S100A10 Mouse

What is S100A10 and what are its key structural features in mice?

S100A10 (also known as p11) is a 97 amino acid protein belonging to the S100 family of EF-hand proteins. Unlike other S100 family members, S100A10 does not bind calcium due to critical amino acid substitutions in its EF-hand domains. The mouse S100A10 protein shares 92% amino acid identity with human S100A10 and spans from Met1 to Lys97 .

Mouse S100A10 possesses two carboxyl-terminal lysine residues that are critical for its function as a plasminogen receptor, as these residues bind to both tissue plasminogen activator (tPA) and plasminogen, facilitating the conversion of plasminogen to plasmin . The protein typically exists as a homodimer and often forms a heterotetramer complex with annexin A2, consisting of two annexin A2 subunits and two S100A10 subunits .

What are the primary cellular locations and functions of S100A10 in mice?

S100A10 has both intracellular and extracellular functions in mice. It is primarily found within or on the surface of various cell types, particularly mast cells . The cellular distribution can be visualized through immunostaining techniques, as demonstrated in TK-1 mouse T cell lymphoma cells where S100A10 localizes predominantly to the cytoplasm .

Functionally, extracellular S100A10 serves as a plasminogen receptor important for plasmin production and cellular invasiveness, while intracellular S100A10 may target ligands to the endoplasmic reticulum . S100A10 also plays critical roles in:

• Fibrinolysis regulation, as demonstrated by increased fibrin deposition in tissues of S100A10-null mice

• Cancer cell invasion and metastasis

• Recruitment of tumor-associated macrophages to tumor sites

• Regulation of various ion channels, including 5-HT1B receptors, with implications for depression-like phenotypes

How is S100A10 expression regulated in mouse tissues?

S100A10 is a highly inducible protein regulated by various physiological and pathophysiological stimuli. Its expression can be modified by:

• Growth factors and cytokines: Epidermal growth factor, transforming growth factor, interferon-α, nerve growth factor, and keratinocyte growth factor

• Other signaling molecules: Retinoic acid and thrombin

• Oncogenes: PML-RAR and KRas have been shown to stimulate S100A10 levels, suggesting its role in oncogenic processes

This regulated expression allows cells to modulate plasmin proteolytic activity in response to diverse physiological stimuli, making S100A10 an important control point in proteolytic cascades.

What is the mechanistic relationship between S100A10 and annexin A2 in mouse models?

The interaction between S100A10 and annexin A2 is complex and functionally significant. Research has shown that:

• S100A10 binds to the N-terminal region of annexin A2, specifically to the first 15 amino acids

• This binding enhances the affinity of S100A10 for plasminogen compared to homodimeric S100A10 alone

• While annexin A2 alone showed minimal stimulation of plasminogen activation (approximately 6-fold), the annexin A2/S100A10 complex significantly enhanced the rate of activation (approximately 341-fold)

• S100A10 is the subunit directly responsible for plasmin generation within the complex, while annexin A2 serves to enhance this activity

Surface plasmon resonance experiments have demonstrated that homodimeric S100A10 binds tPA and plasminogen, but S100A10 complexed with annexin A2 binds plasminogen with higher affinity than the homodimer alone . Importantly, knockout studies in mice have shown that deletion of S100A10 does not affect the protein levels of annexin A2, suggesting independent regulation of these binding partners .

What phenotypes are observed in S100A10-null mice and what do they reveal about S100A10 function?

S100A10-null mice exhibit several distinct phenotypes that have significantly contributed to our understanding of S100A10 function:

• Fibrinolysis defects: These mice show increased fibrin deposition in various tissues including lungs, liver, spleen, and kidney

• Impaired clot clearance: They demonstrate an inability to clear microclots formed by snake venom (batroxobin)

• Depression-like behavior: S100A10-null mice exhibit a depression-like phenotype with reduced responses to 5-HT1B receptor agonists, indicating S100A10's role in serotonergic signaling

• Viable development: Despite these phenotypes, S100A10-null mice are viable, suggesting S100A10 is not essential for normal mouse development

These phenotypes collectively demonstrate S100A10's critical roles in regulating fibrinolysis and certain neurological functions, while also highlighting the potential compensatory mechanisms that allow for viable development in its absence.

How does mouse S100A10 contribute to cancer progression and metastasis?

