Nicotinamide adenine dinucleotide (NAD) is an important electron and hydrogen carrier for oxidative metabolism and involved in energy production, antioxidant responses, and signal transduction within cells. NAD-consuming enzymes can mediate post-translational modifications, such as deacylation and ADP-ribosylation, and the production of Ca2+ -mobilizing second messengers, including OAADPR, ADPR, cADPR, and NAADP, to regulate metabolic homeostasis, DNA damage and gene expression. Inflammatory bowel disease (IBD) is a condition characterized by impaired intestinal barrier, disturbed intestinal mucosal immunity, and abnormal intestinal repair, that is caused by genetic susceptibility and environmental factors. Although various components involved in NAD biosynthesis and metabolism are upregulated in IBD, it remains disputed whether increased NAD turnover drives or counterbalances IBD progression. This review discusses the significance of increased NAD turnover in the intestinal barrier integrity and the inflammation resolution in IBD conditions. We propose that a better understanding of the reasons for the altered NAD metabolism in IBD may help identify novel treatment approaches.

For many inflammatory cytokines, the response elicited is dependent on the recruitment of the tumour necrosis factor receptor-associated factor (TRAF) family of adaptor proteins. All TRAF proteins have a trimeric C-terminal TRAF domain, while at the N-terminus most TRAFs have a RING domain that forms dimers. The symmetry mismatch of the N- and C-terminal halves of TRAF proteins means that when receptors cluster, it is presumed that RING dimers connect TRAF trimers to form a network. Here, using purified TRAF6 proteins, we provide direct evidence in support of this model, and we show that TRAF6 trimers bind Lys63-linked ubiquitin chains to promote their processive assembly. This study provides critical evidence in support of TRAF trimers as key players in signalling.

Clear cell Renal Cell Carcinoma (ccRCC) is the most common and metastatic urological cancer. Molecular players of ccRCC progression and metastasis are not completely known. Here, using primary cell cultures from patients' specimens, we found that TGFβ1/Smad signalling is more activated in high versus low grade ccRCC and inversely correlates with Abl2 tyrosine kinase protein expression. TGFβ1 treatment increased ubiquitination and degradation of Abl2 protein in ccRCC cell lines by TGFβ1/Smad pathway activation and reactive oxygen species production. 3D invasion and matrix degradation assays showed that Abl2 promoted TGFβ1-induced ccRCC cell invasion and maturation of invadopodia, a hallmark of tumour invasion and metastasis. Our findings define Abl2 as a new downstream molecule of TGFβ1 signalling and putative target to counteract advanced ccRCC.

DOCK proteins are a family of multi-domain guanine nucleotide exchange factors (GEFs) that activate the RHO GTPases CDC42 and RAC1, thereby regulating several RHO GTPase-dependent cellular processes. DOCK proteins are characterized by the catalytic DHR2 domain (DOCKDHR2 ), and a phosphatidylinositol(3,4,5)P3 -binding DHR1 domain (DOCKDHR1 ) that targets DOCK proteins to plasma membranes. DOCK-family GEFs are divided into four subfamilies (A to D) differing in their specificities for CDC42 and RAC1, and the composition of accessory signalling domains. Additionally, the DOCK-A and DOCK-B subfamilies are constitutively associated with ELMO proteins that auto-inhibit DOCK GEF activity. We review structural studies that have provided mechanistic insights into DOCK-protein functions. These studies revealed how a conserved nucleotide sensor in DOCKDHR2 catalyses nucleotide exchange, the basis for how different DOCK proteins activate specifically CDC42 and RAC1, and sometimes both, and how up-stream regulators relieve the ELMO-mediated auto-inhibition. We conclude by presenting a model for full-length DOCK9 of the DOCK-D subfamily. The involvement of DOCK GEFs in a range of diseases highlights the importance of gaining structural insights into these proteins to better understand and specifically target them.

Extracellular signal-regulated kinase 7 (ERK7), also known as ERK8 and MAPK15, is an atypical member of the MAP kinase family. Compared with other MAP kinases, the biological roles of ERK7 remain poorly understood. Recent work, however, has revealed several novel functions for ERK7. These include a highly conserved essential role in ciliogenesis, the ability to control cell growth, metabolism and autophagy, as well as the maintenance of genomic integrity. ERK7 functions through phosphorylation-dependent and -independent mechanisms and it is activated by cellular stressors, including DNA-damaging agents, and nutrient deprivation. Here, we summarize recent developments in understanding ERK7 function, emphasizing its conserved roles in cellular and physiological regulation.

Small GTPases orchestrate numerous cellular pathways, acting as molecular switches and regulatory hubs to transmit molecular signals and because of this, they are often the target of pathogens. During infection, pathogens manipulate host cellular networks using post-translational modifications (PTMs). AMPylation, the modification of proteins with AMP, has been identified as a common PTM utilized by pathogens to hijack GTPase signalling during infection. AMPylation is primarily carried out by enzymes with a filamentation induced by cyclic-AMP (Fic) domain. Modification of small GTPases by AMP renders GTPases impervious to upstream regulatory inputs, resulting in unregulated downstream effector outputs for host cellular processes. Here, we overview Fic-mediated AMPylation of small GTPases by pathogens and other related PTMs catalysed by Fic enzymes on GTPases.

Aminopeptidase I (Ape1) is one of the major cargoes of the cytoplasm-to-vacuole targeting (Cvt) pathway, which is a kind of selective autophagy, in Saccharomyces cerevisiae. After synthesis, the Ape1 precursor (prApe1) undergoes phase separation to form liquid droplets, termed Ape1 droplets, in the cytoplasm. In this study, we found that cells expressing prApe1-GFP exhibited temperature-sensitive formation of Ape1 droplets, which affected its transport. Moreover, we showed that endogenous Ape1 transport was defective at high temperatures in various laboratory strains due to the defect in the formation of Ape1 droplets at these temperatures. Finally, we found that gene disruptants showing heat-tolerant growth suppressed the temperature sensitivity of the Ape1 transport. The formation of Ape1 droplets might be an indicator of cytoplasmic integrity at high temperature.