Recombinant Human Membrane protein FAM159B (FAM159B)

What is FAM159B and what is its cellular localization?

FAM159B functions as a transmembrane adaptor protein involved in regulating other transmembrane receptors and proteins . Although its exact function remains incompletely characterized, it is known to be an essential component in numerous cell signaling pathways . Immunocytochemical experiments have revealed predominantly cytoplasmic expression of this adaptor protein . The protein belongs to the Shisa-like protein family, and vertebrates have two copies: FAM159A and FAM159B .

Which tissues express FAM159B in humans?

FAM159B shows a distinct expression pattern with predominance in neuronal and neuroendocrine tissues. Immunohistochemical analysis has detected FAM159B expression in:

• Neuronal tissues: cortex, trigeminal ganglia, dorsal root ganglia, intestinal ganglia

• Neuroendocrine tissues: pancreatic islets, neuroendocrine cells of the bronchopulmonary and gastrointestinal tract

• Other tissues: syncytiotrophoblasts of the placenta

• Kidney: mesangial cells of the glomeruli, visceral and parietal layers of Bowman's capsule, and varying degrees in tubules

• Immune cells: macrophages in thymus, spleen, and liver (Kupffer cells)

What antibodies are recommended for FAM159B detection?

The rabbit polyclonal anti-human FAM159B antibody HPA011778 (Atlas Antibodies) has been well-characterized for studying FAM159B expression . This antibody has been validated through:

• Western blot analyses confirming specificity

• Immunocytochemistry in cell lines

• Verification using targeted siRNA in BON-1 cells (a neuroendocrine tumor cell line endogenously expressing FAM159B)

• Cross-reactivity testing with rat and mouse FAM159B (the sequence has one amino acid difference)

• Preadsorption tests with the immunizing peptide PrEST Antigen FAM159B (APrEST71583)

For immunofluorescence double-labeling experiments, this antibody can be effectively paired with monoclonal antibodies against insulin, glucagon, or somatostatin (SST-14/28) to study co-expression patterns .

How does FAM159B expression differ between normal and neoplastic tissues?

FAM159B is expressed in numerous tumor entities, with particularly high levels observed in:

• Medullary and anaplastic thyroid carcinomas

• Parathyroid adenomas

• Lung and ovarian carcinomas

• Lymphomas

• Neuroendocrine tumors of different origins

Co-expression analysis in neuroendocrine cancer cell lines (BON-1, PC3, NCI-h82, and OH-1) has revealed association of FAM159B with various neuroendocrine-specific markers including:

• Chromogranin A

• Neuron-specific enolase

• Insulinoma-associated protein 1

• Neural cell adhesion molecule 1

• Dopamine receptor 2

• Regulator of G-protein signaling 9

• Somatostatin receptors 2, 4, and 5

What are the species-specific differences in FAM159B expression?

Significant species differences have been observed in FAM159B expression patterns, particularly in pancreatic islets. The table below summarizes key differences:

The most notable difference is in pancreatic islets, where FAM159B is expressed throughout the entire structure in humans but restricted to peripheral cells in rodents .

How does FAM159B expression correlate with islet hormones across species?

Double-labeling immunohistochemical experiments have revealed significant species differences in the co-expression patterns of FAM159B with pancreatic hormones:

In humans:

• FAM159B partially overlaps with insulin (β-cells)

• FAM159B partially overlaps with glucagon (α-cells)

• FAM159B partially overlaps with somatostatin (δ-cells)

In rats and mice:

• No overlap between FAM159B and insulin

• No overlap between FAM159B and glucagon

• Complete colocalization between FAM159B and somatostatin

These findings indicate that while FAM159B is expressed in multiple endocrine cell types in human islets, it is restricted to δ-cells in rodent islets, highlighting important physiological differences in islet function across species.

What methodological approaches are recommended for studying FAM159B in tissue samples?

Based on published research methodologies, the following protocol is recommended:

• Tissue preparation: Use formalin-fixed, paraffin-embedded tissue samples sectioned at 2-4 μm thickness .

