C1QTNF3 Human

What is C1QTNF3 and what are its structural characteristics?

C1QTNF3 is a protein-coding gene located on chromosome 5 that encodes the Complement C1q tumor necrosis factor-related protein 3. It is also known as C1ATNF3, CORCS, CORS, CORS-26, CORS26, and CTRP3 . C1QTNF3 belongs to the C1q/TNF-related protein family and shares sequence homology with adiponectin, an insulin-sensitizing and anti-inflammatory adipokine . The protein contains a globular C1q domain and a collagen-like domain, which are characteristic of the C1QTNF family members.

What is the tissue distribution pattern of C1QTNF3?

C1QTNF3 is widely distributed across multiple tissues in humans and rodents. It is highly expressed in adipose tissue and has also been detected in cartilage, kidney, placenta, pancreas, small intestine, colon, brain, thymus, and ovary . At the protein level, expression has been documented in the heart, liver, muscle, and kidney . Within specific tissues, such as the ovary, C1QTNF3 is predominantly expressed in granulosa cells and oocytes of growing follicles, with modest expression in the granulosa cells of atretic follicles and in luteal cells .

What biological functions has C1QTNF3 been implicated in?

C1QTNF3 participates in multiple biological processes including:

• Regulation of glucose and lipid metabolism

• Modulation of inflammatory responses

• Promotion of cell proliferation and differentiation

• Reduction of cell apoptosis through decreased activated CASP3/7 activity

• Enhancement of adiponectin secretion from adipocytes

• Attenuation of diet-induced hepatic steatosis

• Ovarian folliculogenesis through AKT/mTOR pathway activation

• Macrophage recruitment and polarization in various tissues

What are the established methods for measuring C1QTNF3 in human samples?

Researchers can quantify C1QTNF3 using several validated approaches:

Enzyme-Linked Immunosorbent Assay (ELISA):

• Commercial DuoSet ELISA development kits are available for measuring natural and recombinant human C1QTNF3 in cell culture supernatants, serum, and plasma samples

• For complex matrices like serum and plasma, specific diluents should be evaluated prior to use

Gene Expression Analysis:

• Reverse transcription-polymerase chain reaction (RT-PCR) and quantitative real-time PCR (qPCR) are commonly used to measure C1QTNF3 transcript abundance

• Standard cycling conditions include 5 minutes at 95°C, followed by 40-45 cycles of 15 seconds at 95°C and 60 seconds at 60°C

Protein Detection in Tissues:

• Immunohistochemistry and immunofluorescence can be used to visualize C1QTNF3 protein localization in tissue sections

• Western blotting can be employed for semi-quantitative protein analysis

How should researchers approach studying C1QTNF3 function in cell culture models?

When designing in vitro experiments to investigate C1QTNF3 function, consider the following methodology:

Recombinant Protein Treatment:

• Use recombinant C1QTNF3 protein dissolved in appropriate buffer (e.g., Tris-HCL 10 mM, EDTA 1 mM, glycerol 10% at pH 8)

• Treatment concentration of 1μg/ml has been used effectively in functional assays

Cell Types for Study:

• Choose relevant cell types based on research questions:

  • Macrophages (for immune modulation studies)

  • Adipocytes (for metabolic studies)

  • Granulosa cells (for reproductive biology research)

  • Fibroblasts (for tissue remodeling studies)

Functional Readouts:

• Proliferation assays

• Apoptosis assessment (e.g., activated CASP3/7 activity)

• Signaling pathway analysis (Western blotting for AKT/mTOR/p70S6K/4EBP1 phosphorylation)

• Metabolic assessment (Seahorse XF analyzer for mitochondrial function)

• Expression of downstream targets (e.g., CCND2 for cell cycle regulation)

Control Considerations:

• Include appropriate buffer-only controls to account for potential buffer effects

• Consider including positive controls (e.g., known pathway activators)

What approaches can be used to study C1QTNF3 function in animal models?

For in vivo studies of C1QTNF3, researchers should consider:

Neutralization Studies:

• Anti-C1QTNF3 antibodies can be administered intraperitoneally (0.5 mg/kg every second day)

• For tissue-specific effects, localized administration may be appropriate (e.g., ovarian intrabursal administration)

Genetic Models:

• Knockout or transgenic overexpression models can provide insights into physiological functions

Tissue Collection and Analysis:

• Store tissue samples at -80°C until analysis

• For folliculogenesis studies, follicles of different sizes can be isolated and analyzed separately

Physiological Challenges:

• High-fat diet models can be used to study metabolic aspects

• Gonadotropin administration to study hormonal regulation

• Tumor transplantation models to study cancer-related effects

How does C1QTNF3 influence macrophage function and inflammatory processes?

C1QTNF3 exhibits complex immunomodulatory functions that are context-dependent:

Macrophage Recruitment:

• C1QTNF3 exerts chemotactic actions on both M1- and M2-polarized macrophages in vitro

• Administration of C1QTNF3 neutralizing antibodies inhibits macrophage accumulation in tumor-associated inguinal adipose tissue

Macrophage Polarization:

• C1QTNF3 treatment of M2-type macrophages stimulates the ERK and Akt pathways

• This stimulation is associated with increased M1-like polarization as evidenced by:

  • Increased expression of M1-macrophage markers

  • Increased production of nitric oxide

  • Reduced oxygen consumption

  • Increased glycolysis

Anti-inflammatory Effects:

• C1QTNF3 can inhibit LPS-induced inflammatory responses in fibroblasts, adipocytes, and macrophages

• C1QTNF3 knockout mice are more susceptible to collagen-induced arthritis, suggesting a protective role against inflammation in certain contexts

What is known about C1QTNF3 regulation in metabolic disorders?

