Interspecies Systems Biology Uncovers Metabolites Affecting C. elegans Gene Expression and Life History Traits
Diet greatly influences gene expression and physiology. In mammals, elucidating the effects and mechanisms of individual nutrients is challenging due to the complexity of both the animal and its diet. Here, we used an interspecies systems biology approach with Caenorhabditis elegans and two of its bacterial diets, Escherichia coli and Comamonas aquatica, to identify metabolites that affect the animal's gene expression and physiology. We identify vitamin B12 as the major dilutable metabolite provided by Comamonas aq. that regulates gene expression, accelerates development, and reduces fertility but does not affect lifespan. We find that vitamin B12 has a dual role in the animal: it affects development and fertility via the methionine/S-Adenosylmethionine (SAM) cycle and breaks down the short-chain fatty acid propionic acid, preventing its toxic buildup. Our interspecies systems biology approach provides a paradigm for understanding complex interactions between diet and physiology.
Diet affects cellular metabolism and organismal life history traits. Pang and Curran (2014) use Caenorhabditis elegans and its bacterial diets to unveil genetic perturbations in proline catabolism that shorten lifespan, but, only on specific Escherichia coli diets, thereby unveiling a genome-encoded adaptive response to different nutritional states.
Tissue-dependent T Cell Apoptosis and Transcriptional Regulation of Memory CD8+T Cell Differentiation During Viral Infections: A Dissertation
Activation and proliferation of antigen-specific T cells is the hallmark of an anti-viral immune response. Effector T cells generated during an immune response are heterogeneous in regards to their ability to populate the memory pool once the immune response has resolved. Initial T cell activation takes place in the lymphoid organs, after which T cells migrate into the non-lymphoid tissues. The presence of memory T cells at non-lymphoid tissue sites has been shown to be critical for protection against secondary virus challenge. Our lab has previously demonstrated that during and after the resolution of the immune response to Lymphocytic choriomeningitis virus (LCMV) CD8+T cells in the nonlymphoid tissues are more resistant to apoptosis than those in the lymphoid organs. This stability of T cells in the non-lymphoid tissues may be critical in ensuring protection against a secondary virus challenge.
Mechanisms regulating tissue-dependent differences in CD8+T cell apoptosis were studied in an acute LCMV infection model. Virus-specific CD8+T cells from lymphoid (spleen, mesenteric lymph nodes (MLN), inguinal lymph nodes (ILN)) and non-lymphoid tissues (peritoneal exudate cells (PEC), fat-pads) were compared for expression of surface antigenic markers known to correlate with a memory phenotype. Non-lymphoid tissues were enriched in IL-7Rhi, KLRG-1lo, CD27hi and CXCR3hi virus-specific CD8+ T cells, and the presence of these antigenic markers correlated with increased memory potential and survival. Transcription factors in addition to cell surface antigens were assessed as correlates of resistance to apoptosis. Virus-specific CD8+T cells in the nonlymphoid tissues were enriched in cells expressing T cell factor-1 (TCF-1), which correlated with increased memory potential and survival. CD8+T cells in the peritoneum of TCF-1-deficient mice had decreased survival during resolution of the immune response to LCMV, suggesting a role for TCF-1 in promoting survival in the non-lymphoid tissues.
As an additional mechanism, I investigated whether apoptosis-resistant CD8+T cells migrate to non-lymphoid tissues and contribute to tissue-dependent apoptotic differences. CXCR3+ CD8+T cells resisted apoptosis and accumulated in the lymph nodes of mice treated with FTY720, which blocks the export of lymph node cells into the peripheral tissues. The PECs expressed increased amounts of CXCR3 ligands, CXCL9 and CXCL10, which may have recruited the non-apoptotic cells from the lymph nodes. By adoptively transferring splenic T cells into the spleen or PEC environment I showed that the peritoneal environment through a yet undefined factor promoted survival of CD8+T cells. In this study I have elucidated the mechanisms by which CD8+T cells preferentially survive in the non-lymphoid tissues. I found that non-lymphoid tissues were enriched in memory-phenotype CD8+T cells which were intrinsically resistant to apoptosis irrespective of the tissue environment. Furthermore, apoptosisresistant CD8+T cells may preferentially migrate into the non-lymphoid tissues where the availability of tissue-specific factors may enhance memory cell survival.
