Progress in understanding the neuronal SNARE function and its regulation

Vesicle budding and fusion underlies many essential biochemical deliveries in eukaryotic cells, and its core fusion machinery is thought to be built on one protein family named soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE). Recent technical advances based on site-directed fluorescence labelling and nano-scale detection down to the single-molecule level rapidly unveiled the protein and the lipid intermediates along the fusion pathway as well as the molecular actions of fusion effectors. Here we summarize these new exciting findings in context with a new mechanistic model that reconciles two existing fusion models: the proteinaceous pore model and the hemifusion model. Further, we attempt to locate the points of action for the fusion effectors along the fusion pathway and to delineate the energetic interplay between the SNARE complexes and the fusion effectors. Received 01 July 2008; received after revision 29 August 2008; accepted 23 September 2008     

Sulfatase activities towards the regulation of cell metabolism and signaling in mammals

In higher vertebrates, sulfatases belong to a conserved family of enzymes that are involved in the regulation of cell metabolism and in developmental cell signaling. They cleave the sulfate from sulfate esters contained in hormones, proteins, and complex macromolecules. A highly conserved cysteine in their active site is post-translationally converted into formylglycine by the formylglycine-generating enzyme encoded by SUMF1 (sulfatase modifying factor 1). This post-translational modification activates all sulfatases. Sulfatases are extensively glycosylated proteins and some of them follow trafficking pathways through cells, being secreted and taken up by distant cells. Many proteoglycans, glycoproteins, and glycolipids contain sulfated carbohydrates, which are sulfatase substrates. Indeed, sulfatases operate as decoding factors for a large amount of biological information contained in the structures of the sulfated sugar chains that are covalently linked to proteins and lipids. Modifications to these sulfate groups have pivotal roles in modulating specific signaling pathways and cell metabolism in mammals.     

New concepts in regulation and function of the insulin-like growth factors: implications for understanding normal growth and neoplasia

The insulin-like growth factors (IGFs) are a ubiquitous family of growth factors, binding proteins and receptors that are involved in normal growth and development. They are also implicated in numerous pathological states, including malignancy. IGF-II is a commonly expressed growth factor in many tumors and may enhance tumor growth, acting via the overexpressed IGF-I receptor, a cell-surface tyrosine kinase receptor. The IGF-I receptor may be overexpressed due to mutations in tumor suppression gene products such as p53 and WT-1 or growth factors such as bFGF and PDGF. Thus, this family of growth factors, especially the IGF-I receptor, may present an excellent target for new therapeutic agents in the treatment of cancer and other disorders of excessive cellular proliferation.     

A Smurf1 tale: function and regulation of an ubiquitin ligase in multiple cellular networks

Since being discovered and intensively studied for over a decade, Smad ubiquitylation regulatory factor-1 (Smurf1) has been linked with several important biological pathways, including the bone morphogenetic protein pathway, the non-canonical Wnt pathway, and the mitogen-activated protein kinase pathway. Multiple functions of this ubiquitin ligase have been discovered in cell growth and morphogenesis, cell migration, cell polarity, and autophagy. Smurf1 is related to physiological manifestations in terms of age-dependent deficiency in bone formation and invasion of tumor cells. Smurf1-knockout mice have a significant phenotype in the skeletal system and considerable manifestations during embryonic development and neural outgrowth. In depth studying of Smurf1 will help us to understand the etiopathological mechanisms of related disorders. Here, we will summarize historical and recent studies on Smurf1, and discuss the E3 ligase-dependent and -independent functions of Smurf1. Moreover, intracellular regulations of Smurf1 and related physiological phenotypes will be described in this review.     

Decreased levels of complex III core protein 1 and complex V beta chain in brains from patients with Alzheimer's disease and Down syndrome

Ubiquinol:cytochrome c oxidoreductase (complex III) and ATP synthase (complex V) are important enzymes in the mitochondrial electron transport chain. Defects in mitochondrial respiratory enzymes have been reported for several neurodegenerative diseases. In this study, we applied the proteomic approach to investigate protein levels of complex III core protein and complex V beta chain in brain regions of Alzheimer's disease (AD) and Down syndrome (DS) patients. Complex III core protein 1 was significantly reduced in the temporal cortex of AD patients. Complex V beta chain was significantly reduced in the frontal cortex of DS patients. We conclude that decreased mitochondrial respiratory enzymes could contribute to the impairment of energy metabolism observed in DS. These decreases could also cause the generation of reactive oxygen species and neuronal cell death (apoptosis) in DS as well as AD.     

