Recombinant Chicken Melatonin receptor type 1C

What is Melatonin Receptor Type 1C and how does it differ from other melatonin receptor subtypes?

Melatonin Receptor Type 1C (MTNR1C/Mel1c) is one of three melatonin receptor subtypes found in non-mammalian vertebrates. It belongs to the G-protein-coupled receptor (GPCR) superfamily and shares specific short amino acid sequences with other melatonin receptors (MT1 and MT2). Unlike the other subtypes, Mel1c is not found in therian mammals, where it evolved into GPR50 - an orphan receptor that does not bind melatonin . In chicken, MTNR1C is encoded by the MTNR1C gene and functions in the melatonin signaling pathway, which regulates various biological functions through melatonin binding .

What are the molecular characteristics of recombinant chicken MTNR1C?

Recombinant chicken MTNR1C produced in E. coli expression systems typically has the following characteristics:

• Predicted molecular weight: 36.1 kDa

• Accurate molecular weight (observed in SDS-PAGE): 39 kDa

• Typically includes N-terminal His and GST tags

• Expressed residues: Generally Gly293~Leu346 of the native protein

• Isoelectric point: 11.0

• High purity (>90% by SDS-PAGE)

• Subcellular location in native form: Membrane protein

What expression systems are most effective for producing functional recombinant chicken MTNR1C?

For research purposes, E. coli expression systems are predominantly used for recombinant chicken MTNR1C production . This prokaryotic expression system allows for:

• High yield production of the receptor fragment

• Addition of fusion tags (His, GST) to facilitate purification and detection

• Expression of specific domains rather than the complete transmembrane protein

• Protein that can be used as a positive control or immunogen

For functional studies requiring properly folded transmembrane domains and post-translational modifications, mammalian expression systems like CHO cells or COS7 cells have been proven effective, as demonstrated in studies with other Mel1c receptors from species like Xenopus laevis .

What are the optimal storage and reconstitution conditions for maintaining recombinant MTNR1C stability?

For optimal stability and activity of recombinant chicken MTNR1C:

Reconstitution:

• Use 10 mM PBS (pH 7.4) to a concentration of 0.1-1.0 mg/mL

• Do not vortex during reconstitution to prevent protein denaturation

• Gentle mixing is recommended

Storage:

• Short-term storage (up to 1 month): 2-8°C

• Long-term storage (up to 12 months): -80°C after aliquoting

• Avoid repeated freeze/thaw cycles

• Lyophilized protein exhibits greater stability than reconstituted protein

Accelerated thermal degradation tests have shown less than 5% loss when incubated at 37°C for 48 hours under appropriate conditions, indicating good stability of the recombinant protein .

How can researchers effectively validate the binding activity of recombinant chicken MTNR1C?

Several methodological approaches can be employed to validate binding activity:

• Radioligand binding assays:

  • Use 2-[125I]-iodomelatonin as the radioligand

  • Include cold melatonin (10⁻⁶ M) to define non-specific binding

  • Incubate at 25-37°C for 90 minutes to reach equilibrium

  • Calculate specific binding by subtracting non-specific binding from total binding

• Competition binding assays:

  • Use fixed concentration of 2-[125I]-iodomelatonin (80-100 pM)

  • Test competition with varying concentrations of unlabeled melatonin and analogs

  • Compare binding profiles with known melatonin receptor subtypes

• Functional assays in expression systems:

  • Measure inhibition of forskolin-stimulated cAMP formation

  • Assess protein kinase A activity modulation

  • Analyze G-protein coupling using pertussis toxin sensitivity tests

What signaling pathways are activated by chicken MTNR1C and how can they be measured?

Chicken MTNR1C, like other melatonin receptors, primarily couples to multiple signaling pathways:

• cAMP/PKA pathway:

  • Typically inhibits forskolin-stimulated cAMP formation

  • Reduces protein kinase A activity

  • Can be measured using ELISA-based cAMP detection kits or reporter gene assays

• MAPK pathway activation:

  • Increases phosphorylation of MEK1/2 and ERK1/2

  • Activates JNK via both pertussis toxin-sensitive and -insensitive G proteins

  • Can be measured using phospho-specific antibodies in Western blotting

• Cell-specific pathways:

  • In melanophores (demonstrated with Xenopus Mel1c): pigment aggregation response

  • In rod photoreceptors: modulation of photoreceptor responsiveness

  • These functional responses can be measured using specialized cellular assays

Signaling outcomes appear to be highly cell- and tissue-dependent, emphasizing the impact of system bias on the functional outcome of receptor activation .

How has MTNR1C evolved across vertebrate species and what insights does this provide for research?