Few transcription factors have been identified that regulate CD8+T cell effector-memory differentiation during an immune response. In this thesis, I have also studied the mechanism by which the transcription factor Blimp-1 regulates the generation of effector and memory CD8+T cells. Blimp-1 is known to repress a large number of target genes, and ChIP (chromatin immunoprecipitation) sequencing analysis done by Dr. HyunMu Shin in the lab of Dr. Leslie J. Berg identified CD25 (IL-2Rα) and CD27 as potential targets of Blimp-1. I found that Blimp-1-deficient CD8+T cells had sustained expression of CD25 (IL-2Rα) and CD27 during peak and resolution of the immune response to LCMV. By performing adoptive transfers of CD25hi and CD27hi CD8+T cells I showed that CD25 and CD27 expression on CD8+T cells during resolution of the immune response correlates with enhanced survival. Silencing Il2rα and Cd27 expression reduced the Blimp-1-deficient CD8+T cell response, suggesting that sustained expression of CD25 and CD27 was in part responsible for the enhanced CD8+T cell response seen in the Blimp-1-deficient mice. Furthermore, our collaborator Dr. HyunMu Shin showed that CD25 and CD27 are direct targets of Blimp-1, and that Blimp-1 recruits histone modifying enzymes to Il2rα and Cd27 loci to suppress their expression during the peak of the anti-viral immune response. This study identifies one of the mechanisms by which Blimp-1 regulates the balance between generation of effector and memory CD8+T cells.
In this thesis work I also studied the function of the transcription factor ROG (Repressor of GATA-3) in regulating in vivo T cell responses during both acute and chronic LCMV infection. ROG-deficient mice had increased CD8+T cell responses during an acute LCMV infection. ROG deficiency also led to the generation of memory T cells with an enhanced recall response compared to WT controls. By using LCMV-specific P14+ TCR transgenic ROG-deficient CD8+T cells these defects were shown to be T cell intrinsic. ROG-deficient mice had enhanced CD8+T cell responses and viral clearance during a persistent high dose LCMV Clone 13 infection. During chronic LCMV infection ROG-deficient mice also had increased lung pathology and mortality. The results indicate that ROG negatively regulates T cell responses and memory generation during both acute and chronic LCMV infection.
The studies highlighted in this thesis elucidate the mechanisms promoting CD8+T cell survival in non-lymphoid tissues as well as transcription factormediated regulation of memory CD8+T cell differentiation. Knowledge of this will help us better understand T cell immunity after infections and may eventually help develop better vaccines.
Understanding the experiences of women who have experienced perinatal depression may help inform needed changes in how health care professionals and organizations screen, diagnose, and treat perinatal depression.
The age-dependent decline in the self-renewal capacity of stem cells plays a critical role in aging, but the precise mechanisms underlying this decline are not well understood. By limiting proliferative capacity, senescence is thought to play an important role in age-dependent decline of stem cell self-renewal, although direct evidence supporting this hypothesis is largely lacking. We have previously identified the E3 ubiquitin ligase Smurf2 as a critical regulator of senescence. In this study, we found that mice deficient in Smurf2 had an expanded hematopoietic stem cell (HSC) compartment in bone marrow under normal homeostatic conditions, and this expansion was associated with enhanced proliferation and reduced quiescence of HSCs. Surprisingly, increased cycling and reduced quiescence of HSCs in Smurf2-deficient mice did not lead to premature exhaustion of stem cells. Instead, HSCs in aged Smurf2-deficient mice had a significantly better repopulating capacity than aged wild-type HSCs, suggesting that decline in HSC function with age is Smurf2 dependent. Furthermore, Smurf2-deficient HSCs exhibited elevated long-term self-renewal capacity and diminished exhaustion in serial transplantation. As we found that the expression of Smurf2 was increased with age and in response to regenerative stress during serial transplantation, our findings suggest that Smurf2 plays an important role in regulating HSC self-renewal and aging.
Summary of Project
Background: Over the last several decades, mindfulness and programs in mind-body stress reduction (MBSR) have emerged as potential therapeutic options for patients with medical conditions such as depression, anxiety, chronic pain, fibromyalgia, insomnia, post-myocardial infarction treatment, and others. Evidence has also emerged that mindfulness may be an effective tool for medical students and healthcare practitioners in reducing stress and anxiety associated with training and practice. It has also shown promise for improving empathy and job satisfaction, while possibly preventing burn-out.
