Volume 399, Issue 1

The primary cilium is a sensory organelle that is vital in regulating several signalling pathways. Unlike most organelles cilia are open to the rest of the cell, not enclosed by membranes. The distinct protein composition is crucial to the function of cilia and many signalling proteins and receptors are specifically concentrated within distinct compartments. To maintain this composition, a mechanism is required to deliver proteins to the cilium whilst another must counter the entropic tendency of proteins to distribute throughout the cell. The combination of the two mechanisms should result in the concentration of ciliary proteins to the cilium. In this review we will look at different cellular mechanisms that play a role in maintaining the distinct composition of cilia, including regulation of ciliary access and trafficking of ciliary proteins to, from and within the cilium.

Eremophilanes are sesquiterpenes with a rearranged carbon skeleton formed both by plants and fungi, however, almost no plant eremophilanes are found in fungi. These eremophilanes possess mainly phytotoxic, antimicrobial, anticancer and immunomodulatory properties and in this review fungal eremophilanes with bioactivities of potential medicinal applications are reviewed and discussed. A special focus is set on natural products bearing highly functionalized fatty acids at C-1 or C-3 position of the eremophilane backbone. Many of these fatty acids seem to contribute to the bioactivity of the metabolites enhancing the activity of the sesquiterpene moieties. Several approaches for optimization of these natural products for clinical needs and testing of the resulting derivatives are presented and discussed. The combination of identification of bioactive natural products with their subsequent improvement using a variety of genetical or chemical tools and the pharmacokinetic assessment of the products is presented here as a promising approach to new drugs.

Mitochondria are indispensable cellular organelles providing ATP and numerous other essential metabolites to ensure cell survival. Reactive oxygen species (ROS), which are formed as side reactions during oxidative phosphorylation or by external agents, induce molecular damage in mitochondrial proteins, lipids/membranes and DNA. To cope with this and other sorts of organellar stress, a multi-level quality control system exists to maintain cellular homeostasis. One critical level of mitochondrial quality control is the removal of damaged mitochondria by mitophagy. This process utilizes parts of the general autophagy machinery, e.g. for the formation of autophagosomes but also employs mitophagy-specific factors. Depending on the proteins utilized mitophagy is divided into receptor-mediated and ubiquitin-mediated mitophagy. So far, at least seven receptor proteins are known to be required for mitophagy under different experimental conditions. In contrast to receptor-mediated pathways, the Pink-Parkin-dependent pathway is currently the best characterized ubiquitin-mediated pathway. Recently two additional ubiquitin-mediated pathways with distinctive similarities and differences were unraveled. We will summarize the current state of knowledge about these multiple pathways, explain their mechanism, and describe the regulation and crosstalk between these pathways. Finally, we will review recent evidence for the evolutionary conservation of ubiquitin-mediated mitophagy pathways.

Targeted degradomics integrates positional information into mass spectrometry (MS)-based targeted proteomics workflows and thereby enables analysis of proteolytic cleavage events with unprecedented specificity and sensitivity. Rapid progress in the establishment of protease-substrate relations provides extensive degradomics target lists that now can be tested with help of selected and parallel reaction monitoring (S/PRM) in complex biological systems, where proteases act in physiological environments. In this minireview, we describe the general principles of targeted degradomics, outline the generic experimental workflow of the methodology and highlight recent and future applications in protease research.

Due to an aging society with an increased dementia-induced threat to higher cognitive functions, it has become imperative to understand the molecular and cellular events controlling the memory and learning processes in the brain. Here, we suggest that the novel master gene pair |-SRGAP2–FAM72-| (SLIT-ROBO Rho GTPase activating the protein 2, family with sequence similarity to 72) reveals a new dogma for the regulation of neural stem cell (NSC) gene expression and is a distinctive player in the control of human brain plasticity. Insight into the specific regulation of the brain-specific neural master gene |-SRGAP2–FAM72-| may essentially contribute to novel therapeutic approaches to restore or improve higher cognitive functions.

