Recombinant Xenopus laevis Transmembrane protein 147 (tmem147)

What expression systems are most effective for producing recombinant Xenopus laevis TMEM147?

Researchers studying TMEM147 have successfully used several expression systems, with HEK293T cells being particularly effective for membrane proteins from Xenopus:

Recommended expression systems:

For Xenopus TMEM147, HEK293T cells provide appropriate post-translational modifications and membrane environment. When expressing in HEK293T cells, researchers have successfully used vectors like pcDNA6/V5-His for human TMEM147 and pCDNA4/TO/Myc-His for zebrafish TMEM147 . Similar vectors with appropriate restriction sites (EcoRI and XhoI) could be employed for Xenopus TMEM147.

What are effective strategies for cloning and expressing functional Xenopus laevis TMEM147?

When cloning Xenopus laevis TMEM147, researchers should follow these methodological steps:

• cDNA source selection: Use cDNA from Xenopus embryos (preferably early developmental stages) or adult tissues where TMEM147 is expressed .

• Primer design considerations:

  • Include appropriate restriction sites (e.g., EcoRI and XhoI)

  • Add Kozak sequence for optimal translation initiation

  • Consider adding epitope tags (V5, Myc, or His) for detection and purification

• Expression validation:

  • Western blot with anti-tag antibodies

  • Immunofluorescence to confirm proper membrane localization

  • Co-immunoprecipitation with known partners (e.g., LBR or nicalin)

Based on successful approaches with human and zebrafish TMEM147, avoid heating lysates above 60°C during SDS-PAGE to prevent protein aggregation .

What purification protocols yield highest purity and activity for recombinant Xenopus TMEM147?

Purification of transmembrane proteins like TMEM147 presents significant challenges. For optimal results:

• Membrane protein extraction:

  • Use mild detergents (DDM, CHAPS, or digitonin) for initial solubilization

  • Maintain low temperatures (4°C) throughout extraction

  • Include protease inhibitors to prevent degradation

• Affinity purification approaches:

  • Utilize His-tag for IMAC purification

  • For co-immunoprecipitation studies, protein G-Sepharose coupled with anti-tag antibodies (2 μg anti-Myc or 1 μg anti-V5) provides high specificity

  • Consider magnetic bead coupling for higher yield and functional studies

• Quality control:

  • Size exclusion chromatography for final purification

  • Western blotting to confirm purity

  • Functional assays to verify activity

Pre-coupled magnetic beads (as described for Rhesus TMEM147) allow for convenient and fast capture of target molecules with high specificity while maintaining protein functionality .

How can researchers assess the interaction between Xenopus TMEM147 and the nuclear envelope components?

To study TMEM147's interactions with nuclear envelope components:

• Co-immunoprecipitation assays:

  • Immunoprecipitate tagged recombinant TMEM147 and probe for nuclear envelope proteins (particularly LBR)

  • Use crosslinking agents to stabilize transient interactions

  • Perform reciprocal IPs to confirm specificity

• Microscopy approaches:

  • Immunofluorescence co-localization studies with nuclear envelope markers

  • Super-resolution microscopy for precise localization

  • Live-cell imaging with fluorescently tagged proteins

• Functional assays:

  • TMEM147 knockdown followed by assessment of nuclear envelope integrity

  • Evaluation of chromatin organization using Hoechst staining

  • Analysis of LBR localization and H3K9me3 levels

Evidence from human cell studies suggests that TMEM147 depletion causes mislocalization of LBR to the ER and affects chromatin condensation , which would be important phenotypes to assess in Xenopus studies.

What approaches are effective for studying TMEM147's role in the ER translocon complex in Xenopus systems?

To investigate TMEM147's function in the ER translocon:

• Protein interaction studies:

  • Mass spectrometry following TMEM147 pull-down to identify Xenopus-specific interactors

  • Proximity labeling techniques (BioID or APEX) to identify neighboring proteins

  • Yeast two-hybrid screening using TMEM147 domains as bait

• ER morphology assessment:

  • Immunostaining for ER markers CKAP4 (CLIMP-63) and RTN4 (NOGO), which are upregulated upon TMEM147 depletion

  • Electron microscopy to examine ultrastructural changes in the ER

  • Live-cell imaging to track dynamic changes

• Functional assessment:

  • Protein translation efficiency in TMEM147-depleted cells

  • Tracking protein trafficking through the secretory pathway

  • ER stress response markers analysis

Studies have shown that TMEM147 silencing alters CLIMP-63/RTN4 ER labeling and affects ER structure, suggesting its importance in maintaining ER morphology and function .

How does TMEM147 expression change during Xenopus development, and what are the implications?

