Recombinant Human GLIPR1-like protein 2 (GLIPR1L2)

What is the structural composition of GLIPR1L2?

GLIPR1L2 is a member of the GLIPR1 family of proteins characterized by a multi-domain structure. The protein contains a signal peptide that directs its secretion, followed by a conserved cysteine-rich CAP (cysteine-rich secretory proteins, antigen 5, and pathogenesis-related 1 proteins) domain, and a transmembrane domain that anchors it to cellular membranes . This structure is similar to its family member GLIPR1, though there may be specific variations in the CAP domain that account for functional differences. The CAP domain is particularly significant as it contains flexible loop/turn regions that may be involved in protein-protein interactions and potential binding sites for metal ions such as Zn²⁺, which could modulate its activity in inflammatory processes .

What methods are commonly used to produce recombinant GLIPR1L2 for research purposes?

Production of recombinant GLIPR1L2 typically involves expressing the protein in prokaryotic or eukaryotic expression systems. For prokaryotic expression, E. coli strains optimized for protein expression (such as BL21(DE3)) are commonly used with vectors containing strong promoters like T7. For eukaryotic expression, systems like HEK293 or CHO cells may be preferable to ensure proper post-translational modifications.

The methodology often includes:

• Designing expression constructs with appropriate tags (e.g., His-tag, FLAG-tag) for detection and purification

• Transformation or transfection into the chosen expression system

• Induction of protein expression (e.g., with IPTG in bacterial systems)

• Cell lysis and protein extraction

• Purification using affinity chromatography (e.g., Ni-NTA for His-tagged proteins)

• Verification of purity by SDS-PAGE and Western blotting

• Assessment of glycosylation status using deglycosylation enzymes such as PNGase F and Endo H

This process requires optimization of expression conditions including temperature, induction time, and media composition to maximize yield and minimize the formation of inclusion bodies.

How is GLIPR1L2 related to other members of the GLIPR1 family?

GLIPR1L2 belongs to the GLIPR1 family, which includes GLIPR1 and GLIPR1L1. These proteins share significant structural similarities but differ in their expression patterns and potentially in their functions . All family members contain the characteristic CAP domain, but while GLIPR1 and GLIPR1L2 are expressed in various tissues and both contain transmembrane domains, GLIPR1L1 is mainly expressed in testis .

The relationship between these proteins extends beyond structural similarities. They may have evolved from a common ancestral gene through duplication events, with subsequent divergence leading to specialized functions. The presence of transmembrane domains in both GLIPR1 and GLIPR1L2 suggests they may function as membrane-bound proteins, potentially involved in cell signaling or cell-cell interactions . Their differential expression patterns indicate they may have tissue-specific roles, which could be important when considering them as potential therapeutic targets.

What is the significance of GLIPR1L2 methylation status in cancer research?

The methylation status of GLIPR1L2 has emerged as a critical factor in understanding its role in cancer pathogenesis, particularly in lung adenocarcinomas. Recent genome-wide methylation analyses have revealed distinct patterns associated with different PD-L1 expression profiles. Specifically, GLIPR1L2 has been found to be hypomethylated in both PD-L1 high and negative expression groups, with methylation levels of 19% and 30% respectively (p-value = 0.008) .

This hypomethylation appears to correlate with the loss of GLIPR1L2's tumor-suppressive function, potentially contributing to cancer development and progression. The mechanism behind this relationship may involve the following pathways:

• Altered gene expression due to changes in promoter accessibility

• Modified protein-protein interactions affecting downstream signaling

• Disrupted regulation of immune response pathways

Research methodologies to study GLIPR1L2 methylation typically involve:

• Bisulfite sequencing to map methylation sites with single-nucleotide resolution

• Methylation-specific PCR to quantify methylation levels at specific CpG islands

• Genome-wide methylation arrays to identify differential methylation patterns

• Integration of methylation data with transcriptome analysis to correlate with expression levels

Understanding these methylation patterns could potentially lead to the development of epigenetic therapies targeting GLIPR1L2 or the use of GLIPR1L2 methylation status as a biomarker for cancer diagnosis or prognosis .

