FKBP1A Mouse

What is FKBP1A and what are its fundamental biological functions in mice?

FKBP1A is a ubiquitously expressed 12 kDa peptidyl-prolyl cis-trans isomerase that catalyzes the rotation of peptide bonds from trans to cis configuration at proline residues . As a member of the FK506-binding protein family, it binds to immunosuppressive drugs FK506 and rapamycin, inhibiting calcineurin and mTOR activity respectively . Beyond its enzymatic function, FKBP1A associates with multiple intracellular protein complexes including BMP/Activin/TGFβ type I receptors, calcium-release channels, and voltage-gated sodium channels . This protein plays crucial roles in cardiac development, cancer progression, and cellular signaling networks that control diverse physiological processes .

What are the common synonyms and alternative names for FKBP1A in scientific literature?

When conducting literature searches or database queries, researchers should be aware of the multiple nomenclatures used:

These various identifiers appear throughout the literature and in product descriptions, making comprehensive search strategies essential for thorough reviews .

What is the molecular structure and biochemical properties of mouse FKBP1A?

Mouse FKBP1A in its native form contains 108 amino acids, while recombinant versions often include additional sequences such as the 24 amino acid His-tag as described in commercial preparations . The protein has a molecular mass of approximately 14.4kDa when produced recombinantly with tags . As a peptidyl-prolyl isomerase, it catalyzes the cis-trans isomerization of proline imidic peptide bonds, potentially affecting protein folding and function . The protein is typically stable when stored properly at -20°C, particularly when a carrier protein is added for long-term storage .

What genetic models are available for studying FKBP1A function in mice?

Researchers have developed several genetic models to study FKBP1A function:

• Global knockout mice: Complete FKBP1A deficiency leads to embryonic lethality with severe cardiac defects, limiting their use to early developmental studies .

• Conditional knockout models: Using the Cre-loxP system, researchers have generated tissue-specific knockouts including:

  • Endothelial-specific ablation using endothelial-specific Cre lines

  • Cardiomyocyte-specific deletion using cardiomyocyte-specific Cre lines

  • Cardiac progenitor cell deletion using Nkx2.5-Cre

• Floxed FKBP1A mice: These contain loxP-flanked FKBP1A alleles (Fkbp1a flox) that can be crossed with various Cre lines to achieve cell lineage-restricted deletion .

These models enable precise investigation of FKBP1A functions in specific tissues and developmental contexts .

What are effective methods for measuring FKBP1A activity in mouse experimental models?

Several approaches can assess FKBP1A functionality:

• Luciferase reporter assays: Especially useful for studying FKBP1A's role in Notch signaling, using reporters like Hes1-pGL3 co-transfected with Notch1, Dll4, and FKBP1A expression plasmids .

• MEF and endothelial cell isolation: Primary cells from FKBP1A knockout and control mice serve as valuable in vitro models for mechanistic studies .

• Protein stability assays: Assessing how FKBP1A affects stability of interaction partners, particularly N1ICD (Notch1 intracellular domain) .

• Phenotypic assessment: Analyzing cardiac development abnormalities, particularly trabeculation and compaction defects, in various knockout models .

• Gene expression analysis: Examining downstream target expression, such as Bmp10, Sdc1, and MMP9, which mediate FKBP1A's effects on development and cancer progression .

What considerations are important when using recombinant FKBP1A protein in mouse studies?

When working with recombinant FKBP1A:

• Storage conditions: Store at 4°C if using within 2-4 weeks, or at -20°C for longer periods, preferably with carrier protein addition (0.1% HSA or BSA) .

• Stability issues: Avoid multiple freeze-thaw cycles to maintain protein integrity .

• Buffer composition: Typical formulations contain phosphate-buffered saline (pH 7.4) with 20% glycerol and 1mM DTT .

• Tags and modifications: Consider how N-terminal His-tags or other modifications might affect protein function when designing experiments .

• Purity assessment: Verify protein purity (typically >95% by SDS-PAGE) before experimental use .

• Laboratory use restrictions: Commercial preparations are typically designated for laboratory research only, not for therapeutic applications .

How does FKBP1A regulate ventricular myocardium trabeculation and compaction?

FKBP1A plays a critical role in cardiac development through its function in endocardial cells rather than cardiomyocytes themselves . The mechanism involves:

• Notch1 regulation: FKBP1A functions as a negative modulator of activated Notch1, controlling its activity levels in endocardial cells .

