CISD1 Human

What is CISD1 and what is its primary function in human cells?

CISD1 is a homodimeric mitochondrial iron-sulfur-binding protein that plays critical roles in mitochondrial bioenergetics, quality control, defense against oxidative stress, and iron metabolism. The protein contains a CDGSH domain that binds an iron-sulfur (Fe-S) cluster, existing in either holo (Fe-S bound) or apo (Fe-S depleted) forms .

Its primary functions include:

• Regulation of mitochondrial iron homeostasis

• Protection against oxidative stress

• Maintenance of mitochondrial membrane integrity

• Modulation of cellular bioenergetics

CISD1's importance is underscored by its involvement in multiple cellular pathways that, when dysregulated, contribute to conditions including Parkinson's disease, breast cancer, and diabetes mellitus .

How is CISD1 expression altered in different disease states?

CISD1 expression patterns vary significantly between normal and pathological states:

In breast cancer specifically, CISD1 shows significantly higher expression in tumor tissue compared to adjacent normal tissue. This overexpression correlates with clinicopathological parameters including N stage (p=0.012), M stage (p=0.047), PR status (p<0.001), and ER status (p<0.001) .

What experimental models are most effective for studying CISD1 function?

Based on current research approaches, several experimental models have proven valuable for CISD1 research:

Cellular Models:

• Patient-derived dopaminergic neurons (for neurodegenerative research)

• CISD1 knockout cell lines (mouse embryonic fibroblasts)

• Cells expressing mutant CISD1 lacking iron/sulfur cluster capability

Animal Models:

• Pink1 and Parkin mutant Drosophila (fly) models

• Diabetic mouse models

Analytical Techniques:

• Immunoblotting with dimer/monomer separation

• Subcellular fractionation

• siRNA-mediated knockdown

• Quantitative PCR

• Single-sample Gene Set Enrichment Analysis (ssGSEA)

The choice of model depends on the specific research question. For investigating CISD1's role in Parkinson's disease, iPSC-derived dopaminergic neurons from patients with PINK1 mutations provide valuable insights into human pathophysiology . For broader mitochondrial function studies, CISD1 knockout models help elucidate the protein's fundamental roles .

How should researchers design experiments to study CISD1 dimer formation?

CISD1 dimer formation is a critical aspect of its function, particularly in disease states. Experimental design should consider:

Methodological Approach:

• Between-subjects experimental design: When comparing CISD1 dimer formation between different groups (e.g., patient vs. control), ensure random assignment to eliminate confounding factors .

• Sample preparation protocols: Non-reducing conditions must be maintained during protein extraction and gel electrophoresis to preserve dimer structures.

• Controls for antibody specificity: Include CISD1 knockout samples to confirm antibody specificity.

• Quantification methods: Use densitometry to calculate dimer-to-monomer ratios.

• Statistical analysis: Apply parametric tests (student's t-test) for normally distributed data or non-parametric tests (Mann-Whitney) for non-normal distributions .

In the study by Bitar et al., researchers successfully demonstrated increased CISD1 dimer formation in dopaminergic neurons from Parkinson's disease patients with PINK1 Q456X mutations using these methodological approaches .

How is CISD1 implicated in Parkinson's disease pathogenesis?

CISD1 appears to be a downstream mediator in Parkinson's disease pathogenesis, particularly in PINK1 and Parkin-associated familial forms:

Experimental Evidence:

• In dopaminergic neurons derived from patients with PINK1 Q456X mutation, CISD1 shows a significantly increased propensity to form dimers .

• This heightened dimer formation corresponds to CISD1's iron-depleted (apo) state .

• PINK1 mutant neurons show reduced PINK1 mRNA levels and tyrosine hydroxylase expression .

Mechanistic Model:

• PINK1 mutations lead to mitochondrial dysfunction

• This promotes formation of apo-CISD1 (iron-depleted state) dimers

• Apo-CISD1 accumulation contributes to pathology

• Complete loss of CISD1 can rescue detrimental effects of PINK1 loss of function in fly models

These findings suggest that apo-CISD1 accumulation is not merely a consequence but an active contributor to disease progression in PINK1-associated Parkinson's disease.

What methodological approaches are recommended for studying CISD1 in human neuronal models?

