PDGFRB Human

What is PDGFRB and what are its primary biological functions?

PDGFRB is a cell-surface receptor tyrosine kinase encoded by the PDGFRB gene located on chromosome 5q33.1 in humans . It is primarily expressed in cells of mesenchymal origin, including fibroblasts, pericytes, and vascular smooth muscle cells . PDGFRB functions as a receptor for platelet-derived growth factors, particularly PDGF-BB.

The primary biological functions of PDGFRB include:

• Regulation of cell proliferation and migration in mesenchymal cells

• Maintenance of blood-brain barrier (BBB) integrity through pericyte function

• Vascular development and stability during embryogenesis and adult life

• Signal transduction through multiple downstream pathways including MAPK/ERK and PI3K/Akt

• Regulation of inflammatory responses in specific cell types

These functions make PDGFRB essential for normal development and tissue homeostasis, while its dysregulation contributes to various pathological conditions.

What PDGF ligands interact with PDGFRB and how is binding specificity determined?

Five distinct PDGF ligands can interact with PDGFRB, each with specific binding properties:

The binding specificity is determined by the structural features of both the ligand and receptor . PDGF ligands exist in dimeric forms and induce receptor dimerization upon binding. This dimerization is crucial for activating the intracellular tyrosine kinase domains and initiating downstream signaling cascades .

How do different downstream signaling pathways mediate PDGFRB functions?

PDGFRB activates multiple signaling pathways that mediate distinct cellular responses:

ERK Pathway:

• Promotes proliferation of pericytes and protection from apoptosis

• Regulates cell migration and differentiation

• Essential for vascular development and maintenance

Akt Pathway:

• Augments pericyte-derived inflammatory secretions

• Regulates metabolism and protein synthesis

• Influences cell survival signals

These pathways can be experimentally dissected using pharmacological inhibitors, revealing that PDGFRB signaling through ERK promotes cell proliferation and survival, while signaling through Akt specifically enhances inflammatory responses . This differential regulation explains how a single receptor can mediate diverse cellular responses in different contexts.

What experimental approaches are most effective for detecting PDGFRB in human tissues?

Several validated approaches exist for detecting PDGFRB in human tissues:

Immunohistochemistry/Immunofluorescence:

• Goat Anti-Human PDGF R beta Antigen Affinity-purified Polyclonal Antibody (AF385) has been validated for paraffin-embedded tissues

• Optimal concentration: 15 μg/mL for IHC-P applications

• Co-staining with COL4 (collagen IV) allows visualization of pericyte-vessel relationships

Western Blot Analysis:

• 2 μg/ml of AF385 antibody effectively detects PDGFRB in human cell lysates

• PDGFRB appears as a band at approximately 190 kDa under reducing conditions

• SH-SY5Y and U2OS cell lines serve as positive controls for PDGFRB expression

Flow Cytometry:

• Surface expression can be detected on intact cells

• CD140b (alternative name for PDGFRB) antibodies are available for flow cytometry

For visualizing PDGFRB-positive pericytes along blood vessels, dual immunofluorescence staining with endothelial markers provides the most informative results, as demonstrated in studies examining the blood-brain barrier .

How can researchers experimentally manipulate PDGFRB signaling?

Researchers can manipulate PDGFRB signaling through several approaches:

Activation Methods:

• Recombinant PDGF-BB (4 ng/mL is commonly used)

• PDGF-DD for selective PDGFRB activation

• Chimeric/engineered PDGF ligands with altered specificity

Inhibition Methods:

• Neutralizing antibodies:

  • Anti-PDGFRB antibodies (e.g., AF385)

  • Typical ND50: 10-40 μg/mL in presence of 2 μg/mL PDGF R beta Fc Chimera

• Recombinant decoy receptors:

  • PDGF R beta Fc Chimera effectively inhibits PDGF-BB activity at 2 μg/mL

• Signaling pathway inhibitors:

  • ERK pathway: U0126, PD98059

  • PI3K/Akt pathway: LY294002, wortmannin

  • These allow dissection of distinct aspects of the PDGF-BB response

• Genetic approaches:

  • siRNA/shRNA knockdown

  • CRISPR/Cas9 gene editing

  • Expression of dominant-negative constructs

These approaches allow researchers to selectively manipulate specific aspects of PDGFRB signaling for mechanistic studies.

