Examining the longitudinal associations between activity limitations, instrumental supports and social participation in osteoarthritis: A CLSA population-based study.

OBJECTIVE: In osteoarthritis (OA) research, disability is largely studied within the context of activities of daily living. Broader consequences for social participation are often overlooked. In prior work, instrumental supports received and their perceived availability were shown to play a role in the maintenance of social participation. Two indicators of social participation were identified, diversity and intensity. The current study extends the findings from this prior cross-sectional work by examining these relationships longitudinally. METHODS: Data are from the baseline and 3-year follow-up questionnaires of the Canadian Longitudinal Study on Aging, a population-based study of people ages 45-85 years at baseline. The sample was restricted to those who at baseline reported a doctor diagnosis of OA (n = 4104). Using structural equation modeling, latent variables were derived at each time point for activity limitations, instrumental supports perceived and received, and social participation diversity and intensity. Longitudinal factorial invariance was assessed. Model covariates included age, sex, education, income, marital status, smoking status, obesity, and number of chronic conditions. RESULTS: For all latent variables, strong factorial longitudinal invariance was found. Activity limitations increased over time. Greater baseline social participation intensity was associated with increases in later intensity and diversity. Increasing activity limitations were associated with decreases in social participation and with increasing receipt of instrumental supports; they were not associated with changes in perceived availability of supports. However, increasing perceived availability was positively associated with social participation intensity. CONCLUSIONS: With a goal of increasing social participation, findings suggest a focus on interventions to reduce activity limitations in OA is necessary. Findings additionally highlight an important role for perceived availability of instrumental supports in maintaining or improving social participation in OA, in addition to current social participation, particularly intensity, for future social participation status.

A Comprehensive Assessment Protocol for Swallowing (CAPS): Paving the Way towards Computer-Aided Dysphagia Screening.

Dysphagia is one of the most common problems among older adults, which might lead to aspiration pneumonia and eventual death. It calls for a feasible, reliable, and standardized screening or assessment method to prompt rehabilitation measures and mitigate the risks of dysphagia complications. Computer-aided screening using wearable technology could be the solution to the problem but is not clinically applicable because of the heterogeneity of assessment protocols. The aim of this paper is to formulate and unify a swallowing assessment protocol, named the Comprehensive Assessment Protocol for Swallowing (CAPS), by integrating existing protocols and standards. The protocol consists of two phases: the pre-test phase and the assessment phase. The pre-testing phase involves applying different texture or thickness levels of food/liquid and determining the required bolus volume for the subsequent assessment. The assessment phase involves dry (saliva) swallowing, wet swallowing of different food/liquid consistencies, and non-swallowing (e.g., yawning, coughing, speaking, etc.). The protocol is designed to train the swallowing/non-swallowing event classification that facilitates future long-term continuous monitoring and paves the way towards continuous dysphagia screening.

Cardiovascular Risk Profile and Osteoarthritis-Considering Sex and Multisite Joint Involvement: A Canadian Longitudinal Study on Aging.

OBJECTIVE: The objective of this study was to investigate a profile of cardiovascular disease (CVD) risk factors by sex among individuals with and without osteoarthritis (OA) and to consider single-site and multisite joint OA. METHODS: Data were sourced from Cycle 1, Comprehensive Cohort, Canadian Longitudinal Study on Aging, a national sample of individuals ages 45 to 85 years. Systemic inflammatory/metabolic CVD risk factors collected were high-sensitivity C-reactive protein (hsCRP) level, high-density lipoprotein, triglycerides, total cholesterol, body mass index (BMI), systolic blood pressure, and hemoglobin A1c. Smoking history was also collected. Respondents indicated doctor-diagnosed OA in the knees, hips, and/or hands and were characterized as yes/no OA and single site/multisite OA. Individuals with OA were age- and sex-matched to non-OA controls. Covariates were age, sex, education, income, physical activity, timed up and go test findings, and comorbidities. A latent CVD risk variable was derived in women and men; standardized scores were categorized as follows: lowest, mid-low, mid-high, and highest risk. Associations with OA were quantified using ordinal logistic regressions. RESULTS: A total of 6,098 respondents (3,049 with OA) had a median age of 63 years, and 55.8% were women. One-third of OA respondents were in the highest risk category versus one-fifth of non-OA respondents. Apart from BMI (the largest contributor in both sexes), hsCRP level (an inflammation marker) was predominant in women, and metabolic factors and smoking were predominant in men. Overall, OA was associated with worse CVD risk quartiles compared with non-OA. OA was increasingly associated with worse CVD risk quartiles with increasing risk thresholds among women with multisite OA, but not men. CONCLUSION: Findings suggest unique CVD risks by sex/multisite subgroups and point to a potentially important role for inflammation in OA over and above traditional CVD risk factors.