S100A10 plays two major roles in oncogenesis as revealed by studies in mouse models:

• Regulation of cancer cell invasion and metastasis: Studies using antisense RNA or small interfering RNA (shRNA) to deplete S100A10 established that it contributes significantly to total cellular plasmin generation, which cancer cells utilize to promote invasion and metastasis

• Recruitment of tumor-associated cells: S100A10 regulates the recruitment of tumor-associated macrophages to the tumor site, which can influence tumor microenvironment and progression

The oncogenes PML-RAR and KRas stimulate S100A10 levels, suggesting its involvement in oncogenic-mediated increases in plasmin production . This connection between oncogene activity and S100A10 expression provides a mechanistic link between common oncogenic drivers and the proteolytic activity that facilitates tumor cell invasion.

What are the most effective methods for detecting S100A10 in mouse tissues and cells?

Based on the research literature, several validated methods exist for detecting S100A10 in mouse samples:

For optimal results in immunodetection, it's recommended that dilutions be determined by each laboratory for specific applications, as antibody performance can vary based on sample type and experimental conditions .

How can researchers effectively generate and validate S100A10 knockdown or knockout models in mice?

For researchers studying S100A10 function through loss-of-function approaches, several validated strategies have been employed:

• Genetic knockout models: Complete S100A10-null mouse models have been successfully generated and characterized, showing specific phenotypes including depression-like behavior, increased fibrin deposition, and impaired fibrinolysis . These models are valuable for studying systemic effects of S100A10 loss.

• Cell-specific knockdown approaches: For more targeted studies, antisense RNA or small interfering RNA (shRNA) have been effectively used to selectively deplete S100A10 from specific cell types . These approaches established that S100A10 contributes significantly to total cellular plasmin generation.

• Validation strategies:

  • Western blot analysis using specific anti-S100A10 antibodies to confirm protein depletion

  • Functional assays such as plasmin generation tests to confirm loss of S100A10-dependent plasminogen activation

  • Phenotypic assays such as fibrin clearance tests (e.g., batroxobin-induced microclot clearance) or behavioral tests for depression-like phenotypes

These approaches have provided complementary insights into S100A10 function, with genetic models revealing systemic roles and cell-specific approaches identifying tissue-specific functions.

What experimental approaches can be used to study S100A10-dependent plasminogen activation in mouse models?

Several experimental approaches have been validated for studying S100A10's role in plasminogen activation:

• In vitro plasminogen activation assays: Using purified components, researchers have demonstrated that the annexin A2/S100A10 complex stimulates the rate of activation of [Glu] plasminogen approximately 341-fold compared with an approximate 6-fold stimulation by monomeric annexin A2 . These assays can measure the conversion of plasminogen to plasmin using chromogenic or fluorogenic substrates.

• Surface plasmon resonance: This technique has been used to examine the interaction of tPA and plasminogen with homodimeric S100A10 and S100A10 complexed with annexin A2, revealing that the complex binds plasminogen with higher affinity .

• Fibrinolysis models in S100A10-null mice: These mice show impaired ability to clear microclots formed by snake venom (batroxobin), providing an in vivo model to study S100A10-dependent fibrinolysis .

• Cell-based plasmin generation assays: Using cells with manipulated S100A10 levels (through knockdown or overexpression), researchers can measure plasmin generation at the cell surface and correlate it with invasive capacity .

These complementary approaches allow researchers to study S100A10-dependent plasminogen activation at multiple levels, from molecular interactions to cellular and whole-animal phenotypes.

How should researchers interpret conflicting data on S100A10 function between different mouse cell types?

When faced with conflicting data on S100A10 function across different mouse cell types, researchers should consider several factors:

• Cell-type specific protein expression patterns: S100A10 has been detected in multiple mouse cell types, including T cells (TK-1), monocyte/macrophage cells (Raw264), lung tissue, and embryonic feeder cells . Its function may vary based on relative expression levels and binding partners in these different contexts.

• Subcellular localization differences: While S100A10 shows predominantly cytoplasmic localization in some cell types like TK-1 mouse T cells , its function as a plasminogen receptor requires cell surface expression. Differences in subcellular distribution could explain functional variations.

• Compensatory mechanisms: In S100A10-null mice, while certain phenotypes are evident (depression-like behavior, fibrinolysis defects), the mice remain viable , suggesting compensatory mechanisms may exist in some tissues but not others.

• Methodological considerations: Different detection methods (Western blot, immunofluorescence, flow cytometry) may have varying sensitivities, potentially explaining some discrepancies in reported expression levels or functions.

What are the key considerations when comparing human and mouse S100A10 functions in research studies?

