Recombinant Mouse Tumor suppressor candidate 3 (Tusc3)
Description
Genomic Organization and Expression
Tusc3 is identified as a candidate tumor suppressor gene across multiple species. In humans, the TUSC3 gene comprises 11 exons spanning approximately 349,435 base pairs of genomic DNA, located on chromosome 8p22 . The mouse ortholog (gene ID: 80286) maintains significant structural similarity, although specific genomic coordinates differ from the human version . Tusc3 expression patterns indicate presence in most non-lymphoid tissues, with notable expression in prostate, lung, liver, and colon tissues . This widespread expression pattern suggests fundamental cellular functions beyond tumor suppression alone.
Protein Structure and Cellular Localization
The TUSC3 protein consists of 348 amino acids, including an N-terminal region with 170 residues and four transmembrane domains . The protein is primarily localized in the endoplasmic reticulum, where it functions as a subunit of the endoplasmic reticulum-bound oligosaccharyltransferase (OST) complex . This complex plays a crucial role in protein N-linked glycosylation, catalyzing the transfer of a 14-sugar oligosaccharide from dolichol to nascent proteins during protein maturation processes . Mouse Tusc3 likely maintains similar structural characteristics, although specific differences in amino acid sequence may exist between species.
Functional Domains
The structure of Tusc3 contains several notable functional elements. The protein harbors a characteristic Cys-Xaa-Xaa-Cys motif containing active-site cysteine pairs . These unpaired cysteine residues have significant potential to regulate glycosylation efficiency through transient interaction with target proteins. The similarities in primary and secondary structure between human TUSC3 and yeast Ost3p suggest evolutionary conservation of OST regulatory subunits across diverse species .
Role in N-Glycosylation
The primary function of Tusc3 involves participation in the N-glycosylation process of nascent proteins. As a component of the OST complex, Tusc3 contributes to the transfer of oligosaccharides to asparagine residues in the consensus sequence Asn-X-Ser/Thr (where X represents any amino acid except proline) . This post-translational modification is crucial for proper protein folding, stability, and function. In normal cells, Tusc3 proteins can form oligomers that delay oxidative substrate folding through mixed disulfide formation . This mechanism increases the probability of sequon recognition and glycosylation by the catalytic subunit Stt3A/B as nascent polypeptide chains pass through the OST complex during co-translational translocation .
Magnesium Transport Functionality
Studies have demonstrated that Tusc3, beyond its role in glycosylation, functions as a magnesium transporter involved in magnesium homeostasis . This characteristic is significant as magnesium transport plays important roles in various physiological processes including learning and memory, embryonic development, and testis maturation . The dual functionality of Tusc3 in both glycosylation and magnesium transport suggests multiple mechanisms through which its dysfunction could contribute to pathological states.
Tumor Suppression Mechanisms
The designation of Tusc3 as a tumor suppressor candidate stems from its location within homozygously deleted regions observed in metastatic prostate cancer . While specific tumor suppression mechanisms remain under investigation, current evidence suggests that Tusc3 dysfunction or deletion may exert oncological effects by inhibiting glycosylation efficiency . This inhibition consequently induces endoplasmic reticulum stress and can trigger malignant cell transformation . Comparative analysis with other tumor suppressors indicates distinct mechanisms, as observed when contrasting with BTG3, which functions as a direct p53 target with antiproliferative effects .
Expression Systems for Recombinant Production
Recombinant mouse Tusc3 represents a bioengineered version of the native protein produced through molecular cloning techniques. Though specific production methodologies for mouse Tusc3 are not detailed in the available search results, standard recombinant protein production typically involves cloning the gene of interest into expression vectors, followed by expression in suitable host systems. For membrane proteins like Tusc3, mammalian expression systems may provide advantages in ensuring proper folding and post-translational modifications.