Rasal is a modular multi-domain protein of the GTPase-activating protein 1 (GAP1) family; its four known members, GAP1m, Rasal, GAP1 IP4BP and Capri, have a Ras GTPase-activating domain (RasGAP). This domain supports the intrinsically slow GTPase activity of Ras by actively participating in the catalytic reaction. In the case of Rasal, GAP1 IP4BP and Capri, their remaining domains are responsible for converting the RasGAP domains into dual Ras- and Rap-GAPs, via an incompletely understood mechanism. Although Rap proteins are small GTPase homologues of Ras, their catalytic residues are distinct, which reinforces the importance of determining the structure of full-length GAP1 family proteins. To date, these proteins have not been crystallized, and their size is not adequate for nuclear magnetic resonance (NMR) or for high-resolution cryo-electron microscopy (cryoEM). Here we present the low resolution structure of full-length Rasal, obtained by negative staining electron microscopy, which allows us to propose a model of its domain topology. These results help to understand the role of the different domains in controlling the dual GAP activity of GAP1 family proteins.

Tyrosinase, a melanosomal glycoenzyme, catalyzes initial steps of the melanin biosynthesis. While glycosylation was previously studied in vivo , we present three recombinant mutant variants of human tyrosinase, which were obtained using multiple site-directed mutagenesis, expressed in insect larvae, purified and characterized biochemically. The mutagenesis demonstrated the reduced protein expression and enzymatic activity due to possible loss of protein stability and protein degradation. However, the complete deglycosylation of asparagine residues in vitro , including the residue in position 371, interrupts tyrosinase function, which is consistent with a melanin loss in oculocutaneous albinism type 1 (OCA1) patients.

Modulation of neuropeptide receptors is important for pancreatic β-cell function. Here, islet distribution and effects of the neurotensin (NT) receptor modulators, xenin and NT, was examined. Xenin, but not NT, significantly improved glucose disposal and insulin secretion, in mice. However, both peptides stimulated insulin secretion from rodent β-cells at 5.6 m m glucose, with xenin having similar insulinotropic actions at 16.7 m m glucose. In contrast, NT inhibited glucose-induced insulin secretion. Similar observations were made in human 1.1B4 β-cells and isolated mouse islets. Interestingly, similar xenin levels were recorded in pancreatic and small intestinal tissue. Arginine and glucose stimulated xenin release from islets. Streptozotocin treatment decreased and hydrocortisone treatment increased β-cell mass in mice. Xenin co-localisation with glucagon was increased by streptozotocin, but unaltered in hydrocortisone mice. This corresponded to elevated plasma xenin levels in streptozotocin mice. In addition, co-localisation of xenin with insulin was increased by hydrocortisone, and decreased by streptozotocin. Further in vitro investigations revealed that xenin and NT protected β-cells against streptozotocin-induced cytotoxicity. Xenin augmented rodent and human β-cell proliferation, whereas NT displayed proliferative actions only in human β-cells. These data highlight the involvement of NT signalling pathways for the possible modulation of β-cell function.

This study was intended to analyze effects of lncRNA CRNDE on cervical cancer cell growth and metastasis. Fifty pairs of cervical cancer tissues and corresponding adjacent tissues were collected. Expressions of long non-coding RNAs (lncRNAs) in tissue samples were detected by microarray analysis. Expression levels of CRNDE in cervical cancer cells and normal cells were detected by qRT-PCR. Cell-counting kit-8 (CCK-8) assay and clone formation assay were utilized to evaluate cell growth. Wound healing assay and Transwell assay were conducted to detect the migratory and invasive capability of cervical cancer cells. The expressions of CRNDE in cervical cancer tissues and cells were higher than those in normal tissues and cells. CCK-8 assay and clone formation assay showed that the knockdown of CRNDE could inhibit the cell proliferation of HeLa and C-33A cells. Wound healing assay indicated that the downregulation of CRNDE expression could suppress the cell migration. The result of a Transwell assay demonstrated that the number of invasion cells reduced in the CRNDE-si group in comparison with the Mock group. LncRNA CRNDE could promote the cell growth and stimulate the metastasis of cervical cancer cells.