Recombinant Human Interleukin-20 protein (IL20) (Active)

What is the basic structure of Human IL-20?

Human IL-20 is synthesized as a 176 amino acid (aa) precursor with a 24 aa signal sequence and a 152 aa mature segment. Although it belongs to the IL-10 family, IL-20 functions as a monomer rather than the typical dimeric structure of other family members. There are no N-linked glycosylation sites, suggesting that the native molecule is not glycosylated. The protein shares less than 40% amino acid sequence identity with other IL-10 family members, positioning it as a distant relative within this cytokine group.

How does human IL-20 compare to mouse IL-20?

Mouse and human IL-20 share approximately 77% amino acid sequence identity in their mature segments, indicating substantial evolutionary conservation. This high degree of homology has important experimental implications, as human IL-20 demonstrates biological activity on mouse cells. This cross-species reactivity allows researchers to use human recombinant IL-20 in mouse models, facilitating translational research between these two mammalian systems.

What are the physicochemical properties of recombinant human IL-20?

What receptor complexes does IL-20 utilize for signaling?

IL-20 utilizes two distinct heterodimeric receptor complexes for cellular signaling. The first complex consists of IL-20 receptor alpha (IL-20Rα) and IL-20 receptor beta (IL-20Rβ). The second complex comprises IL-22 receptor (IL-22R) and IL-20Rβ. These receptor configurations create interesting signaling overlaps with other cytokines: the IL-20Rα/IL-20Rβ complex is shared with both IL-19 and IL-24, while the IL-22R/IL-20Rβ complex is shared with IL-24/mda-7. This receptor promiscuity suggests potential functional redundancy or synergy between these related cytokines in biological systems.

What is the tissue distribution of IL-20 receptors?

IL-20 receptors exhibit a tissue-specific distribution pattern that explains the selective action of this cytokine. The IL-20R complex is predominantly expressed in lungs, ovary, skin, and placenta. At the cellular level, the main targets of IL-20 are keratinocytes, endothelial cells, and adipocytes. This distribution pattern aligns with the reported biological functions of IL-20 in epidermal inflammation, wound healing, and potential roles in metabolic regulation, providing researchers with key target tissues for experimental investigation.

How does IL-20 activate intracellular signaling pathways?

IL-20 primarily signals through the Signal Transducer and Activator of Transcription 3 (STAT3) pathway in target cells. Upon binding to either of its receptor complexes, IL-20 triggers receptor dimerization and subsequent phosphorylation of STAT3 proteins. The activated STAT3 transcription factors then translocate to the nucleus, where they regulate gene expression. In keratinocytes, this signaling cascade promotes proliferation and inflammatory responses, highlighting a mechanistic link between IL-20 receptor engagement and its biological effects in epidermal inflammation. Researchers investigating IL-20 signaling should consider monitoring STAT3 phosphorylation as a proximal readout of receptor activation.

What is the optimal storage protocol for recombinant human IL-20?

For optimal stability of recombinant human IL-20, store the lyophilized product at -20°C to -80°C, where it remains stable for up to 12 months from the date of receipt. After reconstitution, the protein can be stored at 4°C for approximately one month. For longer storage of reconstituted protein (up to three months), aliquot and store at -20°C to -80°C to minimize freeze-thaw cycles. Each freeze-thaw cycle can significantly reduce protein activity, so it is imperative to prepare single-use aliquots when dividing the reconstituted protein for storage. Always centrifuge the vial before opening to ensure all material is at the bottom of the tube.

What is the recommended reconstitution procedure for lyophilized IL-20?

For optimal reconstitution of lyophilized IL-20, first centrifuge the vial to ensure all material is at the bottom. Gently pipet and wash down the sides of the vial with the reconstitution solution to ensure complete recovery of the protein. The recommended reconstitution concentration is 0.1 mg/ml using sterile water. After initial reconstitution, the solution can be further diluted into other aqueous buffers as required for specific experimental applications. Allow the protein to sit for at least 10 minutes at room temperature after adding the reconstitution solution to ensure complete solubilization before subsequent handling or dilution.

How can I confirm the activity of recombinant IL-20 in experimental systems?

The biological activity of recombinant human IL-20 can be verified through receptor binding assays or functional cellular responses. In receptor binding assays, immobilized recombinant human IL-20 binds to human IL-20Rβ in a dose-dependent manner, with an ED50 (effective dose for 50% binding) range of 1.3-10 μg/mL. For functional assays, researchers can monitor STAT3 phosphorylation in responsive cell lines like keratinocytes. Alternative readouts include proliferation assays with keratinocytes or multipotential hematopoietic progenitor cells, or measurement of proinflammatory mediator release from IL-20 receptor-expressing cells. When designing these assays, include appropriate positive controls and dose-response analyses to confirm specific IL-20-mediated effects.

