Browsing by Subject "Stress, Physiological"

Now showing 1 - 6 of 6
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    Haemophilus ducreyi RpoE and CpxRA Appear To Play Distinct yet Complementary Roles in Regulation of Envelope-Related Functions
    (Journal of Bacteriology, 2014-12) Gangaiah, Dharanesh; Zhang, Xinjun; Baker, Beth; Fortney, Kate R.; Liu, Yunlong; Munson, Robert S. Jr.; Spinola, Stanley M.; Department of Microbiology & Immunology, IU School of Medicine
    Haemophilus ducreyi causes the sexually transmitted disease chancroid and a chronic limb ulceration syndrome in children. In humans, H. ducreyi is found in an abscess and overcomes a hostile environment to establish infection. To sense and respond to membrane stress, bacteria utilize two-component systems (TCSs) and extracytoplasmic function (ECF) sigma factors. We previously showed that activation of CpxRA, the only intact TCS in H. ducreyi, does not regulate homologues of envelope protein folding factors but does downregulate genes encoding envelope-localized proteins, including many virulence determinants. H. ducreyi also harbors a homologue of RpoE, which is the only ECF sigma factor in the organism. To potentially understand how H. ducreyi responds to membrane stress, here we defined RpoE-dependent genes using transcriptome sequencing (RNA-Seq). We identified 180 RpoE-dependent genes, of which 98% were upregulated; a major set of these genes encodes homologues of envelope maintenance and repair factors. We also identified and validated a putative RpoE promoter consensus sequence, which was enriched in the majority of RpoE-dependent targets. Comparison of RpoE-dependent genes to those controlled by CpxR showed that each transcription factor regulated a distinct set of genes. Given that RpoE activated a large number of genes encoding envelope maintenance and repair factors and that CpxRA represses genes encoding envelope-localized proteins, these data suggest that RpoE and CpxRA appear to play distinct yet complementary roles in regulating envelope homeostasis in H. ducreyi.
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    Mitochondrial Ca2+ Uniporter and CaMKII in heart
    (Nature Publishing Group, 2014-09-25) Fieni, Francesca; Johnson, Derrick E.; Hudmon, Andy; Kirichok, Yuriy; Department of Biochemistry & Molecular Biology, IU School of Medicine
    The influx of cytosolic Ca2+ into mitochondria is mediated primarily by the mitochondrial calcium uniporter (MCU), a small-conductance, Ca2+-selective channel-. MCU modulates intracellular Ca2+ transients and regulates ATP production and cell death. Recently, Joiner et al. reported that MCU is regulated by mitochondrial CaMKII, and this regulation determines stress response in heart. They reported a very large current putatively mediated by MCU that was about two orders of magnitude greater than the MCU current (IMCU) that we previously measured in heart mitochondria. Also, the current traces presented by Joiner et al. showed unusually high fluctuations incompatible with the low single-channel conductance of MCU. Here we performed patch-clamp recordings from mouse heart mitochondria under the exact conditions used by Joiner et al. We confirmed that IMCU in cardiomyocytes is very small and showed that it is not directly regulated by CaMKII. Thus the currents presented by Joiner et al. do not correspond to MCU, and there is no direct electrophysiological evidence that CaMKII regulates MCU.
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    Muscimol acts in dorsomedial but not paraventricular hypothalamic nucleus to suppress cardiovascular effects of stress
    (Society for Neuroscience, 1996-02-01) Stotz-Potter, E. H.; Willis, L. R.; DiMicco, J. A.; Pharmacology and Toxicology, School of Medicine
    Both the dorsomedial hypothalamic nucleus (DMH) and the paraventricular hypothalamic nucleus (PVN) have been implicated in the neural control of the cardiovascular response to stress. We used the GABAA agonist muscimol to inhibit neuronal activation and attempted to identify hypothalamic nuclei required for the cardiovascular response to air stress. Chronically instrumented rats received bilateral injections of either 80 pmol of muscimol or 100 nl of saline vehicle into the DMH, the PVN, or an intermediate area (including the rostral edge of the DMH and the region between the two nuclei) and were placed immediately in a restraining tube and subjected to 20 min of air stress. In all rats, air stress after vehicle injections caused marked increases in heart rate (137 +/- 6 beats/min) and blood pressure (26 +/- 2 mmHg). Microinjection of muscimol into the DMH suppressed the heart rate and blood pressure response by 85 and 68%, respectively. Identical microinjection of muscimol into the intermediate area between the DMH and the PVN attenuated the increases in heart rate by only 46% and in blood pressure by 52%. In contrast, similar injections into the vicinity of the PVN failed to alter the cardiovascular response to air stress. These findings demonstrate that muscimol-induced inhibition of neuronal activity in the region of the DMH blocks air stress-induced increases in heart rate and arterial pressure, whereas similar treatment in the area of the PVN has no effect.
