Resistin Human, His

What is human resistin and how does it differ from murine resistin?

Human resistin is a 12.5 kDa cysteine-rich protein that functions primarily as a proinflammatory cytokine. Unlike murine resistin which is produced by adipocytes and links obesity to insulin resistance in mice, human resistin is predominantly expressed in mononuclear cells and macrophages . This fundamental expression pattern difference has significant implications for research models and translational studies. Human resistin exists in an oligomeric polydispersed state and shows concentration-dependent conformational changes that are crucial for its biological functions .

What is the significance of the His-tag in recombinant human resistin studies?

The histidine (His) tag is a common affinity tag used in recombinant protein production that facilitates purification via immobilized metal affinity chromatography. For human resistin research, His-tagged versions provide several advantages: (1) enhanced purification efficiency, (2) improved stability during experimental procedures, and (3) the ability to perform pulldown assays to identify binding partners. When conducting experiments with His-tagged human resistin, researchers should verify that the tag does not interfere with the protein's oligomeric structure or chaperone-like functions, as these are critical for its biological activity .

What cellular compartments typically contain human resistin?

While human resistin is primarily known as a secreted protein, research has demonstrated that during endoplasmic reticulum (ER) stress, it can be retained inside cells . This retention appears to be functionally significant, as intracellular resistin demonstrates chaperone-like properties that may protect cells from apoptosis during stress conditions. The highest expression of human resistin is observed in bone marrow, with significant expression also seen in peritoneal macrophages, especially following inflammatory stimulation .

What transgenic models are available for studying human resistin in vivo?

Several important models have been developed to study human resistin's functions in vivo:

• BAC-Retn mice: These transgenic mice lack murine resistin but express human resistin from its human genomic elements. This model provides expression patterns similar to those seen in humans, with highest expression in bone marrow and dramatic induction in peritoneal macrophages upon stimulation .

• Macrophage-specific humanized resistin mice: These models express human resistin constitutively in macrophages, allowing for studies of chronic effects without inflammatory induction .

These models have revealed that human resistin contributes to inflammation-induced insulin resistance, particularly in the liver, providing valuable insights into metabolic disease mechanisms .

How can researchers assess human resistin's chaperone activity?

To evaluate the chaperone-like functions of human resistin, researchers can employ several methodological approaches:

• Thermal aggregation assays: Monitor the ability of human resistin to protect heat-labile enzymes (such as citrate synthase and Nde1) from thermal aggregation using light scattering measurements .

• Enzyme activity recovery assays: Assess resistin's ability to refold and restore enzymatic activities after heat or chemical denaturation .

• Binding assays with misfolded proteins: Evaluate the selective binding of human resistin to misfolded, but not properly folded, protein substrates .

• Hydrophobicity blocking: Use compounds like Bis-ANS that block surface hydrophobicity to confirm the importance of hydrophobic regions in resistin's chaperone function .

These methodologies can be complemented with molecular dynamics simulations to understand the association-dissociation kinetics of human resistin subunits .

What are recommended protocols for studying inflammatory induction of human resistin?

To investigate inflammatory induction of human resistin, researchers should consider:

• LPS (lipopolysaccharide) treatment: Both in vitro cell culture models and in vivo systems can be stimulated with LPS to induce human resistin expression .

• Cell models: RAW.264 murine macrophages transfected with human resistin constructs show marked induction of resistin expression following LPS treatment .

• Primary cell isolation: Peritoneal macrophages from BAC-Retn mice demonstrate dramatic induction of human resistin and serve as excellent primary cell models .

• Acute and chronic endotoxemia: These models help assess the metabolic and molecular phenotypes associated with inflammation-induced human resistin expression .

Quantitative PCR and ELISA assays are essential tools for measuring resistin expression and secretion in these experimental setups.

How does human resistin contribute to insulin resistance during inflammation?

Human resistin acts as a molecular link between inflammation and insulin resistance through several mechanisms:

• In BAC-Retn transgenic mice, LPS-induced endotoxemia leads to increased inflammation and hepatic insulin resistance compared to resistin-knockout mice .

• Human resistin primarily affects insulin signaling in the liver during inflammatory states, suggesting tissue-specific effects .

• The inflammation-specific induction pattern of human resistin distinguishes it from constitutive expression models and highlights its role in acute inflammatory responses .

This relationship suggests that targeting human resistin could potentially ameliorate inflammation-induced insulin resistance, particularly in conditions like sepsis, obesity, and type 2 diabetes where inflammation is a significant component .

What structural features enable human resistin's chaperone-like activity?