Structure of the phosphoinositide 3-kinase (PI3K) p110γ-p101 complex reveals molecular mechanism of GPCR activation.

The class IB phosphoinositide 3-kinase (PI3K), PI3Kγ, is a master regulator of immune cell function and a promising drug target for both cancer and inflammatory diseases. Critical to PI3Kγ function is the association of the p110γ catalytic subunit to either a p101 or p84 regulatory subunit, which mediates activation by G protein-coupled receptors. Here, we report the cryo-electron microscopy structure of a heterodimeric PI3Kγ complex, p110γ-p101. This structure reveals a unique assembly of catalytic and regulatory subunits that is distinct from other class I PI3K complexes. p101 mediates activation through its Gßγ-binding domain, recruiting the heterodimer to the membrane and allowing for engagement of a secondary Gßγ-binding site in p110γ. Mutations at the p110γ-p101 and p110γ-adaptor binding domain interfaces enhanced Gßγ activation. A nanobody that specifically binds to the p101-Gßγ interface blocks activation, providing a novel tool to study and target p110γ-p101-specific signaling events in vivo.

Targeting AXL kinase sensitizes leukemic stem and progenitor cells to venetoclax treatment in acute myeloid leukemia.

The abundance of genetic abnormalities and phenotypic heterogeneities in acute myeloid leukemia (AML) poses significant challenges to the development of improved treatments. Here, we demonstrated that a key growth arrest-specific gene 6/AXL axis is highly activated in cells from patients with AML, particularly in stem/progenitor cells. We developed a potent selective AXL inhibitor that has favorable pharmaceutical properties and efficacy against preclinical patient-derived xenotransplantation (PDX) models of AML. Importantly, inhibition of AXL sensitized AML stem/progenitor cells to venetoclax treatment, with strong synergistic effects in vitro and in PDX models. Mechanistically, single-cell RNA-sequencing and functional validation studies uncovered that AXL inhibition, alone or in combination with venetoclax, potentially targets intrinsic metabolic vulnerabilities of AML stem/progenitor cells and shows a distinct transcriptomic profile and inhibits mitochondrial oxidative phosphorylation. Inhibition of AXL or BCL-2 also differentially targets key signaling proteins to synergize in leukemic cell killing. These findings have a direct translational impact on the treatment of AML and other cancers with high AXL activity.

Predictors of response following standardized education and self-management recommendations for low back pain stratified by dominant pain location.

