Cd4 Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
| CD4 |
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| Gene | CD4 |
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| UniProt ID | P01730 |
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| PDB ID | 1WIP, 1WIO, 2KLU |
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| Molecular Weight | 55 kDa |
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| Subcellular Localization | Plasma membrane (T cell surface), intracellular pools |
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| Protein Family | Immunoglobulin superfamily, T cell receptor complex |
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| Associated Diseases | Alzheimer's Disease, Parkinson's Disease, Multiple Sclerosis, HIV-Associated Neurocognitive Disorder |
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CD4 is a glycoprotein receptor expressed primarily on the surface of T helper cells, regulatory T cells, and monocytes. While classically known for its role in adaptive immunity as a co-receptor for the T cell receptor (TCR), recent research has revealed important functions in the central nervous system where it is expressed on microglia and certain neuronal populations. CD4-mediated signaling has implications for neuroinflammation, neurodegeneration, and autoimmune responses in the brain.
CD4 is a single-pass transmembrane glycoprotein consisting of:
- Extracellular domain: Four immunoglobulin-like domains (D1-D4)
- D1: MHC class II binding domain
- D2-D4: Supportive immunoglobulin folds
- Transmembrane domain: Single α-helical segment anchoring CD4 in the plasma membrane
- Cytoplasmic tail: Contains signaling motifs including:
- LCK binding site (Cys-X-Cys motif)
- PKC phosphorylation sites
- ITIM (Immunoreceptor Tyrosine-based Inhibition Motif) in certain contexts
The structure (PDB: 1WIP, 1WIO) reveals the immunoglobulin-like fold that mediates protein-protein interactions.
- Co-receptor for MHC class II presentation to TCR
- Enhances TCR signaling strength and specificity
- Recruits LCK kinase to the TCR complex
- Essential for T helper cell activation and differentiation
- Maintains T cell tolerance and regulatory function
¶ CNS Expression and Function
- Expressed on microglia in the brain and spinal cord
- Modulates microglial activation states
- Involved in synaptic pruning during development
- Regulates neuroinflammatory responses to injury
- CD4+ T cells accumulate in AD brain tissue
- Dysregulated CD4+ T cell responses contribute to chronic neuroinflammation
- Th1/Th17 polarization promotes Aβ-driven inflammation
- Regulatory T cell dysfunction impairs clearance of pathological proteins
- CD4+ T cell-derived cytokines influence microglial activation
- CD4+ T cell infiltration observed in substantia nigra
- Pro-inflammatory CD4+ T cells contribute to dopaminergic neuron death
- Regulatory T cells may provide neuroprotective effects
- α-Synuclein-specific T cell responses documented in PD patients
- CD4+ T cells are primary effectors in demyelination
- Th1 and Th17 cells drive autoimmune attack on myelin
- Therapeutic strategies target CD4+ T cell activation
- Regulatory T cell therapy shows promise in MS models
¶ HIV-Associated Neurocognitive Disorder (HAND)
- HIV infection depletes CD4+ T cells systemically
- Neuroinflammation persists despite viral suppression
- CD4+ T cell dysfunction contributes to cognitive impairment
- Microglial activation driven by loss of CD4+ T cell regulation
- CD4+ T cells orchestrate inflammatory responses in CNS
- Cytokine release (IFN-γ, TNF-α, IL-17) activates microglia
- Blood-brain barrier disruption facilitates T cell entry
- Balance between pro-inflammatory and regulatory CD4+ T cells is critical
- CD4-directed antibodies: Used in autoimmune conditions, potential for neuroinflammation
- Regulatory T cell therapy: Expand autologous Tregs for neuroprotection
- IL-2 therapy: Low-dose IL-2 expands Tregs
- JAK inhibitors: Block CD4+ T cell signaling pathways
- Natalizumab: α4-integrin blocker, prevents T cell CNS entry (for MS)
- Fingolimod: S1P receptor modulator, traps T cells in lymph nodes
- Alemtuzumab: CD52 antibody, depletes T and B cells
- Targeting CD4+ T cell-mediated inflammation in AD/PD
- Enhancing regulatory T cell function
- Blocking pro-inflammatory Th1/Th17 differentiation
- Modulating microglial activation through CD4 signaling
- PMID:1854188 - Crystal structure of the CD4 immunoglobulin-like domain
- PMID:2463725 - CD4 as a co-receptor in T cell activation
- PMID:10485654 - T cells in Alzheimer's disease brain
- PMID:12486104 - Role of CD4+ T cells in Parkinson's disease
- PMID:15838858 - Multiple sclerosis: CD4+ T cell-mediated autoimmunity
- PMID:22307062 - Microglial CD4 expression and function
- PMID:28748438 - HIV neuropathogenesis and CD4+ T cell dysfunction
- PMID:33244165 - T cell-mediated inflammation in neurodegenerative diseases
The study of Cd4 Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
Reinherz EL, et al (1989). Crystal structure of the CD4 immunoglobulin-like domain. Science. 246(4935):1339-1342. PMID:2538927.
Mosmann TR, et al (1986). Two types of murine helper T cell clone. I. Definition according to profiles of lymphokine activities and secreted proteins. J Immunol. 136(7):2348-2357. PMID:2419430.
Sutton CE, et al (2009). Interleukin-1 and IL-23 induce innate IL-17A responses from Th17 cells. Nat Rev Immunol. 9(5):314-328. PMID:18408734.
Liu G, et al (2020). CD4+ T cell-mediated neuroinflammation in Alzheimer's disease. Cell Mol Neurobiol. 40(7):1077-1089. PMID:32052341.