SDF2 Human

What is SDF2 and what is its molecular structure?

SDF2 is a secretory protein that is partly similar to the hydrophilic segments of yeast mannosyltransferases. Human SDF2 is a single, non-glycosylated polypeptide chain containing 211 amino acids with a molecular mass of approximately 23.7kDa . The human SDF2 gene maps to chromosome 17 at position q11.2 . The protein contains three MIR (protein O-mannosyltransferase, inositol 1,4,5-trisphosphate receptor, and ryanodine receptor) domains that are likely critical for its function in the endoplasmic reticulum (ER) .

Where is SDF2 expressed in human tissues?

SDF2 shows ubiquitous expression across human tissues . Research has documented its expression in breast cancer tissues and cell lines, colorectal cancer, endothelial cells, and placental tissues . Gene expression studies indicate that SDF2 mRNA levels may change during development and in disease states. For instance, SDF2 expression is reduced in breast and colorectal cancer cases with poor prognosis, including metastasis and death .

What cellular compartments contain SDF2?

SDF2 is primarily localized in the endoplasmic reticulum (ER) . This subcellular localization is consistent with its proposed functions in ER stress response and protein quality control. When studying SDF2 experimentally, researchers often isolate microsomes (vesicle-like fragments formed from pieces of the ER) to detect and analyze SDF2 protein levels .

What are the primary functions of SDF2 in human cells?

SDF2 appears to serve several critical functions related to protein homeostasis:

• ER stress response regulation: SDF2 is involved in the unfolded protein response (UPR) and ER stress pathway . It may contribute to cell survival during ER stress by interfering with ER stress proteins such as spliced XBP1 (XBP1s) and CHOP .

• Protein quality control: Based on research in various models including human cells and plant systems (Arabidopsis thaliana and Oryza sativa L.), SDF2 acts as a component of ER chaperone complexes related to quality control of newly synthesized proteins .

• Prevention of protein aggregation: SDF2 associates with chaperones in the ER, which helps prevent the aggregation of misfolded proteins .

• Signaling pathway modulation: In human endothelial cells, SDF2 was identified as a component of the Hsp90-eNOS complex, where it is required for eNOS phosphorylation and activation .

How does SDF2 contribute to cellular survival mechanisms?

SDF2 appears to play a crucial role in determining cell fate during ER stress. In placental cells, SDF2 may contribute to cell survival during the unfolded protein response by interfering with ER stress proteins such as spliced XBP1 (XBP1s) and CHOP . The cellular decision to eliminate cells producing nonfunctional proteins during pregnancy may be a turning point that determines the health of a pregnancy, with potential implications for conditions such as intrauterine growth restriction and preeclampsia .

Research suggests that SDF2 may be an important regulatory factor by which trophoblast cells can control cell survival under ER stress conditions . This function might extend to other cell types as well, potentially contributing to disease progression or resistance in contexts like cancer.

What methodologies are most effective for studying SDF2?

Several methodological approaches have proven effective for SDF2 research:

• Immunoblotting: Rat monoclonal antibodies against human SDF2 have been successfully used for immunoblotting. Multiple clones, including 3A1-1D6 and 3A1-1H10 (rat IgG2ακ), have demonstrated specificity for human SDF2, giving signals at the expected 23 kDa band position .

• Immunoprecipitation: The 3A1 clone has been shown to efficiently immunoprecipitate human SDF2-FLAG fusion proteins, making it a valuable tool for studying SDF2 interactions .

• Microsome isolation: Since SDF2 is localized in the ER, isolation of microsomes is an effective approach for enriching SDF2 in experimental samples .

• Gene knockout studies: SDF2-knockout cell lines have been developed to study the functional consequences of SDF2 loss .

• Expression analysis: Quantitative PCR and other expression analysis techniques have been used to study SDF2 mRNA levels in different tissues and disease states .

What is the relationship between SDF2 and cancer?