While specific data on TMEM147 expression during Xenopus development is limited, insights can be drawn from developmental proteomics studies and conservation with other species:

• Expression pattern analysis:

  • Based on proteomic analyses of Xenopus development, membrane protein expression significantly increases during the transition to functional organ systems (tadpole stage)

  • TMEM147, as a membrane protein involved in fundamental cellular processes, likely follows patterns similar to other ER/nuclear envelope proteins

• Developmental significance:

  • Nuclear envelope organization changes dramatically during development

  • ER expansion and specialization occurs during organogenesis

  • TMEM147's dual roles in these processes suggest important developmental functions

• Experimental approaches:

  • In situ hybridization to track TMEM147 mRNA expression

  • Immunohistochemistry with TMEM147-specific antibodies

  • Western blot analysis across developmental stages

  • Morpholino knockdown to assess developmental phenotypes

The significant proteome changes observed in Xenopus development (approximately 15,000 proteins across 11 developmental timepoints) provide context for studying stage-specific TMEM147 functions.

How can Xenopus TMEM147 studies inform our understanding of human neurodevelopmental disorders?

Bi-allelic loss-of-function variants in human TMEM147 cause neurodevelopmental disorders with intellectual disability . Xenopus models offer unique advantages for studying these conditions:

• Disease modeling advantages:

  • Xenopus embryos develop externally and transparently

  • Relatively easy genetic manipulation

  • Conserved developmental pathways

  • Ability to perform high-throughput studies

• Relevant approaches:

  • CRISPR/Cas9 to generate TMEM147 mutants mimicking human variants

  • Mosaic analysis through targeted injections

  • Rescue experiments with wild-type vs. mutant TMEM147

  • Behavioral assays in tadpoles to assess neurological phenotypes

• Translational relevance:

  • Assessment of neural cell migration and differentiation

  • Analysis of nuclear envelope stability in neural tissues

  • Evaluation of ER stress responses in developing neurons

  • Testing potential therapeutic approaches

Human studies have demonstrated that TMEM147 deficiency leads to abnormal nuclear segmentation, chromatin compaction issues, and ER dysfunction - all processes that can be effectively studied in the Xenopus model system.

What are the challenges and solutions for structural studies of recombinant Xenopus TMEM147?

Membrane proteins like TMEM147 present significant structural biology challenges:

• Main challenges:

  • Maintaining native conformation during extraction

  • Obtaining sufficient quantities of pure protein

  • Preventing aggregation

  • Determining appropriate detergent/lipid environments

• Recommended approaches:

  • Cryo-electron microscopy (cryo-EM) is particularly suitable as it has resolved structures of similar multi-pass membrane proteins

  • Nanodiscs or amphipols to maintain native-like membrane environment

  • Expression of domains separately if full-length protein proves challenging

  • Fusion with crystallization chaperones to enhance stability

• Expression considerations:

  • Codon optimization for Xenopus sequence in expression systems

  • Use of insect cell expression for complex eukaryotic proteins

  • Scale-up strategies for sufficient yield

Based on electron microscopy studies of intelectins from Xenopus, which revealed distinctive lobed structures , similar approaches might be applicable to TMEM147 structural studies.

How can proteomics and phospho-proteomics approaches enhance our understanding of TMEM147 function in Xenopus?

Proteomics approaches offer powerful insights into TMEM147 biology:

• Interaction proteomics:

  • IP-MS (immunoprecipitation coupled with mass spectrometry) to identify interaction partners

  • BioID or APEX proximity labeling to map spatial protein networks

  • Cross-linking mass spectrometry (XL-MS) to capture transient interactions

• Phospho-proteomics applications:

  • Identification of phosphorylation sites on TMEM147

  • Mapping phosphorylation changes in response to TMEM147 manipulation

  • Developmental phosphorylation patterns across Xenopus stages

• Data analysis pipeline:

  • Creation of homology maps between Xenopus and human phosphorylation sites

  • Network analysis to identify functional clusters

  • Integration with transcriptomic data

Large-scale proteomics studies in Xenopus have already identified ~15,000 proteins and ~11,500 phospho-sites across developmental stages , providing valuable context for TMEM147-specific studies.

What are the optimal conditions for studying TMEM147-containing protein complexes in Xenopus?

For successful analysis of TMEM147-containing complexes:

• Extraction conditions:

  • Mild detergents (digitonin or CHAPS at 0.5-1%) preserve complex integrity

  • Maintain physiological pH (7.2-7.4)

  • Include calcium in buffers (1-2 mM) to stabilize membrane protein interactions

  • Add protease and phosphatase inhibitors to prevent degradation

• Complex isolation approaches:

  • Blue native PAGE to separate intact complexes

  • Gradient centrifugation for large complexes

  • Size exclusion chromatography under native conditions

  • Multi-step affinity purification for specific complexes

• Validation methods:

  • Reciprocal co-immunoprecipitation of complex components

  • Functional reconstitution assays

  • Cross-validation with microscopy techniques

Based on successful approaches with the Nicalin-NOMO-TMEM147 complex, hierarchical assembly starts with Nicalin-NOMO intermediate formation, with Nicalin being the limiting factor regulating assembly by stabilizing other components .