What cell and animal models are appropriate for studying PDGFRB function?

Multiple experimental models have been validated for PDGFRB research:

Cell Culture Models:

• Primary human brain pericytes - ideal for studying BBB-related functions

• NR6R-3T3 mouse fibroblasts - used for PDGF-BB-dependent proliferation assays

• SH-SY5Y neuroblastoma and U2OS osteosarcoma - express detectable PDGFRB

• Vascular smooth muscle cells - for studying vascular functions

Coculture Systems:

• Endothelial cell-pericyte cocultures model the neurovascular unit

• Endothelial progenitor cells with mesenchymal stem cells enhance proliferation and angiogenesis through PDGF signaling

Animal Models:

• Transgenic mice with cell-type specific PDGFRB deletion

• Mouse models of Alzheimer's disease to study PDGFRB in neurodegeneration

• Zebrafish models for vascular development studies

Human Tissue Models:

• Paraffin-embedded human tissue sections for IHC studies

• Human-derived organoids, particularly kidney and brain organoids

Each model system offers specific advantages depending on the research question, with primary human pericytes providing the most translational relevance for human disease studies.

How is PDGFRB signaling altered in Alzheimer's disease?

PDGFRB signaling shows significant alterations in Alzheimer's disease (AD):

Vascular PDGFB Reduction:

• Human AD brains exhibit a marked reduction in vascular PDGFB expression

• This reduction compromises PDGF-BB:PDGFRβ signaling in brain pericytes

Pericyte Loss and BBB Dysfunction:

• Pericyte loss is a well-established feature of AD vasculopathy

• BBB impairment occurs early in AD pathogenesis, preceding amyloid deposition

• Vascular changes exacerbate other AD pathologies, including plaque load and neuronal loss

Mechanistic Implications:

• Reduced PDGFRB signaling leads to pericyte dysfunction and death

• This contributes to BBB breakdown, which allows neurotoxic blood components into the brain

• Pericytes normally internalize and clear aggregated amyloid-β42 through an LRP1-dependent mechanism

• PDGFRB dysfunction compromises this clearance mechanism

Therapeutic Potential:

• Supplementing PDGF-BB signaling could potentially stabilize the cerebrovasculature in AD

• Targeting specific downstream pathways (ERK vs. Akt) might allow for more precise interventions

These findings highlight PDGFRB as a critical component in AD vascular pathology and a potential therapeutic target.

What genetic alterations of PDGFRB occur in human diseases?

PDGFRB mutations contribute to several human diseases:

Fusion Proteins in Hematological Malignancies:

• ETV6-PDGFRB fusion in myeloproliferative neoplasms

• FIP1L1-PDGFRA structurally similar to PDGFRB fusions

• EBF1-PDGFRB in B-cell acute lymphoblastic leukemia

These fusion proteins typically contain:

• N-terminal domain from the fusion partner

• C-terminal kinase domain from PDGFRB

• Constitutive activation through either:

  • Disruption of the autoinhibitory juxtamembrane domain

  • Constitutive oligomerization driven by the partner protein

Non-Cancerous PDGFRB-Related Disorders:

• Skeletal defects

• Primary familial brain calcification

• Vascular anomalies

Expression Changes:

• Reduced vascular PDGFB in Alzheimer's disease

• Altered expression in multiple cancer types

• Changes in aging-related vascular pathology

Understanding these genetic alterations provides insights into disease mechanisms and potential therapeutic approaches.

How does PDGFRB contribute to pericyte function in vascular maintenance?

