Recombinant Danio rerio Solute carrier family 25 member 42 (slc25a42)

What is SLC25A42 and what is its function in Danio rerio?

SLC25A42 is a mitochondrial coenzyme A (CoA) transporter localized at the inner mitochondrial membrane. In Danio rerio (Zebrafish), as in other organisms, it plays a critical role in energy metabolism and CoA homeostasis. The protein consists of six transmembrane alpha-helices, similar to other proteins of the solute carrier family 25 . It functions primarily by facilitating the uptake of CoA into the mitochondria in counter exchange with (deoxy)adenine nucleotides and adenosine 3′,5′-diphosphate (PAP) .

The protein is widely expressed in various tissues, particularly in brain regions, indicating its importance in "basal brain function" . The zebrafish model provides an excellent system for studying this protein due to the high conservation of mitochondrial transporters across vertebrate species.

What are the proper storage and handling protocols for recombinant Danio rerio SLC25A42?

Proper storage and handling are essential for maintaining protein integrity:

For reconstitution:

• Briefly centrifuge the vial prior to opening to bring contents to the bottom

• Reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL

• Add glycerol to a final concentration of 5-50% (default recommendation: 50%) for long-term storage

• Aliquot to avoid repeated freeze-thaw cycles, which can degrade the protein

What forms of recombinant Danio rerio SLC25A42 are available for research?

Recombinant Danio rerio SLC25A42 is available in several formats:

• Physical states: Liquid solution or lyophilized powder

• Protein length: Full-length or partial-length versions

• Expression systems: Primarily mammalian cell-derived

• Purity levels: Typically >80% (by SDS-PAGE) or >85% (by SDS-PAGE)

• Tags: Various configurations including His-tagged versions for purification and detection purposes

• Storage buffer: Typically PBS buffer for liquid formulations

When selecting a form, researchers should consider their specific experimental requirements, including needed purity level, detection methods, and functional assays.

How can I assess the functional integrity of recombinant Danio rerio SLC25A42 in in vitro studies?

Functional assessment of recombinant SLC25A42 requires multiple approaches:

• Transport activity assays:

  • Measure CoA uptake into proteoliposomes containing reconstituted SLC25A42

  • Monitor counter-exchange with labeled nucleotides

  • Quantify activity using radioisotope-labeled substrates or fluorescent analogs

• Oxygen consumption rate (OCR) measurements:

  • Utilize platforms like Seahorse XF96 Analyzer

  • Compare OCR with different substrates (e.g., glucose/pyruvate vs. palmitate-BSA)

  • Monitor response to inhibitors like oligomycin, FCCP, and rotenone/antimycin A

• CoA level quantification:

  • Measure intracellular CoA levels in complemented SLC25A42-deficient cells

  • Assess response to supplements like pantothenic acid

• Structural integrity:

  • Perform circular dichroism to confirm proper protein folding

  • Use size exclusion chromatography to verify oligomerization state

A typical experiment would involve reconstituting the protein in liposomes, verifying insertion using Western blotting, then measuring transport activity under various conditions including pH, temperature, and substrate concentration gradients.

What are the implications of SLC25A42 mutations for mitochondrial function studies?

SLC25A42 mutations provide critical insights into mitochondrial metabolism:

• Energy metabolism disruption: Mutations in SLC25A42 lead to reduced CoA levels, affecting multiple metabolic pathways, particularly fatty acid β-oxidation . This manifests as reduced oxygen consumption rates in affected tissues.

• Clinical-biochemical correlation: The varying clinical presentations, even among siblings with identical mutations, suggests complex metabolic compensation mechanisms that can be studied in model systems .

• Tissue specificity: SLC25A42 deficiency affects high-energy demanding tissues differently, with particular impact on the brain (putamen abnormalities on MRI) and skeletal muscle .

• Experimental considerations:

  • Include appropriate controls when studying specific mutations

  • Consider metabolic stress conditions (e.g., glucose deprivation, fatty acid loading)

  • Integrate multi-omics approaches to capture compensatory mechanisms

• Therapeutic investigations: Mutations create opportunities to study potential interventions, such as pantothenic acid supplementation, which has shown promising results in increasing CoA levels in patient fibroblasts .

