Recombinant Danio rerio Diacylglycerol O-acyltransferase 2 (dgat2)

What is Danio rerio Diacylglycerol O-acyltransferase 2 and its primary function?

Danio rerio (zebrafish) Diacylglycerol O-acyltransferase 2 (dgat2) is a key enzyme involved in the final step of triglyceride synthesis. It catalyzes the formation of triglycerides by transferring an acyl group from acyl-CoA to diacylglycerol. DGAT2 is expressed prominently in liver and adipose tissue, while its isoform DGAT1 is expressed mostly in intestine and at lower levels in other tissues . DGAT2 plays a crucial role in lipid metabolism and is essential for the formation of lipid droplets, which are critical for energy storage and cellular homeostasis .

In research contexts, recombinant Danio rerio DGAT2 refers to the artificially produced version of this enzyme, typically expressed in bacterial systems like E. coli for various experimental applications .

How does zebrafish DGAT2 compare to DGAT2 from other species?

Zebrafish DGAT2 shares significant structural and functional similarities with DGAT2 from other vertebrates, making it a valuable model for comparative studies. The full-length protein consists of 361 amino acids , and while species-specific variations exist, the catalytic domains remain highly conserved across species.

When comparing zebrafish DGAT2 with plant DGAT2 enzymes (such as those from Arabidopsis, soybean, and castor), researchers have observed that all DGAT2 enzymes tend to utilize PC-derived DAG pools for TAG biosynthesis, but they may access different substrate pools compared to DGAT1 enzymes . This differential substrate access reflects evolutionary adaptations to specific metabolic requirements in different organisms.

Unlike mammalian systems where DGAT2 can localize to lipid droplets and utilize bulk DAG pools that phase partition into lipid droplets, zebrafish DGAT2 characteristics merit specific investigation to determine if such localization patterns are conserved .

What are the key structural features of recombinant Danio rerio DGAT2?

Recombinant Danio rerio DGAT2 exhibits several important structural features:

• Protein Length: Full-length protein consisting of 361 amino acids

• Transmembrane Domains: Contains multiple transmembrane regions that anchor it to cellular membranes

• Oligomerization State: Based on studies of DGAT2 from other species, zebrafish DGAT2 likely exists in both monomeric and dimeric forms

• Association Patterns: Research suggests that DGAT2 associates with other proteins, lipids, and membranes, forming functional complexes involved in lipid metabolism

What is the optimal protocol for expressing recombinant Danio rerio DGAT2 in E. coli?

Based on established protocols for DGAT2 expression, the following optimized method is recommended for Danio rerio DGAT2:

• Vector Selection: Use a dual-tag vector system (such as pMBP-DGAT2-His) that incorporates both MBP (maltose-binding protein) for solubility enhancement and a His-tag for purification

• E. coli Strain: Transform the expression vector into E. coli BL21(DE3) strain using electroporation

• Culture Conditions:

  • Inoculate a single colony into LB-tetracycline (15 μg/mL) medium

  • Grow overnight with shaking at 37°C

  • Dilute the overnight culture 1:20 into fresh medium

  • Grow at 37°C until reaching OD600 of 0.6-1.0

• Induction Parameters:

  • Add IPTG to a final concentration of 0.4 mM

  • Continue incubation at 37°C for 3 hours

• Cell Harvest:

  • Collect cells by centrifugation at 5,000 g for 10 minutes

  • Resuspend in appropriate buffer containing protease inhibitors

This protocol has been shown to yield functional recombinant DGAT2 while minimizing the formation of inclusion bodies and protein aggregates.

What purification strategies are most effective for recombinant DGAT2?

