ACPP Mouse
Description
Overview of ACPP in Mouse Models
Prostatic acid phosphatase (ACPP) is a non-specific tyrosine phosphatase that dephosphorylates substrates under acidic conditions (pH 4–6). In mice, the Acpp gene (UniProt ID: Q8CE08) is orthologous to human ACPP and is implicated in prostate biology and disease . While no standalone "ACPP Mouse" model is widely recognized, Acpp modifications are often studied in conjunction with other genes in polyposis or cancer research .
Key Mouse Models Involving Apc and Related Pathways
The Adenomatous polyposis coli (Apc) gene is a critical regulator of intestinal tumorigenesis. Several Apc mutant mouse models (e.g., Apc<sup>Min/+</sup>) have been developed to study colorectal cancer and polyposis. These models often involve compound mutations or genetic background variations .
Intersection with Alzheimer’s Disease Models
While Acpp itself is not directly linked to Alzheimer’s disease (AD), amyloid precursor protein (APP) mouse models dominate AD research. These models, such as 5XFAD and 3xTg-AD, incorporate multiple familial AD (FAD) mutations in APP and PSEN1 to accelerate Aβ deposition and cognitive deficits .
Phenotypic Comparison of APP Models:
Emerging Models and Genetic Tools
Recent advancements include knock-in (KI) models like NL-F and NL-G-F, which avoid overexpression artifacts by integrating mutations into the endogenous App locus. These models enable precise studies of Aβ production and neuroinflammation without confounding overexpression effects .
Key Advantages of Second-Generation Models:
-
Endogenous expression: Avoids artificial overexpression of APP fragments .
-
Pathological relevance: Aβ deposits resemble human AD pathology (e.g., Aβ<sub>1–42</sub> dominance) .
-
Compatibility with modifiers: Enables crossbreeding with other mutants (e.g., CAST knockout) to study calpain activation and Aβ toxicity .
Critical Considerations for Model Selection
-
Overexpression artifacts: Traditional APP-Tg models (e.g., Tg2576) may exhibit non-AD-related phenotypes due to supraphysiological APP levels .
-
Genetic background: Strains like C57BL/6 and BALB/c differentially affect aggression, lifespan, and pathology .
-
Biomarker discovery: Knock-in models (e.g., NL-F) are optimal for identifying CSF and plasma biomarkers due to physiological APP processing .
Product Specs
Prostatic Acid Phosphatase (ACPP) belongs to the histidine acid phosphatase protein family. It catalyzes the hydrolysis of phosphate monoesters and phosphorylated proteins. ACPP exhibits optimal activity within a pH range of 4-6. Its catalytic activity is inhibited by L(+)-tartrate. Notably, ACPP can function as a lipid phosphatase, demonstrating the ability to inhibit lysophosphatidic acid in seminal plasma.
ACPP Mouse, expressed in Sf9 Baculovirus cells, is a single, glycosylated polypeptide chain. It comprises 356 amino acids (32-381 aa) and has a molecular weight of 41.3kDa. The protein includes a 6 amino acid His tag fused at the C-terminus and is purified using proprietary chromatographic techniques.
The ACPP solution is provided at a concentration of 0.5mg/ml in a buffer consisting of 10% Glycerol and Phosphate-Buffered Saline (pH 7.4).
For short-term storage (2-4 weeks), the product can be stored at 4°C. For extended storage, freezing at -20°C is recommended. Adding a carrier protein (0.1% HSA or BSA) is advisable for long-term storage. Repeated freezing and thawing should be avoided.
The purity is determined to be greater than 95.0% using SDS-PAGE analysis.
The specific activity of the enzyme is measured to be greater than 80,000 units per milligram (unit/mg). Specific activity is defined as the amount of enzyme required to hydrolyze 1.0 nanomole of p-nitrophenyl phosphate (pNPP) per minute at a pH of 5.0 and a temperature of 37°C.
acid phosphatase, prostate, ACP3, ACP-3, ACPP, EC 3.1.3.2, PAP, Prostatic Acid Phosphatase, prostatic acid phosphatase, 5-nucleotidase, 5'-NT, Acid phosphatase 3, Ecto-5'-nucleotidase, Fluoride-resistant acid phosphatase, FRAP, Thiamine monophosphatase, TMPase, A030005E02Rik, Lap, PAP, Ppal.