BACKGROUND: Low back pain (LBP) is a leading cause of disability globally. Risk-stratification systems (e.g. STarT Back) have been proposed to guide treatment, but with varying success. We investigated factors associated with poor response to standardized LBP education and self-management recommendations stratified by dominant pain location (back or leg). METHODS: LBP patients underwent a standardized primary care model of care of education and self-management recommendations. Poor response was defined as an Oswestry Disability Index (ODI) change score <10 units by 6 months. Multivariable logistic regression was used to identify poor response risk factors, stratified by back-dominant and leg-dominant back pain. Baseline factors: age, sex, body mass index, ODI, LBP/leg-pain intensity, LBP/leg-pain duration, STarT Back chronicity-risk, smoking, comorbidity count, and self-efficacy. RESULTS: The sample consisted of 767 patients (443 back-dominant, 324 leg-dominant). Mean age was 53 years, and 59% were female. Females accounted for 66% of back-dominant and 50% of leg-dominant patients. Chronicity risk was 'high' for 18% of back-dominant and 29% of leg-dominant patients. Poor response was higher in back- (57%) compared to leg-dominant (42%) patients. Adjusted stratified analyses: female sex, moderate or high chronicity-risk, and increasing age were associated with increased risk of poor response, and greater self-efficacy with favourable response, in leg-dominant patients; these were not the cases among back-dominant patients. Increased comorbidity count was associated with poor response in back dominant patients. In both patient groups, higher baseline ODI score was associated with favorable response, and smoking and longer pain duration with poor response. CONCLUSIONS: Differences in the influence of sex and chronicity risk in particular on outcome by dominant pain location suggests that considering these patients as a single group may not be appropriate. Furthermore, findings suggest that stratification by pain dominance may enhance the use of established risk stratification tools such as the STarT Back.

Understanding the Association Between Osteoarthritis and Social Participation: The Canadian Longitudinal Study on Aging.

OBJECTIVE: The focus on disability in osteoarthritis (OA) has largely been on the ability to perform specific activities, which neglects the greater implications for social participation. We investigated the association between OA and social participation, considering activity limitations and instrumental supports as intervening variables in the association. METHODS: Data were from 21,214 respondents, ages 45-85 years, from cycle 1 of the Canadian Longitudinal Study on Aging. The questionnaire elicited information regarding self-reported doctor-diagnosed OA, difficulty with 14 activities, perceived availability and receipt of instrumental supports, and 17 social participation activities. Structural equation modeling was used. The primary outcome was social participation, and the primary predictor was OA. The intervening variables included activity limitations, received instrumental supports, and perceived instrumental supports. Latent variables were developed for intervening and social participation variables. The covariates included age, sex, body mass index, income, education, smoking, and comorbidity count. RESULTS: The mean age of the respondents was 63 years, 51% were female, and 26.5% reported having OA. Two distinct social participation indicators were identified, including social participation-diversity and social participation-intensity. When intervening variables were not considered, minimal/no association was found between OA and social participation. When intervening variables were considered, unique pathways linking OA and social participation were found. The overall negative association between activity limitations and social participation was partially direct and partially buffered by both receipt of and perceived availability of instrumental supports. In the absence of activity limitations, OA was associated with greater social participation. CONCLUSION: Enhanced social participation in people with OA who do not have activity limitations may reflect proactive steps taken by those with mild OA to maintain activity and social engagement. For those with activity limitations, findings highlight the need for interventions to mitigate limitations and draw particular attention to the importance of both provision and awareness of available instrumental supports in maintaining social participation.

The impact of multijoint symptoms on patient-reported disability following surgery for lumbar spine osteoarthritis.

