Ubiquitin Modulates Liquid-Liquid Phase Separation of UBQLN2 via Disruption of Multivalent Interactions

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The Role of RNA in Biological Phase Separations

Phase transitions that alter the physical state of ribonucleoprotein particles contribute to the spacial and temporal organization of the densely packed intracellular environment. This allows cells to organize biologically coupled processes as well as respond to environmental stimuli. RNA plays a key role in phase separation events that modulate various aspects of RNA metabolism. Here, we review the role that RNA plays in ribonucleoprotein phase separations.     

RGG/RG Motif Regions in RNA Binding and Phase Separation

RGG/RG motifs are RNA binding segments found in many proteins that can partition into membraneless organelles. They occur in the context of low-complexity disordered regions and often in multiple copies. Although short RGG/RG-containing regions can sometimes form high-affinity interactions with RNA structures, multiple RGG/RG repeats are generally required for high-affinity binding, suggestive of the dynamic, multivalent interactions that are thought to underlie phase separation in formation of cellular membraneless organelles. Arginine can interact with nucleotide bases via hydrogen bonding and π-stacking; thus, nucleotide conformers that provide access to the bases provide enhanced opportunities for RGG interactions. Methylation of RGG/RG regions, which is accomplished by protein arginine methyltransferase enzymes, occurs to different degrees in different cell types and may regulate the behavior of proteins containing these regions.     

Integration of aerobic granular sludge and membrane bioreactors for wastewater treatment

Environmental deterioration together with the need for water reuse and the increasingly restrictive legislation of water quality standards have led to a demand for compact, efficient and less energy consuming technologies for wastewater treatment. Aerobic granular sludge and membrane bioreactors (MBRs) are two technologies with several advantages, such as small footprint, high-microbial density and activity, ability to operate at high organic- and nitrogen-loading rates, and tolerance to toxicity. However, they also have some disadvantages. The aerobic granular sludge process generally requires post-treatment in order to fulfill effluent standards and MBRs suffer from fouling of the membranes. Integrating the two technologies could be a way of combining the advantages and addressing the main problems associated with both processes. The use of membranes to separate the aerobic granules from the treated water would ensure high-quality effluents suitable for reuse. Moreover, the use of granular sludge in MBRs has been shown to reduce fouling. Several recent studies have shown that the aerobic granular membrane bioreactor (AGMBR) is a promising hybrid process with many attractive features. However, major challenges that have to be addressed include how to achieve granulation and maintain granular stability during continuous operation of reactors. This paper aims to review the current state of research on AGMBR technology while drawing attention to relevant findings and highlight current limitations.     

Fate of the sea urchin egg receptor for sperm following fertilization

The sea urchin egg receptor for sperm is a 350 kDa glycoprotein containing a large extracellular domain that contains the sperm binding site, a transmembrane domain and a short COOH- terminal intracellular domain. During oogenesis, the receptor protein is first detected in Golgi-associated vesicles and cortical granules. Not until the egg is mature does the receptor appear on the cell surface; at this stage the intact receptor is found in approximately equal quantities on the egg cell surface and in cortical granules. As a potentially unique type of receptor, we were interested in its fate following fertilization. Several techniques have revealed that, following sperm binding, the amount of receptor markedly decreases. Using western blot analysis as well as direct measurement of the receptor protein, it was found that the membrane-bound form of the receptor rapidly disappeared following sperm binding to the egg, with only 3% of the receptor remaining after 30 s. Analysis by immupoelectron microscopy revealed that 30 s after sperm binding, 30% of the initial level of receptor was present. This remaining 30% was found mostly within the perivitelline space formed by the raised fertilization envelope. The disparity between these two sets of results (i.e. 3 vs 30%) is most likely accounted for by the exocytosis of receptor molecules from cortical granules; this fraction of the receptor would have been lost during isolation of the membrane-bound form of the receptor. Thus, unlike other cell surface receptors, the sea urchin egg receptor for sperm is not endocytosed and recycled following ligand binding. Rather, it disappears, presumably as a result of proteolysis. Transiently, the cortical granule form of the receptor is found released into the perivitelline space where it may bind to sperm and thereby prevent polyspermy. Despite the apparent secretion of this form of the receptor, experiments with antibodies to the extracellular and intracellular domains indicate that the receptors in cortical granules and in the plasmic membrane are similar, if not identical.     