Evolutionary analysis of MTNR1C provides significant insights:

• Phylogenetic distribution:

  • Present in non-mammalian vertebrates (birds, amphibians, fish)

  • Absent in therian mammals (placental and marsupial)

  • Present in monotremes (platypus) as a functional melatonin receptor

  • Suggests that loss of melatonin binding ability evolved after the divergence of monotremes, less than 190 million years ago

• Transformation in mammals:

  • In therian mammals, evolved into GPR50

  • Lost melatonin binding capacity while maintaining structural similarity

  • GPR50 can regulate MT1 receptor activity through dimerization

• Functional conservation:

  • Studies comparing platypus Mel1c with bird and Xenopus Mel1c show conserved pharmacological profiles

  • Chicken and Xenopus Mel1c receptors both couple to inhibitory G-proteins

This evolutionary perspective has implications for using chicken MTNR1C as a model to understand ancestral melatonin receptor functions that may have been lost or modified in mammals.

What structural features differentiate chicken MTNR1C from mammalian melatonin receptors?

Key structural distinctions between chicken MTNR1C and mammalian melatonin receptors include:

• Binding pocket differences:

  • Chicken MTNR1C maintains residues critical for melatonin binding that are altered in mammalian GPR50

  • Pharmacological profile of chicken MTNR1C makes it resemble human MT1 more than MT2

• Sequence variations:

  • Chicken MTNR1C shares only partial sequence homology with mammalian MT1 and MT2 receptors

  • The receptor's C-terminal domain (Gly293~Leu346) contains unique regulatory elements

• Signaling interfaces:

  • Different G-protein coupling interface regions that influence signaling specificity

  • Unique dimerization potential with other GPCRs

Understanding these structural differences can help researchers design selective ligands and predict how different melatonin analogs might interact with each receptor subtype.

How can recombinant chicken MTNR1C be utilized in developmental and reproductive studies?

Recombinant chicken MTNR1C has several applications in developmental and reproductive research:

• Egg production studies:

  • MTNR1C gene has significant associations with egg production traits in chickens

  • The GG genotype of MTNR1C correlates with higher egg numbers (NE360d) and egg production per month (E/M) compared to the AA genotype

  • Research data shows GG genotypes were associated with 195.61 eggs and 16.30 eggs per month, versus 181.09 eggs and 15.09 eggs per month for AA genotypes

• Photoperiodic regulation studies:

  • MTNR1C mediates melatonin's effects on photoperiodic responses

  • Can be used to investigate how melatonin signaling impacts seasonal reproduction

  • Serves as a comparative model to understand how non-mammalian vertebrates regulate reproduction in response to photoperiod

• Genetic association studies:

  • PCR-RFLP genotyping of the MTNR1C gene can be used to investigate associations with various production traits

  • Transgenic expression systems can help elucidate receptor function in different tissues

What techniques are most effective for studying MTNR1C expression and localization in chicken tissues?

For optimal investigation of MTNR1C expression and localization:

• Gene expression analysis:

  • RT-PCR for detecting tissue-specific expression patterns

  • qPCR for quantitative comparison across tissues and developmental stages

  • In situ hybridization for spatial localization within tissues

• Protein detection and localization:

  • Immunohistochemistry using antibodies against chicken MTNR1C

  • Western blotting for protein expression levels across tissues

  • For recombinant proteins with tags, anti-tag antibodies (anti-His, anti-GST) can be used

• Functional expression systems:

  • Transgenic expression of MTNR1C-GFP fusion proteins

  • Mel1c-GFP fusion proteins can be visualized using confocal microscopy

  • Facilitates detection of subcellular localization (e.g., in rod photoreceptor inner segments as demonstrated with Xenopus Mel1c)

• Receptor autoradiography:

  • Using 2-[125I]-iodomelatonin to map receptor distribution

  • Competitive binding with unlabeled melatonin to confirm specificity

How do heterologous expression systems affect the pharmacological properties of recombinant chicken MTNR1C?

Expression system selection can significantly impact the pharmacological characteristics of recombinant chicken MTNR1C:

• E. coli expression limitations:

  • Lacks post-translational modifications required for full receptor functionality

  • Primarily useful for producing receptor fragments for antibody production and binding studies

  • Cannot reproduce the membrane environment necessary for proper receptor conformation

• Mammalian cell effects:

  • Different mammalian cell lines (CHO, COS7, NIH-3T3) may express varying levels of G-proteins and signaling components

  • The presence of endogenous GPCRs can lead to heterodimer formation, altering signaling properties

  • System bias can significantly influence pharmacological outcomes, making comparative studies challenging

• Specialized functional systems:

  • Xenopus melanophores provide a specialized system for functional studies (pigment aggregation)

  • High receptor densities in certain systems may expose partial agonist activities not observed in native tissues with lower receptor expression

Researchers should carefully select expression systems based on their specific research questions and be aware of the potential system-dependent variations in receptor pharmacology.

What are the emerging approaches for studying receptor-protein interactions of chicken MTNR1C?

