Quantitative Proteomics of Yeast Post-Golgi Vesicles Reveals a Discriminating Role for Sro7p in Protein Secretion

We here report the first comparative proteomics of purified yeast post-Golgi vesicles (PGVs). Vesicle samples isolated from PGV-accumulating sec6-4 mutants were treated with isobaric tags (iTRAQ) for subsequent quantitative tandem mass spectrometric analysis of protein content. After background subtraction, a total of 66 vesicle-associated proteins were identified, including known or assumed vesicle residents as well as a fraction not previously known to be PGV associated. Vesicles isolated from cells lacking the polarity protein Sro7p contained essentially the same catalogue of proteins but showed a reduced content of a subset of cargo proteins, in agreement with a previously shown selective role for Sro7p in cargo sorting

Protein kinase A controls yeast growth in visible light

Background: A wide variety of photosynthetic and non-photosynthetic species sense and respond to light, having developed protective mechanisms to adapt to damaging effects on DNA and proteins. While the biology of UV light-induced damage has been well studied, cellular responses to stress from visible light (400–700 nm) remain poorly understood despite being a regular part of the life cycle of many organisms. Here, we developed a high-throughput method for measuring growth under visible light stress and used it to screen for light sensitivity in the yeast gene deletion collection. Results: We found genes involved in HOG pathway signaling, RNA polymerase II transcription, translation, diphthamide modifications of the translational elongation factor eEF2, and the oxidative stress response to be required for light resistance. Reduced nuclear localization of the transcription factor Msn2 and lower glycogen accumulation indicated higher protein kinase A (cAMP-dependent protein kinase, PKA) activity in many light-sensitive gene deletion strains. We therefore used an ectopic fluorescent PKA reporter and mutants with constitutively altered PKA activity to show that repression of PKA is essential for resistance to visible light. Conclusion: We conclude that yeast photobiology is multifaceted and that protein kinase A plays a key role in the ability of cells to grow upon visible light exposure. We propose that visible light impacts on the biology and evolution of many non-photosynthetic organisms and have practical implications for how organisms are studied in the laboratory, with or without illumination

Trait Variation in Yeast Is Defined by Population History

A fundamental goal in biology is to achieve a mechanistic understanding of how and to what extent ecological variation imposes selection for distinct traits and favors the fixation of specific genetic variants. Key to such an understanding is the detailed mapping of the natural genomic and phenomic space and a bridging of the gap that separates these worlds. Here we chart a high-resolution map of natural trait variation in one of the most important genetic model organisms, the budding yeast Saccharomyces cerevisiae, and its closest wild relatives and trace the genetic basis and timing of major phenotype changing events in its recent history. We show that natural trait variation in S. cerevisiae exceeds that of its relatives, despite limited genetic variation, and follows the population history rather than the source environment. In particular, the West African population is phenotypically unique, with an extreme abundance of low-performance alleles, notably a premature translational termination signal in GAL3 that cause inability to utilize galactose. Our observations suggest that many S. cerevisiae traits may be the consequence of genetic drift rather than selection, in line with the assumption that natural yeast lineages are remnants of recent population bottlenecks. Disconcertingly, the universal type strain S288C was found to be highly atypical, highlighting the danger of extrapolating gene-trait connections obtained in mosaic, lab-domesticated lineages to the species as a whole. Overall, this study represents a step towards an in-depth understanding of the causal relationship between co-variation in ecology, selection pressure, natural traits, molecular mechanism, and alleles in a key model organism

