Nrf2 (nuclear factor erythroid 2 (NF-E2)-related factor 2) transcription factor is recognized for its pro-survival and cell protective role upon exposure to oxidative, chemical, or metabolic stresses. Nrf2 controls a number of cellular processes such as proliferation, differentiation, apoptosis, autophagy, lipid synthesis, and metabolism and glucose metabolism and is a target of activation in chronic diseases like diabetes, neurodegenerative, and inflammatory diseases. The dark side of Nrf2 is revealed when its regulation is imbalanced (e.g., via oncogene activation or mutations) and under such conditions constitutively active Nrf2 promotes cancerogenesis, metastasis, and radio- and chemoresistance. When there is no stress, Nrf2 is instantly degraded via Keap1-Cullin 3 (Cul3) pathway but despite this, cells exhibit a basal activation of Nrf2 target genes. It is yet not clear how Nrf2 maintains the expression of its targets under homeostatic conditions. Here, we found a stable 105 kDa Nrf2 form that is resistant to Keap1-Cul3-mediated degradation and translocates to the nucleus of lung cancer cells. RNA-Seq analysis indicate that it might originate from the exon 2 or exon 3-truncated transcripts. This stable 105 kDa Nrf2 form might help explain the constitutive activity of Nrf2 under normal cellular conditions.

The interferon signalling system elicits a robust cytokine response against a wide range of environmental pathogenic and internal pathological signals, leading to induction of a subset of interferon-induced proteins. We applied DSS (disuccinimidyl suberate) mediated cross-linking mass spectrometry (CLMS) to capture novel protein–protein interactions within the realm of interferon induced proteins. In addition to the expected interferon-induced proteins, we identified novel inter- and intra-molecular cross-linked adducts for the canonical interferon induced proteins, such as MX1, USP18, OAS3, and STAT1. We focused on orthogonal validation of a cohort of novel interferon-induced protein networks formed by the HLA-A protein (H2BFS-HLA-A-HMGA1) using co-immunoprecipitation assay, and further investigated them by molecular dynamics simulation. Conformational dynamics of the simulated protein complexes revealed several interaction sites that mirrored the interactions identified in the CLMS findings. Together, we showcase a proof-of-principle CLMS study to identify novel interferon-induced signaling complexes and anticipate broader use of CLMS to identify novel protein interaction dynamics within the tumour microenvironment.

The Nrf2 pathway is an essential defense pathway in a cell. It responds to oxidative and electrophilic stress via de-repression of Nrf2 from Keap1-Cul3-mediated degradation, accumulation of Nrf2 in the nucleus and transcriptional activation of a number of detoxifying and cell protective Nrf2 target genes. Here we report that normal and cancer cells also express the N-terminally truncated Nrf2 isoform (ΔN-Nrf2), which originates from an alternative promoter. Co-immunoprecipitation together with molecular dynamics simulation showed that the binding between ΔN-Nrf2 and Keap1 is impaired, resulting in the much higher stability of this form. ΔN-Nrf2 is retained in the cytoplasm in response to electrophilic stress, indicating that it does not regulate transcription under the same stress stimuli as the full-length Nrf2. Altogether this data suggests that Nrf2 has other functions in cells than transcriptional activation of genes, which most probably rely on the protein-protein interactions in the cytoplasm. The regulation between these functions takes place on the level of transcription.

Nanotechnology has emerged as a promising tool for the early diagnosis and treatment of cancer. [1][2][3] During the past decades, several nanotechnology-based therapies have been approved for clinical use. [4] However, the success rate of nanomedicines entering clinical trials is extremely low. [5][6][7] There is also a great number of nanomedicines being developed that show high efficacy in studies in vitro, yet they fail at in vivo tests. [8,9] Thus, new more advanced preclinical models with improved predictive value are required to be able to advance the clinical translation of nanomedicines. In this regard, tumor-on-a-chip (ToC) microfluidic devices are new testing platforms with greater physiological relevance than the traditional 2D cell cultures. They are capable of recapitulating key physiological aspects of the tumor microenvironment, like perfused 3D cellular microenvironments, allowing for the dynamic tuning of the physicochemical parameters. [9][10][11][12][13] As such, these devices may provide more clinically relevant models to study the transport process of nanomedicines across the biological barriers for a better prediction of their in vivo performance. [14,15] During the recent years, several ToC devices have been developed as in vitro models to investigate different processes of the tumor biology. ToCs have been used to get a better understanding of cancer progression and metastasis, [16][17][18][19][20] as well as angiogenesis and blood vessel formation. [21][22][23][24] ToC devices have been also developed for the evaluation of new therapeutic approaches against cancer, including nanomedicines. [25][26][27][28] However, up-to-date, ToC devices have failed to model some of the main critical components involved in nanomedicine delivery to the tumor site. During the tumor delivery process, nanomedicines need to leave the bloodstream, penetrate into the interstitial tumor matrix and, ultimately, into the tumor cells. Here,

The Major Histocompatibility Complex class I (MHC-I) molecules present antigenic peptides (AP) to CD8+ T cells for self versus non-self recognition. Loading of AP on MHC-I takes place in the endoplasmic reticulum (ER), upon shuttling of cytoplasmic AP substrates to the ER. Understanding of this process has been influenced by the view that MHC-I antigens are produced from the proteasomal degradation of cellular proteins. Recent observations on the intronic and untranslated region-derived peptides as well as on the non-AUG translation products presented on the MHC-I open the possibility that antigenic peptides can derive from pre-spliced mRNAs translated in the nuclear compartment. In this brief report, we show that a fraction of human MHC-I molecules (human leukocyte antigens type A, HLA-A) is present in the nuclei of cells, in the proximity of histone H2B. With this finding, we hope to initiate a new direction of research on the nuclear role of MHC-I and ask whether the loading of antigens can take place in the nuclear compartment.