PDGFRB plays a critical role in pericyte-mediated vascular maintenance:

Pericyte Development and Recruitment:

• PDGF-BB secreted by endothelial cells acts as a chemoattractant for PDGFRB-expressing pericytes

• This signaling axis ensures proper pericyte coverage of blood vessels

Blood-Brain Barrier Integrity:

• PDGFRB is highly expressed in brain pericytes, which are essential for BBB maintenance

• PDGF-BB:PDGFRβ signaling maintains pericyte survival and function

• Pericytes enhance tight junction formation in endothelial cells and reduce transcytosis

• PDGFRB-positive pericytes can be visualized along capillaries using immunofluorescence

Vascular Stability:

• Pericytes regulate vascular diameter and cerebral blood flow

• They contribute to basement membrane formation

• PDGFRB signaling influences pericyte contractility, affecting vascular tone

Amyloid-β Clearance:

• BBB-associated pericytes internalize and clear aggregated amyloid-β42

• This occurs through an LRP1-dependent, apolipoprotein E isoform-specific mechanism

• PDGFRB signaling is essential for maintaining this clearance function

These functions highlight why PDGFRB-positive pericytes are crucial for vascular health, particularly in the brain, and why their dysfunction contributes to neurodegenerative diseases.

How do ERK and Akt pathways differentially regulate PDGFRB responses in pericytes?

PDGF-BB:PDGFRβ signaling activates both ERK and Akt pathways, but with distinct functional outcomes in pericytes:

ERK Pathway-Mediated Effects:

• Promotes pericyte proliferation

• Protects pericytes from apoptosis

• Essential for vascular development and maintenance

• Critical for recovery from vascular injury

Akt Pathway-Mediated Effects:

• Augments pericyte-derived inflammatory secretions

• Regulates metabolic functions

• Influences protein synthesis pathways

• May contribute to inflammatory aspects of vascular pathology

What is the role of PDGFRB in aging and age-related vascular changes?

PDGFRB has been identified as a gene associated with human aging processes :

Age-Related PDGFRB Changes:

• PDGFRB binds PDGFB and may be related to age-related changes in the heart

• Aging can alter PDGFRB expression in vascular tissues

• PDGFRB is associated with the GO term "aging" (GO:0007568)

Impact on Vascular Function:

• Age-related decreases in PDGFRB signaling contribute to reduced pericyte coverage

• This leads to increased vascular permeability and altered blood flow regulation

• In the brain, these changes contribute to BBB breakdown with aging

Relationship to Age-Related Diseases:

• Vascular changes mediated by decreased PDGFRB signaling precede neurodegeneration

• This creates a mechanistic link between vascular aging and neurodegenerative diseases like Alzheimer's

• The temporal relationship suggests vascular dysfunction may be causative rather than consequential

Understanding PDGFRB's role in vascular aging may reveal new targets for preventing age-related diseases.

How can PDGFRB research inform therapeutic strategies for neurovascular diseases?

Research on PDGFRB pathways reveals several therapeutic opportunities:

Potential Therapeutic Approaches:

• Supplementing PDGF-BB signaling to stabilize the cerebrovasculature in AD

• Selective pathway modulation (enhancing ERK while limiting Akt activation)

• Targeting pericyte-specific PDGFRB signaling to preserve BBB function

Translational Considerations:

• PDGFRB fusion proteins in hematological malignancies represent established therapeutic targets

• Similar targeting approaches could be adapted for neurovascular applications

• Understanding pathway-specific effects allows more precise intervention

Therapeutic Challenges:

• Delivery of biologics across the BBB

• Potential side effects of systemic PDGFRB modulation

• Need for cell-type specific targeting strategies

Combination Approaches:

• Combining PDGFRB modulation with anti-amyloid therapies

• Addressing both vascular and neuronal aspects of neurodegenerative diseases

• Preventive strategies targeting PDGFRB in high-risk populations

The critical role of PDGFRB in vascular maintenance positions it as a promising target for diseases with vascular components, particularly neurodegenerative conditions where vascular dysfunction precedes other pathologies .