Inflammasomes: current understanding and open questions

The innate immune system relies on its capability to detect invading microbes, tissue damage, or stress via evolutionarily conserved receptors. The nucleotide-binding domain leucine-rich repeat (NLR)-containing family of pattern recognition receptors includes several proteins that drive inflammation in response to a wide variety of molecular patterns. In particular, the NLRs that participate in the formation of a molecular scaffold termed the “inflammasome” have been intensively studied in past years. Inflammasome activation by multiple types of tissue damage or by pathogen-associated signatures results in the autocatalytic cleavage of caspase-1 and ultimately leads to the processing and thus secretion of pro-inflammatory cytokines, most importantly interleukin (IL)-1β and IL-18. Here, we review the current knowledge of mechanisms leading to the activation of inflammasomes. In particular, we focus on the controversial molecular mechanisms that regulate NLRP3 signaling and highlight recent advancements in DNA sensing by the inflammasome receptor AIM2.     

Positive regulation of apoptosis signal-regulating kinase 1 by dual-specificity phosphatase 13A

Apoptosis signal-regulating kinase 1 (ASK1), a member of the MAP kinase kinase kinase, is activated by several death stimuli and is tightly regulated by several mechanisms such as interactions with regulatory proteins and post-translational modifications. Here, we report that dual-specificity phosphatase 13A (DUSP13A) functions as a novel regulator of ASK1. DUSP13A interacts with the N-terminal domain of ASK1 and induces ASK1-mediated apoptosis through the activation of caspase-3. DUSP13A enhances ASK1 kinase activity and thus its downstream factors. Small interfering RNA (siRNA) analyses show that knock-down of DUSP13A in human neuroblastoma SK-N-SH cells reduces ASK1 kinase activity. The phosphatase activity of DUSP13A is not required for the regulation of ASK1. This regulatory action of DSUP13 on ASK1 activity involves competition with Akt1, a negative regulator of ASK1, for binding to ASK1. Taken together, this study provides novel insights into the role of DUSP13A in the precise regulation of ASK1.     

Role of adenosine A1 and A2 receptors in the regulation of aldosterone production in rat adrenal glands

To investigate the roles of adenosine A1 and A2 receptors in the regulation of aldosterone production, we examined the effects of adenosine and adenosine agonists (N6-cyclohexyl adenosine; selective adenosine A1 receptor agonist and 5'-N-ethylcarboxamine adenosine; selective adenosine A2 receptor agonist) on aldosterone and cyclic AMP production in rat adrenal capsular cells. Neither adenosine nor 5'-N-ethylcarboxamine adenosine caused significant effects on basal aldosterone or cyclic AMP production. Also, adenosine (10(-3) M) showed no consistent effects on aldosterone and cyclic AMP production induced by ACTH. On the other hand, N6-cyclohexyl adenosine exhibited a significant inhibition of basal aldosterone and cyclic AMP production at doses of 10(-4) M and 10(-3) M; furthermore, 10(-3) M N6-cyclohexyl adenosine inhibited aldosterone and cyclic AMP production stimulated by ACTH. These results suggest that adenosine A1 receptors are coupled to and inhibit adenylate cyclase and may be involved in the inhibition of aldosterone production.     

Role of adenosine A1 and A2 receptors in the regulation of aldosterone production in rat adrenal glands

Summary To investigate the roles of adenosine A₁ and A₂ receptors in the regulation of aldosterone production, we examined the effects of adenosine and adenosine agonists (N⁶-cyclohexyl adenosine; selective adenosine A₁ receptor agonist and 5-N-ethylcarboxamine adenosine; selective adenosine A₂ receptor agonist) on aldosterone and cyclic AMP production in rat adrenal capsular cells. Neither adenosine nor 5-N-ethylcarboxamine adenosine caused significant effects on basal aldosterone or cyclic AMP production. Also, adenosine (10^–3M) showed no consistent effects on aldosterone and cyclic AMP production induced by ACTH. On the other hand, N⁶-cyclohexyl adenosine exhibited a significant inhibition of basal aldosterone and cyclic AMP production at doses of 10^–4 M and 10^–3 M; furthermore, 10^–3 M N⁶-cyclohexyl adenosine inhibited aldosterone and cyclic AMP production stimulated by ACTH. These results suggest that adenosine A₁ receptors are coupled to and inhibit adenylate cyclase and may be involved in the inhibition of aldosterone production.     