Morphological Analysis of an Isolated Fraction Containing Secretory Granules from the Submandibular Gland of Trypanosoma cruzi Infected and Normal Rats

Normal and Trypanosoma cruzi infected submandibular glands from 42 male Holtzman rats were homogenized in 340 mM sucrose and 0.5 mM EDTA in 10 mM HEPES buffer at pH 7.4. The extract was centrifuged and filtered to prepare a granule rich fraction. Isolated secretory granules are similar morphologically to granules observed in whole submandibular gland preparations. Our results suggest that our isolation technic can be used for morphological and biochemical studies.     

细胞胞吐的分子基础

近年来对神经末梢突触小泡膜蛋白的蛋白质化学,药理学研究及酵母细胞蛋白运输及分泌的遗传学的研究,发现了胞吐蛋白复合体的存在。ＳＮＡＲＥ假说的提出使得对神经递质释放,内外分泌细胞分泌机制的研究有了突飞猛进的进展。     

Oxidative injury to isolated rat pancreatic acinar cells vs. isolated zymogen granules

This study compares the susceptibility of pancreatic acinar cells and zymogen granules against oxidative injury and analyzes the mechanisms involved. Zymogen granules and acinar cells, isolated from rat pancreas, were exposed to a reaction mixture containing xanthine oxidase, hypoxanthine, and chelated iron. Cell function and viability were assessed by various techniques. Trypsin activation was quantified by an Elisa for trypsinogen activating peptide. Integrity of granules was determined by release of amylase. The reaction mixture rapidly generated radicals as assessed by deoxyribose and luminol assays. This oxidative stress caused lysis of granules in a matter of minutes but significant cell death only after some hours. Nevertheless, radicals initiated intracellular vacuolization, morphological damage to zymogen granules and mitochondria, increase in trypsinogen activating peptide, and decrease in ATP already after 5–30 min. Supramaximal caerulein concentrations also caused rapid trypsin activation. Addition of cells but not of granules reduced deoxyribose oxidation, suggesting that intact cells act as scavengers. Caerulein pretreatment only slightly increased the susceptibility of cells but markedly that of granules. In conclusion, isolated zymogen granules are markedly more susceptible to oxidative injury than intact acinar cells, in particular, in early stages of caerulein pancreatitis. The results show that oxidative stress causes a rapid trypsin activation that may contribute to cell damage by triggering autodigestion. Zymogen granules and mitochondria appear to be important targets of oxidative damage inside acinar cells. The series of intracellular events initiated by oxidative stress was similar to changes seen in early stages of pancreatitis.     

Proteasome dynamics between proliferation and quiescence stages of Saccharomyces cerevisiae

The ubiquitin-proteasome system (UPS) plays a critical role in cellular protein homeostasis and is required for the turnover of short-lived and unwanted proteins, which are targeted by poly-ubiquitination for degradation. Proteasome is the key protease of UPS and consists of multiple subunits, which are organized into a catalytic core particle (CP) and a regulatory particle (RP). In Saccharomyces cerevisiae, proteasome holo-enzymes are engaged in degrading poly-ubiquitinated substrates and are mostly localized in the nucleus during cell proliferation. While in quiescence, the RP and CP are sequestered into motile and reversible storage granules in the cytoplasm, called proteasome storage granules (PSGs). The reversible nature of PSGs allows the proteasomes to be transported back into the nucleus upon exit from quiescence. Nuclear import of RP and CP through nuclear pores occurs via the canonical pathway that includes the importin-αβ heterodimer and takes advantage of the Ran-GTP gradient across the nuclear membrane. Dependent on the growth stage, either inactive precursor complexes or mature holo-enzymes are imported into the nucleus. The present review discusses the dynamics of proteasomes including their assembly, nucleo-cytoplasmic transport during proliferation and the sequestration of proteasomes into PSGs during quiescence.

     

小建中颗粒治疗慢性浅表性胃炎合并消化不良的效果观察

目的:观察小建中颗粒在慢性浅表性胃炎合并消化不良中的应用效果。方法:选取我院收治的慢性浅表性胃炎合并消化不良患者166例,采取数字随机法分成观察组(n=83)和对照组(n=83)。对照组采取常规西药治疗,观察组在对照组基础上采取小建中颗粒治疗,比较两组临床效果。结果:观察组与对照组总有效率分别为91.57%、79.52%,观察组总有效率高于对照组,差异具有统计学意义(P0.05)。两组不良反应发生率比较,差异无统计学意义(P0.05)。结论:小建中颗粒在慢性浅表性胃炎合并消化不良中的应用效果显著,可复合奥美拉唑进行治疗,保证安全的基础上提高临床疗效。