POM121/POM121B/POM121C Antibody
Description
Introduction to POM121 Protein Family
POM121 (POM121 membrane glycoprotein), also known as POM121A, NUP121 (nucleoporin Nup121), or pore membrane protein of 121 kDa, is a 1,249 amino acid single-pass membrane protein that exists as three alternatively spliced isoforms and belongs to the POM121 family . The protein is encoded by a gene mapping to human chromosome 7q11.23 and is highly conserved across species . POM121 predominantly localizes to the nuclear membrane and endoplasmic reticulum membrane, serving as an essential architectural component of the nuclear pore complex (NPC) .
The functional significance of POM121 extends beyond mere structural support. It plays a mandatory role in nuclear envelope formation and may contribute significantly to NPC biogenesis . A distinguishing characteristic of POM121 is its association with the central spoke ring complex, where it anchors components of the pore complex to the pore membrane through its F-X-F-G repeat-containing domain . Notably, research has shown that overexpression of POM121 can induce the formation of cytoplasmic annulate lamellae (AL), suggesting its role in organelle organization .
Recent investigations have revealed that POM121 functions not merely as a structural nucleoporin but also as a chaperone-operated signaling molecule that enables TFEB-mediated autophagy . This multifaceted protein has further been implicated in regulating the subcellular localization and transport of transcription factors, including PPARγ, across the NPC—actions that significantly impact genes involved in metabolic regulation and tumor control .
Types and Sources
Antibodies targeting POM121 and its isoforms are available from multiple commercial sources and are predominantly produced in rabbit hosts . Most commercially available options are polyclonal antibodies, which can recognize multiple epitopes on their target proteins, providing robust detection capabilities across various applications .
An interesting characteristic of POM121 is that its observed molecular weight in laboratory conditions (typically 140-150 kDa) differs significantly from the calculated molecular weight of 99 kDa based on amino acid sequence alone . This discrepancy likely stems from post-translational modifications such as glycosylation or phosphorylation, which affect protein migration during electrophoresis.
Reactivity and Applications
POM121 antibodies demonstrate reactivity with samples from multiple species, including human, mouse, and rat tissues . Their versatility makes them valuable tools across numerous laboratory techniques, including:
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Western Blotting (WB)
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Immunohistochemistry (IHC)
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Immunofluorescence/Immunocytochemistry (IF/ICC)
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Immunofluorescence on paraffin-embedded tissues (IF-P)
For optimal immunohistochemistry results with paraffin-embedded tissues, heat-induced epitope retrieval (HIER) at pH 6 is recommended . When performing immunocytochemistry or immunofluorescence, paraformaldehyde fixation with Triton X-100 permeabilization typically yields the best results .
Nuclear Pore Complex Structure and Function
POM121 is a 121 kDa type-1 transmembrane protein with a distinctive structural organization that includes three key domains: a single-pass N-terminal membrane-spanning domain, an internal nuclear localization sequence (NLS) that interacts with importin-α/β, and a C-terminal cytoplasmic/nucleoplasmic domain featuring phenylalanine-glycine (FG) repeats that facilitate cargo transfer . This architectural arrangement enables POM121 to serve as an integral component of the nuclear pore complex, effectively anchoring the NPC to the nuclear membrane .
The three isoforms—POM121, POM121B, and POM121C—likely possess distinct but overlapping functions within this complex structure. Their differential expression and localization patterns may contribute to tissue-specific variations in nuclear transport dynamics and regulation.
Protein Interactions and Signaling Pathways
POM121 engages in complex interactions with multiple proteins, including SIGMAR1 and KPNB1 (importin β1), forming functional complexes essential for nucleocytoplasmic transport . Co-immunoprecipitation experiments have conclusively demonstrated these protein associations, highlighting POM121's pivotal role in facilitating bidirectional molecular traffic between nuclear and cytoplasmic compartments .
Detailed molecular studies have revealed that SIGMAR1 proteins bind and chaperone POM121, facilitating the recruitment of KPNB1 for the nucleocytoplasmic transport of various nucleus-bound cargos, including the transcription factor TFEB . This sophisticated molecular interplay is critical for maintaining cellular homeostasis and orchestrating appropriate responses to various stress conditions.
