PHKB Antibody

The Target Protein: PHKB

Phosphorylase kinase beta (PHKB) is a regulatory subunit of phosphorylase kinase (PHK), an enzyme complex composed of four subunits (alpha, beta, gamma, and delta) that plays a critical role in glycogen metabolism . The PHKB gene encodes the beta subunit which, together with the alpha subunit, regulates the activity of the catalytic gamma subunit . Functionally, PHKB is involved in glycogen biosynthesis and metabolism, participating in the cascade activation of glycogenolysis through the stimulation of energy production from glycogen .

The protein has a molecular weight of approximately 124-125 kDa and consists of 1086 amino acids . PHKB activity is regulated by phosphorylation of various serine residues, which in turn catalyzes the phosphorylation of serine in certain substrates, including troponin I .

PHKB Antibodies: Overview

PHKB antibodies are immunoglobulins developed to recognize and bind to specific epitopes on the PHKB protein. These antibodies serve as valuable tools for detecting, quantifying, and studying the PHKB protein in various experimental contexts . They are utilized across multiple research applications including Western blotting, immunohistochemistry, immunoprecipitation, and ELISA techniques .

Types of PHKB Antibodies

PHKB antibodies are available in two main types:

1. Polyclonal antibodies: These are mixtures of immunoglobulins that recognize multiple epitopes on the PHKB protein. They are typically produced in rabbits through immunization with PHKB recombinant proteins or synthetic peptides derived from human PHKB sequences .

2. Monoclonal antibodies: These are homogeneous antibodies that recognize a single epitope on the PHKB protein. For example, Abcam offers a recombinant monoclonal antibody (clone EPR9035(2)) developed specifically against PHKB .

Host Species and Clonality

The majority of commercially available PHKB antibodies are produced in rabbits, with some produced in mice:

Immunogens and Binding Specificity

PHKB antibodies are generated using various immunogens:

• Recombinant proteins (e.g., NovoPro #113820 uses PHKB recombinant protein with accession number XM_005255984)

• Synthetic peptides corresponding to specific amino acid sequences (e.g., Anti-PHKB Antibody A28091 uses a synthetic peptide corresponding to amino acids 699-744 of Human PHKB)

• Fusion proteins with tags such as GST (e.g., ABIN562212 uses PHKB partial recombinant protein with GST tag)

Western Blotting (WB)

PHKB antibodies are extensively used in Western blotting to detect the PHKB protein in tissue and cell lysates. The recommended dilutions typically range from 1:200 to 1:2000 . Validated reactivity has been demonstrated in:

• Human cell lines: HepG2, Jurkat, K-562, LNCaP

• Mouse tissues: heart, skeletal muscle, liver

• Rat tissues: heart, skeletal muscle

The observed molecular weight in Western blotting is approximately 124-125 kDa, which correlates with the predicted molecular weight of the PHKB protein .

Immunohistochemistry (IHC)

PHKB antibodies are used for localizing the PHKB protein in tissue sections, with recommended dilutions ranging from 1:20 to 1:500 . Validated reactivity has been shown in:

• Human tissues: skeletal muscle, liver

• Mouse tissues: skeletal muscle, liver

In IHC applications, PHKB staining is primarily observed in the cytoplasm of positive cells .

Immunoprecipitation (IP)

PHKB antibodies have been validated for immunoprecipitation applications, particularly for pulling down PHKB protein complexes to study protein-protein interactions. This has been crucial in research investigating PHKB's interactions with other proteins such as KIAA1199 and PYGB .

The recommended dilution for IP applications ranges from 1:200 to 1:2000, with 0.5-4.0 μg of antibody typically used for 1.0-3.0 mg of total protein lysate .

ELISA Applications

Several PHKB antibodies are validated for ELISA applications, providing quantitative measurements of PHKB protein levels . These assays are particularly useful in high-throughput screening and for measuring PHKB levels in complex biological samples.

Major Suppliers and Products

Multiple vendors offer PHKB antibodies with various specifications and validations:

Role in Glycogen Metabolism Research

PHKB antibodies have been instrumental in studying the role of PHKB in glycogen breakdown. Research using these antibodies has helped elucidate how phosphorylase kinase regulates glycogen phosphorylase and consequently affects glycogen metabolism .

One significant finding involves the interaction between KIAA1199 protein and PHKB under nutrient-deprived conditions, which promotes glycogen breakdown and cancer cell survival. This interaction was demonstrated through immunoprecipitation experiments using PHKB antibodies .

PHKB in Cancer Research

Recent studies using PHKB antibodies have revealed surprising roles for PHKB in cancer biology:

1. Hepatocellular Carcinoma (HCC): Contrary to expectations, PHKB expression is significantly decreased in HCC tissues compared to normal liver tissue. Low expression of PHKB correlates with poor prognosis in HCC patients. Tissue microarray analysis using PHKB antibodies demonstrated that PHKB could serve as an independent indicator for predicting poor prognosis in HCC .

2. Tumor Suppressor Function: Functional experiments showed that PHKB knockdown significantly promoted cell proliferation both in vitro and in vivo, whereas PHKB overexpression inhibited cancer cell growth. These findings suggest that PHKB may function as a tumor suppressor in HCC .

3. Epithelial-Mesenchymal Transition (EMT): PHKB expression was found to be associated with EMT status in HCC. Specifically, PHKB expression positively correlated with E-cadherin (epithelial marker) and negatively correlated with N-cadherin (mesenchymal marker), suggesting that PHKB suppresses the EMT process, which is crucial for cancer invasion and metastasis .

4. Signaling Pathway Regulation: Mechanistically, PHKB was found to inhibit AKT and STAT3 signaling pathway activation in HCC. These pathways are well-known for their roles in promoting cancer cell survival and proliferation .

PHKB Antibodies in Interaction Studies

PHKB antibodies have been crucial in identifying novel protein-protein interactions:

A study by Terashima et al. used PHKB antibodies to demonstrate that KIAA1199 interacts with PHKB and glycogen phosphorylase brain form (PYGB) under serum-free conditions. This interaction promoted glycogen breakdown and cancer cell survival, suggesting a potential metabolic adaptation mechanism in cancer cells .

Validation Methods

Commercial PHKB antibodies undergo various validation methods to ensure specificity and reliability:

1. Western blotting: Validated in multiple cell lines and tissue samples to confirm the correct molecular weight band (124-125 kDa) .

2. Immunohistochemistry: Tested on paraffin-embedded tissue sections to confirm specific staining patterns in tissues known to express PHKB .

3. Immunoprecipitation: Validated through pull-down assays to confirm the ability to isolate PHKB from complex protein mixtures .

Specificity Testing

Specificity of PHKB antibodies is typically assessed through:

1. Antigen competition: Pre-incubation of the antibody with the immunizing peptide or protein to block specific binding.

2. Cross-reactivity testing: Evaluation of the antibody's reactivity across multiple species to determine conservation of the recognized epitope.

3. Knockdown/knockout validation: Testing antibody specificity in cells where PHKB expression has been reduced or eliminated through genetic manipulation .