When investigating CISD1 in human neuronal contexts, researchers should consider:

Cell Model Generation:

• Generate iPSCs from patient samples with relevant mutations (e.g., PINK1 Q456X)

• Create gene-corrected controls using CRISPR-Cas9

• Differentiate cells into neuroepithelial stem cells

• Further differentiate into midbrain-specific dopaminergic neurons

Analysis Methods:

• Quantitative PCR for mRNA expression

• Immunoblotting for protein expression and dimer formation

• Mitochondrial functional assays

• Verification of dopaminergic identity using markers like tyrosine hydroxylase

• Neuronal marker verification (e.g., beta-tubulin 3)

Statistical Considerations:

• Test data for normality using Shapiro-Wilk test

• Use appropriate parametric or non-parametric tests based on data distribution

• For multiple group comparisons, apply ANOVA or Kruskal-Wallis followed by post-hoc tests

This methodological approach enables researchers to connect CISD1 dysfunction directly to human disease pathophysiology while controlling for genetic background.

What is the relationship between CISD1 expression and breast cancer prognosis?

CISD1 has emerged as a potential prognostic biomarker in breast cancer:

Expression Pattern:

Clinical Correlations:
CISD1 expression in breast cancer significantly associates with:

Immune Infiltration:

• High CISD1 expression correlates with reduced plasmacytoid dendritic cell (pDC) and natural killer (NK) cell infiltration in the tumor microenvironment .

• This immune cell pattern may contribute to the poorer prognosis observed in high CISD1-expressing tumors.

These findings suggest CISD1 may serve as both a prognostic biomarker and potential therapeutic target in breast cancer .

How should researchers design experiments to investigate CISD1's role in tumor progression?

When studying CISD1 in cancer contexts, researchers should consider:

Data Acquisition:

• Obtain RNA-seq data from tumor and normal tissues (e.g., from TCGA database)

• Convert data to appropriate format (e.g., TPM - transcripts per million)

• Verify protein expression using immunohistochemistry (e.g., from Human Protein Atlas)

Analytical Approaches:

Protein Interaction Studies:

• Use STRING database for protein-protein interaction analysis

• Apply STITCH for chemical-protein interaction analysis

• Identify key interaction partners for functional studies

This comprehensive approach allows researchers to develop a detailed understanding of CISD1's role in cancer progression beyond mere expression differences.

How does CISD1 connect diabetes mellitus and cancer risk?

CISD1 appears to represent a molecular link between diabetes and cancer, particularly breast cancer:

Molecular Connections:

• There are 138 shared genes between CISD1 co-expressed gene pool in breast cancer and diabetes mellitus-related genes .

• These shared genes primarily enrich in "cell cycle" pathways.

Functional Evidence:

• Mutant CISD1 can lower glucose levels in models for studying human diabetes-related diseases .

• A novel CISD1 ligand named TT01001 improves diabetes .

• Pioglitazone (a diabetes medication), iron-sulfur clusters, and zinc have been identified as functional partners with CISD1 .

Research Implications:
This molecular overlap suggests CISD1-targeting therapies might simultaneously address both diabetes and cancer, particularly in patients with comorbid conditions. The cell cycle pathway enrichment provides a mechanistic framework for understanding how metabolic dysregulation could promote oncogenesis .

What methodological approaches should be used to investigate CISD1's role in metabolism?

When exploring CISD1's metabolic functions, researchers should consider:

Bioinformatic Methods:

• Gene set enrichment analysis: Apply tools like Metascape for pathway analysis

• Transcription factor prediction: Identify regulatory elements controlling CISD1 expression

• Molecular Complex Detection (MCODE): Identify functional clusters in protein networks

Chemical-Protein Interaction Analysis:

• Analyze CISD1 interactions with metabolic compounds

• Focus on validated partners including pioglitazone, thiazolidi.ne, iron-sulfur clusters, chloride, and Zn(II)

Experimental Validation:

• Measure glucose metabolism in CISD1 mutant models

• Assess effects of CISD1 ligands on metabolic parameters

• Investigate mitochondrial function and bioenergetics

These approaches provide a comprehensive framework for understanding CISD1's role at the intersection of metabolism and disease, potentially leading to novel therapeutic strategies for both diabetes and cancer.