How does GLIPR1L2 contribute to immune defense mechanisms?

GLIPR1L2 plays a significant role in immune defense, although the precise mechanisms remain under investigation. As a member of the CAP protein family, GLIPR1L2 shares structural similarities with proteins involved in inflammatory modulation and immune response .

The contribution of GLIPR1L2 to immune defense likely involves multiple pathways:

• Regulation of inflammatory responses: Similar to other CAP family proteins, GLIPR1L2 may coordinate with cytokines and chemokines to modulate inflammation at sites of infection or tissue damage.

• Interaction with immune cells: GLIPR1L2 could potentially interact with various immune cell populations, including T cells, B cells, and antigen-presenting cells, influencing their activation, proliferation, or effector functions.

• Modulation of the tumor microenvironment: In cancer contexts, GLIPR1L2 may alter the immune landscape within the tumor microenvironment, potentially affecting the recruitment and function of tumor-infiltrating lymphocytes.

Experimental approaches to study these mechanisms include:

• Co-culture systems with immune cells and recombinant GLIPR1L2

• Flow cytometry and cytokine profiling to assess immune cell activation

• In vivo models with GLIPR1L2 knockout or overexpression

• Proximity labeling techniques to identify GLIPR1L2 interaction partners in immune cells

Understanding GLIPR1L2's immune function is particularly relevant in the context of cancer immunotherapy, as it may influence response to treatments such as immune checkpoint inhibitors .

What experimental challenges exist in studying GLIPR1L2 function, and how can they be addressed?

Studying GLIPR1L2 function presents several significant experimental challenges that researchers must navigate:

• Protein solubility issues: As a membrane-associated protein with transmembrane domains, full-length GLIPR1L2 can be difficult to express and purify in a soluble, functional form. This challenge can be addressed by:

  • Creating truncated soluble domains (similar to approaches used for GLIPR1)

  • Using detergent-based extraction methods optimized for membrane proteins

  • Employing nanodiscs or liposome reconstitution to maintain native conformation

• Post-translational modifications: GLIPR1L2 likely undergoes glycosylation and potentially other modifications that affect its function. Researchers should:

  • Compare expressions in prokaryotic vs. eukaryotic systems

  • Analyze glycosylation patterns using PNGase F and Endo H treatments

  • Consider mass spectrometry-based approaches to map all modifications

• Functional redundancy with other family members: Distinguishing GLIPR1L2-specific functions from those of related proteins requires:

  • Developing highly specific antibodies or nanobodies

  • Creating cell lines with CRISPR-mediated knockout of individual or multiple family members

  • Using RNA interference with validated specificity

• Tissue heterogeneity: Given GLIPR1L2's varied expression across tissues, researchers should:

  • Employ single-cell approaches to resolve cell type-specific expression

  • Use laser capture microdissection for tissue-specific analyses

  • Develop conditional expression systems for in vivo studies

• Structural characterization challenges: Understanding GLIPR1L2's structure-function relationships requires:

  • X-ray crystallography or cryo-EM of the CAP domain

  • Molecular dynamics simulations to predict flexible regions

  • Mutagenesis studies targeting predicted functional sites

By addressing these challenges with appropriate methodological approaches, researchers can more effectively elucidate GLIPR1L2's functions in normal physiology and disease states.

How do epigenetic modifications affect GLIPR1L2 expression and function in different cancers?

Epigenetic modifications, particularly DNA methylation, play a crucial role in regulating GLIPR1L2 expression across different cancer types, with distinct patterns emerging that may influence treatment responses and disease progression.

In lung adenocarcinomas, genome-wide methylation analysis has revealed that GLIPR1L2 is hypomethylated in both PD-L1 high-expressing (19% methylation) and PD-L1 negative-expressing (30% methylation) tumors . This hypomethylation appears to correlate with reduced tumor-suppressor functionality of GLIPR1L2, suggesting that epigenetic regulation significantly impacts its cancer-related functions.