Research Applications
Recombinant mouse Tusc3 provides valuable research tools for investigating tumor suppressor functions. Pure recombinant protein enables detailed structure-function studies, interaction analyses, and development of targeted therapies. While specific applications of recombinant mouse Tusc3 are not explicitly described in the search results, similar tumor suppressor proteins are commonly used to:
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Study protein-protein interactions within the endoplasmic reticulum
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Investigate N-glycosylation mechanisms
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Explore magnesium transport pathways
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Develop targeted cancer therapies
Antibody Development
Commercial antibodies against Tusc3 have been developed, including those produced in rabbits that recognize human, mouse, and rat Tusc3 . These antibodies facilitate detection through various techniques including ELISA, immunofluorescence, western blot, and immunohistochemistry . Such tools are essential for studying expression patterns, localization, and functional aspects of the protein in both normal and pathological contexts.
Tusc3 in Cancer Development
The potential role of Tusc3 as a tumor suppressor has been investigated across multiple cancer types. Its location in a homozygously deleted region of metastatic prostate cancer provides strong circumstantial evidence for its role in cancer development . While specific mouse models focused on Tusc3 are not detailed in the available search results, comprehensive analyses of differential gene expression in mouse cancer models demonstrate the complexity of tumor suppressor networks . For instance, in the analysis of differentially expressed genes in various cell line comparisons, cancer consistently emerges as the top associated disease, with numerous cancer-related molecules identified .
Comparison with Other Tumor Suppressors
Research on tumor suppressors such as BTG3 provides comparative insights that may be relevant to understanding Tusc3 function. Studies have demonstrated that knockdown of tumor suppressors can alter cell proliferation rates, with BTG3 knockdown cells outgrowing control cells despite being deterred by ionizing radiation . Similarly, overexpression of tumor suppressors typically suppresses cell growth, as revealed by colony formation assays . Long-term survival studies further indicate that the loss of tumor suppressors like BTG3 is unfavorable for cell survival, especially after DNA damage . These findings suggest possible parallel mechanisms in Tusc3 function.
Differential Expression Data
Differential gene expression analyses in cancer models provide broader context for understanding tumor suppressor functions. While Tusc3 is not specifically highlighted in the differential expression data presented in search result , the analysis demonstrates consistent association with cancer across multiple comparisons . The presented data table shows numerous differentially expressed genes, with significance values ranging from 2.8E-04 to 1.2E-51, and approximately 50-53% of analyzed molecules involved in cancer-related processes .
Therapeutic Potential
The potential role of Tusc3 in tumor suppression suggests opportunities for therapeutic development. Understanding the mechanism by which Tusc3 influences cellular transformation could identify novel targets for cancer treatment. Future research might explore:
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Small molecule modulators of Tusc3 activity
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Gene therapy approaches to restore Tusc3 function in cancers with deletions or mutations
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Targeting downstream pathways affected by Tusc3 dysfunction
Biomarker Development
As a potential tumor suppressor with altered expression in cancer, Tusc3 may serve as a valuable biomarker for cancer diagnosis, prognosis, or treatment response. Future studies might investigate correlation between Tusc3 expression levels and clinical outcomes across various cancer types.
Product Specs
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Target Background
Q&A
What is the molecular function of TUSC3?
TUSC3 functions as a subunit of the endoplasmic reticulum (ER)-bound oligosaccharyltransferase (OST) complex that catalyzes a critical step in protein N-glycosylation . Research demonstrates that TUSC3 shares homology with the yeast OST complex subunit Ost3p, confirming its evolutionary conservation and fundamental role in glycosylation processes . Experimental evidence indicates that TUSC3 affects N-linked glycosylation in mammalian cells, with its downregulation or loss impacting ER structure and stress response mechanisms . The protein contains a transmembrane domain between amino acids 277-297, which is essential for its proper localization and function .
Where is TUSC3 expressed in mouse tissues?
While the provided search results don't specifically detail tissue-specific expression patterns, functional studies indicate that TUSC3 is expressed in multiple tissues. The gene has been detected at low levels in peripheral blood, though expression analysis via RT-qPCR has shown limited sensitivity for quantification in this tissue . Research focusing on neurodevelopmental disorders has demonstrated functional TUSC3 expression in neural tissues, as its absence correlates with nonsyndromic mental retardation . Additionally, studies in prostate cancer models indicate expression in prostate tissue, where its loss contributes to increased cell proliferation, migration, and invasion .
How does TUSC3 loss affect cellular signaling pathways in prostate cancer models?