Role in Gene Expression Regulation
Beyond its structural contributions, POM121 exerts significant influence on gene expression patterns by modulating the subcellular localization of key transcription factors. It interacts directly with PPARγ, preventing its nuclear accumulation and consequently down-regulating transcription from PPARγ target genes . This regulatory function has profound implications for metabolic processes and tumor development.
Additionally, N- or C-terminally truncated variants of POM121, which lack transmembrane domains and/or nuclear localization sequences, function as cytoplasmic chaperones and coregulators of chromatin structure and gene expression by binding to various transcription factors . These variants may include forms related to POM121B and POM121C, suggesting these isoforms may possess specialized regulatory functions.
Detection and Quantification Methods
Antibodies targeting POM121 and its isoforms serve as indispensable tools for detecting and quantifying these proteins across diverse biological samples. ELISA kits incorporating POM121 antibodies enable precise quantitative measurement of POM121 in human serum, plasma, cell culture supernatants, tissue homogenates, and various other biological fluids .
These specialized immunoassay kits typically employ a sandwich enzyme technique, where an antibody specific for Human POM121 is pre-coated onto a microplate. When standards and samples are introduced to the wells, any POM121 present binds to the immobilized antibody, forming the foundation for subsequent detection and quantification . This methodology offers high sensitivity and specificity, making it valuable for both basic research and potential clinical applications.
Immunolocalization Studies
Visualizing the spatial distribution of POM121 and its isoforms within cellular contexts is crucial for elucidating their functional roles. Immunocytochemistry and immunofluorescence techniques utilizing POM121 antibodies have revealed precise localization patterns at the nuclear membrane, often in close proximity to chromosomal DNA (as indicated by DAPI staining) and in association with other regulatory proteins such as SIGMAR1 .
These microscopy-based studies have confirmed that POM121 colocalizes with SIGMAR1 at the nuclear membrane, providing compelling visual evidence of their functional relationship . Similar methodologies can be applied to investigate the localization patterns of POM121B and POM121C, potentially uncovering distinct spatial arrangements or functional associations that differentiate these isoforms.
Protein Interaction Analyses
POM121 antibodies facilitate comprehensive studies of protein-protein interactions through techniques such as co-immunoprecipitation. Such experimental approaches have successfully demonstrated complex formation between POM121, SIGMAR1, and KPNB1, providing valuable insights into the molecular mechanisms underlying nucleocytoplasmic transport .
Overexpression studies utilizing tagged versions of POM121 (such as POM121-MYC/DDK) have demonstrated increased co-immunoprecipitation between interaction partners, further validating these protein associations . Similar methodological approaches can be employed to investigate the specific interaction networks of POM121B and POM121C, potentially revealing unique binding partners or regulatory mechanisms.
POM121 and Its Isoforms in Disease Mechanisms
POM121 isoforms have been implicated in various pathological conditions, including neurodegenerative diseases, inflammatory disorders, and viral replication processes . The protein's fundamental role in regulating nuclear transport and gene expression positions it as a potential contributor to multiple disease mechanisms.
In colorectal cancer (CRC), research has demonstrated that POM121 mRNA is enriched and POM121 protein co-expressed with PPARγ in patient tissues, correlating with poor prognosis . The interaction between POM121 and PPARγ affects the subcellular localization of the latter, potentially disrupting normal transcriptional regulation and contributing to cancer progression through altered expression of metabolic and proliferative genes.
Diagnostic and Therapeutic Potential
The association between POM121 isoforms and various disease states suggests promising diagnostic applications for antibodies targeting these proteins. Detection and quantification of POM121, POM121B, and POM121C in patient samples could provide valuable biomarkers for disease diagnosis, prognosis assessment, or treatment monitoring.
Research utilizing these antibodies may also uncover targetable molecular pathways for therapeutic intervention, particularly in conditions characterized by dysregulated nuclear transport or altered gene expression profiles. The specificity of antibodies capable of distinguishing between POM121, POM121B, and POM121C could be especially valuable for developing precise diagnostic or therapeutic approaches tailored to specific disease contexts.
Recent Research Advances
Recent scientific investigations have substantially expanded our understanding of POM121 beyond its traditional structural role in the nuclear pore complex. The groundbreaking discovery that POM121 functions as a chaperone-operated signaling molecule enabling TFEB-mediated autophagy represents a significant advancement in the field .