The relationship between epigenetic modifications and GLIPR1L2 function likely involves:

• Promoter methylation: Changes in CpG island methylation at the GLIPR1L2 promoter region may directly affect transcription factor binding and gene expression

• Histone modifications: Alterations in histone acetylation and methylation states could create a chromatin environment that influences GLIPR1L2 accessibility to transcriptional machinery

• microRNA regulation: Post-transcriptional regulation by microRNAs may further modulate GLIPR1L2 expression levels

• Long non-coding RNA interactions: These may influence the three-dimensional chromatin structure around the GLIPR1L2 locus

To study these epigenetic effects, researchers typically employ:

• Chromatin immunoprecipitation sequencing (ChIP-seq) to map histone modifications

• Assay for Transposase-Accessible Chromatin sequencing (ATAC-seq) to identify open chromatin regions

• Chromosome conformation capture techniques to understand three-dimensional interactions

• DNA methylation arrays and bisulfite sequencing for methylation profiling

The varying epigenetic regulation of GLIPR1L2 across different cancer types suggests cancer-specific mechanisms that could potentially be exploited for targeted therapies or as biomarkers for treatment response prediction .

What is the role of GLIPR1L2 in tumor suppression and cancer progression?

GLIPR1L2 exhibits a complex role in tumor biology, functioning primarily as a tumor suppressor whose downregulation contributes to cancer progression. In lung cancer specifically, research indicates that GLIPR1L2 expression is significantly downregulated during tumorigenesis, suggesting its normal function may inhibit cancer development .

The tumor suppressive mechanisms of GLIPR1L2 likely involve multiple pathways:

• Cell cycle regulation: GLIPR1L2 may influence cell cycle checkpoints, potentially inducing cell cycle arrest in pre-malignant cells

• Apoptotic signaling: Similar to other tumor suppressors, GLIPR1L2 might promote apoptosis in cells with DNA damage or other oncogenic changes

• Inhibition of invasion and metastasis: GLIPR1L2 could potentially suppress epithelial-to-mesenchymal transition (EMT) and other processes associated with cancer cell invasiveness

• Immune surveillance modulation: Given its role in immune defense, GLIPR1L2 may enhance recognition and elimination of cancer cells by immune effectors

The loss of GLIPR1L2 function in cancer appears to be mediated through epigenetic mechanisms rather than genetic mutations. Specifically, hypomethylation of the gene seems to correlate with reduced tumor suppressor activity , though the precise molecular mechanism for this apparent paradox requires further investigation.

Experimental approaches to study GLIPR1L2's tumor suppressor function include:

• Overexpression studies in cancer cell lines to assess effects on proliferation, migration, and invasion

• Mouse models with conditional GLIPR1L2 knockout to observe tumor development

• Patient-derived xenograft models treated with recombinant GLIPR1L2

• Analysis of patient samples to correlate GLIPR1L2 expression with clinical outcomes

Understanding GLIPR1L2's role in tumor suppression may lead to novel therapeutic strategies aimed at restoring its expression or function in cancers where it is downregulated .

What are the optimal conditions for expressing and purifying recombinant GLIPR1L2?

The expression and purification of recombinant GLIPR1L2 present specific challenges due to its membrane-associated nature and potential post-translational modifications. Based on approaches used for related proteins, the following methodological considerations are recommended:

Expression Systems and Constructs:

• Eukaryotic expression systems are generally preferred for full-length GLIPR1L2 to ensure proper folding and post-translational modifications:

  • HEK293F cells for mammalian expression

  • Insect cells (Sf9 or Hi5) with baculovirus vectors

  • Pichia pastoris for high-yield secreted expression

• Construct design considerations:

  • Include a cleavable signal peptide for secretion

  • Consider removing the transmembrane domain for improved solubility

  • Add affinity tags (His6, FLAG, or GST) separated by a TEV protease cleavage site

  • Codon optimization for the selected expression system

Purification Protocol:

• Initial capture using affinity chromatography:

