The Coordination of Signaling by 3' Phosphoinositide Concentration Thresholds during Phagocytosis.

Phagocytosis plays important roles in immune responses by ingesting and destroying pathogens. This thesis addresses the overall question of how signaling during Fcγ receptor (FcR)-mediated phagocytosis is coordinated. The magnitude of signal molecule recruitment into forming phagosomes was measured as a function of ligand density, using a newly developed recruitment measurement method based on ratiometric fluorescence microscopy. Although early FcR-dependent signals correlated with IgG density on beads, later signals showed a threshold response which was regulated by the concentrations of 3’ phosphoinositides in phagocytic cups. The suprathreshold concentrations of 3’ phosphoinositides were required for the commitment to later stages of phagosome formation. Rho-family GTPases displayed an activity transition during phagocytosis. In particular, Rac1 was active throughout phagosome formation, Cdc42 activity was restricted to early stages after receptor ligation but Rac2 activity increased later during phagosome closure. Inhibition of PI3-kinases, which generate 3’ phosphoinositides following FcR ligation, resulted in persistently active Cdc42 and Rac1, but not Rac2, indicating a role for 3’ phosphoinositides in the Rho GTPase activity transition. Expression of constitutively active Cdc42 inhibited phagocytosis by a mechanism that was additive with PI3-Kinase inhibition, indicating that Rho GTPase activity transition was also required for the commitment to later stages of phagosome formation. In addition, 3’ phosphoinositide concentration thresholds correlated with the phenomenon that the shape of target particles affected phagocytosis. Target geometry modulated the generation of intracellular 3’ phosphoinositides, whose concentrations can affect the late stage signals and outcome of phagocytosis. In summary, this thesis establishes that 3’ phosphoinositide concentration thresholds regulate commitment to phagocytosis by regulating late stage signal protein recruitment and GTPase activity transitions.Ph.D.BiophysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64744/1/yxzhang_1.pd

A two-sample mendelian randomization study of atherosclerosis and dementia

The causality between atherosclerosis and dementia remains unclear. This study aimed to explore the causal effect of atherosclerosis related indicators on dementia risk based on two-sample Mendelian randomization (MR) using summary statistics of genome-wide association studies (GWASs). The inverse variance weighted (IVW) method was performed as the main analysis, supplemented by different sensitivity analyses. Suggestive evidence indicated that peripheral arterial disease (PAD) (odds ratio (OR): 0.864, 95% confidence interval (CI): 0.797–0.937), coronary atherosclerosis (CoAS) (OR: 0.927, 95% CI: 0.860–0.998) and atherosclerosis, excluding cerebral, coronary, and PAD (ATHSCLE) (OR: 0.812, 95% CI: 0.725–0.909) were inversely associated with the risk of AD. The sensitivity analysis confirmed a suggestive reverse effect of ATHSCLE on the risk of frontotemporal dementia (FTD) (OR, 0.812, 95% CI, 0.725–0.909). Findings provide suggestive evidence that PAD, CoAS, and ATHSCLE might be associated with the risk of AD or FTD, which requires further exploration in larger samples

CDK5 positively regulates notch1 signaling in pancreatic cancer cells by phosphorylation

The marked overexpression of cyclin-dependent kinase 5 (CDK5) or Notch1 receptor, which plays critical roles in pancreatic ductal adenocarcinoma (PDAC) development, has been detected in numerous PDAC cell lines and tissues. Although, a previous study has demonstrated that CDK5 inhibition disrupts Notch1 functions in human umbilical vein endothelial cells, the mechanism underlying Notch1 activation regulated by CDK5 remains unclear. Herein, we identified a physical interaction between CDK5 and Notch1 in PDAC cells, with the Notch1 peptide phosphorylated by CDK5/p25 kinase. CDK5 blockade resulted in the profound inhibition of Notch signaling. Accordingly, CDK5 inhibition sensitized PDAC cell proliferation and migration following Notch inhibition. In conclusion, CDK5 positively regulates Notch1 function via phosphorylation, which in turn promotes cell proliferation and migration. The combinational inhibition of CDK5 and Notch signaling may be an effective strategy in the treatment of PDAC

Clathrin and AP2 are required for PtdIns(4,5)P2-mediated formation of LRP6 signalosomes