The most effective purification strategy for recombinant Danio rerio DGAT2 involves a multi-step approach:

• Initial Homogenization:

  • Sonicate cells in homogenization buffer (either amylose resin wash buffer or Ni-NTA resin wash buffer)

  • Include protease inhibitors: 0.2-1 mM PMSF and 1:100-1:500 dilution of protease inhibitor cocktail

  • Centrifuge at 2,000 g for 10 minutes to remove cell debris

  • Further centrifuge at 10,000 g for 10 minutes to remove inclusion bodies and protein aggregates

• Primary Affinity Purification (Ni-NTA chromatography):

  • Apply the 10,000 g supernatant to Ni-NTA beads

  • Wash extensively to remove non-specifically bound proteins

  • Elute the bound proteins with an imidazole gradient (50-1000 mM)

  • Majority of recombinant DGAT2 typically elutes at 150-200 mM imidazole

• Secondary Affinity Purification (if using MBP-tag):

  • Pool imidazole-eluted fractions

  • Apply to amylose resin

  • Elute with buffer containing maltose

• Considerations:

  • Be aware that a significant portion of recombinant DGAT2 may not bind to either affinity resin

  • Both monomeric and dimeric forms of DGAT2 may be present in eluted fractions

  • The protein may remain associated with other proteins and lipids despite purification efforts

Given these challenges, researchers should consider the intended application when determining the required purity level. For enzymatic assays, the primary Ni-NTA purification may be sufficient, while structural studies might require additional purification steps.

What are the major challenges in expressing recombinant DGAT2 and how can they be addressed?

Recombinant DGAT2 expression presents several significant challenges:

• Limited Solubility:

  • Challenge: As a membrane-associated protein, DGAT2 has hydrophobic domains that can lead to poor solubility and inclusion body formation

  • Solution: Use fusion partners like MBP to enhance solubility, optimize expression temperature (consider lower temperatures like 16-20°C), and include solubilizing agents in buffers

• Protein Stability:

  • Challenge: DGAT2 can be susceptible to proteolytic degradation

  • Solution: Include multiple protease inhibitors in all buffers, work quickly during purification, and maintain samples at 4°C throughout processing

• Oligomerization:

  • Challenge: DGAT2 tends to form dimers and potentially higher-order oligomers

  • Solution: Include reducing agents in buffers to prevent disulfide-mediated aggregation, and consider size exclusion chromatography to separate different oligomeric states

• Association with Host Lipids and Proteins:

  • Challenge: Recombinant DGAT2 often co-purifies with host cell lipids and proteins

  • Solution: Consider detergent treatments to remove associated lipids if needed for the specific application, but recognize that such treatments may affect enzyme activity

• Low Binding Efficiency to Affinity Resins:

  • Challenge: Studies have shown that a significant portion of the recombinant DGAT2 may not bind to Ni-NTA or amylose resins

  • Solution: Consider using multiple purification approaches, optimize buffer conditions to enhance binding, and potentially explore alternative tag systems

These challenges can significantly impact yield and purity, but with careful optimization of expression and purification conditions, functional recombinant DGAT2 can be successfully produced for research applications.

What methods are used to assess the enzymatic activity of recombinant Danio rerio DGAT2?

Several approaches can be employed to evaluate the enzymatic activity of recombinant Danio rerio DGAT2:

• In Vitro Acyltransferase Assay:

  • Incubate purified recombinant DGAT2 with diacylglycerol (DAG) substrate and radiolabeled acyl-CoA (e.g., [14C]oleoyl-CoA)

  • Extract lipids using chloroform:methanol

  • Separate reaction products by thin-layer chromatography (TLC)

  • Quantify radiolabeled triacylglycerol formation by scintillation counting

• Metabolic Labeling in Cellular Systems:

  • Express recombinant DGAT2 in appropriate cell lines

  • Incubate with [14C]glycerol or [14C]acetate precursors

  • Monitor incorporation rates into lipid species including TAG, DAG, and phospholipids

  • This approach reveals substrate preferences and metabolic pathways

• Lipid Droplet Formation Analysis:

  • Express DGAT2 in cells with low endogenous DGAT activity

  • Stain cells with lipophilic dyes such as BODIPY or Nile Red

  • Quantify lipid droplet formation using fluorescence microscopy and image analysis

