Janoš Terzić

IL-6 and Stat3 Are Required for Survival of Intestinal Epithelial Cells and Development of Colitis-Associated Cancer

Colitis-associated cancer (CAC) is the most serious complication of inflammatory bowel disease. Proinflammatory cytokines have been suggested to regulate preneoplastic growth during CAC tumorigenesis. Interleukin 6 (IL-6) is a multifunctional NF-kappaB-regulated cytokine that acts on epithelial and immune cells. Using genetic tools, we now demonstrate that IL-6 is a critical tumor promoter during early CAC tumorigenesis. In addition to enhancing proliferation of tumor-initiating cells, IL-6 produced by lamina propria myeloid cells protects normal and premalignant intestinal epithelial cells (IECs) from apoptosis. The proliferative and survival effects of IL-6 are largely mediated by the transcription factor Stat3, whose IEC-specific ablation has profound impact on CAC tumorigenesis. Thus, the NF-kappaB-IL-6-Stat3 cascade is an important regulator of the proliferation and survival of tumor-initiating IECs.

Inflammation and Colon Cancer

The connection between inflammation and tumorigenesis is well-established and in the last decade has received a great deal of supporting evidence from genetic, pharmacological, and epidemiological data. Inflammatory bowel disease is an important risk factor for the development of colon cancer. Inflammation is also likely to be involved with other forms of sporadic as well as heritable colon cancer. The molecular mechanisms by which inflammation promotes cancer development are still being uncovered and could differ between colitis-associated and other forms of colorectal cancer. Recent work has elucidated the role of distinct immune cells, cytokines, and other immune mediators in virtually all steps of colon tumorigenesis, including initiation, promotion, progression, and metastasis. These mechanisms, as well as new approaches to prevention and therapy, are discussed in this review.

Nix is a selective autophagy receptor for mitochondrial clearance

Autophagy is the cellular homeostatic pathway that delivers large cytosolic materials for degradation in the lysosome. Recent evidence indicates that autophagy mediates selective removal of protein aggregates, organelles and microbes in cells. Yet, the specificity in targeting a particular substrate to the autophagy pathway remains poorly understood. Here, we show that the mitochondrial protein Nix is a selective autophagy receptor by binding to LC3/GABARAP proteins, ubiquitin‐like modifiers that are required for the growth of autophagosomal membranes. In cultured cells, Nix recruits GABARAP‐L1 to damaged mitochondria through its amino‐terminal LC3‐interacting region. Furthermore, ablation of the Nix:LC3/GABARAP interaction retards mitochondrial clearance in maturing murine reticulocytes. Thus, Nix functions as an autophagy receptor, which mediates mitochondrial clearance after mitochondrial damage and during erythrocyte differentiation.

SHARPIN forms a linear ubiquitin ligase complex regulating NF-κB activity and apoptosis

SHARPIN is a ubiquitin-binding and ubiquitin-like-domain-containing protein which, when mutated in mice, results in immune system disorders and multi-organ inflammation. Here we report that SHARPIN functions as a novel component of the linear ubiquitin chain assembly complex (LUBAC) and that the absence of SHARPIN causes dysregulation of NF-κB and apoptotic signalling pathways, explaining the severe phenotypes displayed by chronic proliferative dermatitis (cpdm) in SHARPIN-deficient mice. Upon binding to the LUBAC subunit HOIP (also known as RNF31), SHARPIN stimulates the formation of linear ubiquitin chains in vitro and in vivo. Coexpression of SHARPIN and HOIP promotes linear ubiquitination of NEMO (also known as IKBKG), an adaptor of the IκB kinases (IKKs) and subsequent activation of NF-κB signalling, whereas SHARPIN deficiency in mice causes an impaired activation of the IKK complex and NF-κB in B cells, macrophages and mouse embryonic fibroblasts (MEFs). This effect is further enhanced upon concurrent downregulation of HOIL-1L (also known as RBCK1), another HOIP-binding component of LUBAC. In addition, SHARPIN deficiency leads to rapid cell death upon tumour-necrosis factor α (TNF-α) stimulation via FADD- and caspase-8-dependent pathways. SHARPIN thus activates NF-κB and inhibits apoptosis via distinct pathways in vivo.

Ubiquitin-independent function of optineurin in autophagic clearance of protein aggregates

Summary Aggregation of misfolded proteins and the associated loss of neurons are considered a hallmark of numerous neurodegenerative diseases. Optineurin is present in protein inclusions observed in various neurodegenerative diseases including amyotrophic lateral sclerosis (ALS), Huntingtons disease, Alzheimers disease, Parkinsons disease, Creutzfeld-Jacob disease and Picks disease. Optineurin deletion mutations have also been described in ALS patients. However, the role of optineurin in mechanisms of protein aggregation remains unclear. In this report, we demonstrate that optineurin recognizes various protein aggregates via its C-terminal coiled-coil domain in a ubiquitin-independent manner. We also show that optineurin depletion significantly increases protein aggregation in HeLa cells and that morpholino-silencing of the optineurin ortholog in zebrafish causes the motor axonopathy phenotype similar to a zebrafish model of ALS. A more severe phenotype is observed when optineurin is depleted in zebrafish carrying ALS mutations. Furthermore, TANK1 binding kinase 1 (TBK1) is colocalized with optineurin on protein aggregates and is important in clearance of protein aggregates through the autophagy-lysosome pathway. TBK1 phosphorylates optineurin at serine 177 and regulates its ability to interact with autophagy modifiers. This study provides evidence for a ubiquitin-independent function of optineurin in autophagic clearance of protein aggregates as well as additional relevance for TBK1 as an upstream regulator of the autophagic pathway.