KELKFVTLVF RHGDRGPIET FPTDPITESS WPQGFGQLTQ WGMEQHYELG SYIRKRYGRF LNDTYKHDQI YIRSTDVDRT LMSAMTNLAA LFPPEGISIW NPRLLWQPIP VHTVSLSEDR LLYLPFRDCP RFEELKSETL ESEEFLKRLH PYKSFLDTLS SLSGFDDQDL FGIWSKVYDP LFCESVHNFT LPSWATEDAM IKLKELSELS LLSLYGIHKQ KEKSRLQGGV LVNEILKNMK LATQPQKYKK LVMYSAHDTT VSGLQMALDV YNGVLPPYAS CHMMELYHDK GGHFVEMYYR NETQNEPYPL TLPGCTHSCP LEKFAELLDP VISQDWATEC MATSSHQGRN HHHHHH.
Q&A
What are ACPP Mouse models and how do they differ from conventional CPP models?
ACPPs represent an evolution of cell penetrating peptides (CPPs) designed to overcome limitations of traditional CPPs in mouse models. While conventional CPPs maintain constant adhesiveness, ACPPs consist of a polycationic CPP (typically arg₉ or r₉) connected via a cleavable linker to a matching polyanion (typically glu₉ or e₉), reducing the net charge to nearly zero until activation .
The key functional difference lies in the conditional activation mechanism. Upon cleavage of the linker by specific enzymes or conditions, the polyanion separates from the polycation, unmasking the polyarginine and restoring its inherent adhesiveness. This mechanism enables more controlled delivery compared to conventional CPPs, which bind non-specifically to tissues immediately upon administration .
What is the basic mechanism of action for ACPPs in mouse models?
The mechanism of action for ACPPs in mouse models is based on an elegant charge-masking principle that enables conditional activation:
-
The polycationic CPP component (typically D-arginine nonamers) provides cell penetration capability but is initially neutralized
-
The matching polyanionic component (typically D-glutamate nonamers) masks the positive charge through intramolecular interactions
-
The cleavable linker connecting these components is designed to be targeted by specific enzymes present in target tissues
D-amino acids are preferred within both the polyanion and polycation components to minimize proteolysis in vivo. The affinity between the polyglutamate and polyarginine components is carefully balanced to be strong enough for efficient intramolecular hairpin formation yet weak enough to allow dissociation after linker cleavage .
How do ACPPs distribute in mouse tissues compared to CPPs?
ACPPs demonstrate markedly different tissue distribution patterns compared to conventional CPPs in mouse models:
| Parameter | CPPs | ACPPs |
|---|---|---|
| Initial distribution | Remain localized at injection site | Diffuse evenly throughout tissues |
| Circulation time | Rapid clearance (3 minutes) | Extended circulation (30 minutes) |
| Tissue penetration | Limited by adhesive nature | More complete distribution throughout tissues |
| Target tissue retention | Variable, often non-specific | Enhanced retention in tissues with active linker cleavage |
In experimental comparisons, ACPPs appeared more fully distributed throughout tissues after 30 minutes, suggesting that inhibition of the adhesive polyarginine by the polyglutamate enables much greater initial distribution throughout the mouse. After 6 hours, while circulating ACPP peptide was largely washed out, cleaved ACPPs showed enhanced retention in target tissues such as tumors .
What analytical methods are used to evaluate ACPP distribution in mouse models?
Multiple complementary approaches are necessary for comprehensive evaluation of ACPP distribution:
-
Standardized Uptake Value (SUV) calculation: Quantifies tissue concentration using the formula (moles recovered/g tissue)/(moles injected/weight of animal)
-
Confocal microscopy: Enables visualization of subcellular distribution using co-markers such as:
-
Hoechst 33342 for nuclei staining
-
Rhodamine dextran (5 MDa) for blood pool visualization
-
-
Ex vivo tissue imaging: Provides macroscopic distribution assessment across organs
-
Tissue-specific analysis protocols: Different tissues require specific handling approaches. When conducting sequential imaging, tissues should be processed in order of decreasing tolerance to hypoxia (kidney, liver, tumor, muscle) .