Similarly, the finding that POM121 participates in the transport of PPARγ across the NPC to regulate its transcriptional activity on genes involved in metabolic and tumor control opens new avenues for research into cancer biology and metabolic disorders . Ongoing exploration of the specific roles of POM121B and POM121C may reveal additional unique functions or disease associations for these isoforms, potentially leading to novel therapeutic targets.
Product Specs
Q&A
What are POM121, POM121B, and POM121C proteins and their functional significance?
POM121 family proteins are integral membrane proteins that localize to the central spoke ring complex of the nuclear pore complex (NPC). These proteins play critical roles in anchoring the nuclear pore complex to the nuclear envelope, thereby regulating nucleocytoplasmic transport. POM121 (also known as POM121A) is approximately 127.7 kilodaltons, while POM121C is reported to be 125.1 kilodaltons in mass. These proteins are critical components of nuclear envelope architecture and function in various cellular processes, including nuclear transport, nuclear envelope assembly, and potentially gene regulation . When designing experiments investigating nuclear envelope integrity or nucleocytoplasmic transport, researchers should consider the specific roles of each family member, as they may have overlapping but distinct functions within the nuclear pore complex.
What are the key structural and functional differences between POM121, POM121B, and POM121C?
While all three proteins are transmembrane nucleoporins, they display distinct structural characteristics and potentially specialized functions. POM121 (POM121A) is the most extensively studied, with a calculated molecular weight of 99 kDa (984 amino acids) but typically observed at 140-150 kDa in experimental conditions due to post-translational modifications. POM121C (also known as POM121-2) is structurally similar but may have evolved specialized functions in certain cell types or developmental stages . The differences in molecular weight, domain organization, and tissue expression patterns should be carefully considered when selecting antibodies for specific experimental applications, particularly when investigating tissue-specific nuclear envelope regulation.
What species cross-reactivity can be expected when working with POM121 family antibodies?
Based on available antibody products, most POM121/POM121B/POM121C antibodies demonstrate reactivity with human samples, while many also cross-react with mouse and rat orthologs . Some specialized antibodies may also recognize canine, porcine, and non-human primate orthologs. When designing comparative studies across species, researchers should verify the cross-reactivity profile of their selected antibody through validation data or preliminary experiments before proceeding with full-scale investigations.
How should I select the appropriate POM121 family antibody for my specific research application?
Selection should be based on several key factors: (1) Target specificity - determine whether your research requires antibodies specific to one family member or those recognizing multiple POM121 variants; (2) Application compatibility - verify validated applications match your experimental approach (WB, IHC, IF, ELISA); (3) Species reactivity - ensure the antibody recognizes your model organism; (4) Validated literature - prioritize antibodies with published citation records in applications similar to yours . For investigations requiring discrimination between highly homologous family members, prioritize antibodies raised against unique regions rather than conserved domains.
What are the optimal sample preparation methods for different applications using POM121 family antibodies?
For Western blotting, nuclear fraction enrichment is often beneficial as these are nuclear envelope proteins. Cell lysis buffers containing 1% NP-40 or Triton X-100 with protease inhibitors are typically effective. For immunohistochemistry with POM121 antibodies, antigen retrieval using TE buffer at pH 9.0 is recommended, though citrate buffer at pH 6.0 can serve as an alternative . For immunofluorescence applications, paraformaldehyde fixation (4%) followed by permeabilization with 0.2% Triton X-100 typically yields optimal results. These preparation methods should be optimized based on your specific sample type and antibody characteristics.
What controls should be included when performing experiments with POM121 family antibodies?
Rigorous experimental design requires appropriate controls: (1) Positive controls - HeLa cells for Western blotting and human colon tissue for IHC have been validated ; (2) Negative controls - samples with known absence of target or secondary antibody-only controls; (3) Knockdown/knockout validation - where possible, include POM121-depleted samples via siRNA or CRISPR methods as specificity controls; (4) Competing peptide controls - especially when testing new applications or tissues. Published literature indicates that knockdown/knockout approaches have been successfully used with POM121 antibodies, providing strong validation options .
What are the recommended protocols for Western blotting with POM121 family antibodies?
For optimal Western blot results, follow these guidelines: (1) Sample preparation - enrich nuclear fractions when possible; (2) Gel selection - use 6-8% gels due to the high molecular weight of POM121 proteins (observed at 140-150 kDa); (3) Transfer conditions - extend transfer time for large proteins, preferably using wet transfer systems; (4) Blocking - 5% non-fat dry milk in TBST for 1 hour at room temperature; (5) Primary antibody dilution - typically 1:1000-1:4000 as recommended for POM121 antibodies ; (6) Secondary antibody - select based on host species of primary antibody; (7) Detection - both chemiluminescence and fluorescence-based systems are suitable. When troubleshooting weak signals, consider longer exposure times and reduced wash stringency.