Functional characterisation of the yeast tumour suppressor homologue Sro7p

Correct targeting of newly synthesized proteins to appropriate domains of the cell membrane is crucial to cellular architecture, polarity and function, making it no surprise that many proteins of the secretory machinery are conserved throughout evolution. This work presents a functional characterisation of the Saccharomyces cerevisiae cell polarity protein and tumour suppressor homologue, Sro7p. This protein, and its paralogue Sro77p, belong to the Lgl-family of WD-40 repeat proteins that are conserved from yeast to human. Deletion of Lgl genes produces different phenotypes that all seem to share the common denominator of defective targeting of critical cell surface proteins. Yeast cells lacking SRO7 become sensitive to NaCl and we here show that this defect is due to mis-targeting of the sodium transporter Ena1p. In sro7 mutants Ena1p becomes routed to the vacuole for degradation via the multi-vesicular body (MVB) pathway, instead of being properly expressed at the cell surface. Isolation and analysis of post-Golgi secretory vesicles showed a defective sorting of Ena1p into these vesicles from sro7 mutants, implying mis-sorting in late Golgi or early endosomes. The diversion of Ena1p into the MVB pathway further required ubiquitylation by the ubiquitin ligase Rsp5p. Isolation of suppressors of the sro7 salt sensitivity identified two genes of unknown function, RSN1 encoding a trans-membrane protein, and ART5 (RSN2), encoding an arrestin-like protein. Deletion of either gene in sro7 mutants re-establishes salt tolerance and retargets Ena1p to the cell surface. Previous proteomic studies have shown that Art5p interacts with Rsp5p and we showed that deletion of ART5 in sro7 mutants inhibits ubiquitylation of Ena1p. Our data are consistent with Art5p being a selective adaptor protein that helps Rsp5p recruiting Ena1p for ubiquitylation. To identify further candidate proteins for mis-sorting in salt stressed sro7 mutants we performed the first proteomic analysis of purified yeast post-Golgi vesicles (PGVs), using quantitative proteomics techniques. By this analysis we could identify 107 genuine vesicle residents in control yeast cells, including a number of cargo proteins not previously identified in PGVs. Vesicles derived from sro7 mutants contained essentially the same list of proteins but were depleted of a subset of proteins, thus being candidates for mis-routing. The present study finally analysed possible Lgl conservation in plants by characterising two Arabidopsis thaliana Lgl homologues. Sequence based modelling showed that both proteins can fold into the twin β-propellers shown by the published Sro7p crystal structure. However, only one of the proteins, AtLGL1, could partially substitute for the yeast Sro7/77 proteins. The other, AtLGL2 showed structural similarities with tomosyn that is known to regulate vesicle fusion in mammals. Homozygous T-DNA insertion mutants in A. thaliana exhibited defects in lateral root formation, a phenotype associated with changed cell- and tissue polarity

Inequalities in pharmacologic treatment of spasticity in Sweden : health economic consequences of closing the treatment gap

Background The Swedish Healthcare Act states that patients should have equal access to healthcare. This study addresses at how this translates to pharmacological treatment of adult spasticity, including injections with botulinum toxin A (BoNT-A) and pumps for intrathecal baclofen (ITB). To address potential economic incentives for treatment differences, the results are also set into a health economic perspective. Thus, the current study provides a detailed and comprehensive overview for informed decision- and policymaking. Methods Botulinum toxin use was retrieved from sales data. Clinical practice regarding mean BoNT-A treatment dose and proportion used for spasticity indication were validated in five county councils, while the number of ITB pumps were mapped for all county councils. Published costs and quality of life data was used for estimating required responder rates for cost-balance or cost-effectiveness. Results The proportion of patients treated with BoNT-A varied between 5.8% and 13.6% across healthcare regions, with a mean of 9.2% on a national level. The reported number of ITB pumps per 100,000 inhabitants varied between 3.6 and 14.1 across healthcare regions, with a national mean of 6/100,000. The estimated incremental cost for reaching treatment equity was EUR 1,976,773 per year for BoNT-A and EUR 3,326,692 for ITB pumps. Based on expected cost-savings, responder rates ranging between 4% and 15% cancelled out the incremental cost for BoNT-A. Assuming no cost-savings, responder rates of 14% or 36% was required for cost-effectiveness. Conclusions There is a marked variation in pharmacologic treatment of adult spasticity in Sweden. Overall, the results indicate an underuse of treatment and need for harmonisation of clinical practice. Furthermore, the incremental cost for reaching treatment equity is likely to be offset by spasticity-associated cost-savings.Funding Agencies|Ipsen; University of Linkoping</p

Short- and long-term direct and indirect costs of illness after ostomy creation – a Swedish nationwide registry study

Abstract Background Despite advance in care of people with an ostomy, related complications remain prevalent. The objective of this study was to examine short- and long-term healthcare resource utilization and associated costs after ostomy creation. Methods This observational study was based on retrospectively collected data from national and regional Swedish registries. The population consisted of people living in Sweden, who had an ostomy created. The earliest index date was 1 January 2006, and people were followed for ten years, until death, reversal of temporary ostomy, termination of purchases of ostomy products, or end of study, which was 31 December 2019. Each person with an ostomy was matched with two controls from the general population based on age, gender, and region. Results In total, 40,988 persons were included: 19,645 with colostomy, 16,408 with ileostomy, and 4,935 with urostomy. The underlying diseases for colostomy and ileostomy creations were primarily bowel cancer, 50.0% and 55.8% respectively, and additionally inflammatory bowel disease for 20.6% of ileostomies. The underlying cause for urostomy creation was mainly bladder cancer (85.0%). In the first year after ostomy creation (excl. index admission), the total mean healthcare cost was 329,200 SEK per person with colostomy, 330,800 SEK for ileostomy, and 254,100 SEK for urostomy (100 SEK was equivalent to 9.58 EUR). Although the annual mean healthcare cost decreased over time, it remained significantly elevated compared to controls, even after 10 years, with hospitalization being the main cost driver. The artificial opening was responsible for 19.3–22.8% of 30-day readmissions after ostomy creation and for 19.7–21.4% of hospitalizations during the entire study period. For the ileostomy group, dehydration was responsible for 13.0% of 30-day readmissions and 4.5% of hospitalization during the study period. Conclusions This study reported a high disease burden for persons with an ostomy. This had a substantial impact on the healthcare cost for at least ten years after ostomy creation. Working ability seemed to be negatively impacted, indicated by increased cost of sickness absence and early retirement. This calls for improved management and support of ostomy care for the benefit of the affected persons and for the cost of society

