Recombinant Mouse Lysophosphatidic acid receptor 6 (Lpar6)
Description
Gene and Protein Nomenclature
Recombinant Mouse Lysophosphatidic acid receptor 6 is encoded by the Lpar6 gene, which has several alternative identifiers in scientific literature and databases. The gene is also known by the synonyms P2ry5, P2y5, and 2610302I02Rik, reflecting its historical classification within the purinergic receptor family before its role as an LPA receptor was established . This nomenclature diversity highlights the evolving understanding of this receptor's functions and ligand specificity over time. The connection to purinergic receptors is particularly notable as it places Lpar6 in the non-EDG (Endothelial Differentiation Gene) family of lysophospholipid receptors, distinguishing it structurally and functionally from classical LPA receptors (LPAR1-3) .
Production and Purification
Recombinant Mouse Lpar6 protein is typically produced using cell-free expression systems, which allow for efficient production of functional membrane proteins. Commercial preparations of this recombinant protein generally achieve a purity level of 85% or greater as determined by SDS-PAGE analysis . The availability of this purified recombinant protein has been instrumental in facilitating structural and functional studies of Lpar6. Alternative expression systems including E. coli, yeast, baculovirus, and mammalian cell-based systems can also be employed for production of partial Lpar6 proteins, offering flexibility for different experimental requirements .
Protein Structure and Ligand Binding
Recent cryo-electron microscopy studies have provided breakthrough insights into the structural aspects of LPAR6, revealing its molecular architecture when bound to its natural ligand LPA. While these studies specifically examined human LPAR6, they offer valuable insights applicable to mouse Lpar6 given the conserved functional domains between species . The structural data reveals that LPA binding to LPAR6 involves its charged head forming an extensive polar interaction network with key residues located on the extracellular side of transmembrane helices 5-6 and the extracellular loop 2 . This binding mechanism differs significantly from that observed in LPAR1, highlighting the unique structural characteristics of non-EDG family LPA receptors like LPAR6 .
Role in Vascular Function
Mouse Lpar6 plays a significant role in vascular development and function, as evidenced by studies using Lpar6-deficient (Lpar6−/−) mice. These knockout mice display a marked reduction in vascular network density correlated with decreased branching in the vascular system . Furthermore, while Lpar6-deficient mice maintain normal blood pressure and heart rate under basal conditions, they exhibit significantly attenuated pressor responses to vasoactive compounds including phenylephrine and norepinephrine . This impaired vasoactivity suggests that Lpar6 contributes to normal vascular tone regulation and vascular reactivity to autonomic stimuli.
LPA Signaling and Blood Pressure Regulation
Lpar6 serves as a key mediator in LPA-induced hypertensive responses. In experimental models, Lpar6-deficient mice demonstrate impaired pressor responses to LPA, particularly at higher dosages . Interestingly, while responses to lower LPA dosages (0.014 mg/kg) remain largely intact in these mice, the hypertensive effects of higher LPA concentrations are significantly blunted . This suggests a dose-dependent role for Lpar6 in LPA-mediated blood pressure regulation, potentially involving different signaling thresholds or receptor reserve dynamics.
Role in Hair Development and Growth
One of the most well-characterized functions of LPAR6/Lpar6 across species is its critical role in hair growth and development. Mutations in human LPAR6 (P2RY5) cause a rare inherited form of hair loss called hypotrichosis simplex, indicating its essential function in normal hair follicle development and maintenance . The conservation of this function across species is demonstrated by the fact that LPAR6 mutations are responsible for the distinctive short, woolly hair characteristic of the Cornish Rex cat breed . While mouse-specific hair phenotypes related to Lpar6 mutations aren't explicitly detailed in the search results, the conserved nature of this receptor's role in hair biology suggests similar functions exist in mice.
G-Protein Interactions
Recent structural studies have significantly advanced our understanding of how LPAR6 couples to G-proteins to initiate downstream signaling cascades. The cryo-electron microscopy structure of human LPAR6 has been resolved in complex with mini G13 and Gq proteins, providing detailed insights into the molecular interactions that facilitate signal transduction . These structures reveal the specific conformational changes that occur upon LPA binding and how these alterations promote coupling with different G-protein subtypes. The principles of G-protein coupling identified in these studies likely apply to mouse Lpar6 as well, given the conserved nature of GPCR signaling mechanisms across mammalian species.
