Influence of hydrophobic mismatch on the catalytic activity of Escherichia coli GlpG rhomboid protease

Rhomboids comprise a broad family of intramembrane serine proteases that are found in a wide range of organisms and participate in a diverse array of biological processes. High-resolution structures of the catalytic transmembrane domain of the Escherichia coli GlpG rhomboid have provided numerous insights that help explain how hydrolytic cleavage can be achieved below the membrane surface. Key to this are observations that GlpG hydrophobic domain dimensions may not be sufficient to completely span the native lipid bilayer. This formed the basis for a model where hydrophobic mismatch Induces thinning of the local membrane environment to promote access to transmembrane substrates. However, hydrophobic mismatch also has the potential to alter the functional properties of the rhomboid, a possibility we explore in the current work. For this purpose, we purified the catalytic transmembrane domain of GlpG into phosphocholine or maltoside detergent micelles of varying alkyl chain lengths, and assessed proteolytic function with a model water-soluble substrate. Catalytic turnover numbers were found to depend on detergent alkyl chain length, with saturated chains containing 10–12 carbon atoms supporting maximal activity. Similar results were obtained in phospholipid bicelles, with no proteolytic activity being detected in longer-chain lipids. Although differences in thermal stability and GlpG oligomerization could not explain these activity differences, circular dichroism spectra suggest that mismatch gives rise to a small change in structure. Overall, these results demonstrate that hydrophobic mismatch can exert an inhibitory effect on rhomboid activity, with the potential for changes in local membrane environment to regulate activity in vivo.     

Genome-wide siRNA Screening at Biosafety Level 4 Reveals a Crucial Role for Fibrillarin in Henipavirus Infection

Hendra and Nipah viruses (genus Henipavirus, family Paramyxoviridae) are highly pathogenic bat-borne viruses. The need for high biocontainment when studying henipaviruses has hindered the development of therapeutics and knowledge of the viral infection cycle. We have performed a genome-wide siRNA screen at biosafety level 4 that identified 585 human proteins required for henipavirus infection. The host protein with the largest impact was fibrillarin, a nucleolar methyltransferase that was also required by measles, mumps and respiratory syncytial viruses for infection. While not required for cell entry, henipavirus RNA and protein syntheses were greatly impaired in cells lacking fibrillarin, indicating a crucial role in the RNA replication phase of infection. During infection, the Hendra virus matrix protein co-localized with fibrillarin in cell nucleoli, and co-associated as a complex in pulldown studies, while its nuclear import was unaffected in fibrillarin-depleted cells. Mutagenesis studies showed that the methyltransferase activity of fibrillarin was required for henipavirus infection, suggesting that this enzyme could be targeted therapeutically to combat henipavirus infections.     

Photo-movement in the sea anemone Aiptasia influenced by light quality and symbiotic association

Coral Reefs - The relationship between cnidarians and their micro-algal symbionts is crucial for normal animal function and the formation of coral reefs. We used the sea anemone Exaiptasia pallida...     

Beneficial intergenerational effects of exercise on brain and cognition: a multilevel meta-analysis of mean and variance