Objectives: This project aimed to study the role that mindfulness may play as an adjunct therapy for patients with chronic diseases, as well as its benefits for medical students and healthcare practitioners.
Methods: Online lectures and published articles were reviewed for studies that evaluated mindfulness as a treatment for chronic medical conditions and as a part of training for medical students and healthcare workers.
Results: (1) Mindfulness as a therapeutic option for patients with chronic medical conditions: Mindfulness and MBSR have been investigated as potential adjunct therapies for a wide range of chronic medical conditions. Investigation into its role in alleviating suffering has grown significantly, with a growing number of studies published in recent years. While individual trials have shown promising results, meta-analyses describe the challenge of aggregating data due to poor quality or inconsistent methodologies across studies. For example, authors of one meta-analysis found 64 relevant studies but could only include 20 of these in their analysis. (2) Mindfulness and healthcare professionals: The articles identified highlight the negative impact that stress can have on medical students and healthcare professionals. The documented negative effects of stress on healthcare workers include anxiety, depression, decreased job satisfaction, diminished personal relationships, and psychological distress. Professional effectiveness may decrease and patients may not get optimal care when practitioners are under severe stress. Mindfulness has been shown to positively benefit students and healthcare practitioners by reducing stress and anxiety, while increasing empathy and job satisfaction. Limitations to these findings are discussed below.
Conclusions: Mindfulness and MBSR may be beneficial, cost-effective interventions for many chronic conditions, including both mental and physical ailments. The data in support of mindfulness and MBSR as an adjunct therapy was strongest for alleviating pain, anxiety, and a wide range of symptoms associated with chronic medical conditions. Physical and mental conditions have been shown to improve with mindfulness and MBSR treatment. The studies reviewed showed potential benefits of mindfulness and MBSR on medical students and healthcare workers. However, future studies are needed that include more robust sample sizes, limit biases such as self-selecting subjects, include adequate control groups, maintain consistent methodology (such as standardized training of mindfulness and MBSR instructors) and statistical analysis across studies, measure long-term effects, and have more objectively defined study end-points.
Should patients with acute coronary disease be stratified for management according to their risk? Derivation, external validation and outcomes using the updated GRACE risk score
OBJECTIVES: Risk scores are recommended in guidelines to facilitate the management of patients who present with acute coronary syndromes (ACS). Internationally, such scores are not systematically used because they are not easy to apply and some risk indicators are not available at first presentation. We aimed to derive and externally validate a more accurate version of the Global Registry of Acute Coronary Events (GRACE) risk score for predicting the risk of death or death/myocardial infarction (MI) both acutely and over the longer term. The risk score was designed to be suitable for acute and emergency clinical settings and usable in electronic devices.
DESIGN AND SETTING: The GRACE risk score (2.0) was derived in 32 037 patients from the GRACE registry (14 countries, 94 hospitals) and validated externally in the French registry of Acute ST-elevation and non-ST-elevation MI (FAST-MI) 2005.
PARTICIPANTS: Patients presenting with ST-elevation and non-ST elevation ACS and with long-term outcomes.
OUTCOME MEASURES: The GRACE Score (2.0) predicts the risk of short-term and long-term mortality, and death/MI, overall and in hospital survivors.
RESULTS: For key independent risk predictors of death (1 year), non-linear associations (vs linear) were found for age (p
CONCLUSIONS: The updated GRACE risk score has better discrimination and is easier to use than the previous score based on linear associations. GRACE Risk (2.0) performed equally well acutely and over the longer term and can be used in a variety of clinical settings to aid management decisions.
Diet quality has not been well studied in relation to positive psychological traits. Our purpose was to investigate the relationship between optimism and diet quality in postmenopausal women enrolled in the Women's Health Initiative observational study (OS) and clinical trials (CTs), and to determine whether optimism was associated with diet change after a 1-year dietary intervention. Diet quality was scored with the Alternate Healthy Eating Index (AHEI) and optimism assessed with the Life Orientation Test-Revised. Baseline characteristics were compared across AHEI quintiles or optimism tertiles using regression models with each variable of interest as a function of quintiles or tertiles (OS, n=87,630; CT, n=65,360). Association between optimism and baseline AHEI and change in AHEI over 1 year were tested using multivariate linear regression (CT, n=13,645). Potential interaction between optimism and trial arm and demographic/lifestyle factors on AHEI change was tested using likelihood ratio test (CT intervention, n=13,645; CT control, n=20,242). Women reporting high AHEI were non-Hispanic white, educated, physically active, past or never smokers, hormone therapy users, had lower body mass index and waist circumference, and were less likely to have chronic conditions. In the CT intervention, higher optimism was associated with higher AHEI at baseline and with greater change over 1 year (P=0.001). Effect modification by intervention status was observed (P=0.014), whereas control participants with highest optimism achieved threefold greater AHEI increase compared with those with the lowest optimism. These data support a relationship between optimism and dietary quality score in postmenopausal women at baseline and over 1 year.