What are the primary cellular sources of IL-20 production?

IL-20 is produced by several cell types with distinct tissue localization patterns. The primary cellular sources include activated keratinocytes in the skin and various immune cells including monocytes/macrophages, lymphocytes, and neutrophils. IL-20 expression is upregulated in response to inflammatory stimuli such as lipopolysaccharide (LPS), tumor necrosis factor (TNF), interleukin-1β (IL-1β), interleukin-17 (IL-17), and interleukin-22 (IL-22). This induction profile suggests that IL-20 acts within inflammatory cascades, potentially amplifying or modulating ongoing immune responses. In experimental design, researchers should consider these induction factors when studying IL-20 expression in cellular systems.

What role does IL-20 play in skin biology and pathology?

IL-20 serves as a critical regulator of keratinocyte function during epidermal inflammation. Through activation of the STAT3 signaling pathway, IL-20 stimulates keratinocyte proliferation and differentiation, contributing to epidermal remodeling in inflammatory skin conditions. The cytokine also promotes the release of proinflammatory mediators from keratinocytes, potentially establishing positive feedback loops in skin inflammation. Given these functions, IL-20 has been implicated in the pathogenesis of several inflammatory skin disorders, including psoriasis. Experimental models examining epidermal inflammation should consider IL-20 as a potential therapeutic target or biomarker for disease progression and treatment response.

How is IL-20 involved in cardiovascular pathology?

IL-20 has emerged as a significant factor in cardiovascular pathology, particularly in atherosclerosis. The cytokine is expressed in atherosclerotic plaques from patients with established disease, suggesting localized production within vascular lesions. In experimental models, IL-20 promotes atherosclerosis development in apolipoprotein E-deficient mice, a standard model for studying this disease. The mechanisms may involve modulation of endothelial cell function, inflammatory responses, and potentially lipid metabolism, given that adipocytes are among the cellular targets of IL-20. Researchers investigating vascular inflammation should consider incorporating IL-20 expression analysis in their experimental designs and evaluating IL-20-blocking strategies in intervention studies.

How can I address inconsistent results when using IL-20 in cell culture systems?

Inconsistent results with IL-20 in cell culture experiments can stem from several factors. First, verify receptor expression in your target cells, as IL-20 responsiveness depends on expression of either IL-20Rα/IL-20Rβ or IL-22R/IL-20Rβ complexes. Second, ensure the recombinant IL-20 is active by testing on positive control cells with known receptor expression. Third, optimize the concentration range, as biological responses may follow a bell-shaped curve. Fourth, consider the timing of IL-20 treatment, as receptor expression and signaling pathways can fluctuate with cell cycle and differentiation state. Finally, examine culture conditions including serum levels, cell density, and the presence of other cytokines that might synergize with or antagonize IL-20 effects. Systematic troubleshooting of these variables should help establish consistent IL-20 responses in your experimental system.

What approaches can resolve discrepancies between in vitro and in vivo IL-20 studies?

When facing discrepancies between in vitro and in vivo IL-20 studies, several methodological approaches can help reconcile the differences. First, evaluate the complexity of receptor expression across different tissues in vivo compared to simplified cell culture systems. Second, consider the pharmacokinetics of IL-20 in vivo, including circulation time, tissue distribution, and potential neutralization by soluble receptors or antibodies. Third, examine the influence of the broader cytokine milieu in vivo, which may modulate IL-20 effects through receptor competition or signaling pathway cross-talk. Fourth, assess differences in cellular differentiation states between cultured cells and their in vivo counterparts. Finally, develop ex vivo models using primary cells or tissue explants that better recapitulate the in vivo environment while allowing more controlled experimental manipulation. These approaches can bridge the gap between isolated cellular systems and the integrated physiological context.

How should researchers interpret conflicting data on IL-20's role in hematopoiesis?

Interpreting conflicting data regarding IL-20's role in hematopoiesis requires careful consideration of several experimental variables. First, analyze the specific hematopoietic progenitor populations studied, as IL-20 may affect distinct progenitor subsets differently. Second, examine the cytokine concentrations used, as dose-dependent effects may explain seemingly contradictory outcomes. Third, consider the microenvironmental context, including the presence of other growth factors that might synergize with or antagonize IL-20. Fourth, evaluate the readouts used to measure hematopoietic effects (proliferation, differentiation, survival, or functional capacity). Fifth, assess potential differences between species or between normal and malignant hematopoiesis. Finally, consider genetic or epigenetic variability in IL-20 receptor expression or downstream signaling components. Systematically analyzing these variables across conflicting studies can help identify conditional factors that determine IL-20's effects on hematopoietic cells and resolve apparent contradictions in the literature.