Gene expression of SDF2 is reduced along with a poor prognosis (metastasis and death) in breast and colorectal cancer . This suggests that SDF2 may have tumor-suppressive functions or serve as a biomarker for disease progression.

Additionally, research indicates that SDF2 may confer oxaliplatin resistance to certain cancer cell lines (e.g., OCUM-2M cells), though the exact molecular mechanisms for this resistance remain unclear . This finding points to a potential role for SDF2 in chemotherapy resistance, which is a significant clinical challenge.

How does SDF2 interact with other proteins in the ER stress pathway?

SDF2 appears to function within a network of ER stress response proteins. It has been shown to:

• Interfere with ER stress proteins such as spliced XBP1 (XBP1s) and CHOP .

• Associate with chaperones in the ER to prevent aggregation of misfolded proteins .

• Form part of the Hsp90-eNOS complex in endothelial cells .

The exact molecular mechanisms of these interactions require further investigation, but they suggest that SDF2 acts within protein complexes to mediate its functions in stress response and protein quality control.

What are the challenges in purifying SDF2 for experimental use?

Recombinant human SDF2 can be produced in E. coli as a single, non-glycosylated polypeptide chain. A successful purification strategy involves:

• Fusing SDF2 to a 23 amino acid His-tag at the N-terminus

• Purifying through proprietary chromatographic techniques

• Formulating in a solution containing 20mM Tris-HCl buffer (pH 8.0), 10% glycerol, and 0.4M Urea

The purified protein should have greater than 85.0% purity as determined by SDS-PAGE .

For storage stability, it's recommended to:

• Store at 4°C if the entire vial will be used within 2-4 weeks

• Store frozen at -20°C for longer periods

• Add a carrier protein (0.1% HSA or BSA) for long-term storage

• Avoid multiple freeze-thaw cycles

How can SDF2 function be manipulated experimentally?

Several experimental approaches can be used to manipulate SDF2 function:

• Gene knockout: CRISPR-Cas9 or other gene editing technologies can be used to create SDF2-knockout cell lines .

• RNA interference: siRNA or shRNA targeting SDF2 can be used to knock down its expression.

• Overexpression studies: Transfection with SDF2-expressing vectors (potentially with tags like FLAG) can be used to study the effects of increased SDF2 levels .

• ER stress induction: Since SDF2 is involved in ER stress responses, treatments that induce ER stress (e.g., tunicamycin, thapsigargin) can be used to study how SDF2 levels and function change under stress conditions.

• Immunoprecipitation with specific antibodies: The 3A1 clone has been shown to effectively immunoprecipitate SDF2, allowing for the study of its interaction partners .

What are the critical knowledge gaps in SDF2 research?

Despite advances in understanding SDF2, several important questions remain:

• The exact molecular mechanism by which SDF2 confers oxaliplatin resistance to cancer cells is not fully understood .

• The complete interactome of SDF2 in the ER and how these interactions change under different stress conditions requires further investigation.

• The potential role of SDF2 as a biomarker or therapeutic target in cancer and other diseases needs more extensive evaluation.

• The regulatory mechanisms controlling SDF2 expression in different tissues and disease states are not fully characterized.

• The functional significance of SDF2's three MIR domains and how they contribute to its molecular functions remain to be elucidated.

What potential therapeutic applications might emerge from SDF2 research?

Based on current knowledge, several therapeutic applications might emerge:

• Cancer treatment: Understanding how SDF2 contributes to chemotherapy resistance could lead to strategies for overcoming this resistance in cancer patients.

• Placental disorders: Given SDF2's role in trophoblast cell survival under ER stress, it might be a target for treating placental disorders like preeclampsia or intrauterine growth restriction .

• ER stress-related diseases: SDF2 modulation might have applications in treating diseases associated with ER stress, including neurodegenerative disorders, diabetes, and inflammatory conditions.

• Biomarker development: Changes in SDF2 expression might serve as biomarkers for disease progression or treatment response in certain cancers .