  • This assay is particularly relevant as DGAT2 has been shown to promote lipid droplet formation

• PC-derived DAG Utilization Assessment:

  • Employ dual labeling approaches to track the origin of DAG substrates

  • Monitor the relative rates of PC, DAG, and TAG labeling over time

  • This can reveal whether DGAT2 accesses the larger bulk DAG pool as suggested by comparative studies

When interpreting activity data, it's important to consider that zebrafish DGAT2, like other DGAT2 enzymes, likely utilizes a specific pool of DAG that is in equilibrium with phosphatidylcholine (PC), which differs from the substrate pools accessed by DGAT1 enzymes .

How does Danio rerio DGAT2 interact with other proteins in lipid metabolism pathways?

Danio rerio DGAT2, like its counterparts in other species, participates in complex protein-protein interactions within lipid metabolism pathways:

• Metabolic Channeling:

  • DGAT2 is likely part of a metabolic channeling system where substrate (DAG) is transferred between enzymes without equilibrating with the bulk cellular pool

  • Unlike DGAT1, which accesses initially produced PC-derived DAG, DGAT2 appears to utilize a larger pool of PC-derived DAG that is in equilibrium with PC

• Lipid Droplet-Associated Proteins:

  • While specific data for zebrafish DGAT2 is limited, mammalian DGAT2 localizes to lipid droplets and interacts with proteins involved in lipid droplet formation and dynamics

  • These interactions may be mediated through specific protein domains or scaffolding proteins

• Membrane Protein Complexes:

  • DGAT2 likely forms complexes with other membrane-bound enzymes involved in TAG synthesis

  • These interactions facilitate coordinated lipid synthesis and trafficking

• Potential Viral Protein Interactions:

  • Research on DGAT2 from other species has shown that it can interact with viral proteins, particularly non-structural proteins of flaviviruses

  • For example, DGAT2 can be recruited into viral replication complexes during Zika virus infection

• Enzyme Modifications:

  • DGAT2 may undergo post-translational modifications or proteolytic processing that affects its interactions

  • Viral proteases like NS2B3 can cleave DGAT2, creating a more stable product that promotes lipid droplet formation independent of enzymatic activity

Further research using techniques such as co-immunoprecipitation, proximity labeling, and fluorescence resonance energy transfer (FRET) could provide more detailed insights into the specific protein interactions of Danio rerio DGAT2.

What is known about the subcellular localization of DGAT2 and its significance for function?

The subcellular localization of DGAT2 is critical for its function in lipid metabolism:

• Endoplasmic Reticulum (ER) Localization:

  • DGAT2 primarily localizes to the ER membrane, where many steps of lipid synthesis occur

  • This localization facilitates access to newly synthesized DAG substrates

• Lipid Droplet Association:

  • Based on studies in mammalian systems, DGAT2 can also localize to lipid droplets or the ER-lipid droplet interface

  • This dual localization allows DGAT2 to access the bulk DAG pool that phase partitions into lipid droplets

  • The ability to relocate to lipid droplets distinguishes DGAT2 from DGAT1 and may explain their differential substrate access patterns

• Dynamic Redistribution:

  • DGAT2 localization is not static but can change in response to cellular conditions

  • During active lipid synthesis, DGAT2 may redistribute between the ER and expanding lipid droplets

• Functional Implications:

  • The unique localization pattern of DGAT2 explains its access to specific pools of DAG substrate

  • While DGAT1 utilizes the small initially produced PC-derived DAG pool (possibly by substrate channeling), this pool appears inaccessible to DGAT2

  • Instead, DGAT2 accesses a larger bulk DAG pool that is in equilibrium with PC

• Viral Infection Context:

  • During flavivirus infections, DGAT2 can be recruited to viral replication complexes

  • This altered localization contributes to its proviral role by promoting lipid droplet formation, which provides a favorable environment for viral replication

Understanding the subcellular dynamics of DGAT2 is essential for interpreting its functional role in both normal lipid metabolism and pathological states.