What are the key considerations for immunofluorescence applications with POM121 family antibodies?
For successful immunofluorescence, consider: (1) Fixation - 4% paraformaldehyde for 15 minutes at room temperature preserves nuclear envelope structure; (2) Permeabilization - 0.2% Triton X-100 for 10 minutes; (3) Blocking - 3% BSA in PBS for 1 hour; (4) Antibody dilution - validated dilutions range from 1:50-1:500 for IF-P and 1:200-1:800 for IF/ICC applications ; (5) Nuclear counterstain - DAPI or Hoechst at 1:1000-1:5000 dilution; (6) Mounting - use anti-fade mounting media to preserve signal during imaging; (7) Imaging - confocal microscopy is preferred for precise nuclear envelope localization. Positive staining should reveal a characteristic nuclear rim pattern consistent with nuclear pore complex localization.
What dilution ranges and optimization strategies are recommended for immunohistochemistry with POM121 antibodies?
For IHC applications with POM121 antibodies, dilutions typically range from 1:50-1:500 . Optimization strategies include: (1) Antigen retrieval testing - compare TE buffer pH 9.0 (recommended) versus citrate buffer pH 6.0; (2) Titration series - test 3-4 dilutions spanning the recommended range; (3) Incubation conditions - compare overnight at 4°C versus 1-2 hours at room temperature; (4) Detection systems - HRP-polymer systems often provide cleaner results than avidin-biotin systems; (5) Counterstaining - adjust hematoxylin counterstaining time to maintain nuclear detail while allowing visualization of the nuclear envelope signal. Human colon tissue has been validated as a positive control for POM121 IHC applications .
How can I address weak or absent signals when using POM121 family antibodies?
Troubleshooting weak signals requires systematic approach: (1) Antibody concentration - increase antibody concentration or incubation time; (2) Sample preparation - ensure protein denaturation is complete for WB applications; (3) Antigen retrieval optimization - test both alkaline (pH 9.0) and acidic (pH 6.0) conditions for IHC; (4) Protein abundance - POM121 proteins may have variable expression levels across tissues, consider enrichment steps; (5) Epitope accessibility - in fixed tissues, extended permeabilization may improve results; (6) Signal amplification - consider biotin-streptavidin systems or tyramide signal amplification for low-abundance targets; (7) Antibody quality - verify antibody functionality with positive controls (HeLa cells for WB, human colon tissue for IHC) .
What strategies can resolve non-specific binding or background issues with POM121 antibodies?
High background can be addressed through: (1) Blocking optimization - increase blocking agent concentration (5-10% BSA or serum) or duration; (2) Antibody dilution - use more dilute antibody preparations while extending incubation times; (3) Wash stringency - increase detergent concentration (0.1-0.3% Tween-20) or wash duration; (4) Cross-adsorption - pre-adsorb antibodies with tissue powder from relevant species; (5) Secondary antibody selection - highly cross-adsorbed secondary antibodies reduce species cross-reactivity; (6) Tissue fixation - overfixation can increase background, optimize fixation duration; (7) Autofluorescence quenching - for IF applications, Sudan Black B treatment can reduce tissue autofluorescence.
How can I confirm antibody specificity when working with highly homologous POM121 family members?
Validating specificity between homologous family members requires: (1) Peptide competition assays - pre-incubate antibody with immunizing peptide; (2) Genetic validation - use siRNA knockdown or CRISPR knockout models targeting specific family members; (3) Recombinant protein controls - express tagged versions of each family member; (4) Mass spectrometry validation - confirm immunoprecipitated proteins; (5) Comparative analysis - test multiple antibodies targeting different epitopes; (6) Western blot analysis - look for distinct molecular weight patterns characteristic of each family member (POM121 typically observed at 140-150 kDa) . Published knockout/knockdown validations provide strong evidence for antibody specificity and should be prioritized when available.
How should I interpret different molecular weight observations when detecting POM121 family proteins?