  • Ni-NTA for His-tagged constructs

  • Anti-FLAG resin for FLAG-tagged proteins

  • Glutathione Sepharose for GST fusion proteins

• Secondary purification steps:

  • Ion exchange chromatography (typically Q Sepharose at pH 8.0)

  • Size exclusion chromatography in a physiological buffer

• Quality control assessments:

  • SDS-PAGE and Western blotting

  • Dynamic light scattering for homogeneity

  • Circular dichroism for secondary structure verification

  • Mass spectrometry for intact mass and modification analysis

  • Deglycosylation assays using PNGase F and Endo H

Optimization Considerations:

For structural studies or applications requiring higher purity, additional considerations include removing the flexible regions that might impede crystallization, similar to approaches used for GLIPR1 structural studies .

What analytical techniques are most effective for studying GLIPR1L2 interactions with other proteins?

Understanding GLIPR1L2's interactions with other proteins is crucial for elucidating its function in normal and disease states. Several complementary analytical techniques are particularly effective for studying these interactions:

In vitro Interaction Analysis:

• Surface Plasmon Resonance (SPR):

  • Provides real-time kinetic measurements (kon/koff)

  • Requires immobilization of purified GLIPR1L2 or its binding partners

  • Can determine binding affinity (KD) values

  • Allows testing of different buffer conditions to optimize interactions

• Isothermal Titration Calorimetry (ITC):

  • Measures binding thermodynamics (ΔH, ΔS, ΔG)

  • Does not require protein immobilization or labeling

  • Provides stoichiometry information

  • Requires larger amounts of purified protein

• Microscale Thermophoresis (MST):

  • Needs minimal amounts of protein

  • Can detect interactions in complex biological samples

  • Allows for measurements in various buffer conditions

  • Requires fluorescent labeling of one interaction partner

Cell-Based Interaction Analysis:

• Proximity Ligation Assay (PLA):

  • Detects protein-protein interactions in situ with high sensitivity

  • Provides spatial information about interactions

  • Suitable for fixed cells or tissue samples

  • Requires highly specific antibodies

• FRET/BRET Approaches:

  • Allows monitoring of dynamic interactions in living cells

  • Can detect conformational changes upon binding

  • Requires expression of fluorescent fusion proteins

  • Provides temporal resolution of interactions

• Co-Immunoprecipitation with Mass Spectrometry:

  • Identifies novel interaction partners

  • Can be performed with endogenous proteins

  • Allows for quantitative comparison between conditions

  • May identify indirect interactions within complexes

Advanced Structural Techniques:

• Hydrogen-Deuterium Exchange Mass Spectrometry (HDX-MS):

  • Maps interaction interfaces with peptide-level resolution

  • Requires no crystallization

  • Provides information about conformational dynamics

  • Works with relatively large protein complexes

• Cryo-Electron Microscopy:

  • Visualizes complex structural arrangements

  • Works with membrane proteins in near-native environments

  • Can capture different conformational states

  • Increasingly achievable at high resolution

• Cross-linking Mass Spectrometry (XL-MS):

  • Identifies amino acids in close proximity between interaction partners

  • Captures transient interactions

  • Provides distance constraints for structural modeling

  • Compatible with complex biological samples

For studying GLIPR1L2 interactions specifically in cancer contexts, these techniques can be applied to compare interaction profiles between normal and cancerous tissues, potentially revealing mechanistic insights into how altered GLIPR1L2 function contributes to tumorigenesis .

How can CRISPR-Cas9 gene editing be optimized for studying GLIPR1L2 function?