How is recombinant DGAT2 being used to study nonalcoholic steatohepatitis (NASH) and fatty liver disease?

Recombinant DGAT2 serves as a valuable tool in NASH and fatty liver disease research:

• Target Validation Studies:

  • Recombinant DGAT2 enables structural studies to understand enzyme-inhibitor interactions

  • These insights guide the development of more specific DGAT2 inhibitors for therapeutic applications

• Mechanistic Understanding:

  • Studies using recombinant DGAT2 have helped elucidate its key role in triglyceride synthesis

  • DGAT2 has been identified as a prominent contributor to hepatic steatosis, as it is expressed predominantly in liver and adipose tissue

• Therapeutic Development Models:

  • Researchers have used RNAi therapeutics targeting hepatic DGAT2 in mouse models of obesity

  • In these studies, DGAT2 silencing prevented and reversed triglyceride accumulation (>85%, p < 0.0001) without increased accumulation of diglycerides

  • This resulted in significant improvement of fatty liver phenotype

• Differential Effects on Disease Progression:

  • Interestingly, while DGAT2 inhibition reduces liver fat, studies have shown that this reduction doesn't necessarily translate to similar improvements in inflammation and fibrosis

  • This suggests that DGAT2 inhibition alone may be insufficient for treating all aspects of NASH, highlighting the need for combinatorial approaches targeting multiple pathways

• Translational Research:

  • Short-term human trials using pharmacological or antisense oligonucleotide (ASO) approaches to target DGAT2 have shown promising results

  • These interventions diminished liver triglycerides and suggested lower liver damage and fibrosis, though long-term efficacy remains under investigation

What role does DGAT2 play in viral infections and how is recombinant DGAT2 advancing this research?

Recombinant DGAT2 has revealed critical insights into host-virus interactions:

• Zika Virus (ZIKV) Replication:

  • Recent research has identified DGAT2 as a crucial factor in ZIKV replication

  • Using short hairpin RNA-based gene knockdown techniques, studies have demonstrated that ZIKV replication is significantly inhibited by DGAT2 depletion in multiple cell lines

  • This inhibition can be reversed through trans-complementation with DGAT2

• Viral Protein Interactions:

  • Recombinant DGAT2 studies have shown that the enzyme is recruited into viral replication complexes through interactions with non-structural (NS) proteins

  • Most notably, both human and murine DGAT2 can be cleaved by the viral protease NS2B3 at the 122R-R-S124 site

• Post-cleavage Stability and Function:

  • The cleaved product of DGAT2 becomes more stable than the full-length protein

  • Importantly, this cleaved form promotes lipid droplet formation independent of its enzymatic activity, creating favorable environments for viral replication

• Therapeutic Target Potential:

  • These findings position DGAT2 as a potential target for antiviral therapeutics

  • Inhibiting DGAT2 or its interaction with viral proteins could disrupt viral replication in flavivirus infections

• Broader Implications:

  • The identification of DGAT2 as a target of viral proteases like NS2B3 provides new insights into host-flavivirus interactions

  • This mechanical understanding may extend to other flaviviruses beyond ZIKV, potentially including dengue and West Nile viruses

Recombinant DGAT2 continues to be instrumental in elucidating these mechanisms and developing potential interventions for flavivirus infections.

How do comparative studies of DGAT1 and DGAT2 inform potential therapeutic strategies?

Comparative studies between DGAT1 and DGAT2 have revealed important distinctions that inform therapeutic development:

These comparative insights suggest that optimal therapeutic strategies might involve targeted inhibition of DGAT2 in combination with other approaches addressing inflammation and fibrosis, rather than DGAT2 inhibition alone.

What are the latest methodological advances in studying recombinant DGAT2 structure-function relationships?

