In hypoxic cells, dysfunctional mitochondria are selectively removed by a specialized autophagic process called mitophagy. The ERmitochondrial contact site (MAM) is essential for fission of mitochondria prior to engulfment, and the outer mitochondrial membrane protein FUNDC1 interacts with LC3 to recruit autophagosomes, but the mechanisms integrating these processes are poorly understood. Here, we describe a new pathway mediating mitochondrial fission and subsequent mitophagy under hypoxic conditions. FUNDC1 accumulates at the MAM by associating with the ER membrane protein calnexin. As mitophagy proceeds, FUNDC1/ calnexin association attenuates and the exposed cytosolic loop of FUNDC1 interacts with DRP1 instead. DRP1 is thereby recruited to the MAM, and mitochondrial fission then occurs. Knockdown of FUNDC1, DRP1, or calnexin prevents fission and mitophagy under hypoxic conditions. Thus, FUNDC1 integrates mitochondrial fission and mitophagy at the interface of the MAM by working in concert with DRP1 and calnexin under hypoxic conditions in mammalian cells.

Graphical AbstractHighlights d RB specifically binds to p65, but not other NF-kB/Rel family proteins d RB-p65 interaction relies on CDK4/6 S249/T252 phosphorylation of RB d S249/T252-phosphorylated RB inhibits NF-kB activity and PD-L1 expression d S249/T252 phospho-mimetic peptide promotes cancer immunity via PD-L1 suppression SUMMARY Aberrant expression of programmed death ligand-1 (PD-L1) in tumor cells promotes cancer progression by suppressing cancer immunity. The retinoblastoma protein RB is a tumor suppressor known to regulate the cell cycle, DNA damage response, and differentiation. Here, we demonstrate that RB interacts with nuclear factor kB (NF-kB) protein p65 and that their interaction is primarily dependent on CDK4/6-mediated serine-249/threonine-252 (S249/T252) phosphorylation of RB. RNA-seq analysis shows a subset of NF-kB pathway genes including PD-L1 are selectively upregulated by RB knockdown or CDK4/6 inhibitor. S249/T252phosphorylated RB inversely correlates with PD-L1 expression in patient samples. Expression of a RB-derived S249/T252 phosphorylation-mimetic peptide suppresses radiotherapy-induced upregulation of PD-L1 and augments therapeutic efficacy of radiation in vivo. Our findings reveal a previously unrecognized tumor suppressor function of hyperphosphorylated RB in suppressing NF-kB activity and PD-L1 expression and suggest that the RB-NF-kB axis can be exploited to overcome cancer immune evasion triggered by conventional or targeted therapies.

In humans, oxidative stress and antioxidant defenses are the sum of a complicated network of enzymatic and non-enzymatic processes. Depending on the stage and severity of diseases, a patient's antioxidant armamentarium may increase as an appropriate response to an oxidant challenge, whereas others may decrease as an indication of unbalanced consumption. In some cases, the formation of reactive oxygen species is a requisite and healthy event. In fact, free radicals can affect intracellular signal transduction and gene regulation, resulting in cytokine production essential to the inflammatory process. In many other cases, especially liver diseases, excessive oxidative stress undoubtedly contributes to the progression and pathological findings of disease and serves as a prognostic indicator. Reactive oxygen species are highly reactive molecules that are naturally generated in small amounts through metabolism and could damage cellular molecules such as lipids, proteins or DNA. Oxidative stress plays a major role in many liver diseases. In this review, we summarize the biological character of free radicals and some antioxidants, and the related methods of analysis. Then, we discusses the association of oxidative stress to many types of liver diseases.

Androgen receptor (AR) splice variants (ARVs) are implicated in development of castration-resistant prostate cancer (CRPC). Upregulation of ARVs often correlates with persistent AR activity after androgen deprivation therapy (ADT). However, the genomic and epigenomic characteristics of ARV-dependent cistrome and the disease relevance of ARV-mediated transcriptome remain elusive. Through integrated chromatin immunoprecipitation coupled sequencing (ChIP-seq) and RNA sequencing (RNA-seq) analysis, we identified ARV-preferential-binding sites (ARV-PBS) and a set of genes preferentially transactivated by ARVs in CRPC cells. ARVs preferentially bind to enhancers located in nucleosome-depleted regions harboring the full AR-response element (AREfull), while full-length AR (ARFL)-PBS are enhancers resided in closed chromatin regions containing the composite FOXA1-nnnn-AREhalf motif. ARV-PBS exclusively overlapped with AR binding sites in castration-resistant (CR) tumors in patients and ARV-preferentially activated genes were up-regulated in abiraterone-resistant patient specimens. Expression of ARV-PBS target genes, such as oncogene RAP2A and cell cycle gene E2F7, were significantly associated with castration resistance, poor survival and tumor progression. We uncover distinct genomic and epigenomic features of ARV-PBS, highlighting that ARVs are useful tools to depict AR-regulated oncogenic genome and epigenome landscapes in prostate cancer. Our data also suggest that the ARV-preferentially activated transcriptional program could be targeted for effective treatment of CRPC.