Loss of TUSC3 expression in prostate cancer cell lines (DU145 and PC3) leads to significant alterations in cellular signaling networks, particularly affecting the Akt signaling pathway . Experimental evidence demonstrates that TUSC3 downregulation disrupts normal endoplasmic reticulum (ER) structure and modifies the ER stress response . These changes result in enhanced Akt signaling, which is a well-established pro-survival and pro-growth pathway in cancer cells.
The connection between TUSC3 loss and increased Akt activation appears particularly significant in a PTEN-negative background, suggesting a potential synergistic effect between these two tumor suppressor proteins . When TUSC3 expression is reduced, prostate cancer cells demonstrate increased proliferation, enhanced migration, and greater invasive potential in vitro . Moreover, xenograft studies show accelerated tumor growth when TUSC3 is downregulated, providing in vivo validation of its tumor suppressor function .
What is the relationship between TUSC3 mutations and neurodevelopmental disorders?
TUSC3 mutations have been directly implicated in autosomal recessive mental retardation (ARMR), specifically nonsyndromic ARMR (NS-ARMR) . Genome-wide SNP typing and haplotype analyses in consanguineous families with multiple affected individuals have identified homozygous deletions partially removing TUSC3 as causative for this condition . Notably, TUSC3 is only the fifth gene implicated in NS-ARMR and the first for which mutations have been reported in more than one family, underscoring its importance in neurodevelopment .
A specific case study identified a homozygous truncating intragenic duplication in TUSC3 that led to a premature termination codon, resulting in a truncated protein with interruption in the transmembrane domain . This mutation caused rare autosomal recessive nonsyndromic intellectual disability without additional clinical or biochemical manifestations typically associated with congenital disorders of glycosylation . RT-PCR analysis verified the complete absence of functional TUSC3 transcript in affected patients, confirming the causative nature of these mutations .
How does TUSC3's role in N-glycosylation relate to its tumor suppressor function?
TUSC3's dual functions in N-glycosylation and tumor suppression represent an intriguing mechanistic connection that is still being fully elucidated. As a component of the oligosaccharyltransferase complex, TUSC3 participates in the addition of N-linked glycans to nascent proteins in the endoplasmic reticulum . Proper N-glycosylation is essential for correct protein folding, trafficking, and function.
The tumor suppressor properties of TUSC3 appear to be linked to its glycosylation functions through several potential mechanisms:
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Regulation of ER stress response: TUSC3 loss alters endoplasmic reticulum structure and modifies the cellular response to ER stress . This may affect protein quality control mechanisms and allow cancer cells to adapt to stressful conditions.
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Modulation of receptor glycosylation: Many growth factor receptors and adhesion molecules require proper N-glycosylation for their function. Alterations in this process could affect receptor activation, signaling, and cell-cell interactions.
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Influence on Akt signaling: TUSC3 downregulation results in increased Akt signaling , potentially through altered glycosylation of components in this pathway. The enhanced Akt activation promotes cancer cell survival and proliferation.
Research in prostate cancer cell lines demonstrates that when TUSC3 expression is lost, cells exhibit enhanced proliferation, migration, and invasion capabilities, along with accelerated tumor growth in xenograft models . These findings suggest that the glycosylation function of TUSC3 is intrinsically linked to its ability to suppress malignant cellular behavior.
What are the optimal storage and reconstitution conditions for recombinant mouse TUSC3?
Recombinant mouse TUSC3 protein is typically supplied as a lyophilized powder and requires careful handling to maintain its activity . The recommended storage protocol includes:
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Upon receipt, briefly centrifuge the vial to bring contents to the bottom
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Store the lyophilized protein at -20°C to -80°C
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Avoid repeated freeze-thaw cycles by preparing working aliquots
For reconstitution:
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Reconstitute the protein in deionized sterile water to a concentration of 0.1-1.0 mg/mL
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Add glycerol to a final concentration of 5-50% (50% is the standard recommendation)
The protein is typically supplied in a Tris/PBS-based buffer containing 6% Trehalose at pH 8.0, which helps maintain stability during storage .
What experimental approaches can detect functional TUSC3 in cellular systems?