• Tissue-specific action: Surprisingly, endothelial cell-specific (not cardiomyocyte-specific) deletion of FKBP1A recapitulates the ventricular development defects seen in systemic knockouts .

• Endocardial-myocardial communication: FKBP1A-mediated Notch1 regulation influences crucial intercellular signaling between endocardium and myocardium required for proper ventricular wall formation .

• Trabeculation control: In FKBP1A-deficient hearts, hyperactivation of Notch1 leads to ventricular hypertrabeculation and noncompaction, resembling human left ventricular noncompaction cardiomyopathy .

• BMP10 pathway involvement: FKBP1A deficiency leads to elevated Bmp10 expression, which correlates with the ventricular hypertrabeculation phenotype .

What is the relationship between FKBP1A and Notch signaling in cardiac development?

The interplay between FKBP1A and Notch signaling is central to ventricular morphogenesis:

• Negative regulation: FKBP1A directly modulates activated Notch1 (N1ICD) levels, with activated Notch1 significantly upregulated in FKBP1A-ablated endothelial cells both in vivo and in vitro .

• N1ICD stability: Overexpression of FKBP1A significantly reduces N1ICD stability, suggesting a post-translational regulatory mechanism .

• Therapeutic implications: Direct inhibition of Notch signaling significantly reduces hypertrabeculation in FKBP1A-deficient mice, highlighting a potential intervention strategy .

• Hes1 activation: FKBP1A affects Notch target gene activation, as demonstrated by luciferase reporter assays using the Hes1-pGL3 system .

• Molecular mechanism: The peptidyl-prolyl isomerase activity of FKBP1A may influence Notch1 protein folding, stability, or interaction with other signaling components .

What phenotypes distinguish endothelial-specific versus cardiomyocyte-specific FKBP1A knockout mice?

These models reveal tissue-specific functions of FKBP1A:

This differentiation reveals that FKBP1A's role in heart development is primarily mediated through its function in endocardial/endothelial cells rather than in cardiomyocytes directly .

What antitumor activities have been identified for FKBP1A in mouse models?

FKBP1A exhibits several important antitumor functions:

• Antiinvasive activity: Systemic gene transfer studies in tumor-bearing mice identified novel antiinvasive functions for FKBP1A .

• Antimetastatic effects: FKBP1A expression inhibits metastatic progression through specific molecular pathways .

• Gene regulation: FKBP1A expression coordinately induces the antiinvasive syndecan 1 (Sdc1) gene while suppressing the proinvasive matrix metalloproteinase 9 (MMP9) gene .

• Loss-of-function effects: siRNA-mediated suppression of FKBP1A increases tumor cell invasion and MMP9 levels while down-regulating Sdc1, confirming its tumor-suppressive role .

• Rapamycin-independent action: The antitumor effects of FKBP1A gene expression occur through cellular pathways entirely distinct from those activated when FKBP1A binds to rapamycin .

How does FKBP1A regulate genes involved in tumor progression?

FKBP1A influences cancer progression through specific gene regulatory networks:

• Dual regulation mechanism: FKBP1A simultaneously upregulates antiinvasive factors (Sdc1) and downregulates proinvasive factors (MMP9) .

• Regulatory network establishment: FKBP1A helps establish gene regulatory networks that control tumor progression, allowing more accurate modeling of the complex molecular mechanisms of cancer .

• Expression patterns: FKBP1A is downregulated in aggressive tumors, suggesting its expression levels may correlate with cancer progression .

• Functional validation: Systemic gene transfer experiments directly demonstrate that FKBP1A's differential expression in metastatic cancers reflects functional involvement rather than merely correlative changes .

• Integration with expression profiling: Combined approaches of gene expression profiling with specific modulation of FKBP1A expression can identify complex biological functions controlled by this protein .

How does FKBP1A interact with BMP/TGF-β signaling pathways?

FKBP1A modulates BMP/TGF-β signaling through several mechanisms:

• Receptor association: FKBP1A associates with BMP/Activin/TGFβ type I receptors, potentially regulating their activity or availability .

• BMP10 regulation: In FKBP1A-deficient hearts, Bmp10 is significantly upregulated, connecting FKBP1A to this critical developmental pathway .

• Developmental consequences: The elevated Bmp10 levels observed in FKBP1A knockout hearts correlate strongly with ventricular hypertrabeculation and noncompaction phenotypes .

• Comparative genetics: Similar Bmp10 upregulation occurs in both FKBP1A and Nkx2-5 knockout hearts, suggesting convergent regulatory mechanisms .