BACKGROUND CONTEXT: In the lumbar spine osteoarthritis (LS-OA) population having surgery for lumbar spinal stenosis (LSS) symptoms, a significant proportion of patients experience limited benefit following the intervention. Thus, identifying contributing factors to this is important. Individuals with OA often have multiple joint symptoms, yet this has received limited attention in this population. PURPOSE: Document the occurrence of joint symptoms among patients undergoing surgery for LS-OA, and investigate the influence of these symptoms on disability postsurgery. DESIGN: Prospective study of consecutive patients followed to 12-month postsurgery. PATIENT SAMPLE: Patients undergoing surgery (decompression surgery, with or without fusion) for neurogenic claudication with or without back pain due to LSS with a primary pathology diagnosis of LS-OA. OUTCOMES MEASURES: Patient self-reported: Oswestry Disability Index (ODI), completed pre- and 12-month postsurgery; and, completed presurgery, age, sex, education, smoking, comorbid conditions, opioid use, short/long-term disability, depression and anxiety symptoms, back and leg pain intensity, presence of spondylolisthesis, procedure, prior spine surgery, and joints with arthritis and "pain/stiffness/swelling most days of the month" indicated on a homunculus (a joint site count was derived). ASSESSMENTS: Height and weight, used to calculate body mass index; timed-up-and-go performance-based test. METHODS: Outcome of interest was achieving a clinically important improvement (CII) in ODI by 12-month postsurgery (yes/no). The association between joint site count and achieving a CII was examined by multivariable logistic regression analyses, adjusted for other measures. RESULTS: In all, 165 patients were included. The mean age was 67 years (range: 44-90) and 47% were female. Seventy-seven percent reported 1+ joint site other than the back, 62% reported 2+, and 25% reported 4+. Among those achieving a CII, 21% had 4+ joint sites, compared with 31% among those not achieving a CII. Adjusted analyses: Increasing joint site count was associated with increasing risk (odds ratio [OR]: 1.32, 95% confidence interval [CI]: 1.05, 1.66) of not achieving a CII; for those with 4+ joints, adjusted probability of not achieving a CII exceeded 50%. Also associated with an increased risk of not achieving a CII was presurgery anxiety (OR: 2.97, 95% CI: 1.02, 8.65), opioid use (OR: 2.89, 95% CI: 1.07, 7.82), and worse back pain intensity score (OR: 1.27, 95% CI: 1.05, 1.53). CONCLUSIONS: Multijoint involvement was highly prevalent in this LS-OA surgical sample. Its association with poorer postsurgery outcome supports a comprehensive approach to OA management and care. Knowledge of multijoint symptoms should inform patient education, shared decision-making, and recommendations for postsurgical rehabilitation and self-management strategies.

The contribution of age and obesity to the number of painful joint sites in individuals reporting osteoarthritis: a population-based study.

OBJECTIVE: To investigate the association of OA risk factors with number of painful joint sites in a representative population sample. METHODS: Analysis of the 2009 Survey on Living with Chronic Diseases in Canada - Arthritis Component (n = 1614) for respondents reporting symptomatic OA. Variables: painful joints sites (hands, wrists, elbows, shoulders, hips, knees, ankles, feet, back, neck), joint symptom duration, sociodemographic characteristics, smoking, comorbidities and BMI. Zero-truncated negative binomial regressions were used to investigate the association between number of painful joint sites and the variables. Generalizability of findings was assessed by a similar analysis in a clinical hip/knee OA sample. RESULTS: The sample comprised 73% women and 56% were aged <65 years. The mean number of painful joint sites was 3.8: 84% reported pain at ≥2 sites, and 45% at ≥4 sites. Age, BMI, education and smoking were not associated with the number of joint sites. Significant associations were found with being female [rate ratio (RR) = 1.23, 95% CI 1.09, 1.39], having more comorbidities (RR = 1.11, 95% CI 1.07, 1.15) and longer symptom duration (RR = 1.16, 95% CI 1.09, 1.24), although the increase in joint sites with duration was small. Similar regression results were found with the clinical OA sample. CONCLUSION: The lack of an association of age and BMI (obesity) with number of painful joint sites in OA raises questions about the role of these risk factors and our understanding of OA as a multi-joint disease. Filling this knowledge gap is critical to making progress with defining OA phenotypes and identifying potential aetiological mechanisms.

Structural insights into the function of Elongator.

Conserved from yeast to humans, Elongator is a protein complex implicated in multiple processes including transcription regulation, α-tubulin acetylation, and tRNA modification, and its defects have been shown to cause human diseases such as familial dysautonomia. Elongator consists of two copies of six core subunits (Elp1, Elp2, Elp3, Elp4, Elp5, and Elp6) that are organized into two subcomplexes: Elp1/2/3 and Elp4/5/6 and form a stable assembly of ~ 850 kDa in size. Although the catalytic subunit of Elongator is Elp3, which contains a radical S-adenosyl-L-methionine (SAM) domain and a putative histone acetyltransferase domain, the Elp4/5/6 subcomplex also possesses ATP-modulated tRNA binding activity. How at the molecular level, Elongator performs its multiple functions and how the different subunits regulate Elongator's activities remains poorly understood. Here, we provide an overview of the proposed functions of Elongator and describe how recent structural studies provide new insights into the mechanism of action of this multifunctional complex.