CRISPR-Cas9 gene editing offers powerful approaches for investigating GLIPR1L2 function through precise genetic manipulation. Optimizing this technology for GLIPR1L2 studies requires careful consideration of several key factors:

Guide RNA Design and Selection:

• Target site selection:

  • Design multiple sgRNAs targeting early exons to ensure complete loss-of-function

  • Consider targeting the CAP domain for functional studies

  • Avoid regions with known SNPs that might affect guide binding

  • Use algorithms that predict off-target effects (e.g., CRISPOR, CHOPCHOP)

• Guide RNA optimization:

  • Enhance on-target efficiency using established rules (G-rich PAM-proximal region)

  • Ensure minimal predicted off-target sites in coding regions

  • Consider chemical modifications for increased stability in primary cells

Delivery and Editing Strategies:

• Cell type-specific considerations:

  • For cancer cell lines: plasmid or lentiviral delivery systems

  • For primary cells: ribonucleoprotein (RNP) complexes often yield higher efficiency

  • For in vivo editing: AAV-based delivery systems with tissue-specific promoters

• Advanced editing approaches:

  • Homology-directed repair (HDR) for knock-in of reporters or tags

  • Base editing for introducing specific point mutations without DSBs

  • Prime editing for precise insertions or deletions without donor templates

Experimental Design for Functional Studies:

• Generation of cellular models:

  • Complete knockout cell lines for loss-of-function studies

  • Knock-in of fluorescent tags for localization and interaction studies

  • Inducible systems for temporal control of GLIPR1L2 expression

  • Introduction of specific mutations to probe structure-function relationships

• Validation strategies:

  • Genomic verification: PCR, sequencing, and TIDE/ICE analysis

  • Protein level verification: Western blot, immunofluorescence

  • Functional validation: phenotypic assays relevant to cancer hallmarks

Example CRISPR-Cas9 Workflow for GLIPR1L2:

This methodological approach can be particularly valuable for investigating GLIPR1L2's role in tumor suppression and immune modulation, potentially revealing new therapeutic strategies for cancers where GLIPR1L2 function is altered .

How does GLIPR1L2 methylation status correlate with response to immunotherapy in cancer patients?

The relationship between GLIPR1L2 methylation and immunotherapy response represents an emerging area of research with significant clinical implications. Current evidence suggests several important correlations:

GLIPR1L2 methylation patterns show distinct profiles in tumors with different PD-L1 expression levels, which is a critical biomarker for immunotherapy response . Specifically, hypomethylation of GLIPR1L2 has been observed in both PD-L1 high-expressing (19% methylation) and PD-L1 negative-expressing (30% methylation) lung adenocarcinomas . This suggests a complex relationship between GLIPR1L2 epigenetic regulation and the tumor immune microenvironment.

The potential mechanisms linking GLIPR1L2 methylation to immunotherapy response include:

• Immune cell infiltration and activation: GLIPR1L2's role in immune defense suggests it may influence T-cell recruitment and activation within the tumor microenvironment, potentially affecting responses to immune checkpoint inhibitors.

• Cytokine signaling modulation: Altered GLIPR1L2 expression due to methylation changes may affect local cytokine profiles, shifting the balance between pro-inflammatory and immunosuppressive signals.

• Tumor antigen presentation: GLIPR1L2 might influence antigen processing or presentation pathways, affecting tumor visibility to the immune system.

To study these correlations, researchers should consider:

• Prospective collection of tumor samples before immunotherapy initiation with comprehensive methylation profiling

• Integration of GLIPR1L2 methylation data with other biomarkers (tumor mutational burden, PD-L1 expression)

• Development of assays to measure GLIPR1L2 methylation from liquid biopsies for longitudinal monitoring

• Correlation of GLIPR1L2 methylation patterns with spatial distribution of immune cell populations using multiplex immunohistochemistry

This research direction could potentially lead to the development of GLIPR1L2 methylation as a predictive biomarker for immunotherapy response, helping to guide treatment decisions and improve patient outcomes in various cancer types .

What are the emerging therapeutic applications targeting GLIPR1L2 in cancer treatment?

Research into GLIPR1L2-targeted therapeutic approaches is still in early stages, but several promising strategies are emerging based on its role in tumor suppression and immune modulation. These approaches leverage the understanding that GLIPR1L2 functions as a tumor suppressor that is downregulated in cancer contexts .