An AHA Science Advisory recommending that physicians intervene more assertively to get patients to adopt healthier lifestyles, directly targeting smoking, obesity, poor diet, and physical inactivity.
OBJECTIVE: To determine the feasibility, acceptability, and outcomes of a telephone counseling intervention promoting colorectal cancer (CRC) screening when patients are referred for counseling by primary care providers (PCPs). Study Design: Interventional cohort study with no formal control group.
METHODS: PCPs in 3 practices were prompted to address CRC screening in patient encounters and, if appropriate, to recommend referral for telephone counseling. A telephone counselor called referred patients, made an appointment for a counseling call, and mailed an educational booklet to patients. Counseling included education about CRC and screening tests, motivational interviewing, barrier counseling, and facilitated referral for colonoscopy or mailing of a fecal occult blood testing kit. About 7 months following counseling, electronic records were searched for evidence of colonoscopy.
RESULTS: PCPs addressed CRC screening with 1945 patients, most of whom were up-to-date with CRC testing, recommended counseling referral to 362, and of these 180 (49.7%) accepted the referral. A total of 140 (77.8%) of referred patients were contacted and 67 (37.2%) received counseling. After counseling 93.9% were planning on CRC screening compared with 54.6% at the beginning of the call. Of those planning a colonoscopy, 53.2% received one within 7 months.
CONCLUSIONS: Referring patients for telephone counseling to promote CRC screening may be feasible and acceptable to PCPs and to some patients, and may increase CRC screening. Further evaluation of the intervention may be warranted to compare the rate of screening associated with the intervention to rates related to usual care and to other interventions.
BACKGROUND: Alcohol and caffeine intakes may play a role in the development of sudden cardiac death (SCD) because of their effects on cholesterol, blood pressure, heart rate variability, and inflammation.
OBJECTIVE: Our objective was to examine the association between long-term alcohol and caffeine intakes and risk of SCD in women.
DESIGN: We examined 93,676 postmenopausal women who participated in the Women's Health Initiative Observational Study. Women were enrolled between 1993 and 1998 and were followed until August 2009. Women completed a food-frequency questionnaire at baseline and again at year 3. We modeled exposure to alcohol 3 ways: by using baseline intake only, a cumulative average of baseline and year 3 intake, and the most recent reported intake (a simple time-varying analysis).
RESULTS: Intake of 5-15 g alcohol/d (about one drink) was associated with a nonsignificantly reduced risk of SCD compared with 0.1-5 g/d of baseline intake (HR: 0.64; 95% CI: 0.40, 1.02), of cumulative average intake (HR: 0.69; 95% CI: 0.43, 1.11), and of most recent intake (HR: 0.58; 95% CI: 0.35, 0.96), with adjustment for age, race, income, smoking, body mass index, physical activity, hormone use, and total energy. No association was found between SCD and total caffeine intake (mg/d) or cups of caffeinated coffee, decaffeinated coffee, and caffeinated tea.
CONCLUSIONS: Our results suggest that about one drink per day (or 5.1-15 g/d) may be associated with a reduced risk of SCD in this population; however, this association was only statistically significant for a model using the most recent alcohol intake. Total caffeine, regular coffee, decaffeinated coffee, and regular tea intake were not associated with the risk of SCD.
This trial was registered at clinicaltrials.gov as NCT00000611.
Severe obesity, heart disease, and death among white, african american, and hispanic postmenopausal women
OBJECTIVE: To compare mortality, nonfatal coronary heart disease (CHD), and congestive heart failure (CHF) risk across BMI categories in white, African American, and Hispanic women, with a focus on severe obesity (BMI >/= 40), and examine heterogeneity in weight-related CHD risk.