Lower cortisol and higher ACTH levels in individuals with autism

Blood concentrations of pituitary hormones adrenocorticotropin (ACTH), prolactin, growth hormone, and adrenal hormone–cortisol were measured in 36 autistic and 27 control individuals. Individuals with autism had significantly lower serum concentrations of cortisol (p < 10−6), and significantly higher concentrations of ACTH (p = 0.002) than control age- and sex-matched subjects. Also, prolactin concentrations in autistic patients with epilepsy were significantly higher when compared with normal subjects. The observed hormonal changes may indicate dysfunction of the hypothalamo-pituitary-adrenal axis in individuals with autism.

Vitamin D receptor polymorphism and susceptibility to type 1 diabetes in the Dalmatian population

Several studies have found a relationship between polymorphisms of the vitamin D receptor gene (VDR) and development of type 1 diabetes (T1DM). The meaning of this observation remains unclear and its relevance must be checked in different population samples. To examine the association of VDR polymorphisms and susceptibility to T1DM in the Dalmatian population of South Croatia we studied 134 individuals with type 1 diabetes and 132 control subjects. VDR genotyping was performed using PCR and BsmI, ApaI and TaqI restriction enzymes. Data were analysed using the chi(2)-test. The genotype combination which conferred strongest susceptibility to T1DM was BBAAtt (P=0.002). Interestingly, the BAt haplotype was found to be a risk factor in a German population, the only European population tested thus far. Our results indicate that VDR polymorphisms are associated with increased risk of T1DM in the Dalmatian population of South Croatia and warrant further studies.

Mutations in SPRTN cause early onset hepatocellular carcinoma, genomic instability and progeroid features

Age-related degenerative and malignant diseases represent major challenges for health care systems. Elucidation of the molecular mechanisms underlying carcinogenesis and age-associated pathologies is thus of growing biomedical relevance. We identified biallelic germline mutations in SPRTN (also called C1orf124 or DVC1) in three patients from two unrelated families. All three patients are affected by a new segmental progeroid syndrome characterized by genomic instability and susceptibility toward early onset hepatocellular carcinoma. SPRTN was recently proposed to have a function in translesional DNA synthesis and the prevention of mutagenesis. Our in vivo and in vitro characterization of identified mutations has uncovered an essential role for SPRTN in the prevention of DNA replication stress during general DNA replication and in replication-related G2/M-checkpoint regulation. In addition to demonstrating the pathogenicity of identified SPRTN mutations, our findings provide a molecular explanation of how SPRTN dysfunction causes accelerated aging and susceptibility toward carcinoma.

Genome-wide expression analysis of peripheral blood identifies candidate biomarkers for schizophrenia

The aim of this study was to analyze gene expression in blood of patients with newly-diagnosed schizophrenia during their first psychotic episode and subsequent remission. Whole blood samples were obtained from 32 untreated patients presenting with their first psychotic episode suggestive of schizophrenia and 32 age- and gender-matched controls. Using Affymetrix micoarrays, we identified significantly altered expression of 180 gene probes in psychotic patients compared to controls. A subset of four significantly changed genes was further confirmed with QRT-PCR. The following genes were significantly altered in patients: glucose transporter, SLC2A3 (p<0.001) and actin assembly factor DAAM2 (p<0.001) were increased, whereas translation, zinc metallopeptidase, neurolysin 1 and myosin C were significantly decreased (p<0.05). Expression of these candidate markers was also analyzed in a longitudinal study (12-24 months) in 12 patients who achieved full remission. Interestingly, expression of DAAM2 returned to control levels in patients who were in remission after their first psychotic episode, suggesting that its expression correlates with diseases progression and/or response to treatment. In summary, we identified changes of gene expression from peripheral blood which might help discriminate patients with schizophrenia from controls. While these results are promising, especially for DAAM2 whose polymorphic variants have been found significantly associated with schizophrenia, it will be important to analyze larger cohorts of patients in order to firmly establish changes in gene expression as blood markers of schizophrenia.

Dab2 links CIN85 with clathrin-mediated receptor internalization

CIN85 is a multidomain scaffold protein involved in downregulation of receptor tyrosine kinases. Here we show that disabled‐2 (Dab2), an endocytic adaptor molecule implicated in clathrin‐coat assembly, associates with CIN85 in mammalian cells. All three SH3 domains of CIN85 were able to bind to the PKPAPR peptide in the carboxyl‐terminal part of Dab2, possibly enabling CIN85 to simultaneously interact with multiple Dab2 molecules. CIN85 association with Dab2 is essential for its recruitment to clathrin coat and appears to be modulated by growth factor stimulation. Dab2 and clathrin dissociated from CIN85 following growth factor treatment, enabling other molecules, such as Cbl, to bind to CIN85. Taken together, our data indicate a dynamic interplay between CIN85 and its effectors during endocytosis of receptor tyrosine kinases.