Peer-led nutrition education programs for school-aged youth: a systematic review of the literature.

To date, the impacts of school-based, peer-led nutrition education initiatives have not been summarized or assessed collectively. This review presents the current evidence, identifies knowledge gaps, and provides recommendations for future research. PubMed, Scopus, ERIC and Google Scholar were searched for refereed Canadian and American primary studies published between January 2000 and November 2013, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Seventeen articles (11 programs) from Canada (24%) and the United States (76%) were identified. The results were summarized in terms of the study population, program design and main outcomes. Common outcome measures included healthy eating knowledge (n = 5), self-efficacy or attitudes towards healthy eating (n = 13), dietary measures (n = 9) and body mass index (n = 4), all of which tended to improve as a result of the programs. More research is needed to ascertain the effect of improvements in knowledge, self-efficacy and attitudes towards healthy eating on food behaviors. When evaluated, programs were generally well received, while the long-term maintenance of positive impacts was a challenge. Studies of sustainability and feasibility to promote long-term impact are a logical next step.

Structural analysis of the oligomeric states of Helicobacter pylori VacA toxin.

Helicobacter pylori is a Gram-negative bacterium that colonizes the human stomach and contributes to peptic ulceration and gastric adenocarcinoma. H. pylori secretes a pore-forming exotoxin known as vacuolating toxin (VacA). VacA contains two distinct domains, designated p33 and p55, and assembles into large "snowflake"-shaped oligomers. Thus far, no structural data are available for the p33 domain, which is essential for membrane channel formation. Using single-particle electron microscopy and the random conical tilt approach, we have determined the three-dimensional structures of six VacA oligomeric conformations at ~15-Å resolution. The p55 domain, composed primarily of ß-helical structures, localizes to the peripheral arms, while the p33 domain consists of two globular densities that localize within the center of the complexes. By fitting the VacA p55 crystal structure into the electron microscopy densities, we have mapped inter-VacA interactions that support oligomerization. In addition, we have examined VacA variants/mutants that differ from wild-type (WT) VacA in toxin activity and/or oligomeric structural features. Oligomers formed by VacA∆6-27, a mutant that fails to form membrane channels, lack an organized p33 central core. Mixed oligomers containing both WT and VacA∆6-27 subunits also lack an organized core. Oligomers formed by a VacA s2m1 chimera (which lacks cell-vacuolating activity) and VacAΔ301-328 (which retains vacuolating activity) each contain p33 central cores similar to those of WT oligomers. By providing the most detailed view of the VacA structure to date, these data offer new insights into the toxin's channel-forming component and the intermolecular interactions that underlie oligomeric assembly.

Properties of CD34+ CML stem/progenitor cells that correlate with different clinical responses to imatinib mesylate.

Imatinib mesylate (IM) induces clinical remissions in chronic-phase chronic myeloid leukemia (CML) patients but IM resistance remains a problem. We recently identified several features of CML CD34(+) stem/progenitor cells expected to confer resistance to BCR-ABL-targeted therapeutics. From a study of 25 initially chronic-phase patients, we now demonstrate that some, but not all, of these parameters correlate with subsequent clinical response to IM therapy. CD34(+) cells from the 14 IM nonresponders demonstrated greater resistance to IM than the 11 IM responders in colony-forming cell assays in vitro (P < .001) and direct sequencing of cloned transcripts from CD34(+) cells further revealed a higher incidence of BCR-ABL kinase domain mutations in the IM nonresponders (10%-40% vs 0%-20% in IM responders, P < .003). In contrast, CD34(+) cells from IM nonresponders and IM responders were not distinguished by differences in BCR-ABL or transporter gene expression. Interestingly, one BCR-ABL mutation (V304D), predicted to destabilize the interaction between p210(BCR-ABL) and IM, was detectable in 14 of 20 patients. T315I mutant CD34(+) cells found before IM treatment in 2 of 20 patients examined were preferentially amplified after IM treatment. Thus, 2 properties of pretreatment CML stem/progenitor cells correlate with subsequent response to IM therapy. Prospective assessment of these properties may allow improved patient management.