DESIGN AND METHODS: Among 156,775 Women's Health Initiative observational study and clinical trial participants (September 1993-12 September 2005), multivariable Cox models estimated relative risk for mortality, CHD, and CHF. CHD incidence was calculated by anthropometry, race, and cardiovascular risk factors (CVRF).
RESULTS: Mortality, nonfatal CHD, and CHF incidence generally rose with BMI category. For severe obesity versus normal BMI, hazard ratios (HRs, 95% confidence interval) for mortality were 1.97 (1.77-2.20) in white, 1.55 (1.20-2.00) in African American, and 2.59 (1.55-4.31) in Hispanic women; for CHD, HRs were 2.05 (1.80-2.35), 2.24 (1.57-3.19), and 2.95 (1.60-5.41) respectively; for CHF, HRs were 5.01 (4.33-5.80), 3.60 (2.30-5.62), and 6.05 (2.49-14.69). CVRF variation resulted in substantial variation in CHD rates across BMI categories, even in severe obesity. CHD incidence was similar by race/ethnicity when differences in BMI or CVRF were accounted for.
CONCLUSIONS: Severe obesity increases mortality, nonfatal CHD, and CHF risk in women of diverse race/ethnicity. CVRF heterogeneity contributes to variation in CHD incidence even in severe obesity.
Design and Methods for a Comparative Effectiveness Pilot Study: Virtual World vs. Face-to-Face Diabetes Self-Management
BACKGROUND: Type 2 diabetes (diabetes) is a serious threat to public health in the United States and disproportionally affects many racial/ethnic minority groups, including African Americans. Limited access to treatment and high attrition rates further contribute to health disparities in diabetes-related morbidity and mortality among minorities. Greater opportunities for increasing access and decreasing barriers to treatment are needed. Technology-based interventions have potential for accomplishing this goal but evidence of feasibility and potential effectiveness is lacking, especially for populations that traditionally have limited educational attainment and low computer literacy.
OBJECTIVE: This paper describes the design and methods of a pilot randomized clinical trial that will compare the feasibility and potential efficacy of delivering a diabetes self-management intervention via a virtual world vs. a face-to-face format.
METHODS: Study participants (n=100) will be African American women with uncontrolled type 2 diabetes recruited from primary care practices and affiliated health centers at a large safety net hospital in Massachusetts. Participants will be randomized into a virtual world-based (VW) intervention condition or a face-to-face control condition. Both conditions provide the same theory-based curriculum and equivalent exposure to the self-management program (eight group sessions), and both will be delivered by a single intervention team (a dietitian and a diabetes educator). Assessments will be conducted at baseline and 4 months. Feasibility will be determined by evaluating the degree to which participants engage in the VW-based intervention compared to face to face (number of sessions completed). Potential efficacy will be determined by comparing change in physiological (glycemic control) and behavioral (self-reported dietary intake, physical activity, blood glucose self-monitoring, and medication adherence) outcomes between the experimental and control groups.
RESULTS: The primary outcomes of interest are feasibility of the VW intervention and its potential efficacy on glucose control and diabetes self-management behaviors, compared to the face-to-face condition. Analysis will use a two-sample Kolmogorov-Smirnov test for changes in variable distribution. P values will be calculated using binomial tests for proportions and t tests for continuous variables.
CONCLUSIONS: If the intervention is found to be feasible and promising, it will be tested in a larger RCT.
Awareness of diabetes risk factors and prevention strategies among a sample of low-income Latinos with no known diagnosis of diabetes
PURPOSE: This study assessed awareness of type 2 diabetes risk and severity, perceived risk factors, knowledge of diabetes prevention strategies, and challenges of and opportunities for prevention among low-income Latinos in Lawrence, Massachusetts.
METHODS: Qualitative research design. Latinos with no known diagnosis of diabetes participated in 4 focus groups, conducted in Spanish, which were recorded and transcribed for systematic analysis.
RESULTS: The sample, (N = 41) was largely female (85%) with a wide age range (22-76 years), most (71%) had an educational level of high school or less, and less than half (46%) were employed. Participants had basic knowledge of diabetes, but gaps were apparent. Many perceived family history of diabetes, poor diet, emotional distress, and stress associated with the United States as risk factors for diabetes. There was little or no awareness of risk associated with Latino ethnicity, gestational diabetes, hypertension, lipid abnormalities, or obesity. Few cited physical activity or weight loss as diabetes prevention strategies. More than half the participants perceived themselves at low risk for diabetes.
