Physiological IRE-1-XBP-1 and PEK-1 signaling in Caenorhabditis elegans larval development and immunity

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Biology, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 27-29).The endoplasmic reticulum (ER) is responsible for the folding and processing of approximately one third of proteins in eukaryotic cells, and homeostasis in this compartment is tightly regulated. The Unfolded Protein Response, or UPR, is activated in response to perturbations in protein folding in the ER, collectively termed ER stress. This compensatory mechanism, mediated by IRE-1, PERK- 1/PEK-1 and ATF-6 in metazoans, resolves an overcrowded ER lumen in part through the increase of protein degradation and folding. Typical studies focus on activation of the UPR in response to characterized chemical agents that potently alter ER function or protein stability and folding, leaving physiological or native roles for the UPR relatively uncharacterized. Richardson et al previously demonstrated a role for the UPR in innate immunity in C elegans. Here, in an effort to understand this role, we demonstrate that intestinal expression of XBP-1 is sufficient to overcome PMK-1 dependent larval lethality on a lawn of pathogenic Pseudomonas aeruginosa. Further, we demonstrate that XBP-1 deficiency results in constitutive ER stress even in the absence of pathogenic infection. This elevated ER stress is reflected by increased activities of both IRE- 1 and PEK-1 under physiological conditions. Our data suggest that negative feedback loops involving the activation of IRE-1-XBP-1 and PEK-1 pathways serve essential roles not only at the extremes of ER stress but also in the maintenance of ER homeostasis under physiological conditions.by Stephanie A. Kinkel.S.M

mTOR Complex 2 Is Required for the Development of Prostate Cancer Induced by Pten Loss in Mice

mTOR complex 2 (mTORC2) contains the mammalian target of rapamycin (mTOR) kinase and the Rictor regulatory protein and phosphorylates Akt. Whether this function of mTORC2 is critical for cancer progression is unknown. Here, we show that transformed human prostate epithelial cells lacking PTEN require mTORC2 to form tumors when injected into nude mice. Furthermore, we find that Rictor is a haploinsufficient gene and that deleting one copy protects Pten heterozygous mice from prostate cancer. Finally, we show that the development of prostate cancer caused by Pten deletion specifically in prostate epithelium requires mTORC2, but that for normal prostate epithelial cells, mTORC2 activity is nonessential. The selective requirement for mTORC2 in tumor development suggests that mTORC2 inhibitors may be of substantial clinical utility.W. M. Keck FoundationDamon Runyon Cancer Research Foundation (Research Fellowship)Leukemia & Lymphoma Society of America (Career Development Award)Howard Hughes Medical Institute (Investigator)National Institutes of Health (U.S.) (K99 CA1296613-01A1)National Institutes of Health (U.S.) (R01 CA107166)National Institutes of Health (U.S.) (R01 AI04389)National Institutes of Health (U.S.) (R01 CA103866

Physiological IRE-1-XBP-1 and PEK-1 Signaling in Caenorhabditis elegans Larval Development and Immunity

Endoplasmic reticulum (ER) stress activates the Unfolded Protein Response, a compensatory signaling response that is mediated by the IRE-1, PERK/PEK-1, and ATF-6 pathways in metazoans. Genetic studies have implicated roles for UPR signaling in animal development and disease, but the function of the UPR under physiological conditions, in the absence of chemical agents administered to induce ER stress, is not well understood. Here, we show that in Caenorhabditis elegans XBP-1 deficiency results in constitutive ER stress, reflected by increased basal levels of IRE-1 and PEK-1 activity under physiological conditions. We define a dynamic, temperature-dependent requirement for XBP-1 and PEK-1 activities that increases with immune activation and at elevated physiological temperatures in C. elegans. Our data suggest that the negative feedback loops involving the activation of IRE-1-XBP-1 and PEK-1 pathways serve essential roles, not only at the extremes of ER stress, but also in the maintenance of ER homeostasis under physiological conditions.National Institutes of Health (U.S.) (grant R01-GM084477

Evolution over Time of Ventilatory Management and Outcome of Patients with Neurologic Disease∗

OBJECTIVES: To describe the changes in ventilator management over time in patients with neurologic disease at ICU admission and to estimate factors associated with 28-day hospital mortality. DESIGN: Secondary analysis of three prospective, observational, multicenter studies. SETTING: Cohort studies conducted in 2004, 2010, and 2016. PATIENTS: Adult patients who received mechanical ventilation for more than 12 hours. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Among the 20,929 patients enrolled, we included 4,152 (20%) mechanically ventilated patients due to different neurologic diseases. Hemorrhagic stroke and brain trauma were the most common pathologies associated with the need for mechanical ventilation. Although volume-cycled ventilation remained the preferred ventilation mode, there was a significant (p < 0.001) increment in the use of pressure support ventilation. The proportion of patients receiving a protective lung ventilation strategy was increased over time: 47% in 2004, 63% in 2010, and 65% in 2016 (p < 0.001), as well as the duration of protective ventilation strategies: 406 days per 1,000 mechanical ventilation days in 2004, 523 days per 1,000 mechanical ventilation days in 2010, and 585 days per 1,000 mechanical ventilation days in 2016 (p < 0.001). There were no differences in the length of stay in the ICU, mortality in the ICU, and mortality in hospital from 2004 to 2016. Independent risk factors for 28-day mortality were age greater than 75 years, Simplified Acute Physiology Score II greater than 50, the occurrence of organ dysfunction within first 48 hours after brain injury, and specific neurologic diseases such as hemorrhagic stroke, ischemic stroke, and brain trauma. CONCLUSIONS: More lung-protective ventilatory strategies have been implemented over years in neurologic patients with no effect on pulmonary complications or on survival. We found several prognostic factors on mortality such as advanced age, the severity of the disease, organ dysfunctions, and the etiology of neurologic disease