Structure of the human mTOR complex I and its implications for rapamycin inhibition.

The mammalian target of rapamycin complex 1 (mTORC1) regulates cell growth in response to the nutrient and energy status of the cell, and its deregulation is common in human cancers. Little is known about the overall architecture and subunit organization of this essential signaling complex. We have determined the three-dimensional (3D) structure of the fully assembled human mTORC1 by cryo-electron microscopy (cryo-EM). Our analyses reveal that mTORC1 is an obligate dimer with an overall rhomboid shape and a central cavity. The dimeric interfaces are formed by interlocking interactions between the mTOR and raptor subunits. Extended incubation with FKBP12-rapamycin compromises the structural integrity of mTORC1 in a stepwise manner, leading us to propose a model in which rapamycin inhibits mTORC1-mediated phosphorylation of 4E-BP1 and S6K1 through different mechanisms.

CesT is a multi-effector chaperone and recruitment factor required for the efficient type III secretion of both LEE- and non-LEE-encoded effectors of enteropathogenic Escherichia coli.

Enteropathogenic Escherichia coli (EPEC) is an intestinal attaching and effacing pathogen that utilizes a type III secretion system (T3SS) for the delivery of effectors into host cells. The chaperone CesT has been shown to bind and stabilize the type III translocated effectors Tir and Map in the bacterial cytoplasm prior to their delivery into host cells. In this study we demonstrate a role for CesT in effector recruitment to the membrane embedded T3SS. CesT-mediated effector recruitment was dependent on the presence of the T3SS membrane-associated ATPase EscN. EPEC DeltacesT carrying a C-terminal CesT variant, CesT(E142G), exhibited normal cytoplasmic Tir stability function, but was less efficient in secreting Tir, further implicating CesT in type III secretion. In vivo co-immunoprecipitation studies using CesT-FLAG containing EPEC lysates demonstrated that CesT interacts with Tir and EscN, consistent with the notion of CesT recruiting Tir to the T3SS. CesT was also shown to be required for the efficient secretion of several type III effectors encoded within and outside the locus of enterocyte effacement (LEE) in addition to Tir and Map. Furthermore, a CesT affinity column was shown to specifically retain multiple effector proteins from EPEC culture supernatants. These findings indicate that CesT is centrally involved in recruiting multiple type III effectors to the T3SS via EscN for efficient secretion, and functionally redefine the role of CesT in multiple type III effector interactions.

Notch4-induced inhibition of endothelial sprouting requires the ankyrin repeats and involves signaling through RBP-Jkappa.

Notch proteins comprise a family of transmembrane receptors. Ligand activation of Notch releases the intracellular domain of the receptor that translocates to the nucleus and regulates transcription through the DNA-binding protein RBP-Jkappa. Previously, it has been shown that the Notch4 intracellular region (N4IC) can inhibit endothelial sprouting and angiogenesis. Here, N4IC deletion mutants were assessed for their ability to inhibit human microvascular endothelial cell (HMEC) sprouting with the use of a quantitative endothelial sprouting assay. Deletion of the ankyrin repeats, but not the RAM (RBP-Jkappa associated module) domain or C-terminal region (CT), abrogated the inhibition of fibroblast growth factor 2 (FGF-2)- and vascular endothelial growth factor (VEGF)-induced sprouting by Notch4, whereas the ankyrin repeats alone partially blocked sprouting. The ankyrin repeats were also the only domain required for up-regulation of RBP-Jkappa-dependent gene expression. Interestingly, enforced expression of the ankyrin domain alone was sufficient to up-regulate some, but not all, RBP-Jkappa-dependent genes. Although N4IC reduced VEGF receptor-2 (VEGFR-2) and vascular endothelial (VE)-cadherin expression, neither of these events is necessary and sufficient to explain N4IC-mediated inhibition of sprouting. A constitutively active RBP-Jkappa mutant significantly inhibited HMEC sprouting but not as strongly as N4IC. Thus, Notch4-induced inhibition of sprouting requires the ankyrin repeats and appears to involve RBP-Jkappa-dependent and -independent signaling.