How is synaptic plasticity affected in mouse models used for ACPP research?
While the search results don't directly address synaptic plasticity in ACPP mouse models, they provide relevant insights from APP/PS1 transgenic mouse models that are often used in neurodegenerative disease research where ACPPs may be applied:
| Age | Long-Term Potentiation (LTP) | Paired-Pulse Facilitation (PPF) |
|---|---|---|
| 4-5 months | No difference from controls | No difference from controls |
| 6 months | No difference from controls | Slightly increased (p<0.03) |
| 8 months | Greatly impaired (p<0.0001) | No difference from controls |
| 15 months | Significantly impaired (p<0.005) | Significantly reduced at 80ms (p<0.005) and 160ms (p<0.01) intervals |
These progressive changes in synaptic plasticity correlate with increasing amyloid deposition in the hippocampus, showing modest accumulation at 4-6 months with robust increases up to 15 months of age . This temporal pattern is important when designing studies using ACPPs for targeting neurodegenerative pathology.
How do you design effective experimental protocols for evaluating ACPP efficacy in mouse models?
Effective experimental protocols for evaluating ACPP efficacy require rigorous design considerations:
Experimental Controls
-
Include conventional CPPs as positive controls
-
Use non-cleavable ACPPs as negative controls
-
Employ wild-type littermates for comparison with genetically modified mice
-
Include vehicle-only injections to account for procedural effects
Time-Course Design
Evaluate distribution at multiple timepoints (e.g., 30 minutes, 6 hours post-injection) to capture the distinct phases of:
-
Initial distribution and circulation
-
Linker cleavage and activation
-
Retention in target tissues and clearance
Quantification Approaches
-
Standardized uptake value (SUV) for tissue homogenates
-
Fluorescence intensity measurements for intact tissues
-
Subcellular distribution analysis using confocal microscopy
Statistical Analysis
-
Two-way repeated-measures ANOVA for time-course comparisons
-
Appropriate post-hoc tests (e.g., Yuen's test) for specific comparisons
What are the key considerations for analyzing contradictory data in ACPP Mouse studies?
When encountering contradictory data in ACPP mouse studies, researchers should systematically evaluate:
Methodological Inconsistencies
Research has shown discrepancies between different analytical methods. For example, fluorescence intensity in intact tumors often differs from SUV measurements in tumor homogenates, highlighting the importance of using complementary analytical approaches .
Age-Dependent Effects
Results can vary significantly based on the age of mouse models. For instance, synaptic plasticity in APPPS1-21 mice shows progressive impairment from 4 to 15 months, with different responses at different timepoints .
Pharmacokinetic Phase Differences
Measurements taken during different pharmacokinetic phases may yield contradictory results:
-
Distribution phase: ACPPs show wider distribution than CPPs
-
Enzyme activation phase: Tissue-specific retention begins to emerge
-
Elimination phase: Cleaved ACPPs show enhanced retention in target tissues
Mechanism-Based Reconciliation
Develop integrated models that account for:
-
Tissue-specific enzyme expression profiles
-
Differential linker cleavage efficiencies
-
Subcellular compartmentalization effects on detection
How do pharmacokinetic profiles of ACPPs differ from CPPs in various mouse models?
The pharmacokinetic profiles of ACPPs show substantial differences from conventional CPPs:
Circulation and Distribution Parameters
| Parameter | CPPs | ACPPs | Significance |
|---|---|---|---|
| Initial tissue binding | High, immediate | Low, gradual | ACPPs distribute more extensively |
| Blood circulation half-life | <3 minutes | ~30 minutes | ACPPs have greater opportunity for tissue penetration |
| Volume of distribution | Limited | Extensive | ACPPs access more tissues before activation |
| Target tissue retention | Variable, often non-specific | Enhanced in tissues with linker cleavage | Improved targeting specificity |
Organ-Specific Distribution
ACPPs show distinct organ distribution patterns compared to CPPs. While both show accumulation in clearance organs like kidneys, ACPPs demonstrate improved distribution to target tissues. For example, tumor standardized uptake values (SUVs) for ACPPs often exceed those of CPPs at later timepoints, reflecting target-specific retention following activation .