These implications highlight the importance of SLC25A42 in maintaining mitochondrial homeostasis and energy metabolism, making it a valuable target for mitochondrial function studies.

How can recombinant Danio rerio SLC25A42 be used to study CoA homeostasis mechanisms?

Recombinant SLC25A42 provides a powerful tool for investigating CoA homeostasis:

• Reconstituted transport systems:

  • Create proteoliposomes with purified recombinant SLC25A42

  • Manipulate internal and external substrate concentrations

  • Determine kinetic parameters (Km, Vmax) for CoA transport

  • Identify inhibitors and regulators of transport activity

• Cell-based complementation studies:

  • Express recombinant SLC25A42 in SLC25A42-deficient cells

  • Measure restoration of:

    • CoA levels in cytosolic and mitochondrial compartments

    • Metabolic activities dependent on mitochondrial CoA

    • Oxygen consumption rates with various substrates

• Structure-function analyses:

  • Generate site-specific mutants to identify key residues for transport

  • Compare zebrafish SLC25A42 with human counterpart to identify conserved functional domains

  • Map disease-causing mutations onto protein structure

• Regulatory mechanisms:

  • Investigate post-translational modifications affecting transport activity

  • Study interactions with other proteins involved in CoA metabolism

  • Examine transcriptional and translational regulation under various metabolic states

These approaches allow for comprehensive understanding of how SLC25A42 contributes to maintaining proper CoA distribution between cellular compartments, which is essential for numerous metabolic processes.

What experimental approaches can best investigate the interplay between SLC25A42 and fatty acid metabolism?

The following methodological approaches provide comprehensive insights into SLC25A42's role in fatty acid metabolism:

• Metabolic flux analysis:

  • Utilize stable isotope-labeled fatty acids (e.g., 13C-palmitate)

  • Track metabolic fate in wild-type versus SLC25A42-deficient models

  • Quantify oxidation rates and intermediate accumulation

  • Identify metabolic bottlenecks using mass spectrometry

• Bioenergetic profiling:

  • Measure OCR in response to fatty acid substrates using the Seahorse XF96 Analyzer

  • Compare glucose/pyruvate versus palmitate-BSA as substrates

  • Assess the impact of carnitine supplementation

• Lipidomic analyses:

  • Characterize lipid composition changes in SLC25A42-deficient models

  • Identify accumulation of specific fatty acid species

  • Correlate with functional outcomes

• In vivo phenotyping in zebrafish models:

  • Generate SLC25A42 knockout or knockdown zebrafish

  • Assess response to fasting challenges

  • Measure swimming endurance as functional readout

  • Perform whole-organism metabolic rate measurements

• Tissue-specific analyses:

  • Examine tissue-specific effects, focusing on high energy-demanding tissues

  • Visualize lipid accumulation using Oil Red O staining

  • Measure mitochondrial morphology and number

• Rescue experiments:

  • Test pantothenic acid supplementation effects on fatty acid metabolism

  • Compare wild-type versus mutant SLC25A42 complementation

This multi-faceted approach allows researchers to comprehensively characterize how SLC25A42 deficiency affects fatty acid utilization at the molecular, cellular, and organismal levels.

How can I design experiments to study SLC25A42 deficiency effects on zebrafish energy metabolism?

A comprehensive experimental design should include:

• Model generation and validation:

  • Create SLC25A42-deficient zebrafish using CRISPR-Cas9 genome editing

  • Validate using RT-PCR, Western blotting, and functional assays

  • Consider generating specific disease-associated mutations (e.g., p.Glu228Lys, p.Trp132*)

• Developmental phenotyping:

  • Document embryonic development with time-lapse imaging

  • Assess hatching, survival rates, and growth parameters

  • Measure standard length and body mass at defined time points

• Metabolic characterization:

  • Conduct comprehensive metabolomics focusing on:

    • CoA and CoA derivatives

    • TCA cycle intermediates

    • Carnitine and acylcarnitines

    • Amino acids and organic acids

• Functional assessments:

  • Measure basal and maximal oxygen consumption rates

  • Assess spontaneous activity and swimming capacity

  • Evaluate response to:

    • Fasting challenges

    • Temperature changes

    • Metabolic inhibitors

• Tissue-specific analyses:

  • Focus on brain, muscle, and liver as primary affected tissues

  • Perform histological examination

  • Measure tissue-specific metabolite levels

  • Assess mitochondrial morphology using electron microscopy

• Intervention studies:

  • Test pantothenic acid supplementation at various doses

  • Measure CoA levels and functional outcomes

  • Evaluate timing-dependent effects (preventive vs. therapeutic)

• Data integration:

  • Correlate molecular, cellular, and organismal phenotypes

  • Compare with human patient data for translational relevance

This comprehensive approach allows for thorough characterization of the impact of SLC25A42 deficiency on zebrafish energy metabolism and evaluation of potential therapeutic interventions.