Several experimental approaches can be employed to detect and assess functional TUSC3 in cellular systems:
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RNA Expression Analysis:
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RT-PCR using primers spanning different exons can detect TUSC3 transcripts
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RT-qPCR can quantify expression levels, though sensitivity may be limited in tissues with low expression
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For detection of aberrant transcripts, specialized primer combinations targeting suspected altered regions can be used (e.g., forward primer in exon 7 and reverse primer in exon 2 to detect duplications)
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Protein Detection:
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Western blotting using antibodies against TUSC3 or tag epitopes (for recombinant versions)
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Immunofluorescence to visualize localization to the endoplasmic reticulum
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Co-immunoprecipitation to detect interactions with other OST complex components
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Functional Glycosylation Assays:
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Assessment of N-linked glycosylation patterns using glycoprotein-specific stains or lectins
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Monitoring changes in mobility of glycosylated proteins via SDS-PAGE following TUSC3 knockdown or overexpression
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Mass spectrometry analysis of N-glycan profiles
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ER Stress Response Evaluation:
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Measurement of ER stress markers (BiP, CHOP, XBP1 splicing) in response to TUSC3 modulation
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Analysis of the unfolded protein response activation following treatment with ER stressors
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Cell-Based Functional Assays:
How can genomic alterations in TUSC3 be identified and characterized?
Identification and characterization of genomic alterations in TUSC3 require a combination of molecular techniques:
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Genome-wide SNP Analysis:
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Copy Number Variation Detection:
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Junction Fragment Analysis:
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Mutation Screening:
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RNA-based Confirmation:
In one documented case, researchers identified a homozygous deletion in TUSC3 through a systematic approach involving genome-wide SNP typing, copy number analysis, and junction fragment sequencing, followed by comprehensive sequencing of all genes in the linkage interval to exclude other potential causative mutations .
What are the implications of TUSC3 in developing novel cancer therapeutics?
TUSC3's established role as a tumor suppressor in prostate cancer presents several potential avenues for therapeutic development:
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Targeted Restoration of TUSC3 Function:
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Gene therapy approaches to reintroduce functional TUSC3 in tumors with reduced expression
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Small molecules that stabilize remaining TUSC3 protein or enhance its activity
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Exploitation of ER Stress Vulnerability:
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Akt Pathway Inhibition:
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Synthetic Lethality Approaches:
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Identifying genes that, when inhibited, cause selective death in TUSC3-deficient cells
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This approach could provide highly selective therapeutic options
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Biomarker Development:
Research indicates that TUSC3 downregulation accelerates xenograft growth specifically in a PTEN-negative background, suggesting potential synergistic interactions between these tumor suppressors that could be therapeutically exploited .
How can recombinant TUSC3 be used to study congenital disorders of glycosylation?
Recombinant TUSC3 provides a valuable tool for studying congenital disorders of glycosylation (CDG), particularly those associated with nonsyndromic intellectual disability:
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Structure-Function Analysis:
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Comparing wild-type and mutant TUSC3 proteins to understand how specific alterations affect function
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Creating domain-specific mutations to map critical functional regions
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Glycosylation Reconstitution Studies:
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Introducing recombinant TUSC3 into deficient cells to assess rescue of glycosylation defects
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Quantitative assessment of N-glycan profiles before and after reconstitution
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OST Complex Assembly Analysis:
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Using tagged recombinant TUSC3 to study incorporation into the OST complex
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Identifying critical interaction partners within the complex
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Biochemical Characterization:
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In vitro enzymatic assays to directly measure OST activity with different TUSC3 variants
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Determination of binding constants and catalytic parameters
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Genetic Model Development:
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Creating mouse models with specific TUSC3 mutations identified in human patients
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These models could help understand tissue-specific effects of TUSC3 deficiency
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Interestingly, while most congenital disorders of glycosylation present with multisystemic abnormalities, TUSC3 deficiency causes nonsyndromic intellectual disability without the typical clinical or biochemical manifestations of CDG . This unique phenotype suggests TUSC3 may have tissue-specific functions or compensatory mechanisms that could be elucidated through targeted studies with recombinant protein.