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    Proinsulin and heat shock protein 90 as biomarkers of beta-cell stress in the early period after onset of type 1 diabetes
    (Elsevier, 2016-02) Watkins, Renecia A.; Evans-Molina, Carmella; Terrell, Jennifer K.; Day, Kathleen H.; Guindon, Lynette; Restrepo, Ivan A.; Mirmira, Raghavendra G.; Blum, Janice S.; Dimelglio, Linda A.; Department of Pediatrics, IU School of Medicine
    Rapid evaluation of therapies designed to preserve β cells in persons with type 1 diabetes (T1D) is hampered by limited availability of sensitive β-cell health biomarkers. In particular, biomarkers elucidating the presence and degree of β-cell stress are needed. We characterized β-cell secretory activity and stress in 29 new-onset T1D subjects (10.6 ± 3.0 years, 55% male) at diagnosis and then 8.2 ± 1.2 weeks later at first clinic follow-up. We did comparisons with 16 matched healthy controls. We evaluated hemoglobin A1c (HbA1c), β-cell function (random C-peptide [C] and proinsulin [PI]), β-cell stress (PI:C ratio), and the β-cell stress marker heat shock protein (HSP)90 and examined these parameters' relationships with clinical and laboratory characteristics at diagnosis. Mean diagnosis HbA1c was 11.3% (100 mmol/mol) and 7.6% (60 mmol/mol) at follow-up. C-peptide was low at diagnosis (P < 0.001 vs controls) and increased at follow-up (P < 0.001) to comparable with controls. PI did not differ from controls at diagnosis but increased at follow-up (P = 0.003) signifying increased release of PI alongside improved insulin secretion. PI:C ratios and HSP90 concentrations were elevated at both time points. Younger subjects had lower C-peptide and greater PI, PI:C, and HSP90. We also examined islets isolated from prediabetic nonobese diabetic mice and found that HSP90 levels were increased ∼4-fold compared with those in islets isolated from matched CD1 controls, further substantiating HSP90 as a marker of β-cell stress in T1D. Our data indicate that β-cell stress can be assessed using PI:C and HSP90. This stress persists after T1D diagnosis. Therapeutic approaches to reduce β-cell stress in new-onset T1D should be considered.
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    Ribosome Reinitiation Directs Gene-specific Translation and Regulates the Integrated Stress Response
    (American Society for Biochemistry and Molecular Biology, 2015-11-20) Young, Sara K.; Willy, Jeffrey A.; Wu, Cheng; Sachs, Matthew S.; Wek, Ronald C.; Department of Biochemistry & Molecular Biology, IU School of Medicine
    Young, S. K., Willy, J. A., Wu, C., Sachs, M. S., & Wek, R. C. (2015). Ribosome Reinitiation Directs Gene-specific Translation and Regulates the Integrated Stress Response. The Journal of Biological Chemistry, 290(47), 28257–28271. http://doi.org/10.1074/jbc.M115.693184
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    Translational Repression Protects Human Keratinocytes from UVB-Induced Apoptosis through a Discordant eIF2 Kinase Stress Response
    (Nature Publishing Group, 2015-10) Collier, Ann E.; Wek, Ronald C.; Spandau, Dan F.; Department of Dermatology, IU School of Medicine
    This study delineates the mechanisms by which UVB regulates protein synthesis in human keratinocytes and the importance of translational control in cell survival. Translation initiation is regulated by phosphorylation of eukaryotic initiation factor 2 (eIF2-P) that causes decreased global protein synthesis coincident with enhanced translation of selected stress-related transcripts, such as activating transcription factor 4 (ATF4). ATF4 is a transcriptional activator of the integrated stress response (ISR) that has cytoprotective functions as well as apoptotic signals through the downstream transcriptional regulator C/EBP homologous protein (CHOP; GADD153/DDIT3). We determined that UVB irradiation is a potent inducer of eIF2-P in keratinocytes, leading to decreased levels of translation initiation. However, expression of ATF4 or CHOP was not induced by UVB as compared with traditional ISR activators. The rationale for this discordant response is that ATF4 mRNA is reduced by UVB, and despite its ability to be preferentially translated, there are diminished levels of available transcript. Forced expression of ATF4 and CHOP protein before UVB irradiation significantly enhanced apoptosis, suggesting that this portion of the ISR is deleterious in keratinocytes following UVB. Inhibition of eIF2-P and translational control reduced viability following UVB that was alleviated by cycloheximide (CHX), indicating that translation repression through eIF2-P is central to keratinocyte survival.