Signaling Mechanisms and Regulatory Pathways
The distinctive structural features of Lpar6 suggest unique signaling properties compared to other LPA receptors. The substitution of key residues in conserved motifs, such as the DPxxY motif instead of NPxxY, potentially alters the receptor's activation kinetics and downstream signaling preferences . The functional consequences of these structural differences are evident in the phenotypes observed in Lpar6-deficient mice, particularly regarding vascular responses. These mice display normal blood pressure under basal conditions but show impaired responses to both LPA and classical vasoconstrictors like phenylephrine and norepinephrine, suggesting Lpar6 signaling contributes to fundamental aspects of vascular smooth muscle contraction .
Therapeutic Potential
The involvement of Lpar6 in vascular function and hair growth regulation suggests potential therapeutic applications in various conditions. Understanding the molecular mechanisms of Lpar6 function could inform the development of targeted interventions for vascular disorders or hair loss conditions . The recent elucidation of LPA binding mechanisms and G-protein coupling principles for LPAR6 provides a foundation for structure-based drug design approaches . As stated in recent research, "The structural information revealed by our study lays the groundwork for understanding LPAR6 signaling and provides a rational basis for designing compounds targeting LPAR6" .
Product Specs
Note: While we prioritize shipping the format currently in stock, we understand your specific requirements. Please specify your preferred format in your order notes, and we will do our best to fulfill your request.
Note: All protein shipments include standard blue ice packs. If dry ice shipping is preferred, please communicate this in advance as additional fees will apply.
Generally, liquid forms have a shelf life of 6 months at -20°C/-80°C. Lyophilized forms have a shelf life of 12 months at -20°C/-80°C.
Target Background
- Elevated serum ATX levels in hepatic encephalopathy may activate the LPA-LPA6-G12/13-Rho pathway in brain capillary endothelial cells. PMID: 29778535
Q&A
What is Lysophosphatidic acid receptor 6 (LPAR6) and what are its primary functions?
LPAR6 is a G protein-coupled receptor that mediates the biological effects of lysophosphatidic acid (LPA). It plays critical roles in cellular morphology, signaling pathways, and tissue development. In the central nervous system, LPAR6 functions as a negative modulator of myelination-associated gene expression in oligodendrocytes (OLGs) . Outside the nervous system, LPAR6 is highly expressed in epithelial cells and hair follicles, where it mediates cAMP accumulation and Rho-dependent cellular morphological changes . The receptor has been implicated in various physiological and pathological processes, including hair growth, cancer cell proliferation, and potentially multiple sclerosis pathophysiology .
What are the most effective methods for generating recombinant mouse LPAR6 for research purposes?
For generating recombinant mouse LPAR6, researchers typically employ molecular cloning techniques to isolate the LPAR6 gene from mouse tissue or cDNA libraries, followed by insertion into appropriate expression vectors. The process generally involves:
-
PCR amplification of the mouse LPAR6 coding sequence using gene-specific primers
-
Cloning into a mammalian expression vector containing a strong promoter and appropriate selection markers
-
Verification of the construct through sequencing
-
Transfection into a suitable cell line (commonly HEK293 or CHO cells) for protein expression
-
Purification of the recombinant protein using affinity chromatography
For functional studies, researchers frequently use LPAR6-expressing stable cell lines rather than purified recombinant protein. These can be generated by transfecting cells with LPAR6-encoding expression vectors followed by antibiotic selection. For example, studies have used LPAR6-expressing cell systems to characterize receptor-ligand interactions and downstream signaling pathways .
What are the advantages and limitations of LPAR6 knockout mouse models?
Advantages:
-
Allow assessment of LPAR6 function in a physiologically relevant context
-
Enable investigation of developmental roles and tissue-specific functions
-
Facilitate the study of compensatory mechanisms involving other LPA receptors
-
Provide valuable insights into disease mechanisms when combined with disease models
Limitations:
-
Potential for developmental compensation by other LPA receptors, especially LPAR1
-
Challenge in distinguishing direct from indirect effects of LPAR6 deletion
-
Possible embryonic lethality if LPAR6 has critical developmental functions
-
Need for tissue-specific knockout approaches to avoid systemic effects
How does LPAR6 modulate oligodendrocyte maturation and myelination?