What challenges arise in using recombinant Danio rerio SLC25A42 for in vitro transport assays?

Several methodological challenges must be addressed:

• Protein expression and purification:

  • Membrane proteins like SLC25A42 are notoriously difficult to express in functional form

  • Mammalian expression systems yield better folding but lower yields

  • Purification must preserve native conformation and function

  • Tag position can affect transport activity and must be optimized

• Reconstitution into artificial membranes:

  • Lipid composition significantly affects transporter function

  • Protein-to-lipid ratio must be optimized

  • Protein orientation in liposomes is often heterogeneous

  • Internal volume limitations affect substrate concentration

• Transport assay design:

  • CoA has limited membrane permeability, complicating background measurements

  • Counter-exchange mechanism requires pre-loading of liposomes

  • Need for sensitive detection methods for CoA and nucleotide substrates

  • Temperature sensitivity of transport activity requires careful control

• Data interpretation:

  • Distinguishing specific transport from non-specific permeability

  • Accounting for substrate binding without transport

  • Challenges in determining true initial rates

• Controls and validation:

  • Need for appropriate negative controls (heat-inactivated, known inactive mutants)

  • Validation of transport directionality

  • Confirmation of protein incorporation and orientation in liposomes

These challenges can be addressed through careful optimization of each experimental step and inclusion of appropriate controls. Successful transport assays typically show saturation kinetics, substrate specificity, and sensitivity to known inhibitors.

How do mutations in SLC25A42 affect neuronal mitochondrial function, and how can the zebrafish model illuminate these effects?

SLC25A42 mutations have significant neurological implications that can be investigated using zebrafish models:

• Neurological impacts of SLC25A42 deficiency:

  • Clinical findings show symmetrical T2 hyperintensity of the putamen with minor volume depression in brain MRI

  • Patients present with varying degrees of encephalopathy, developmental delay, and movement disorders (choreoathetosis)

  • Neurological impairment likely results from continuous unfulfilled energy demands

• Zebrafish as a neurological model system:

  • Transparent embryos allow in vivo imaging of neural development and function

  • High conservation of mitochondrial biology between zebrafish and humans

  • Established behavioral assays for neurological assessment

• Experimental approaches using zebrafish:

  a. Genetic models:

  • Generate CRISPR-Cas9 knockout or specific disease mutations

  • Create transgenic reporter lines expressing neuronal mitochondrial markers

  b. Structural and functional imaging:

  • Perform in vivo confocal microscopy of labeled neurons

  • Measure mitochondrial membrane potential using voltage-sensitive dyes

  • Assess calcium dynamics with genetically encoded calcium indicators

  • Visualize ATP production using FRET-based ATP sensors

  c. Behavioral phenotyping:

  • Assess touch response and swimming patterns

  • Measure startle response latency and habituation

  • Evaluate complex behaviors like prey capture

  • Test seizure susceptibility and pharmaco-resistance

  d. Biochemical analyses:

  • Measure brain-specific levels of:

    • CoA and CoA thioesters

    • ATP and other high-energy phosphates

    • Lactate and pyruvate ratios

  • Assess oxidative damage markers

  e. Intervention studies:

  • Test pantothenic acid supplementation effects on neuronal function

  • Evaluate metabolic rescue strategies

  • Test neuroprotective compounds

• Translational relevance:

  • Direct comparison with human patient neuroimaging findings

  • Correlation with clinical progression and interventional outcomes

  • Identification of biomarkers for neurological involvement

The zebrafish model offers unique advantages for understanding how SLC25A42 mutations affect neuronal mitochondrial function, potentially leading to new diagnostic and therapeutic approaches for patients with SLC25A42-associated neurological disorders.