While mouse S100A10 shows 92% amino acid identity with human S100A10 , researchers should consider several important factors when translating findings between species:

• Structural similarities and differences: Despite high sequence homology, small differences in structure might affect protein-protein interactions or regulatory mechanisms.

• Expression pattern differences: While both human and mouse S100A10 are regulated by similar factors (growth factors, oncogenes) , the relative expression levels across tissues may differ between species.

• Pathway conservation: The plasminogen activation system is generally well-conserved between humans and mice, but differences in other interacting partners may exist.

• Knockout phenotype relevance: Phenotypes observed in S100A10-null mice (depression-like behavior, fibrinolysis defects) provide valuable insights but may not perfectly mirror human conditions due to species-specific compensatory mechanisms.

• Experimental models: Mouse cancer models used to study S100A10's role in invasion and metastasis may not fully recapitulate human tumor biology despite conserved molecular mechanisms.

When designing translational studies, researchers should validate key findings in both mouse and human systems whenever possible to ensure biological relevance.

How should quantitative changes in S100A10 expression be correlated with functional outcomes in mouse disease models?

When correlating S100A10 expression changes with functional outcomes in mouse disease models, researchers should:

• Establish baseline expression levels: Quantify normal S100A10 expression across relevant tissues using methods like Western blot to establish reference points before analyzing disease-induced changes.

• Use multiple detection methods: Combine protein quantification (Western blot), localization studies (immunofluorescence), and functional assays (plasmin generation) to comprehensively assess both expression and activity changes .

• Consider protein complexes: Since S100A10 functions primarily in complex with annexin A2 , measure both proteins and their association rather than S100A10 alone.

• Employ dose-response studies: In models where S100A10 expression can be experimentally manipulated, establish dose-response relationships between expression levels and functional outcomes like plasmin generation or invasion capacity .

• Control for confounding factors: Consider changes in S100A10 regulators (oncogenes, growth factors) that might indirectly affect the phenotypes being studied.

• Validate in S100A10-null backgrounds: To establish causality, demonstrate restoration of function by reintroducing S100A10 into null backgrounds at defined expression levels .

These approaches will help establish meaningful correlations between quantitative changes in S100A10 expression and functional outcomes in disease models.

What are the most promising therapeutic applications targeting mouse S100A10 for translational research?

Based on current understanding of S100A10 functions in mouse models, several promising therapeutic applications emerge:

• Anti-cancer strategies: Since S100A10 contributes to cancer cell invasion and metastasis through plasmin generation , targeting this protein could reduce metastatic potential. This approach might be particularly relevant for cancers showing upregulated S100A10 expression driven by oncogenes like KRas .

• Anti-depressant development: The depression-like phenotype in S100A10-null mice suggests that enhancing S100A10 function or expression might have antidepressant effects, potentially through modulation of 5-HT1B receptor function .

• Fibrinolytic therapy enhancement: Understanding S100A10's role in fibrinolysis could lead to improved thrombolytic therapies that enhance endogenous fibrinolytic capacity rather than directly introducing exogenous plasminogen activators.

• Inflammation modulation: S100A10's interaction with annexin A2 and its role in cell surface plasmin generation suggest potential applications in inflammatory conditions where proteolytic activity contributes to pathology.

Translational researchers should focus on developing specific inhibitors or enhancers of S100A10 function that could be tested in mouse models before considering human applications.

What unexplored aspects of S100A10 biology in mice warrant further investigation?

Despite significant advances in understanding S100A10 function, several knowledge gaps remain:

• Tissue-specific functions: While S100A10's role in fibrinolysis and depression-like behavior is established , its functions in other tissues and physiological processes remain incompletely characterized.

• Developmental roles: S100A10-null mice are viable , but potential subtle developmental functions, particularly in specific tissues or under stress conditions, warrant investigation.

• Post-translational modifications: The regulation of S100A10 through post-translational modifications beyond complex formation with annexin A2 is poorly understood.

• Non-plasminogen ligands: While S100A10's role as a plasminogen receptor is well-established , other potential extracellular ligands and their functional significance remain to be fully explored.

• Intracellular signaling pathways: The mechanisms by which S100A10 regulates intracellular processes, particularly in relation to ion channel function and trafficking , need further elucidation.

• Immune system functions: The role of S100A10 in immune cell function beyond tumor-associated macrophage recruitment represents an important area for future research.

Investigating these aspects could reveal new functions of S100A10 and potential therapeutic applications beyond those currently recognized.