C1QTNF3 expression is altered in several metabolic conditions:

Obesity and Insulin Resistance:

• Visceral adipose tissue C1QTNF3 levels are reduced in obesity/insulin resistant conditions

• Patients with type-2 diabetes have lower circulating C1QTNF3 levels

Therapeutic Interventions:

• Metformin treatment increases serum C1QTNF3 levels in women with polycystic ovary syndrome (PCOS)

• Administration or transgenic overexpression of C1QTNF3 attenuates diet-induced hepatic steatosis and lowers glucose levels in Ob/Ob mice

Relationship with Other Metabolic Regulators:

• C1QTNF3 has been shown to increase the secretion of adiponectin from adipocytes

• C1QTNF3 is co-regulated with several macrophage markers and chemokines in adipose tissue during tumor progression

How does C1QTNF3 contribute to ovarian function and folliculogenesis?

Recent research has revealed important roles for C1QTNF3 in ovarian physiology:

Expression Pattern:

• C1QTNF3 transcript abundance is higher in large follicles than in small follicles

• C1QTNF3 expression is under gonadotropin influence

• C1QTNF3 is detected mainly in granulosa cells and oocytes of growing follicles

Hormonal Regulation:

• Excess androgen significantly decreases C1QTNF3 expression in ovaries in vivo and in granulosa cells in vitro

• This may have implications for conditions characterized by hyperandrogenism such as PCOS

Functional Significance:

• Recombinant C1QTNF3 protein accelerates the weight gain of ovarian explants and the growth of preantral follicles induced by follicle stimulating hormone (FSH) in vitro

• C1QTNF3 stimulates granulosa cell proliferation and reduces apoptosis

• Ovarian intrabursal administration of C1QTNF3 antibody delays gonadotropin-induced antral follicle development in vivo

Signaling Mechanisms:

• C1QTNF3 initiates AKT, mTOR, p70S6K and 4EBP1 phosphorylation in ovarian cells

• It increases CCND2 expression (promoting cell cycle progression)

• It reduces cleaved CASP3 levels (inhibiting apoptosis)

What are the technical considerations for measuring C1QTNF3 in clinical samples?

Sample Collection and Processing:

• Blood samples should be collected using standardized protocols to minimize variability

• Serum or plasma should be promptly separated and stored at -80°C

• Avoid repeated freeze-thaw cycles which may degrade the protein

Assay Selection:

• Commercial ELISA kits provide standardized methods for C1QTNF3 quantification

• The suggested diluent is suitable for most cell culture supernatants, but specific diluents should be evaluated for complex matrices like serum and plasma

Potential Confounding Factors:

• Medications (particularly those affecting metabolism) may influence C1QTNF3 levels

• Time of day, fasting status, and recent exercise may affect circulating levels

• Age, sex, and comorbidities should be considered in data interpretation

Quality Control:

• Include appropriate standards and controls in each assay

• Consider batch effects when analyzing samples collected at different times

How can researchers effectively compare results across different experimental models?

Standardization Approaches:

• Use consistent protein sources (e.g., same recombinant C1QTNF3 preparation) across experiments

• Adopt standardized protocols for cell culture, animal models, and analytical methods

• Include common reference samples when performing multiple experiments

Cross-Model Validation:

• Validate findings from cell culture in animal models when possible

• Confirm molecular mechanisms across different cell types

• When transitioning from animal to human studies, account for species differences

Data Normalization:

• For gene expression studies, carefully select appropriate housekeeping genes for normalization

• For protein studies, consider normalization to total protein content or specific reference proteins

• When comparing across tissues, acknowledge tissue-specific baseline expression levels

What are potential therapeutic applications of C1QTNF3 research?

Metabolic Disorders:

• C1QTNF3 supplementation or upregulation might represent a therapeutic strategy for type 2 diabetes, given its beneficial effects on glucose metabolism and its reduced levels in diabetic patients

• The ability of C1QTNF3 to attenuate diet-induced hepatic steatosis suggests potential applications in non-alcoholic fatty liver disease

Inflammatory Conditions:

• The anti-inflammatory properties of C1QTNF3 observed in certain contexts might be harnessed for conditions characterized by excessive inflammation

• Understanding the context-dependent effects on macrophage polarization could lead to nuanced immunomodulatory approaches

Reproductive Medicine:

• The role of C1QTNF3 in folliculogenesis suggests potential applications in assisted reproductive technologies

• The reduced C1QTNF3 levels in women with PCOS indicates it might be a therapeutic target for this condition

What methodological approaches will advance understanding of C1QTNF3 receptor biology?

Receptor Identification and Characterization:

• LAMP-1 and LIMP II have been reported as putative receptors of C1QTNF3

• Further validation through techniques such as co-immunoprecipitation, proximity ligation assays, and FRET/BRET approaches

• Receptor binding assays to determine binding kinetics and specificity

Signaling Pathway Elucidation:

• Phospho-proteomic approaches to comprehensively map signaling events triggered by C1QTNF3

• Use of specific pathway inhibitors to delineate primary vs. secondary signaling events

• CRISPR-based screening to identify novel components of C1QTNF3 signaling

Receptor Tissue Distribution:

• Single-cell RNA sequencing to map receptor expression across tissues and cell types

• In situ hybridization combined with immunohistochemistry to correlate mRNA and protein expression

• Functional assays in different cell types to determine tissue-specific signaling outcomes

Table 1: Tissue Distribution and Expression Patterns of C1QTNF3

Table 2: C1QTNF3 Signaling Pathways and Functional Outcomes