Canonical Wnt signaling is initiated by the binding of Wnt proteins to their receptors, low-density lipoprotein-related protein 5 and 6 (LRP5/6) and frizzled proteins, leading to phosphatidylinositol (4,5)bisphosphate (PtdIns(4,5)P2) production, signalosome formation, and LRP phosphorylation. However, the mechanism by which PtdIns(4,5)P2 regulates the signalosome formation remains unclear. Here we show that clathrin and adaptor protein 2 (AP2) were part of the LRP6 signalosomes. The presence of clathrin and AP2 in the LRP6 signalosomes depended on PtdIns(4,5)P2, and both clathrin and AP2 were required for the formation of LRP6 signalosomes. In addition, WNT3A-induced LRP6 signalosomes were primarily localized at cell surfaces, and WNT3A did not induce marked LRP6 internalization. However, rapid PtdIns(4,5)P2 hydrolysis induced artificially after WNT3A stimulation could lead to marked LRP6 internalization. Moreover, we observed WNT3A-induced LRP6 and clathrin clustering at cell surfaces using super-resolution fluorescence microscopy. Therefore, we conclude that PtdIns(4,5)P2 promotes the assembly of LRP6 signalosomes via the recruitment of AP2 and clathrin and that LRP6 internalization may not be a prerequisite for Wnt signaling to β-catenin stabilization

MobiBone:An energy-efficient and adaptive network protocol to support short rendezvous between static and mobile wireless sensor nodes

To ensure long network life-time, the duty-cycle of wireless sensor networks is often set to be low. This brings with itself the risk of either missing a sent packet or delaying the message delivery and dissemination depending on the duration of the duty-cycle and number of hops. This risk is increased in wireless sensor applications with hybrid architecture, in which a static ground wireless sensor network interacts with a network of mobile sensor nodes. Dynamicity and mobility of mobile nodes may lead to only a short rendezvous between them and the backbone network to exchange data. Additionally, such dynamicity generates complex and often random data traffic patterns. To support successful data delivery in case of short rendezvous between static and mobile wireless sensor nodes, we propose MobiBone, an energy-efficient and adaptive network protocol that utilizes data packet traffic to characterize the sleep schedule. Our simulation results show that compared with network protocols with fixed duty-cycles, MobiBone offers a good trade-off between energy consumption, latency, and detection rate of mobile nodes (which indicates awakens of the backbone network at crucial times of mobile node presence)

The prevalence of adverse reactions among individuals with three-dose COVID-19 vaccination

Background: Considering the adverse reactions to vaccination against coronavirus disease 2019 (COVID-19), some people, particularly the elderly and those with underlying medical conditions, are hesitant to be vaccinated. This study aimed to explore the prevalence of adverse reactions and provide direct evidence of vaccine safety, mainly for the elderly and people with underlying medical conditions, to receive COVID-19 vaccination. Methods: From 1st March to 30th April 2022, we conducted an online survey of people who had completed three doses of COVID-19 vaccination by convenience sampling. Adverse reaction rates and 95% confidence intervals were calculated. In addition, conditional logistic regression was used to compare the differences in adverse reactions among the elderly and those with underlying medical conditions with the general population. Results: A total of 3339 individuals were included in this study, of which 2335 (69.9%) were female, with an average age of 32.1 ± 11.4 years. The prevalence of adverse reactions after the first dose of inactivated vaccine was 24.6 % (23.1 – 26.2 %), 19.2 % (17.8 – 20.7 %) for the second dose, and 19.1 % (17.7 – 20.6 %) for the booster dose; among individuals using messenger RNA vaccines, the prevalence was 42.7 % (32.3 – 53.6 %) for the first dose, 47.2 % (36.5 – 58.1 %) for the second dose, and 46.1 % (35.4 – 57.0 %) for the booster dose. Compared with the general population, the prevalence of adverse events did not differ in individuals with underlying medical conditions and those aged 60 and above. Conclusions: For individuals with underlying medical conditions and those aged 60 and above, the prevalence of adverse reactions is similar to that of the general population, which provides a scientific basis regarding vaccination safety for these populations

Targeted suppression of heme oxygenase-1 by small interference RNAs inhibits the production of bilirubin in neonatal rat with hyperbilirubinemia

<p>Abstract</p> <p>Background</p> <p>Excessive accumulation of bilirubin contributes to neonatal hyperbilirubinemia in rats. Heme oxygenase (HO) is one of the rate-limiting enzymes in catabolizing heme to bilirubin. In the present study, we investigated whether suppression of rat HO-1 (rHO-1) expression by small interference RNAs (siRNAs) reduces bilirubin levels in hyperbilirubinemic rats.</p> <p>Results</p> <p>Four pairs of siRNA targeting rHO-1 mRNA were introduced into BRL cells and compared for their inhibitory effect on the expression of <it>rHO-1 </it>gene and production of rHO-1 protein. The siRNA exhibiting the most potent effect on HO-1 expression and activity was then administered intraperitoneally to 7 to 9-day-old rats with hyperbilirubinemia. The siRNA distributed mostly in the liver and spleen of neonatal rat. Serum bilirubin levels and hepatic HO-1 expression were further evaluated. Systemic treatment of siRNA targeting rHO-1 reduced hepatic HO-1 expression and decreased the serum bilirubin levels in a time- and dose-dependent manner, and siRNA decreased the indirect bilirubin levels more effectively than Sn-protoporphyrin (SnPP), an HO-1 inhibitor.</p> <p>Conclusion</p> <p>siRNA targeting rHO-l attenuates hepatic HO-1 expression and serum bilirubin levels. Thus this study provides a novel therapeutic rationale for the prevention and treatment of neonatal hyperbilirubinemia.</p

