| Symbol | PRKCQ |
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| Full Name | Protein Kinase C Theta |
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| Chromosome | 10p15.1 |
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| NCBI Gene ID | [5590](https://www.ncbi.nlm.nih.gov/gene/5590) |
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| UniProt ID | [Q04759](https://www.uniprot.org/uniprot/Q04759) |
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| Ensembl ID | [ENSG0000006555](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG0000006555) |
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PRKCQ (Protein Kinase C Theta) is a member of the novel protein kinase C (nPKC) subfamily, characterized by its calcium-independent activation by diacylglycerol (DAG) and phorbol esters. Unlike conventional PKC isoforms, PRKCQ is predominantly expressed in T-cells and certain neuronal populations, where it plays critical roles in T-cell receptor signaling, synaptic plasticity, and neuronal survival . This isoform has attracted significant attention for its roles in immune-mediated processes relevant to neuroinflammation in neurodegenerative diseases.
PRKCQ is a serine/threonine kinase with several distinctive functional features:
¶ Kinase Structure and Regulation
- DAG-binding C1 Domain: Mediates responsiveness to diacylglycerol and phorbol esters without requiring calcium .
- C3/C4 ATP-binding Domain: Catalytic domain with kinase activity.
- Atypical PKC Interaction: Can interact with other atypical PKCs (ζ, λ/ι) in certain cellular contexts .
- T-cell Activation: PRKCQ is essential for T-cell receptor (TCR) signaling, where it activates NF-κB, AP-1, and NFAT transcription factors critical for T-cell proliferation and cytokine production .
- Synaptic Plasticity: In neurons, PRKCQ localizes to presynaptic terminals and regulates neurotransmitter release, long-term potentiation (LTP), and learning and memory .
- Cytoskeletal Reorganization: Controls actin cytoskeleton dynamics through phosphorylation of downstream substrates, affecting cell morphology and migration .
PRKCQ has several connections to Alzheimer's disease pathogenesis:
- Neuroinflammation: As a key kinase in T-cell signaling, PRKCQ contributes to peripheral T-cell activation and subsequent neuroinflammation in AD. Elevated PRKCQ activity in peripheral immune cells may exacerbate CNS inflammation .
- Amyloid-beta Signaling: PRKCQ can modulate amyloid-beta-induced toxicity in neurons. Studies have shown that PRKCQ inhibition can protect against Aβ-induced neuronal death in vitro .
- Tau Phosphorylation: PKC signaling pathways can influence tau phosphorylation through direct phosphorylation of tau kinases (GSK-3β, CDK5) and phosphatases .
- Synaptic Dysfunction: Given its role in synaptic plasticity, altered PRKCQ signaling may contribute to synaptic deficits in AD .
- Microglial Activation: PRKCQ in microglia contributes to neurotoxic cytokine production in response to dopaminergic neuron degeneration. Targeting PRKCQ has been proposed as a strategy to modulate neuroinflammation in PD .
- Alpha-Synuclein Phosphorylation: PKC isoforms can phosphorylate alpha-synuclein at Ser129, a modification linked to Lewy body formation .
- Mitochondrial Dysfunction: PRKCQ signaling may intersect with mitochondrial pathways relevant to dopaminergic neuron survival .
- T-cell Dysregulation: ALS involves peripheral immune system alterations. PRKCQ-mediated T-cell signaling may contribute to the neuroinflammatory environment in ALS .
- Excitotoxicity: PKC signaling can modulate glutamate receptor activity and excitotoxicity, a key mechanism in motor neuron degeneration .
- Oligodendrocyte Function: PRKCQ is expressed in oligodendrocytes and may affect myelin maintenance. Dysregulated PRKCQ signaling could contribute to oligodendrocyte degeneration in MSA .
- Neuronal Expression: Moderate expression in various brain regions including the cortex, hippocampus, basal ganglia, and cerebellum .
- Glial Expression: Detected in microglia and oligodendrocytes, with higher expression in activated glial cells .
- Synaptic Localization: Presynaptic terminals, where it regulates neurotransmitter release .
- T-cells: Highest expression in T-lymphocytes, particularly in CD4+ and CD8+ T-cells .
- Other Immune Cells: Lower expression in B-cells, NK cells, and macrophages.
- Baier-Bitterlich et al., PKC-θ: structure, function and expression (1996)
- Altman & Villagos, PKC-θ in T-cell activation and function (2002)
- Hanse et al., PKC-θ in synaptic plasticity and learning (2013)
- Moscat et al., PKC-ζ and PKC-λ in cell signaling (2000)
- Lester & Aderem, The Rac and Rho pathway to cytoskeletal reorganization (2000)
- McQuade & Miller, Neuroinflammation in AD and PKC-θ (2010)
- Cheng et al., PKC-θ and amyloid-beta neurotoxicity (2011)
- Takashima, GSK-3β and tau phosphorylation in AD (2006)
- Bido et al., Microglial activation in PD and PKC isoforms (2011)
- Fujiwara et al., Alpha-synuclein phosphorylation by PKC (2003)
- Gandhi et al., Mitochondrial dysfunction in PD (2009)
- Beers et al., T-cell activation in ALS (2006)
- Spires-Jones & Hyman, Excitotoxicity in neurodegenerative disease (2004)
- Wakabayashi & Takahashi, Oligodendrocyte pathology in MSA (2006)
- Brain RNA-seq database: PRKCQ expression (2018)