Human resistin's chaperone function relies on several key structural characteristics:

• Surface hydrophobicity: Crucial for binding to misfolded proteins, this property can be blocked by Bis-ANS, which abrogates resistin's chaperone activity .

• The Phe49 residue: A critical component within the hydrophobic patch, mutation of this residue (F49YhRes) impairs resistin's ability to refold and restore enzyme activities, though it maintains the capacity to prevent thermal aggregation .

• Oligomeric structure: Human resistin exists in a polydispersed state and undergoes concentration-dependent conformational changes that appear important for its chaperone function .

• Exceptional stability: Human resistin demonstrates remarkable resistance to heat and urea denaturation, likely contributing to its function in stress conditions .

These features explain how human resistin can rescue cells from ER stress-induced apoptosis and suggest its role as a molecular link between cellular stress and inflammation during pathological conditions .

How does human resistin relate to other adipokines in disease contexts?

While originally identified in the context of adipokines, human resistin functions distinctly from other fat-derived signals like leptin and adiponectin:

• Unlike these classic adipokines, human resistin is primarily produced by immune cells rather than adipocytes .

• Along with leptin and adiponectin, resistin has been implicated in promoting tumor progression, suggesting complex interactions in the tumor microenvironment .

• The endocrine functions of resistin intersect with metabolic regulation pathways influenced by other adipokines, creating a complex network of signaling in conditions like obesity and diabetes .

Research comparing resistin's effects with those of other adipokines often reveals complementary or antagonistic functions, highlighting the importance of studying these factors as an integrated network rather than in isolation.

What is the relationship between human resistin's cellular retention during ER stress and its secretory patterns?

During endoplasmic reticulum stress, human resistin is retained inside cells rather than being secreted, which appears to be a regulated process with functional significance . This intracellular retention coincides with resistin's chaperone-like activities, suggesting that:

• Cellular stress creates a demand for chaperone function that temporarily repurposes resistin from its secretory fate.

• The switch between secreted proinflammatory cytokine and intracellular chaperone may represent an adaptive response to different types of cellular stress.

• Treatment of U937 cells with ER stress inducers like tunicamycin or thapsigargin results in reduced resistin secretion and concomitant localization in the endoplasmic reticulum .

This dual functionality makes resistin a particularly interesting target for studying the integration of cellular stress responses and inflammatory signaling.

How do post-translational modifications affect human resistin function?

While the search results don't specifically address post-translational modifications of human resistin, research in this area is critical for understanding its diverse functions. When studying His-tagged resistin, researchers should consider:

• Potential glycosylation differences between recombinant and native human resistin.

• How the oligomeric state might be influenced by oxidative conditions, given resistin's cysteine-rich nature.

• Whether phosphorylation events regulate the switch between secretory and chaperone functions.

These modifications may explain some of the context-dependent activities of human resistin observed across different experimental systems.

What methodological approaches can address the apparent contradictions between resistin's proinflammatory and protective chaperone functions?

The dual role of human resistin as both a proinflammatory cytokine and a protective chaperone presents an interesting paradox. Researchers investigating this contradiction might consider:

• Temporal studies examining the sequential activation of these functions during stress responses.

• Compartment-specific analyses separating intracellular from extracellular resistin effects.

• Structure-function studies identifying distinct domains responsible for each activity.

• Context-dependent experimental designs that clarify when each function predominates.

This apparent contradiction may actually represent an evolved mechanism linking cellular stress to subsequent inflammatory responses, with resistin serving as a molecular switch between these states .

What are promising approaches for targeting human resistin therapeutically?

Given resistin's role in inflammation-induced insulin resistance, several therapeutic approaches warrant investigation:

• Antibody-based neutralization of circulating resistin during acute inflammatory conditions.

• Small molecule inhibitors that specifically block resistin's proinflammatory functions while preserving beneficial chaperone activities.

• Targeted approaches to modulate resistin expression in specific cell types, particularly macrophages.

• Combination therapies addressing resistin alongside other inflammatory mediators.

The tissue-specific effects of resistin on insulin signaling suggest that targeted approaches might avoid systemic side effects while addressing pathological resistin activity .

How might human resistin research inform our understanding of conditions beyond metabolic disease?

The chaperone-like properties and inflammation-modulating effects of human resistin suggest relevance to conditions including:

• Neurodegenerative diseases characterized by protein misfolding and inflammation.

• Cancer biology, where resistin has been implicated in tumor progression .

• Infectious diseases, particularly those involving macrophage-pathogen interactions.

• Aging-related conditions where cellular stress responses become dysregulated.

The unique position of resistin at the intersection of cellular stress and inflammation makes it a particularly interesting target for these diverse pathological contexts .