CONCLUSIONS: This Latino sample had limited knowledge of diabetes risk factors and lifestyle changes that can prevent or delay diabetes onset. Insights for intervening for diabetes prevention are offered.
BACKGROUND: The 2007 update to the American Heart Association (AHA) guidelines for cardiovascular disease prevention in women recommend a simplified approach to risk stratification. We assigned Women's Health Initiative participants to risk categories as described in the guideline and evaluated clinical event rates within and between strata.
METHODS AND RESULTS: The Women's Health Initiative enrolled 161 808 women ages 50 to 79 years and followed them prospectively for 7.8 years (mean). Applying the 2007 AHA guideline categories, 11% of women were high risk, 72% at-risk, and 4% at optimal risk; 13% of women did not fall into any category, that is, lacked risk factors but did not adhere to a healthy lifestyle (moderate intensity exercise for 30 minute most days and 20% (area under receiver operating characteristic curve for Framingham risk, 0.724; for AHA risk, 0.664; P<0.0001).
CONCLUSIONS: Risk stratification as proposed in the 2007 AHA guideline is simple, accessible to patients and providers, and identifies cardiovascular risk with accuracy similar to that of the current Framingham algorithm.
Clinical Trial Registration- clinicaltrials.gov. Identifier: NCT00000611.
Optimism, cynical hostility, and incident coronary heart disease and mortality in the Women's Health Initiative
BACKGROUND: Trait optimism (positive future expectations) and cynical, hostile attitudes toward others have not been studied together in relation to incident coronary heart disease (CHD) and mortality in postmenopausal women.
METHODS AND RESULTS: Participants were 97 253 women (89 259 white, 7994 black) from the Women's Health Initiative who were free of cancer and cardiovascular disease at study entry. Optimism was assessed by the Life Orientation Test-Revised and cynical hostility by the cynicism subscale of the Cook Medley Questionnaire. Cox proportional hazard models produced adjusted hazard ratios (AHRs) for incident CHD (myocardial infarction, angina, percutaneous coronary angioplasty, or coronary artery bypass surgery) and total mortality (CHD, cardiovascular disease, or cancer related) over approximately 8 years. Optimists (top versus bottom quartile ["pessimists"]) had lower age-adjusted rates (per 10 000) of CHD (43 versus 60) and total mortality (46 versus 63). The most cynical, hostile women (top versus bottom quartile) had higher rates of CHD (56 versus 44) and total mortality (63 versus 46). Optimists (versus pessimists) had a lower hazard of CHD (AHR 0.91, 95% CI 0.83 to 0.99), CHD-related mortality (AHR 0.70, 95% CI 0.55 to 0.90), cancer-related mortality (blacks only; AHR 0.56, 95% CI 0.35 to 0.88), and total mortality (AHR 0.86, 95% CI 0.79 to 0.93). Most (versus least) cynical, hostile women had a higher hazard of cancer-related mortality (AHR 1.23, 95% CI 1.09 to 1.40) and total mortality (AHR 1.16, 95% CI 1.07 to 1.27; this effect was pronounced in blacks). Effects of optimism and cynical hostility were independent.
CONCLUSIONS: Optimism and cynical hostility are independently associated with important health outcomes in black and white women. Future research should examine whether interventions designed to change attitudes would lead to altered risk.
To examine if an innovative collaborative care model known as Targeted Child Psychiatric Services designed for primary care pediatricians (PCPs) and child psychiatrists (1) was associated with improved access to child psychiatry services, (2) had the potential to identify optimal care settings for pediatric mental health care and (3) examined if pediatricians appeared as likely to accept children back into their practices at discharge from TCPS depending upon diagnostic category, controlling for severity of illness and function. The diagnostic classes examined were ADHD (39%), depression (31%) and anxiety (13%). This prospective cohort design study collected medical records of 329 children referred to TCPS by 139 PCPs. To detect the likelihood of return to referring pediatricians for follow-up care at discharge from TCPS, we employed logistic regression models. Mean age was 12.3 (SD = 4.0); 43% were female. Ninety-three percent of parents complied with pediatricians' recommendations to have their child assessed by a child psychiatrist. A total of 28.0% of referrals returned to PCPs for follow-up care; the remainder were followed in mental health. Regression findings indicated that children with major depression (OR = 7.5) or anxiety disorders (OR = 5.1) were less likely to return to PCPs compared to ADHD even though severity of psychiatric illness and functional levels did not differ across diagnostic groups. Families widely accepted pediatricians' recommendations for referral to child psychiatrists. Depression and anxiety were strong correlates of retention in mental health settings at discharge from TCPS though children with these disorders appeared to be no more severely ill or functionally limited than peers with ADHD. These children possibly could be managed in a less intensive and expensive primary care treatment setting that could access mental health specialty services as needed in a collaborative model of care. TCPS is contrasted with the well-known collaborative model for adult depression in primary care. TCPS could serve as a feasible model of care that addresses the daunting barriers in accessing pediatric mental health services.
