Chromatin-associated protein kinase C-θ regulates an inducible gene expression program and microRNAs in human T lymphocytes

Regulation of PKC-θ function by phosphorylation in T cell receptor signaling

Protein kinase C (PKC)-θ is a serine/threonine kinase belonging to the calcium-independent novel PKC subfamily; its expression is restricted to certain tissues and cell types, including T cells. The signals delivered from T cell receptor (TCR) and CD28 costimulatory molecules trigger PKC-θ catalytic activation and membrane translocation to the immunological synapse, leading to activation of NF-κB, AP-1, and NF-AT. These transcription factors are important for T cell survival, activation, and differentiation. Phosphorylation of PKC-θ at multiple Ser/Thr/Tyr residues is induced in T cells during TCR signaling. Some phosphorylation sites play critical roles in the regulation of PKC-θ function and downstream signaling. The regulation mechanisms for PKC-θ phosphorylation sites are now being revealed. In this review, we discuss the current understanding of the regulation of PKC-θ function by phosphorylation during TCR signaling.

Interaction between pathogenic proteins in neurodegenerative disorders

The misfolding and progressive aggregation of specific proteins in selective regions of the nervous system is a seminal occurrence in many neurodegenerative disorders, and the interaction between pathological/toxic proteins to cause neurodegeneration is a hot topic of current neuroscience research. Despite clinical, genetic and experimental differences, increasing evidence indicates considerable overlap between synucleinopathies, tauopathies and other protein-misfolding diseases. Inclusions, often characteristic hallmarks of these disorders, suggest interactions of pathological proteins enganging common downstream pathways. Novel findings that have shifted our understanding in the role of pathologic proteins in the pathogenesis of Alzheimer, Parkinson, Huntington and prion diseases, have confirmed correlations/overlaps between these and other neurodegenerative disorders. Emerging evidence, in addition to synergistic effects of tau protein, amyloid-β, α-synuclein and other pathologic proteins, suggests that prion-like induction and spreading, involving secreted proteins, are major pathogenic mechanisms in various neurodegenerative diseases, depending on genetic backgrounds and environmental factors. The elucidation of the basic molecular mechanisms underlying the interaction and spreading of pathogenic proteins, suggesting a dualism or triad of neurodegeneration in protein-misfolding disorders, is a major challenge for modern neuroscience, to provide a deeper insight into their pathogenesis as a basis of effective diagnosis and treatment.

PKC theta ablation improves healing in a mouse model of muscular dystrophy

Inflammation is a key pathological characteristic of dystrophic muscle lesion formation, limiting muscle regeneration and resulting in fibrotic and fatty tissue replacement of muscle, which exacerbates the wasting process in dystrophic muscles. Limiting immune response is thus one of the therapeutic options to improve healing, as well as to improve the efficacy of gene- or cell-mediated strategies to restore dystrophin expression. Protein kinase C θ (PKCθ) is a member of the PKCs family highly expressed in both immune cells and skeletal muscle; given its crucial role in adaptive, but also innate, immunity, it is being proposed as a valuable pharmacological target for immune disorders. In our study we asked whether targeting PKCθ could represent a valuable approach to efficiently prevent inflammatory response and disease progression in a mouse model of muscular dystrophy. We generated the bi-genetic mouse model mdx/θ(-/-), where PKCθ expression is lacking in mdx mice, the mouse model of Duchenne muscular dystrophy. We found that muscle wasting in mdx/θ(-/-) mice was greatly prevented, while muscle regeneration, maintenance and performance was significantly improved, as compared to mdx mice. This phenotype was associated to reduction in inflammatory infiltrate, pro-inflammatory gene expression and pro-fibrotic markers activity, as compared to mdx mice. Moreover, BM transplantation experiments demonstrated that the phenotype observed was primarily dependent on lack of PKCθ expression in hematopoietic cells.These results demonstrate a hitherto unrecognized role of immune-cell intrinsic PKCθ activity in the development of DMD. Although the immune cell population(s) involved remain unidentified, our findings reveal that PKCθ can be proposed as a new pharmacological target to counteract the disease, as well as to improve the efficacy of gene- or cell- therapy approaches.

PKC-θ function at the immunological synapse: prospects for therapeutic targeting

Protein kinase C (PKC)-θ regulates conventional effector T (Teff) cell function. Since this initial finding, it has become clear that the role of PKC-θ in T cells is complex. PKC-θ plays a central role in Teff cell activation and survival, and negatively regulates stability of the immunological synapse (IS). Recent studies demonstrated that PKC-θ is required for the development of natural CD4(+)Foxp3(+) regulatory T (Treg) cells, and mediates negative regulation of Treg cell function. Here, we examine the role of PKC-θ in the IS, evidence for its distinct localization in Treg cells and the therapeutic implications of inhibiting PKC-θ in Teff cells, to reduce effector function, and in Treg cells, to increase suppressor function, for the prevention and treatment of autoimmune and alloimmune disease states.