Potential therapeutic strategies include:

• Epigenetic modulation therapies:

  • DNA methyltransferase inhibitors (DNMTi) to reverse hypomethylation patterns

  • Histone deacetylase inhibitors (HDACi) to modify chromatin structure around the GLIPR1L2 locus

  • Targeted epigenetic editing using CRISPR-dCas9 systems coupled with epigenetic modifiers

• Recombinant protein approaches:

  • Development of modified recombinant GLIPR1L2 with enhanced stability and cell penetration

  • Creation of GLIPR1L2 fusion proteins targeting specific tumor antigens

  • Encapsulation in nanoparticles for improved delivery to tumor sites

• Gene therapy strategies:

  • Viral vector-mediated GLIPR1L2 gene delivery to restore expression in tumors

  • mRNA-based therapeutics for transient GLIPR1L2 expression

  • CRISPR-based approaches to correct epigenetic misregulation

• Combination approaches:

  • Synergistic combinations with immune checkpoint inhibitors

  • Sequential therapy with conventional chemotherapeutics

  • Integration with CAR-T or other adoptive cell therapies

Challenges and considerations for therapeutic development:

While still in preclinical development stages, GLIPR1L2-targeted therapies hold promise for addressing the unmet needs in cancer treatment, particularly for tumors that demonstrate altered GLIPR1L2 expression or function . Future research should focus on optimizing delivery methods, understanding mechanism of action, and identifying patient populations most likely to benefit from these approaches.

How do structural variations in GLIPR1L2 affect its function and potential as a therapeutic target?

Understanding the structure-function relationships of GLIPR1L2 is crucial for developing effective therapeutic strategies targeting this protein. While detailed structural data specifically for GLIPR1L2 is limited, insights can be drawn from studies of related proteins in the GLIPR1 family and the broader CAP protein superfamily .

Key Structural Features and Their Functional Implications:

• CAP Domain Structure:

  • The conserved cysteine-rich CAP domain is likely to adopt a compact α-β-α sandwich fold similar to other family members

  • This domain contains flexible loop/turn regions that may be critical for protein-protein interactions

  • Disulfide bonds formed by conserved cysteines contribute to stability and potentially regulate activity

• Potential Metal Binding Sites:

  • Based on structures of related proteins, GLIPR1L2 may contain zinc-binding sites in its CAP domain

  • Such metal coordination could modulate protein function in inflammatory processes

  • Mutations affecting these sites might alter GLIPR1L2's activity in immune regulation

• Transmembrane Domain:

  • The C-terminal transmembrane domain anchors GLIPR1L2 to cellular membranes

  • This membrane association likely influences the protein's localization and interaction partners

  • Structural variations in this region could affect trafficking and downstream signaling

Therapeutic Implications of Structural Variations:

• Targeting Specific Domains:

  • Small molecule inhibitors or activators could be designed to target functional pockets in the CAP domain

  • Antibodies targeting specific epitopes might modulate GLIPR1L2 function without complete inhibition

  • Peptide mimetics of key structural regions could act as competitive inhibitors of protein-protein interactions

• Exploiting Natural Variants:

  • Natural polymorphisms might affect GLIPR1L2 stability or function

  • Patient-specific variations could inform personalized therapeutic approaches

  • Identification of dominant-negative variants could guide protein engineering strategies

• Structure-Based Drug Design:

  • Computational modeling based on homology with GLIPR1 and other CAP proteins

  • Virtual screening for compounds that bind to predicted functional sites

  • Fragment-based approaches targeting multiple sites simultaneously

To advance this area of research, several methodological approaches are recommended:

• X-ray crystallography or cryo-EM studies of purified GLIPR1L2 domains

• Hydrogen-deuterium exchange mass spectrometry to map flexible regions

• Molecular dynamics simulations to predict conformational changes

• Systematic mutagenesis of conserved residues to identify functional hotspots

• Cross-linking studies to identify interaction interfaces with binding partners

Understanding how structural variations impact GLIPR1L2 function will be essential for developing precision therapies that can restore normal activity in cancer contexts or modulate its immune regulatory functions .