Vascular endothelial growth factor and the risk of venous thromboembolism: A genetic correlation and two-sample Mendelian randomization study

Background: The relationship between vascular endothelial growth factor (VEGF) and the risk of venous thromboembolism (VTE) has always been one of the concerns in the medical field. However, the causal inferences from published observational studies on this issue may be affected by confounders or reverse causality. We performed a two-sample bidirectional Mendelian randomization (MR) to infer the associations between VEGF and VTE. Methods: Summary statistics from genome-wide association studies (GWAS) for VEGF and VTE were obtained from published meta-analysis studies and the FinnGen consortium, respectively. Independent genetic variables significantly associated with exposure were selected as instrumental variables. Linkage disequilibrium score regression (LDSC) and five robust MR analytical approaches were conducted to estimate the genetic correlations and causal inference. The MR-Egger intercept, Cochran’s Q, and MR pleiotropy residual sum and outlier (MR-PRESSO) were performed to evaluate the horizontal pleiotropy, heterogeneities, and stability of these genetic variants on outcomes. Notably, replication analyses were performed using different subgroups of VTE. Results: LDSC failed to identify genetic correlations between VEGF and VTE. Based on 9 SNPs, the circulating VEGF level was positively related to the risk of VTE using inverse variance weighting (IVW) method (odds ratio (OR) = 1.064, 95 % confidence interval (CI), 1.009 – 1.122). Reverse MR analyses showed that genetic liability for VTE was not associated with increased VEGF level (β = -0.021, 95 % CI, -0.087-0.045). Pleiotropy-robust methods indicated no bias in any estimates. Conclusions: Our findings failed to detect coheritability between VEGF and VTE. The suggestive positive effect of the higher VEGF level on the VTE risk may have clinical implications, suggesting that VEGF as a possible predictor and therapeutic target for VTE prevention need to be further warranted

Positive correlation between the expression of hEag1 and HIF-1α in breast cancers: An observational study

Objectives: To explore the expression patterns of Eag1 (ether á go-go 1) and HIF-1α (hypoxia-inducible factor 1α) in a cohort of patients with breast cancer. Setting: Department of general surgery in an upper first-class hospital in Xi\u27an, China. Participants: A total of 112 female Han Chinese patients with a diagnosis of invasive ductal carcinoma were included. Patients with main internal diseases, such as cardiovascular, endocrine, gastroenterological, haematological, infectious diseases, etc, were excluded. Primary and secondary outcome measures: Expression profiles of Eag1 and HIF-1α. Results: Eag1 and HIF-1α were overexpressed in the tumour tissues compared with the pair-matched control tissues, p=0.002 and \u3c0.001, respectively. The expression of Eag1 and HIF-1α was negatively correlated with tumour size, p=0.032 and p=0.025, respectively, and lymph node status (p=0.040, p=0.032, respectively). The coexpression of Eag1 and HIF-1α was correlated with tumour size ( p=0.012), lymph node status (p=0.027) and tumour stage (p=0.036). HIF-1α has a strong correlation with hEag1 expression (κ=0.731, p\u3c0.001). Conclusions: HIF-1á expression has a strong correlation with hEag1 expression. We are the first to attempt to explore the correlation at the population level

Remote light-controlled intracellular target recognition by photochromic fluorescent glycoprobes

Development of powerful fluorescence imaging probes and techniques sets the basis for the spatiotemporal tracking of cells at different physiological and pathological stages. While current imaging approaches rely on passive probe-analyte interactions, here we develop photochromic fluorescent glycoprobes capable of remote light-controlled intracellular target recognition. Conjugation between a fluorophore and spiropyran produces the photochromic probe, which is subsequently equipped with a glycoligand "antenna" to actively localize a target cell expressing a selective receptor. We demonstrate that the amphiphilic glycoprobes that form micelles in water can selectively enter the target cell to operate photochromic cycling as controlled by alternate UV/Vis irradiations. We further show that remote light conversion of the photochromic probe from one isomeric state to the other activates its reactivity toward a target intracellular analyte, producing locked fluorescence that is no longer photoisomerizable. We envision that this research may spur the use of photochromism for the development of bioimaging probes