Previously we used mass spectrometry to show that the yeast G protein alpha subunit Gpa1 is ubiquitinated at Lys-165, located within a subdomain not present in other G alpha proteins (Marotti, L. A., Jr., Newitt, R., Wang, Y., Aebersold, R., and Dohlman, H. G. (2002) Biochemistry 41, 5067-5074). Here we describe the functional role of Gpa1 ubiquitination. We find that Gpa1 expression is elevated in mutants deficient in either proteasomal or vacuolar protease function. Vacuolar protease pep4 mutants accumulate monoubiquitinated Gpa1, and much of the protein is localized within the vacuolar compartment. In contrast, proteasome-defective rpt6/cim3 mutants accumulate polyubiquitinated Gpa1, and in this case the protein exhibits cytoplasmic localization. Cells that lack Ubp12 ubiquitin-processing protease activity accumulate both mono- and polyubiquitinated forms of Gpa1. In this case, Gpa1 accumulates in both the cytoplasm and vacuole. Finally, a Gpa1 mutant that lacks the ubiquitinated subdomain remains unmodified and is predominantly localized at the plasma membrane. These data reveal a strong relationship between the extent of ubiquitination and trafficking of the G protein alpha subunit to its site of degradation.
G protein-coupled receptors (GPCRs) mediate responses to a broad range of chemical and environmental signals. In yeast, a pheromone-binding GPCR triggers events leading to the fusion of haploid cells. In general, GPCRs function as guanine-nucleotide exchange factors (GEFs); upon agonist binding, the receptor induces a conformational change in the G protein alpha subunit, resulting in exchange of guanine diphosphate (GDP) for guanine triphosphate (GTP) and in signal initiation. Signaling is terminated when GTP is hydrolyzed to GDP . This well-established paradigm has in recent years been revised to include new components that rates of GDP release, GTP binding [2-8], and GTP hydrolysis[9, 10]. Here we report the discovery of a nonreceptor GEF, Arr4. Like receptors, Arr4 binds directly to the G protein,accelerates guanine-nucleotide exchange, and stabilizes the nucleotide-free state of the a subunit. Moreover, Arr4 promotes G protein-dependent cellular responses, including mitogen-activated protein kinase (MAPK) phosphorylation,new-gene transcription, and mating. In contrast to knownGPCRs, however, Arr4 is not a transmembrane receptor,but rather a soluble intracellular protein. Our data suggest that intracellular proteins function in cooperation with mating pheromones to amplify G protein signaling, thereby leading to full pathway activation.
Emerging evidence suggests that ubiquitination serves as a protein trafficking signal in addition to its well characterized role in promoting protein degradation. The yeast G protein alpha subunit Gpa1 represents a rare example of a protein that undergoes both mono- and poly-ubiquitination. Whereas mono-ubiquitinated Gpa1 is targeted to the vacuole, poly-ubiquitinated Gpa1 is directed instead to the proteasome. Here we investigate the structural requirements for mono- and poly-ubiquitination of Gpa1. We find that variants of Gpa1 engineered to be unstable are more likely to be poly-ubiquitinated and less likely to be mono-ubiquitinated. In addition, mutants that cannot be myristoylated are no longer mono-ubiquitinated but are still polyubiquitinated. Finally, we show that the ubiquitin ligase Rsp5 is necessary for Gpa1 mono-ubiquitination in vivo and that the purified enzyme is sufficient to catalyze Gpa1 mono-ubiquitination in vitro. Taken together, these data indicate that mono- and poly-ubiquitination have distinct enzyme and substrate recognition requirements; whereas poly-ubiquitination targets misfolded protein for degradation, a distinct ubiquitination apparatus targets the fully mature, fully myristoylated G protein for mono-ubiquitination and delivery to the vacuole.