How can researchers optimize linker cleavage specificity in ACPP constructs for targeted delivery?
Optimizing linker cleavage specificity requires multifaceted approaches:
Enzyme-Specific Substrate Design
-
Select peptide sequences that are preferentially cleaved by enzymes overexpressed in target tissues
-
Incorporate D-amino acids in the polyanion and polycation to minimize non-specific proteolysis
-
Consider unnatural amino acids to enhance selectivity for specific proteases
Dual-Trigger Mechanisms
Implement systems requiring two independent conditions for activation:
-
Enzyme cleavage plus pH change
-
Temperature sensitivity combined with protease recognition
-
Photocleavable elements with enzyme-sensitive components
Linker Optimization Matrix
| Parameter | Consideration | Optimization Approach |
|---|---|---|
| Sequence specificity | Kcat/Km for target vs. off-target enzymes | Systematic substitution of amino acids flanking cleavage site |
| Linker accessibility | Steric hindrance affecting enzyme access | Vary linker length and flexibility |
| Cleavage kinetics | Rate of activation in target tissue | Balance between stability in circulation and efficient target activation |
| Secondary structure | Impact on enzyme recognition | Evaluate how hairpin formation affects enzyme accessibility |
Validation Strategies
-
In vitro screening against purified enzymes and cell lines
-
Ex vivo tissue slice models to assess cleavage specificity
-
In vivo comparison across multiple mouse models with varying enzyme expression profiles
What are the current limitations of ACPP mouse models and how might these be addressed?
Current limitations of ACPP mouse models include:
Pharmacokinetic Challenges
While ACPPs demonstrate improved pharmacokinetics compared to CPPs, certain limitations persist:
-
Variable enzyme expression across tissues affects activation consistency
-
Potential for premature activation in circulation by blood proteases
-
Incomplete understanding of the fate of cleaved components
Potential solutions: Develop next-generation ACPPs with enhanced stability against non-specific proteases and incorporate additional blocking groups that require sequential enzymatic processing.
Analytical Limitations
Current methods for analyzing ACPP distribution have inherent limitations:
-
Discrepancies between fluorescence intensity in intact tissues versus SUV measurements
-
Challenges in distinguishing between cleaved and uncleaved peptides in vivo
-
Limited temporal resolution in tracking the activation process
Potential solutions: Develop dual-reporter systems that independently track the polyanion and polycation components after cleavage, coupled with advanced imaging techniques that enable real-time visualization of the activation process.
Model Relevance
Mouse models may not fully recapitulate human disease conditions:
-
Species differences in enzyme expression and activity
-
Accelerated disease progression in mouse models
-
Limitations in modeling complex human pathophysiology
Potential solutions: Develop humanized mouse models expressing human enzymes and establish comprehensive enzyme activity profiles across tissues to better predict translational outcomes .
Product Science Overview
The recombinant mouse prostatic acid phosphatase is typically expressed in HEK293 cells. The DNA sequence encoding the mouse ACPP isoform 1 (Met1-Arg381) is expressed with a C-terminal polyhistidine tag . The recombinant protein consists of 361 amino acids and has a predicted molecular mass of 42 kDa. However, due to glycosylation, its apparent molecular mass is approximately 47 kDa when analyzed by SDS-PAGE under reducing conditions .
Prostatic acid phosphatase is a non-specific phosphomonoesterase that is synthesized and secreted into seminal plasma under androgenic control . The enzyme is a dimer with a molecular weight of around 100 kDa. Its primary function is to dephosphorylate macromolecules, which is facilitated by catalytic residues (His12 and Asp258) located in the cleft between two domains .
Cellular prostatic acid phosphatase (cPAcP) functions as a neutral protein tyrosine phosphatase (PTP) in prostate cancer cells. It dephosphorylates HER-2/ErbB-2/Neu (human epidermal growth factor receptor-2) at the phosphotyrosine residues . This activity is proposed to function as a negative growth regulator of prostate cancer cells, in part through its dephosphorylation of ErbB-2 .