LPAR6 functions as a negative modulator of oligodendrocyte (OLG) maturation and myelination-associated gene expression . Research indicates that:
-
Cell surface accessibility of LPAR6 is restricted to the earlier maturation stages of differentiating OLGs
-
LPAR6 knockout mice exhibit precocious OLG maturation, suggesting that LPAR6 signaling normally delays or regulates the timing of this process
-
LPA signaling via LPAR6 appears to attenuate gene expression associated with OLG maturation
This regulatory role of LPAR6 likely serves a developmental purpose by ensuring proper timing and coordination between neural circuit formation and myelination processes. The temporal regulation of myelination is crucial for synchronized neural communication, and LPAR6 appears to be part of the complex signaling network that orchestrates this developmental sequence .
What evidence suggests LPAR6 as a potential therapeutic target for multiple sclerosis?
Multiple lines of evidence support the potential of LPAR6 as a therapeutic target for multiple sclerosis (MS):
-
LPAR6 protein levels appear elevated in MS brain samples compared to controls
-
As a negative regulator of oligodendrocyte maturation, persistent LPAR6 expression and signaling in MS may inhibit myelin repair processes
-
Targeting LPAR6 could potentially remove this inhibitory signal and promote remyelination in MS lesions
Experimental evidence supporting this therapeutic potential includes:
-
Functional characterization of a novel small molecule ligand with selectivity for LPAR6 that can modulate its activity
-
Observations from LPAR6 knockout mice showing accelerated oligodendrocyte maturation
-
In vitro studies using primary cultures of rat oligodendrocytes and in vivo studies in developing zebrafish that corroborate LPAR6's negative modulatory role
These findings suggest that LPAR6 signaling represents "a potential new druggable pathway suitable to promote myelin repair in MS" .
How is LPAR6 implicated in liver cancer progression and patient outcomes?
LPAR6 has emerged as a significant factor in hepatocellular carcinoma (HCC) development and progression:
-
LPAR6 is highly expressed in liver cancer compared to matched paracancerous tissues
-
High LPAR6 expression promotes cell proliferation in liver cancer
-
Overexpression of LPAR6 in HCC specimens correlates with poor survival outcomes in patient cohorts
Mechanistic studies have revealed that:
-
RNAi-mediated attenuation of LPAR6 impairs HCC tumorigenicity in tumor xenograft assays
-
LPAR6 affects downstream signaling pathways that control cell proliferation and survival
-
LPAR6 expression is regulated by hepatocyte growth factor (HGF), suggesting complex signaling interactions in tumor microenvironments
The clinical significance of these findings is supported by survival analysis of patients, which demonstrated a negative correlation between LPAR6 expression and patient prognosis . These data collectively establish LPAR6 as an important theranostic target in HCC tumorigenesis .
What molecular mechanisms connect LPAR6 signaling to cancer cell proliferation?
Research has uncovered several molecular mechanisms through which LPAR6 promotes cancer cell proliferation:
-
In liver cancer, LPAR6 has been shown to upregulate Pim-3 (a serine/threonine kinase with oncogenic properties) through a STAT3-dependent mechanism
-
LPAR6 mediates cAMP accumulation and Rho-dependent cellular morphological changes that can contribute to malignant transformation
-
In bladder cancer, LPAR6 appears to be involved in the regulation of basal-to-luminal differentiation transitions that influence tumor behavior
The connection between LPAR6 overexpression and Pim-3 upregulation has been validated in HCC clinical specimens, where it associates with high proliferation rates and poorer survival outcomes . This LPAR6-STAT3-Pim-3 signaling axis represents a potential intervention point for therapeutic development.
How can computational approaches be used to identify and characterize novel LPAR6 ligands?
Computational approaches have become valuable tools for identifying and characterizing novel LPAR6 ligands:
-
Homology modeling and molecular docking: These techniques allow researchers to predict the three-dimensional structure of LPAR6 based on known structures of related G protein-coupled receptors, and then computationally screen for molecules that might bind to the receptor .
-
Structure-activity relationship (SAR) studies: By analyzing the structural features of known LPAR6 ligands, researchers can design modified compounds with potentially improved selectivity or activity.
-
In silico screening libraries: Virtual screening of chemical libraries can identify compounds with high predicted binding affinity to LPAR6.
-
Molecular dynamics simulations: These can provide insights into the conformational changes induced by ligand binding and help predict functional outcomes.