Annexin A5: shifting from a diagnostic towards a therapeutic realm

The surge in apoptosis research and the discovery of the phosphatidylserine binding properties of annexin A5 have propelled a tremendous interest in cell death detection technologies. In the past years, annexin A5 has evolved from an efficient assay for detection of apoptotic cells in vitro to an in vivo molecular imaging technology with potential clinical use. A second key discovery, the specific internalization properties of annexin A5, has opened the opportunity to use annexin A5 for therapeutic applications. Annexin A5-mediated internalization creates a novel therapeutic platform for targeted drug delivery and cell entry to treat various diseases, including cancer and cardiovascular disease. Received 29 June 2007; received after revision 19 July 2007; accepted 15 August 2007     

The human genome and understanding of common disease: present and future technologies

The study of candidate genes over the past three decades has yielded notable successes in common-disease genetics. During this time, however, interpretation of genetic association studies has been hampered by the use of clinical cohorts of inadequate power and insufficient information on genetic variation in candidate genes. The unavailability of highthroughput and low-cost genotyping technologies has also limited the scope of complex-disease genetic studies. More recently, however, the sequencing and characterization of variation within the human genome has revolutionized genetic studies and enabled full genome-wide scans for genes associated with disease. The identification of disease-associated (causative) genes has illuminated disease mechanisms. The translation of this knowledge into direct clinical benefit in diagnosis, prognosis and therapy for an individual’s disease still remains a challenge. Received 11 September 2006; received after revision 17 December 2006; accepted 18 January 2007     

Human bodies as chemical sensors: A history of biomonitoring for environmental health and regulation

The testing of human blood and urine for signs of chemical exposure has become the “gold standard” of environmental public health, leading to ongoing population studies in the US and Europe. Such methods first emerged over a century ago in medical and occupational contexts, as a means to calibrate drug doses for patients and prevent injury to workers from chemical or radiation exposure. This paper analyzes how human bodies have come to serve as unconscious sensors of their environments: containers of chemical information determined by expert testers. As seen in the case of lead testing in the US, these bodily traces of contaminants can provide compelling evidence about dangerous exposures in everyday life, useful in achieving stronger regulation of industry. The use of genetic testing of workers by Dow Chemical provides an example of industry itself undertaking biomonitoring, though the company discontinued the program at the same time its studies indicated chromosomal damage in connection with occupational exposure to certain chemicals. In this case and others, biomonitoring raises complex questions about informing subjects, interpreting exposure in the many cases for which health effects at low doses are unknown, and who should take responsibility for protection, compensation, or remediation. Further, the history of biomonitoring complicates how we understand human ‘experience’ of the global environment by pointing to the role of non-sensory—yet detectable—bodily exposures.     

Checkpoint kinase 1 in DNA damage response and cell cycle regulation

Originally identified as a mediator of DNA damage response (DDR), checkpoint kinase 1 (Chk1) has a broader role in checkpoint activation in DDR and normal cell cycle regulation. Chk1 activation involves phosphorylation at conserved sites. However, recent work has identified a splice variant of Chk1, which may regulate Chk1 in both DDR and normal cell cycle via molecular interaction. Upon activation, Chk1 phosphorylates a variety of substrate proteins, resulting in the activation of DNA damage checkpoints, cell cycle arrest, DNA repair, and/or cell death. Chk1 and its related signaling may be an effective therapeutic target in diseases such as cancer.     

基因功能注释——后基因组时代面临的挑战

在已经解序的、数以百计的生物基因组中,存在大量编码未知功能蛋白的基因序列。同时,众多已知功能的酶蛋白在解序的基因组中找不到对应的基因。确定未知功能基因的功能和寻找孤儿酶对应的基因是后基因组时代面临的极具挑战性的科学任务。本文综合讨论了目前基因组中基因功能注释存在的问题及解决这些问题的策略与方法。