The Yeast Tumor Suppressor Homologue Sro7p Is Required for Targeting of the Sodium Pumping ATPase to the Cell Surface

The SRO7/SOP1 encoded tumor suppressor homologue of Saccharomyces cerevisiae is required for maintenance of ion homeostasis in cells exposed to NaCl stress. Here we show that the NaCl sensitivity of the sro7Δ mutant is due to defective sorting of Ena1p, the main sodium pump in yeast. On exposure of sro7Δ mutants to NaCl stress, Ena1p fails to be targeted to the cell surface, but is instead routed to the vacuole for degradation via the multivesicular endosome pathway. SRO7-deficient mutants accumulate post-Golgi vesicles at high salinity, in agreement with a previously described role for Sro7p in late exocytosis. However, Ena1p is not sorted into these post-Golgi vesicles, in contrast to what is observed for the vesicles that accumulate when exocytosis is blocked in sec6-4 mutants at high salinity. These observations imply that Sro7p has a previously unrecognized role for sorting of specific proteins into the exocytic pathway. Screening for multicopy suppressors identified RSN1, encoding a transmembrane protein of unknown function. Overexpression of RSN1 restores NaCl tolerance of sro7Δ mutants by retargeting Ena1p to the plasma membrane. We propose a model in which blocked exocytic sorting in sro7Δ mutants, gives rise to quality control-mediated routing of Ena1p to the vacuole

Health Economic Analysis of Open and Robot-assisted Laparoscopic Surgery for Prostate Cancer Within the Prospective Multicentre LAPPRO Trial

Background: The rapid adoption of robot-assisted laparoscopy in radical prostatectomy has preceded data regarding associated costs. Qualitative evidence regarding cost outcomes is lacking. Objective: This study assessed how costs were affected by robot-assisted laparoscopic prostatectomy (RALP) compared with open surgery. Design, setting, and participants: Cost analysis was based on the dataset of the LAPPRO (Laparoscopic Prostatectomy Robot Open) clinical trial, which is a prospective controlled, nonrandomised trial of patients who underwent prostatectomy at 14 centres in Sweden between September 2008 and November 2011. Currently, data are available from a follow-up period of 24 mo. Intervention: In the LAPPRO trial, RALP was compared with radical retropubic prostatectomy (RRP). Outcome measurements and statistical analysis: Costs per surgical technique were assessed based on resource variable data from the LAPPRO database. The calculation of average costs was based on mean values; Swedish currency was converted to purchasing power parity US dollar (PPP$). All tests were two-tailed and conducted at α = 0.05 significance level. Results and limitations: The cost analysis comprised 2638 men. Based on the LAPPRO trial data, RALP was associated with an increased cost/procedure of PPP$ 3837 (95% confidence interval: 2747–4928) compared with RRP. The result was sensitive to variations in caseload. Main drivers of overall cost were robotic system cost, operation time, length of stay, and sick leave. Limitations of the study include the uneven distribution between RALP and RRP regarding procedures in public/for-profit hospitals and surgeon/centre procedural volume. Conclusions: Based on the LAPPRO trial data, this study showed that RALP was associated with an increased cost compared with RRP in Swedish health care. There are many factors influencing the costs, making the absolute result dependent on the specific setting. However, by identifying the main cost drivers and/or most influential parameters, the study provides support for informed decisions and predictions. Patient summary: In this study, we looked at the cost outcome when performing prostatectomies by robot-assisted laparoscopic technique compared with open surgery in Sweden. We found that the robot-assisted procedure was associated with a higher mean cost. This cost analysis reports that compared with open surgery, robot-assisted laparoscopy for prostate cancer was associated with a net increase in cost. One important conclusion is that widespread implementation of costly new techniques should not precede outcomes from well-designed trials