Modulation of host phosphatidylinositol phosphates by salmonella effector protein SOPB

Salmonella spp. are gram negative bacteria capable of infecting a number of eukaryotic hosts. In humans, Salmonella infection can range anywhere from acute gastroenteritis to typhoid fever which can oftentimes be fatal.Salmonella are facultative intracellular pathogens that have acquired the ability to enter non-phagocytic cells such as those lining the intestinal epithelium. Uptake into epithelial cells is mediated by the Salmonellapathogenicity island 1 (SPI1) encoded type III secretion system (T3SS), a needle-like complex composed of over 20 proteins that translocates effector proteins directly into the host cell cytosol. Salmonella possess a second type III secretion system encoded on Salmonella pathogenicity island 2 (SPI2) that secretes effector proteins involved in Salmonella containing vacuole (SCV) formation, maturation, and intracellular survival. ^ Entrance into epithelial cells is modulated by effector proteins SopE, SopE2 and SopB. SopE and SopE2 having 69% sequence identity are known to be guanine nucleotide exchange factors (GEFs). SopE is a GEF capable of activating both Rac1 and Cdc42 while SopE2 activates Cdc42 only. SopB is a known phosphatidylinositol phosphate phosphatase possessing both 4- and 5-phosphatase activities promoting membrane ruffling and invasion. The mechanisms through which SopB utilizes its phosphatase activities to mediate membrane ruffling and invasion are still unclear. Previous research has demonstrated that SopB is responsible for the production of PtdIns(3)P at the Salmonella induced ruffles, but the mechanism through which SopB acts is still not understood. This work will directly link the phosphatase activity of SopB, demonstrating the requirement of both the 4- phosphatase and 5-phosphatase activities, to ruffle formation and invasion. We found that the 5-phosphatase activity is responsible for generating PtdIns(3,4)P2 which recruits host SNX9, a protein involved in actin modulation to the plasma membrane. The 4-phosphatase activity of SopB is solely responsible for the hydrolysis of host PtdIns(3,4)P2 into PtdIns(3)P which accumulates around the ruffles and becomes incorporated into the forming SCV membrane. Either activity alone does not result in ruffling or invasion, but when acting in conjunction with one another, the 4-phosphatase and 5-phosphatase activities of SopB lead to SNX9- mediated ruffling and Salmonella invasion

Weight-related teasing in the school environment: associations with psychosocial health and weight control practices among adolescent boys and girls

Weight-related teasing has been found to be associated with low self-esteem, depressive symptoms, body dissatisfaction, and weight control behaviors in adolescents. While research has typically examined weight-related teasing directed towards the individual, little is known about weight-related teasing at the school level. This study aimed to determine the association between the school-level prevalence of weight-related teasing and psychosocial factors, body dissatisfaction and weight control behaviors in adolescents. Adolescents (N = 2,793; 53.2 % female) attending 20 US public middle and high schools were surveyed as part of the Eating and Activity in Teens (EAT) 2010 study. Generalized estimating equations were used to estimate the association between school-level weight-related teasing and health variables, controlling for individual-level weight-related teasing, clustering of individuals within schools, and relevant covariates. A greater school-level prevalence of weight-related teasing was associated with lower self-esteem and greater body fat dissatisfaction in girls, and greater depressive symptoms in boys, over and above individual-level weight-related teasing.Dieting was associated with the school-level prevalence of weight-related teasing in analysis adjusted for covariates in girls, but not following adjustment for individual-level weight-related teasing. Unhealthy weight control behaviors, extreme weight control behaviors, and muscle-enhancing behaviors were not associated with the school-level prevalence of weight-related teasing in girls or boys. Findings from the current study, in conjunction with previous findings showing associations between weight-related teasing, psychological concerns, and weight control behaviors, highlight the importance of implementing strategies to decrease weight-related teasing in schools

The EHEC Type III Effector NleL Is an E3 Ubiquitin Ligase That Modulates Pedestal Formation

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 causes hemorrhagic colitis and may result in potentially fatal hemolytic uremia syndrome in humans. EHEC colonize the intestinal mucosa and promote the formation of actin-rich pedestals via translocated type III effectors. Two EHEC type III secreted effectors, Tir and EspFu/TccP, are key players for pedestal formation. We discovered that an EHEC effector protein called Non-LEE-encoded Ligase (NleL) is an E3 ubiquitin ligase. In vitro, we showed that the NleL C753 residue is critical for its E3 ligase activity. Functionally, we demonstrated that NleL E3 ubiquitin ligase activity is involved in modulating Tir-mediated pedestal formation. Surprisingly, EHEC mutant strain deficient in the E3 ligase activity induced more pedestals than the wild-type strain. The canonical EPEC strain E2348/69 normally lacks the nleL gene, and the ectopic expression of the wild-type EHEC nleL, but not the catalytically-deficient nleL(C753A) mutant, in this strain resulted in fewer actin-rich pedestals. Furthermore, we showed that the C. rodentium NleL homolog is a E3 ubiquitin ligase and is required for efficient infection of murine colonic epithelial cells in vivo. In summary, our study demonstrated that EHEC utilizes NleL E3 ubiquitin ligase activity to modulate Tir-mediated pedestal formation.National Institutes of Health (U.S.) (grant AI078092)National Institutes of Health (U.S.) (grant AI068655

