PHB2 Human
Description
Biological Functions and Mechanisms
PHB2 operates through location-dependent mechanisms:
Mitochondrial Roles:
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Mitophagy Regulation: Essential for PINK1-Parkin-mediated mitophagy by stabilizing PINK1 and recruiting Parkin to damaged mitochondria .
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Metabolic Regulation:
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Structural Scaffold: Forms oligomeric complexes with PHB1 to maintain mitochondrial cristae morphology .
Nuclear/Cytoplasmic Roles:
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Represses estrogen receptor (ER) activity via histone deacetylase recruitment .
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Modulates cell cycle progression and apoptosis through interactions with p53 and Hax-1 .
Cancer
PHB2 exhibits dual roles in oncology:
Key Findings:
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PHB2 overexpression correlates with poor prognosis in lung adenocarcinoma (HR = 1.7, p < 0.01) .
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Knockdown reduces NSCLC xenograft tumor volume by 60–70% (p < 0.001) .
Research Tools and Clinical Implications
Experimental Models:
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PHB2 Knockout: Causes embryonic lethality in mice and mitochondrial fragmentation in C. elegans .
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Therapeutic Targets:
Drug Development:
Controversies and Future Directions
Product Specs
Q&A
What experimental approaches are optimal for assessing PHB2’s role in mitochondrial dysfunction?
PHB2’s involvement in mitochondrial integrity can be evaluated through a combination of genetic, biochemical, and imaging techniques:
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Knockdown/Overexpression Models: siRNA-mediated PHB2 silencing in RINm5F β-cells reduced mitophagy under oxidative stress, while PHB2 overexpression restored mitochondrial function . CRISPR-Cas9 knockout models in mice revealed tissue-specific phenotypes (e.g., heart failure in cardiac PHB2-knockout mice) .
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Functional Assays: Measure oxidative phosphorylation (OXPHOS) via Seahorse XF analyzers. PHB2-deficient colorectal cancer cells showed 40–60% reduced OXPHOS activity .
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Mitophagy Quantification: Use tandem fluorescent mKeima reporters or LC3-II/PHB2 co-localization assays. Studies show PHB2-LC3 interaction is critical for Parkin-mediated mitophagy .
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Electron Microscopy: Detect ultrastructural mitochondrial damage (e.g., cristae loss in diabetic rat β-cells) .
How do researchers distinguish PHB2-specific functions from PHB1/PHB2 complex roles?
PHB1 and PHB2 form obligate heterodimers, complicating functional studies. Key strategies include:
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Tissue-Specific Knockouts: Forebrain-specific PHB2 deletion caused tau hyperphosphorylation, while PHB1 levels concurrently dropped, suggesting interdependency .
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Co-Immunoprecipitation (Co-IP): Validate PHB1-PHB2 interactions under experimental conditions. For example, PHB2 knockdown in HEK293T cells reduced PHB1 levels by >70% .
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Rescue Experiments: Overexpress PHB2 in PHB1-deficient cells to test functional redundancy. In β-cells, PHB2 alone restored insulin secretion despite PHB1 depletion .
Table 1: PHB1 vs. PHB2 Functional Overlap and Distinctions
What biomarkers are used to link PHB2 dysregulation to human diseases?
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Immunohistochemistry (IHC): PHB2 is overexpressed in hepatocellular carcinoma (HCC) and NSCLC tissues compared to adjacent normal tissues (2.5–3.1-fold increase) .
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Serum Profiling: In diabetic rats, PHB2 levels in β-cells correlated with insulin secretion (r = 0.82, p < 0.01) .
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Transcriptomics: RNA-seq of PHB2-knockout podocytes identified 312 dysregulated genes, including NLRP3 (↑4.2x) and IL-1β (↑3.8x) .
How do contradictory findings on PHB2’s role in cancer progression arise?
PHB2 exhibits context-dependent oncogenic or tumor-suppressive effects:
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Pro-Tumor Mechanisms:
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Anti-Tumor Effects:
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Resolution Strategies:
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Perform tissue-specific pathway mapping (e.g., AKT/NF-κB in HCC vs. p53 in prostate cancer).
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Use isogenic cell lines with controlled PHB2 expression to isolate microenvironmental influences.
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What methodologies resolve PHB2’s dual role in oxidative stress responses?
PHB2 mediates both protective mitophagy and stress-induced apoptosis depending on redox status:
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Nrf2/PHB2 Pathway:
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Kinetic Studies: Time-course analyses show PHB2 degradation precedes apoptosis (e.g., 6 hr post-H2O2 exposure in β-cells) .
How can researchers model PHB2-associated neurodegenerative diseases?
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Transgenic Mice: Forebrain-specific PHB2 knockout mice develop tauopathy (p-tau ↑3x) and neuronal loss (↓40% at 12 months) .
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iPSC-Derived Neurons: PHB2 knockdown in dopaminergic neurons reduced mitochondrial membrane potential (ΔΨm ↓55%) and increased ROS (↑80%) .
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Cerebrospinal Fluid (CSF) Analysis: PHB2 levels inversely correlate with neurofilament light chain (NfL) in ALS patients (r = −0.67, p = 0.03) .
What in vitro systems best recapitulate PHB2’s metabolic regulatory functions?
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3D Spheroid Cultures: Primary hepatocyte spheroids with PHB2 knockdown showed impaired gluconeogenesis (glucose output ↓70%) .
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Seahorse Metabolomics: PHB2-deficient cardiomyocytes exhibited reduced fatty acid oxidation (OCR ↓45%) .
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Live-Cell Imaging: FRET-based sensors confirmed PHB2-ATAD3A interactions regulate mitochondrial cristae dynamics .
Table 2: Common Technical Pitfalls in PHB2 Research
Emerging Frontiers
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CRISPR Screens: Genome-wide screens identified PHB2 as a synthetic lethal target in AURKA-amplified cancers .
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Cryo-EM Structures: Resolved PHB2-AAA+ protease complexes (4.2 Å resolution) revealing substrate-binding pockets .
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PHB2-Targeted PROTACs: Degraders like PHB2-SMAC achieved 90% protein knockdown in HCC xenografts .
Product Science Overview
Prohibitin 2 is encoded by the PHB2 gene and is composed of 299 amino acids. The recombinant form of this protein, often tagged with a His-tag at the N-terminus, is typically expressed in E. coli for research purposes . The predicted molecular mass of recombinant Prohibitin 2 is approximately 35.7 kDa .
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Transcriptional Regulation: Prohibitin 2 acts as a mediator of transcriptional repression by nuclear hormone receptors. It recruits histone deacetylases, which are enzymes that remove acetyl groups from histones, leading to a more compact and transcriptionally repressive chromatin structure . It functions as an estrogen receptor (ER)-selective coregulator, enhancing the inhibitory activities of antiestrogens and repressing the activity of estrogens .
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Mitochondrial Function: Prohibitin 2 is involved in regulating mitochondrial respiration activity. It forms a complex with Prohibitin 1 (PHB1) within the mitochondria, which is essential for maintaining mitochondrial integrity and function . This complex is believed to play a role in the stabilization of mitochondrial proteins and the regulation of mitochondrial dynamics.
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Cellular Aging: Prohibitin 2 has been implicated in the aging process. Its role in mitochondrial function and transcriptional regulation suggests that it may influence cellular senescence and longevity .
Recombinant Prohibitin 2 is primarily used in research to study its various functions and interactions. It is often utilized in Western Blot (WB) or imaging assays due to its denatured form . Researchers use this protein to investigate its role in transcriptional repression, mitochondrial function, and its potential implications in diseases related to aging and mitochondrial dysfunction.