Recent methodological advances have enhanced our understanding of DGAT2:

These methodological advances offer promising avenues for deeper investigations into DGAT2 structure-function relationships, potentially informing more targeted therapeutic strategies.

What are the critical experimental design considerations when working with recombinant Danio rerio DGAT2?

When designing experiments with recombinant Danio rerio DGAT2, researchers should consider:

• Expression System Selection:

  • E. coli: Suitable for producing large quantities of protein for biochemical studies, but proper folding may be challenging

  • Insect Cells: Better for functional studies as they provide more appropriate post-translational modifications

  • Mammalian Cells: Ideal for localization and interaction studies in a more native-like environment

• Protein Tag Considerations:

  • Tag Position: N-terminal tags are generally preferred as C-terminal tags may interfere with membrane insertion

  • Tag Type: Dual-tag systems (e.g., MBP-DGAT2-His) can improve solubility and purification efficiency

  • Tag Removal: Consider incorporating protease cleavage sites if tag-free protein is required

• Buffer Optimization:

  • Include appropriate detergents to maintain solubility

  • Consider using glycerol (10-20%) to stabilize the protein

  • Ensure presence of reducing agents to prevent disulfide-mediated aggregation

  • Include protease inhibitors to prevent degradation

• Experimental Controls:

  • Negative Controls: Include catalytically inactive mutants (e.g., mutations in conserved active site residues)

  • Positive Controls: Consider using well-characterized DGAT2 from other species as benchmarks

  • System Controls: Validate expression systems with known transmembrane proteins

• Activity Assay Design:

  • Consider the natural substrate preferences of zebrafish DGAT2

  • Monitor both substrate consumption and product formation

  • Account for potential background activity from host cell enzymes

• Data Interpretation Caveats:

  • Be aware that recombinant DGAT2 may exist in multiple oligomeric states

  • Consider that the protein may remain associated with host cell lipids

  • Recognize that membrane environment significantly influences activity

Careful attention to these experimental design considerations will enhance the reliability and relevance of results obtained with recombinant Danio rerio DGAT2.

What emerging research directions are being explored with recombinant DGAT2 in zebrafish and other model systems?

Several promising research directions are emerging for recombinant DGAT2:

• Comparative Evolutionary Studies:

  • Zebrafish DGAT2 provides an excellent model for evolutionary studies of lipid metabolism

  • Comparative analysis with mammalian and other vertebrate DGAT2 enzymes can reveal conserved mechanisms and species-specific adaptations

• Developmental Biology Applications:

  • Zebrafish embryos are transparent and develop rapidly, allowing visualization of lipid metabolism in real-time

  • Recombinant DGAT2 variants can be expressed in zebrafish embryos to study their effects on lipid accumulation and embryonic development

• Drug Discovery Platforms:

  • High-throughput screening assays using recombinant DGAT2 can identify novel inhibitors

  • Zebrafish models expressing fluorescently tagged DGAT2 could serve as in vivo platforms for evaluating compound efficacy and toxicity

• Metabolic Disease Modeling:

  • Zebrafish models with manipulated DGAT2 expression or activity can simulate aspects of human metabolic disorders

  • These models facilitate the study of disease progression and potential interventions

• Host-Pathogen Interactions:

  • Building on findings that DGAT2 is targeted by viral proteins, researchers are investigating how pathogens manipulate lipid metabolism

  • Recombinant DGAT2 serves as a tool to study these interactions at the molecular level

• Synthetic Biology Applications:

  • Engineered DGAT2 variants with altered substrate specificity could produce novel lipid species for industrial or pharmaceutical applications

  • Integration of DGAT2 into synthetic metabolic pathways may enable production of specialized lipids

• Structural Biology Breakthroughs:

  • Ongoing efforts to determine the high-resolution structure of DGAT2 will provide unprecedented insights into its mechanism

  • This structural information could revolutionize rational drug design targeting DGAT2

These emerging directions highlight the continuing importance of recombinant DGAT2 as a research tool across multiple scientific disciplines.