SCA5-associated SPTBN2 mutants

  • Rescue experiments: Test if WT SPTBN2 can restore function in knockout models

  • EAAT4 trafficking assays: Measure impact on glutamate transporter surface expression

  • Neuronal morphology analysis: Assess dendritic architecture in Purkinje cells

• Disease Model Systems:

  • Patient-derived samples: Analyze tissues from SCA5 patients vs. controls

  • Transgenic mouse models: Study SCA5-associated mutations in vivo

  • iPSC-derived neurons: Generate patient-specific neuronal models

  • Cerebellar slice cultures: Examine ex vivo effects on neuronal circuits

• Molecular Interaction Studies:

  • Co-IP comparing WT vs. mutant binding partners: Identify altered interactions

  • Proximity labeling in normal vs. disease state: Map SPTBN2 interactome changes

  • Protein stability assays: Measure half-life differences between normal and mutant proteins

  • Post-translational modification analysis: Identify altered phosphorylation or other modifications