• Mechanistic integration: FKBP1A likely modulates multiple signaling pathways simultaneously, including BMP and Notch, to coordinate proper cardiac development .

What experimental approaches best reveal FKBP1A's role in Notch signaling?

Researchers can employ several techniques to study FKBP1A-Notch interactions:

• Luciferase reporter assays: Using Hes1-pGL3 reporter constructs transfected with Notch1, Dll4, and FKBP1A expression plasmids in FKBP1A knockout and control cells .

• Cell isolation and culture: Working with FKBP1A knockout and control mouse embryonic fibroblasts (MEFs) and endothelial cells for comparative analysis .

• Notch inhibitor studies: Treating FKBP1A-deficient mice with Notch inhibitors to assess phenotypic rescue of hypertrabeculation .

• Protein stability analysis: Examining N1ICD stability in the presence or absence of FKBP1A overexpression .

• Conditional knockout approaches: Using tissue-specific Cre lines to ablate FKBP1A in specific cell types to isolate tissue-specific Notch interactions .

How do FKBP1A's multiple molecular functions integrate in physiological contexts?

FKBP1A's diverse functions converge to regulate complex biological processes:

• Multi-pathway integration: FKBP1A simultaneously affects Notch, BMP/TGF-β, calcium channel regulation, and potentially other pathways to coordinate cellular responses .

• Tissue-specific effects: The dominant function of FKBP1A varies by tissue context - endocardial Notch regulation in cardiac development versus MMP9/Sdc1 regulation in cancer contexts .

• Developmental stage-specific roles: FKBP1A's critical functions may vary across developmental stages, as evidenced by the timing of cardiac defects in knockout models .

• Molecular versatility: As both an enzyme (peptidyl-prolyl isomerase) and a protein-protein interaction scaffold, FKBP1A mediates diverse cellular functions .

• Therapeutic implications: Understanding FKBP1A's integrated functions suggests potential intervention points for both developmental disorders and cancer .

How can FKBP1A mouse models advance understanding of human cardiac disorders?

FKBP1A mouse models serve as valuable tools for studying human cardiac conditions:

• LVNC modeling: FKBP1A-deficient mice phenocopy human left ventricular noncompaction cardiomyopathy, including characteristic hypertrabeculation, deep intertrabecular recesses, noncompaction, and ventricular septal defects .

• Molecular mechanism identification: These models have revealed the critical role of endocardial Notch signaling in trabeculation disorders, providing mechanistic insights for human disease .

• Therapeutic testing: FKBP1A models allow testing of interventions like Notch inhibitors, potentially informing human therapeutic approaches .

• Developmental timing analysis: Studying FKBP1A knockout embryos at various developmental stages helps map the progression of cardiac abnormalities, informing understanding of human developmental defects .

• Endocardial-myocardial communication: These models highlight the importance of cross-talk between endocardium and myocardium in ventricular development, a process likely conserved in humans .

What emerging techniques might enhance FKBP1A functional studies?

Advanced methodologies can further elucidate FKBP1A functions:

• Single-cell transcriptomics: Analyzing gene expression changes in individual cells of FKBP1A-deficient tissues to reveal cell type-specific responses and heterogeneity.

• CRISPR-based approaches: Using precise genome editing to introduce specific FKBP1A mutations or domain alterations to dissect structure-function relationships.

• Protein interaction proteomics: Employing mass spectrometry-based approaches to identify the complete interactome of FKBP1A in different cellular contexts.

• In vivo imaging: Utilizing advanced microscopy techniques to visualize FKBP1A-dependent processes in developing embryos or tumors in real-time.

• Computational modeling: Integrating experimental data into mathematical models to predict FKBP1A's role in complex signaling networks and developmental processes.

How might FKBP1A research inform therapeutic strategies for cancer?

FKBP1A-based cancer research holds several therapeutic implications:

• Gene therapy approaches: Systemic gene transfer of FKBP1A might have therapeutic potential given its demonstrated antiinvasive and antimetastatic functions in mouse models .

• Target gene modulation: Therapeutic strategies targeting downstream effectors like syndecan 1 or MMP9 might mimic FKBP1A's antitumor effects .

• Pathway-specific intervention: Understanding the distinct pathways through which FKBP1A exerts its antitumor effects (separate from rapamycin effects) could inform novel therapeutic approaches .

• Biomarker development: FKBP1A expression levels or those of its target genes might serve as biomarkers for cancer progression or therapeutic response .

• Combination approaches: Integrating FKBP1A-based strategies with existing therapies might enhance anticancer efficacy through complementary mechanisms .