Primitive interleukin 3 null hematopoietic cells transduced with BCR-ABL show accelerated loss after culture of factor-independence in vitro and leukemogenic activity in vivo.

Primitive chronic myeloid leukemia cells display a unique autocrine interleukin 3 (IL-3)/granulocyte-colony-stimluating factor (G-CSF) mechanism that may explain their abnormal proliferation and differentiation control. Here we show that BCR-ABL transduction of primitive Sca-1(+) lin(-) mouse bone marrow (BM) cells causes immediate activation of IL-3, G-CSF, and granulocyte macrophage-colony-stimulating factor (GM-CSF) expression in these cells. Their autocrine IL-3-mediated growth dependence is thus demonstrable only in clonal cultures where paracrine effects are reduced. Interestingly, upon continued culture, these cells produce large populations of rapidly proliferating mast cells in which only the IL-3 autocrine mechanism is consistently maintained, together with evidence of hyperphosphorylation of p210(BCR-ABL) and STAT5 and retention of a multilineage but attenuated in vivo leukemogenic potential characterized by a prolonged latency. BCR-ABL transduction of IL-3(-/-) Sca-1(+) lin(-) BM cells initially activates GM-CSF and G-CSF production, factor independence, and the ability to generate phenotypically indistinguishable populations of mast cells. However, maintenance of factor independence, and p210(BCR-ABL) and STAT 5 activation beyond 4 to 6 weeks, requires rescue with an IL-3 transgene. The cultured BCR-ABL-transduced IL-3(-/-) cells also lack leukemogenic activity in vivo. These findings provide new evidence that IL-3 production is a rapid, sustained, and biologically relevant consequence of BCR-ABL expression in primitive hematopoietic cells with multilineage leukemogenic activity.

Salmonella effectors within a single pathogenicity island are differentially expressed and translocated by separate type III secretion systems.

Pathogenicity islands (PAIs) are large DNA segments in the genomes of bacterial pathogens that encode virulence factors. Five PAIs have been identified in the Gram-negative bacterium Salmonella enterica. Two of these PAIs, Salmonella pathogenicity island (SPI)-1 and SPI-2, encode type III secretion systems (TTSS), which are essential virulence determinants. These 'molecular syringes' inject effectors directly into the host cell, whereupon they manipulate host cell functions. These effectors are either encoded with their respective TTSS or scattered elsewhere on the Salmonella chromosome. Importantly, SPI-1 and SPI-2 are expressed under distinct environmental conditions: SPI-1 is induced upon initial contact with the host cell, whereas SPI-2 is induced intracellularly. Here, we demonstrate that a single PAI, in this case SPI-5, can encode effectors that are induced by distinct regulatory cues and targeted to different TTSS. SPI-5 encodes the SPI-1 TTSS translocated effector, SigD/SopB. In contrast, we report that the adjacently encoded effector PipB is part of the SPI-2 regulon. PipB is translocated by the SPI-2 TTSS to the Salmonella-containing vacuole and Salmonella-induced filaments. We also show that regions of SPI-5 are not conserved in all Salmonella spp. Although sigD/sopB is present in all Salmonella spp., pipB is not found in Salmonella bongori, which also lacks a functional SPI-2 TTSS. Thus, we demonstrate a functional and regulatory cross-talk between three chromosomal PAIs, SPI-1, SPI-2 and SPI-5, which has significant implications for the evolution and role of PAIs in bacterial pathogenesis.