Researchers have successfully applied these approaches to develop novel small molecule ligands with selectivity for LPAR6, which have been subsequently validated through in vitro and in vivo functional characterization . For example, a novel small molecule LPAR6 agonist was characterized in primary cultures of rat oligodendrocytes and in the developing zebrafish model to validate its effects on oligodendrocyte maturation .
What are the most sensitive methods for detecting LPAR6 expression in tissues and cells?
Several complementary methods can be employed for sensitive detection of LPAR6 expression:
-
Immunohistochemistry/Immunofluorescence: These techniques allow visualization of LPAR6 protein expression in tissue sections or cultured cells. Quantification can be performed using metrics such as immunoreactivity score (IRS) or integrated optical density (IOD) . This approach has been used to compare LPAR6 expression between liver cancer and matched paracancerous tissues .
-
Quantitative Real-Time PCR (qRT-PCR): This method enables precise measurement of LPAR6 mRNA expression levels. It has been used to quantify LPAR6 transcript levels in various cell types and tissues .
-
RNA-Seq: This high-throughput approach provides comprehensive transcriptome analysis, allowing detection of LPAR6 expression in the context of global gene expression patterns .
-
Single-cell RNA sequencing: Particularly valuable for heterogeneous tissues, this technique can resolve cell-type-specific expression patterns of LPAR6.
-
Western blotting: This protein detection method can quantify LPAR6 protein levels in tissue or cell lysates.
-
Flow cytometry: For detection of cell surface LPAR6 in individual cells within a population.
The choice of method depends on the research question, sample type, and required sensitivity. For developmental studies of oligodendrocytes, researchers have tracked the cell surface accessibility of LPAR6, which is restricted to earlier maturation stages of differentiating OLGs .
What controls are essential when studying LPAR6 function using recombinant proteins or genetic manipulation?
When studying LPAR6 function, several types of controls are essential to ensure reliable and interpretable results:
For recombinant protein studies:
-
Empty vector control (expressing the same vector without LPAR6 insert)
-
Inactive LPAR6 mutant (e.g., with mutations in key signaling residues)
-
Other LPA receptor subtypes (especially LPAR1) to assess specificity
-
Dose-response controls to determine concentration-dependent effects
-
Vehicle controls for ligand administration
For genetic manipulation studies:
-
Non-targeting guide RNA or scrambled siRNA controls for CRISPR or RNAi approaches
-
Wild-type cells or animals as baseline controls
-
Single knockout controls when studying double knockouts (e.g., LPAR1-/- and LPAR2-/- individual knockouts when studying LPAR1-/-LPAR2-/- double knockouts)
-
Rescue experiments reintroducing LPAR6 expression to confirm specificity of observed phenotypes
Research on LPAR6 and LPAR1 knockout mice has demonstrated the importance of proper controls, as the double knockout mice showed specific phenotypes different from single knockouts, including an increased incidence of perinatal frontal hematoma compared to LPAR1 knockout alone .
How can researchers distinguish between direct LPAR6-mediated effects and indirect downstream consequences?
Distinguishing direct LPAR6-mediated effects from indirect consequences requires a multi-faceted experimental approach:
-
Temporal analysis: Monitoring the sequence of events following LPAR6 activation can help identify primary (direct) versus secondary (indirect) effects. Early responses (seconds to minutes) are more likely to be direct consequences of receptor activation.
-
Pharmacological inhibitors: Using specific inhibitors for downstream signaling components can help define the signaling pathway and distinguish direct from indirect effects.
-
Receptor mutants: Engineered LPAR6 variants with altered coupling to specific G proteins or other signaling molecules can help delineate direct signaling pathways.
-
Signaling-selective ligands: Compounds that preferentially activate specific LPAR6 signaling pathways can help isolate direct receptor functions.
-
In vitro reconstitution: Using purified components to reconstitute signaling in cell-free systems can provide evidence for direct interactions.
-
Conditional and inducible systems: These allow temporal control of LPAR6 expression or activity, facilitating the separation of immediate versus long-term consequences.
For example, researchers studying LPAR6's role in oligodendrocyte maturation used a novel small molecule LPAR6 agonist to directly activate the receptor and observe the immediate effects on myelination-associated gene expression, helping to establish the direct regulatory role of LPAR6 signaling in this process .