Cutting-edge methodologies for investigating MTNR1C protein interactions include:

• Receptor dimerization studies:

  • BRET/FRET techniques to detect receptor homodimerization or heterodimerization with other GPCRs

  • Proximity ligation assays for detecting protein-protein interactions in native tissues

  • Co-immunoprecipitation studies using tagged receptors

• Signaling complex characterization:

  • Proteomic approaches to identify proteins that interact with the receptor

  • Analysis of receptor-associated proteins including heterodimeric partners that may contribute to system bias

  • Investigation of regulators of G-protein signaling (RGS) that modulate receptor function

• Structural studies:

  • Cryo-EM or X-ray crystallography of purified receptors in various activation states

  • Molecular dynamics simulations to predict ligand binding and receptor activation

  • Comparative modeling with related receptors of known structure

• Genetic modification approaches:

  • CRISPR/Cas9 gene editing to study receptor function in vivo

  • Transgenic expression of mutant receptors to identify critical residues for ligand binding and signaling

What strategies can overcome stability and solubility issues with recombinant chicken MTNR1C?

Researchers frequently encounter stability and solubility challenges with recombinant membrane proteins like MTNR1C. These can be addressed through:

• Buffer optimization:

  • Use PBS (pH 7.4) containing stabilizers like 0.01% SKL and 5% Trehalose

  • Avoid detergents that may compromise structural integrity unless necessary for solubilization

  • Consider testing different buffer compositions for specific applications

• Handling procedures:

  • Avoid vortexing during reconstitution

  • Centrifuge tubes before opening to collect all material

  • Use gentle mixing techniques to prevent protein denaturation

• Storage recommendations:

  • Aliquot reconstituted protein to minimize freeze-thaw cycles

  • For frequent use, store at 2-8°C for up to one month

  • For long-term storage, maintain at -80°C in small aliquots

• Expression region selection:

  • Focus on expressing stable domains (e.g., Gly293~Leu346) rather than the full receptor

  • Include fusion partners (GST, MBP) known to enhance solubility

  • Consider codon optimization for the expression host

How can researchers differentiate between MTNR1C and other melatonin receptor subtypes in binding and functional studies?

Distinguishing between melatonin receptor subtypes requires specialized approaches:

• Selective ligands:

  • Use 4-phenyl-2-propionamidotetraline (4P-PDOT) and luzindole which are selective for mammalian MT2 but show poor competition for Mel1c

  • Compare binding profiles with known subtype-selective compounds

  • GR128107 has different activities at different receptor subtypes (partial agonist at Mel1c)

• Pharmacological profiling:

  • Conduct detailed concentration-response studies with a range of melatonin analogs

  • The pharmacological profile of chicken MTNR1C more closely resembles human MT1 than MT2

  • Analyze both binding affinity and functional responses to create comprehensive pharmacological fingerprints

• Molecular techniques:

  • Use receptor-specific primers in PCR to distinguish between receptor subtypes at the mRNA level

  • Employ subtype-specific antibodies when available

  • Perform knockout/knockdown studies to confirm receptor identity in functional assays

• Species comparison:

  • Compare responses to those observed with cloned receptors from other species

  • Platypus Mel1c maintains melatonin binding while mammalian GPR50 does not

  • Consider evolutionary relationships when interpreting binding and signaling data

What are the emerging areas of research involving chicken MTNR1C in comparative endocrinology?

Several promising research directions are developing:

• Comparative signaling mechanisms:

  • Investigating how MTNR1C signaling differs from mammalian MT1/MT2 receptors

  • Understanding how receptor-specific signaling contributes to species-specific physiological responses

  • Exploring the evolutionary significance of signal transduction differences

• Photoperiodic regulation:

  • Elucidating the role of MTNR1C in mediating seasonal changes in reproduction

  • Comparing MTNR1C mechanisms with mammalian melatonin receptors in photoperiodic species

  • Investigating tissue-specific expression patterns in response to changing day length

• Developmental biology:

  • Studying the ontogeny of MTNR1C expression during embryonic and post-hatching development

  • Investigating potential roles in neural development and sensory system maturation

  • Comparing with mammalian systems to understand the evolutionary consequences of GPR50 evolution

How might genetic variations in chicken MTNR1C inform selective breeding strategies for improved egg production?

Research on MTNR1C genetic variations offers insights for poultry breeding:

• Genotype-phenotype correlations:

  • GG genotypes of MTNR1C are associated with higher egg numbers (NE360d) and monthly production (E/M)

  • AA genotypes correlate with higher egg weights (WE360d)

  • These associations provide potential genetic markers for selective breeding programs

• Combined genetic approaches:

  • MTNR1C polymorphisms can be studied alongside other egg production-related genes like NPY

  • The combined effect of MTNR1C and NPY genotypes may provide more comprehensive selection criteria

  • NPY's BB and Bb genotypes show significantly higher egg numbers than bb genotypes

• Population-specific considerations:

  • Genetic associations may vary between different chicken breeds and populations

  • Studies in Thai indigenous chickens show specific associations that might differ in other breeds

  • Comprehensive genotyping across diverse populations can identify the most consistent markers

These research directions highlight the potential for using molecular genetic information about MTNR1C to enhance traditional breeding approaches for improving egg production traits in chickens.