POM121 proteins often display discrepancies between calculated and observed molecular weights. The calculated molecular weight for POM121 is approximately 99 kDa (984 amino acids), but it typically appears at 140-150 kDa in SDS-PAGE . This discrepancy is attributed to: (1) Post-translational modifications - especially glycosylation as suggested by the glycoprotein nomenclature; (2) Protein structure - highly charged regions can affect migration; (3) Isoform expression - alternative splicing may generate variants; (4) Species differences - human versus rodent orthologs may differ in apparent molecular weight. When interpreting results, researchers should be aware that observed molecular weights may vary between experimental systems and tissue sources.
What are the expected localization patterns for POM121 family proteins in different cell types and tissues?
POM121 family proteins display characteristic nuclear envelope rim staining, consistent with their role in nuclear pore complexes. In immunofluorescence applications, expect a punctate pattern around the nuclear periphery, often described as a "nuclear rim" or "nuclear envelope" pattern. This pattern has been validated in various cell types including HCT 116 cells and brain tissue . In polarized or specialized cells, distribution may vary according to nuclear pore complex density. When co-stained with other nuclear envelope markers (e.g., lamin B), expect significant colocalization with partial overlap patterns depending on the subnuclear compartment being visualized.
How can I validate POM121 antibody specificity in my experimental system?
Comprehensive validation includes: (1) Literature corroboration - compare your results with published findings; (2) Multiple detection methods - validate findings across different techniques (WB, IF, IHC); (3) Peptide competition - demonstrate signal reduction with immunizing peptide; (4) Genetic approaches - confirm signal reduction in knockdown/knockout systems; (5) Alternative antibodies - test antibodies targeting different epitopes; (6) Expected localization - confirm nuclear envelope localization; (7) Molecular weight verification - observe bands at expected sizes (140-150 kDa for POM121) . The strongest validation combines genetic approaches with biochemical characterization and subcellular localization analysis.
What methodologies are recommended for studying POM121 family proteins in the context of nuclear pore complex assembly and function?
Advanced research approaches include: (1) Live-cell imaging - using GFP-tagged POM121 constructs to track dynamics; (2) Super-resolution microscopy - techniques like STORM or PALM to resolve individual nuclear pore complexes; (3) Proximity labeling - BioID or APEX approaches to identify interaction partners; (4) FRAP (Fluorescence Recovery After Photobleaching) - to measure protein turnover and dynamics; (5) Correlative light-electron microscopy - to relate fluorescence signals to ultrastructural features; (6) Conditional knockout models - to study developmental or tissue-specific functions. These methodologies can provide insights beyond static localization to understand the dynamic roles of POM121 family members in nuclear envelope biology.
How can POM121 family antibodies be used in studying nuclear envelope pathologies and disease mechanisms?
POM121 antibodies serve as valuable tools for investigating nuclear envelope-related diseases: (1) Laminopathies - examine nuclear pore distribution in diseases like Emery-Dreifuss muscular dystrophy; (2) Cancer research - analyze nuclear transport alterations in malignant cells; (3) Viral infections - study viral interactions with nuclear pore complexes; (4) Aging research - investigate nuclear pore integrity changes during cellular senescence; (5) Neurodegenerative disorders - examine nucleocytoplasmic transport defects. Methodological approaches include comparative immunostaining across patient-derived samples, quantitative image analysis of nuclear pore distribution, and correlation of POM121 expression with disease progression markers.
What are the considerations for multiplexing POM121 antibodies with other nuclear envelope markers?
Effective multiplexing requires: (1) Host species selection - choose primary antibodies from different host species to avoid cross-reactivity; (2) Fluorophore selection - select fluorophores with minimal spectral overlap; (3) Sequential staining - consider sequential rather than simultaneous antibody application for challenging combinations; (4) Epitope accessibility - ensure one antibody doesn't block access to another's epitope; (5) Concentration balancing - adjust concentrations to achieve comparable signal intensities; (6) Controls - include single-stained controls to verify specificity in the multiplexed context. Recommended combinations include POM121 with lamin B1 (nuclear lamina), NUP153 (nuclear basket), or SUN proteins (LINC complex) to investigate different aspects of nuclear envelope organization.
| Recommended Dilutions for POM121 Antibodies by Application |
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| Application |
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| Western Blot |
| Immunohistochemistry |
| Immunofluorescence (Paraffin) |
| Immunofluorescence (Cultured Cells) |
| ELISA |