Physical exercise not only helps to improve physical health but can also enhance brain development and cognition. Recent reports on parental (both maternal and paternal) effects raise the possibility that parental exercise may provide benefits to offspring through intergenerational inheritance. However, the general magnitude and consistency of parental exercise effects on offspring is still controversial. Additionally, empirical research has long overlooked an important aspect of exercise: its effects on variability in neurodevelopmental and cognitive traits. Here, we compiled data from 52 studies involving 4786 rodents (412 effect sizes) to quantify the intergenerational transmission of exercise effects on brain and cognition. Using a multilevel meta-analytic approach, we found that, overall, parental exercise showed a tendency for increasing their offspring's brain structure by 12.7% (albeit statistically non-significant) probably via significantly facilitating neurogenesis (16.5%). Such changes in neural anatomy go in hand with a significant 20.8% improvement in neurobehaviour (improved learning and memory, and reduced anxiety). Moreover, we found parental exercise significantly reduces inter-individual differences (i.e. reduced variance in the treatment group) in progeny's neurobehaviour by 10.2% (coefficient of variation ratio, lnCVR), suggesting the existence of an individual by intervention interaction. The positive effects of exercise are modulated by several covariates (i.e. moderators), such as the exercised parent's sex, offspring's sex, and age, mode of exercise, and exercise timing. In particular, parental forced exercise is more efficient than voluntary exercise at significantly improving offspring neurobehaviour (26.0%) and reducing its variability (14.2%). We observed larger effects when parental exercise started before pregnancy. However, exercising only during pregnancy also had positive effects. Mechanistically, exercise significantly upregulated brain-derived neurotrophic factor (BDNF) by 28.9%, vascular endothelial growth factor (VEGF) by 35.8%, and significantly decreased hippocampal DNA methylation by 3.5%, suggesting that brain growth factor cascades and epigenetic modifications can moderate the transmission of parental exercise effects. Collectively, by coupling mean with variance effects, our analyses draw a more integrated picture of the benefits that parental exercise has on offspring: not only does it improve offspring brain development and cognitive performance, but it also reduces inter-individual differences in cognition-related traits. We advocate that meta-analysis of variation together with the mean of a trait provides novel insights for old controversies as well as emerging new questions, opening up a new era for generating variance-based hypotheses.     

Three‐dimensional mapping of the attenuation coefficient in optical coherence tomography to enhance breast tissue microarchitecture contrast

Effective intraoperative tumor margin assessment is needed to reduce re‐excision rates in breast‐conserving surgery (BCS). Mapping the attenuation coefficient in optical coherence tomography (OCT) throughout a sample to create an image (attenuation imaging) is one promising approach. For the first time, three‐dimensional OCT attenuation imaging of human breast tissue microarchitecture using a wide‐field (up to ~45 × 45 × 3.5 mm) imaging system is demonstrated. Representative results from three mastectomy and one BCS specimen (from 31 specimens) are presented with co‐registered postoperative histology. Attenuation imaging is shown to provide substantially improved contrast over OCT, delineating nuanced features within tumors (including necrosis and variations in tumor cell density and growth patterns) and benign features (such as sclerosing adenosis). Additionally, quantitative micro‐elastography (QME) images presented alongside OCT and attenuation images show that these techniques provide complementary contrast, suggesting that multimodal imaging could increase tissue identification accuracy and potentially improve tumor margin assessment.     

Trans-generational immune priming is not mediated by the sex of the parent primed: a meta-analysis of invertebrate data

Traditionally, only vertebrates were thought capable of acquired immune responses, such as the ability to transfer immunological experience vertically to their offspring (known as trans-generational immune priming, TGIP). Increasing evidence challenges this belief and it is now clear that invertebrates also have the ability to exhibit functionally equivalent TGIP. This has led to a surge in papers exploring invertebrate TGIP, with most focusing on the costs, benefits or factors that affect the evolution of this trait. Whilst many studies have found support for the phenomenon, not all studies do, and there is considerable variation in the strength of positive results. To address this, we conducted a meta-analysis to answer the question: what is the overall effect of TGIP in invertebrates? Then, to understand the specific factors that affect its presence and intensity, we conducted a moderator analysis. Our results corroborate that TGIP occurs in invertebrates (demonstrated by a large, positive effect size). The strength of the positive effect was related to if and how offspring were immune challenged (i.e. whether they were challenged with the same or different insult as their parents or not challenged at all). Interestingly, there was no effect of the ecology or life history of the species or the sex of the parent or the offspring primed, and responses were comparable across different immune elicitors. Our publication bias testing suggests that the literature may suffer from some level of positive-result bias. However, even after accounting for potential bias, our effect size remains positive. Publication bias testing can be influenced by diversity in the data set, which was considerable in our data, even after moderator analysis. It is therefore conceivable that differences among studies could be caused by other moderators that were unable to be included in our meta-analysis. Nonetheless, our results suggest that TGIP does occur in invertebrates, whilst providing some potential avenues to examine the factors that account for variation in effect sizes.