• Immunohistochemistry protocol:

  • Deparaffinize and rehydrate sections

  • Perform heat-induced epitope retrieval

  • Block endogenous peroxidase and non-specific binding

  • Incubate with anti-FAM159B antibody HPA011778 (1:100 dilution) overnight at 4°C

  • Apply appropriate detection system (e.g., EnVision+/HRP, Dako)

• For double-labeling experiments:

  • Co-incubate anti-FAM159B HPA011778 with antibodies against:

    • Insulin (1:100; Abcam)

    • Glucagon (1:500; Sigma-Aldrich)

    • Somatostatin-14/28 (1:300; Abcam)

  • Detect using Cy3-conjugated anti-rabbit secondary antibody and Alexa Fluor 488-conjugated anti-mouse or anti-rat secondary antibody

  • Mount with Fluoromount G containing DAPI

• Analysis methods:

  • Confocal microscopy (e.g., Zeiss LSM 900 Airyscan 2)

  • Digital slide scanning (e.g., Hamamatsu NanoZoomer)

  • Quantification using appropriate software (e.g., NDP.view2 2.9.29)

How is FAM159B expression affected in metabolic disorders?

Analysis of FAM159B expression in lean and obese Zucker rats (a diabetes model) has revealed significant differences:

• Obese Zucker rats exhibit enlarged islets compared to lean controls

• The percentage of FAM159B-positive cells relative to total islet area is significantly smaller in obese rats compared to lean rats

• The absolute area of FAM159B-positive cells relative to total pancreas area is larger in obese rats due to increased islet size

This suggests that diabetes-related islet hyperplasia involves primarily β-cells rather than δ-cells (where FAM159B is expressed in rodents), resulting in a dilution effect of FAM159B-expressing cells within enlarged islets.

What experimental design considerations are important when studying FAM159B across species?

When designing experiments involving FAM159B, researchers should consider:

• Species differences: Findings regarding FAM159B expression and function cannot be directly transferred between rodents and humans due to significant differences in expression patterns .

• Blocking experiments: Include antibody preadsorption with the immunizing peptide (PrEST Antigen FAM159B) as a specificity control .

• Appropriate controls: Include both positive controls (tissues known to express FAM159B) and negative controls (antibody omission and isotype controls) .

• Statistical analysis: As FAM159B expression data may not be normally distributed, non-parametric statistical tests (Kruskal-Wallis, Mann-Whitney U tests, Spearman's rank correlations) are recommended .

• Study design: Implement blocking in experimental design to reduce variability within each experimental group, particularly important when working with tissues that show heterogeneous FAM159B expression .

What cell signaling pathways might involve FAM159B based on current evidence?

While the exact signaling pathways involving FAM159B remain to be fully elucidated, several lines of evidence suggest potential roles:

• As a member of the Shisa-like protein family, FAM159B likely functions as a transmembrane adaptor involved in regulating other transmembrane receptors and proteins .

• Its co-expression with neuroendocrine markers and various receptors (dopamine receptor 2, regulator of G-protein signaling 9, and somatostatin receptors) suggests potential involvement in:

  • G-protein coupled receptor signaling

  • Neuroendocrine secretory pathways

  • Hormone regulation

• In pancreatic islets, its expression has been linked to:

  • β-cell exocytosis

  • β-cell maturation

  • Potentially involved in blood glucose regulation

• The differential expression in metabolic disorders suggests a potential role in pathways related to islet adaptation to metabolic stress .

How can experimental FAM159B knockdown be achieved?

Based on published methodologies, targeted siRNA has been successfully used to knock down FAM159B expression:

• Cell model selection: BON-1 cells (neuroendocrine tumor cell line) endogenously express FAM159B and provide a suitable model .

• siRNA approach:

  • Design siRNA targeting FAM159B mRNA

  • Transfect cells using appropriate reagents following manufacturer's protocols

  • Confirm knockdown efficiency using Western blot and/or qRT-PCR

  • Validate specificity through appropriate controls (scrambled siRNA)

• Alternative approaches:

  • CRISPR-Cas9 gene editing could be employed for more permanent modification

  • Lentiviral shRNA for stable knockdown in long-term studies

What are important considerations for interpreting FAM159B expression in disease models?

When studying FAM159B in disease models, particularly metabolic disorders, researchers should consider:

• The species-specific expression patterns may lead to different functional roles in humans versus rodents.

• Changes in islet composition and architecture can affect the relative proportion of FAM159B-expressing cells, potentially confounding expression analysis.

• Correlation analysis between FAM159B expression and clinical parameters (e.g., blood glucose levels, islet function) should account for these confounding factors.

• Quantitative analysis should incorporate measurements of:

  • Total pancreas area

  • Total islet area

  • Area occupied by FAM159B-positive cells

  • Percentage of FAM159B-positive cells relative to islet area