Our environment contains physical, chemical and pathological agents that challenge the integrity of our DNA. In addition to DNA repair, higher multicellular organisms have evolved multiple pathways of response to damage including programmed cell death-apoptosis. The p53 protein appears to sense multiple types of DNA damage and coordinate with multiple options for cellular response. The p53 protein activities depend upon its DNA binding. Specific p53 protein post-translational modifications are required for efficient sequence-specific binding and transcriptional activities. Non-sequence-specific DNA binding may involve a wide spectrum of p53 proteins and predominate as DNA damage is more severe or p53 protein is more highly induced. p53 protein is not strictly required for DNA damage sensing and repair. Rather, p53 protein may govern an apoptosis checkpoint through competition with DNA repair proteins for non-sequence-specific binding to exposed single-stranded regions in the DNA duplex. This model provides a framework for testing mechanisms of p53-mediated apoptosis dependent upon the p53 protein modification state, the level of p53 protein accumulation, the level of DNA damage and the capacity of the damaged cell to repair.

Optimal autophagic activity is crucial to maintain muscle integrity, with either reduced or excessive levels leading to specific myopathies. LGMD2H is a muscle dystrophy caused by mutations in the ubiquitin ligase TRIM32, whose function in muscles remains not fully understood. Here, we show that TRIM32 is required for the induction of muscle autophagy in atrophic conditions using both in vitro and in vivo mouse models. Trim32 inhibition results in a defective autophagy response to muscle atrophy, associated with increased ROS and MuRF1 levels. The proautophagic function of TRIM32 relies on its ability to bind the autophagy proteins AMBRA1 and ULK1 and stimulate ULK1 activity via unanchored K63-linked polyubiquitin. LGMD2H-causative mutations impair TRIM32’s ability to bind ULK1 and induce autophagy. Collectively, our study revealed a role for TRIM32 in the regulation of muscle autophagy in response to atrophic stimuli, uncovering a previously unidentified mechanism by which ubiquitin ligases activate autophagy regulators.

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Psoriasis is a T cell and IL-17 dependent inflammatory skin disease. Helper T cells have been assumed to be the major source of IL-17 in psoriasis but other cell types can also produce this cytokine. We immunostained human psoriatic lesions (n¼15) and healthy skin (n¼10) for IL-17A, T cells (CD4, CD8) and neutrophils (myeloperoxidase, MPO). We found that 32% of MPO+ neutrophils in psoriasis samples produced IL-17A, compared with less than 1% of total CD4 + and CD8 + cells. There were on average 10.6 IL-17A producing neutrophils per 10 high power fields in psoriasis, compared to 2.7 IL-17A producing T cells (p¼0.008). IL-17A producing neutrophils outnumbered IL-17A producing T cells four-fold demonstrating that neutrophils are an important source of IL-17A in psoriasis. To explore potential interactions between keratinocytes and neutrophils in psoriasis, we co-cultured these cells in vitro and studied neutrophil cytokine production by quantitative RT-PCR and intracellular immunostaining and flow cytometry analysis. Neutrophils co-cultured with keratinocytes upregulated production of IL-17A, IL-17F and IL-22 at both the protein and RNA levels. Neutrophils cultured with keratinocytes lost CD62L and upregulated CD11b, consistent with activation. In summary, this study suggests that neutrophils, known for long to be a part of the histologic landscape of psoriasis, are a major source of IL-17A production and have the potential to contribute to inflammation by producing IL-17F and IL-22. This is, to our knowledge, the first report that human neutrophils can produce IL-17F and IL-22.