Modulation of host cell processes by T3SS effectors

Two of the enteric Escherichia coli pathotypes-enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC)-have a conserved type 3 secretion system which is essential for virulence. The T3SS is used to translocate between 25 and 50 bacterial proteins directly into the host cytosol where they manipulate a variety of host cell processes to establish a successful infection. In this chapter, we discuss effectors from EPEC/EHEC in the context of the host proteins and processes that they target-the actin cytoskeleton, small guanosine triphosphatases and innate immune signalling pathways that regulate inflammation and cell death. Many of these translocated proteins have been extensively characterised, which has helped obtain insights into the mechanisms of pathogenesis of these bacteria and also understand the host pathways they target in more detail. With increasing knowledge of the positive and negative regulation of host signalling pathways by different effectors, a future challenge is to investigate how the specific effector repertoire of each strain cooperates over the course of an infection

Modulation of host phosphatidylinositol phosphates by salmonella effector protein SOPB

Salmonella spp. are gram negative bacteria capable of infecting a number of eukaryotic hosts. In humans, Salmonella infection can range anywhere from acute gastroenteritis to typhoid fever which can oftentimes be fatal. Salmonella are facultative intracellular pathogens that have acquired the ability to enter non-phagocytic cells such as those lining the intestinal epithelium. Uptake into epithelial cells is mediated by the Salmonella pathogenicity island 1 (SPI1) encoded type III secretion system (T3SS), a needle-like complex composed of over 20 proteins that translocates effector proteins directly into the host cell cytosol. Salmonella possess a second type III secretion system encoded on Salmonella pathogenicity island 2 (SPI2) that secretes effector proteins involved in Salmonella containing vacuole (SCV) formation, maturation, and intracellular survival. Entrance into epithelial cells is modulated by effector proteins SopE, SopE2 and SopB. SopE and SopE2 having 69% sequence identity are known to be guanine nucleotide exchange factors (GEFs). SopE is a GEF capable of activating both Rac1 and Cdc42 while SopE2 activates Cdc42 only. SopB is a known phosphatidylinositol phosphate phosphatase possessing both 4- and 5-phosphatase activities promoting membrane ruffling and invasion. The mechanisms through which SopB utilizes its phosphatase activities to mediate membrane ruffling and invasion are still unclear. Previous research has demonstrated that SopB is responsible for the production of PtdIns(3)P at the Salmonella induced ruffles, but the mechanism through which SopB acts is still not understood. This work will directly link the phosphatase activity of SopB, demonstrating the requirement of both the 4- phosphatase and 5-phosphatase activities, to ruffle formation and invasion. We found that the 5-phosphatase activity is responsible for generating PtdIns(3,4)P2 which recruits host SNX9, a protein involved in actin modulation to the plasma membrane. The 4-phosphatase activity of SopB is solely responsible for the hydrolysis of host PtdIns(3,4)P2 into PtdIns(3)P which accumulates around the ruffles and becomes incorporated into the forming SCV membrane. Either activity alone does not result in ruffling or invasion, but when acting in conjunction with one another, the 4-phosphatase and 5-phosphatase activities of SopB lead to SNX9- mediated ruffling and Salmonella invasion

Complex Factors and Challenges that Affect the Pharmacology, Safety and Efficacy of Nanocarrier Drug Delivery Systems

Major developments in nanomedicines, such as nanoparticles (NPs), nanosomes, and conjugates, have revolutionized drug delivery capabilities over the past four decades. Although nanocarrier agents provide numerous advantages (e.g., greater solubility and duration of systemic exposure) compared to their small-molecule counterparts, there is considerable inter-patient variability seen in the systemic disposition, tumor delivery and overall pharmacological effects (i.e., anti-tumor efficacy and unwanted toxicity) of NP agents. This review aims to provide a summary of fundamental factors that affect the disposition of NPs in the treatment of cancer and why they should be evaluated during preclinical and clinical development. Furthermore, this chapter will highlight some of the translational challenges associated with elements of NPs and how these issues can only be addressed by detailed and novel pharmacology studies