The intermediate proteasome is constitutively expressed in pancreatic beta cells and upregulated by stimulatory, low concentrations of interleukin 1 β

Muhammad Saad Khilji; Danielle Verstappen; Tina Dahlby; Michala Cecilie Burstein Prause; Celina Pihl; Sophie Emilie Bresson; Tenna Holgersen Bryde; Phillip Alexander Keller Andersen; Kristian Klindt; Dusan Zivkovic; Marie-Pierre Bousquet-Dubouch; Björn Tyrberg; Thomas Mandrup-Poulsen; Michal Tomasz Marzec

doi:10.1371/journal.pone.0222432

Peer Review History

Original SubmissionAugust 26, 2019
6 Nov 2019 Decision Letter - Corentin Cras-Méneur, Editor PONE-D-19-24067 The intermediate proteasome is constitutively expressed in pancreatic beta cells and upregulated by stimulatory, non-toxic concentrations of interleukin 1 b PLOS ONE Dear Prof. Marzec, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. ============================== As pointed out by the reviewers, a number of issues could be addressed or at least clarified in the text. ============================== We would appreciate receiving your revised manuscript by Dec 16 2019 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols Please include the following items when submitting your revised manuscript: A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'. Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out. We look forward to receiving your revised manuscript. Kind regards, Corentin Cras-Méneur, Ph.D. Academic Editor PLOS ONE Journal Requirements: 1. When submitting your revision, we need you to address these additional requirements. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at http://www.journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and http://www.journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. PLOS ONE now requires that authors provide the original uncropped and unadjusted images underlying all blot or gel results reported in a submission’s figures or Supporting Information files. This policy and the journal’s other requirements for blot/gel reporting and figure preparation are described in detail at https://journals.plos.org/plosone/s/figures#loc-blot-and-gel-reporting-requirements and https://journals.plos.org/plosone/s/figures#loc-preparing-figures-from-image-files. When you submit your revised manuscript, please ensure that your figures adhere fully to these guidelines and provide the original underlying images for all blot or gel data reported in your submission. See the following link for instructions on providing the original image data: https://journals.plos.org/plosone/s/figures#loc-original-images-for-blots-and-gels. In your cover letter, please note whether your blot/gel image data are in Supporting Information or posted at a public data repository, provide the repository URL if relevant, and provide specific details as to which raw blot/gel images, if any, are not available. Email us at plosone@plos.org if you have any questions. 3. Please amend the manuscript submission data (via Edit Submission) to include author Nils Billestrup. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Partly Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 3. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 4. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: This is a descriptive study that examines the expression of subunits of the immune proteasome in pancreatic islets. The authors have used previously published RNAseq evidence to suggest that components of the immune proteasome are expressed at the mRNA level in b-cells and other islet endocrine cells. Overall the study is consistent with other reports showing immune proteasome expression under various conditions with new information suggestive that long exposures with low concentrations of IL-1 are capable of stimulating subunit expression. There are a number of concerns that could be addressed or clarified in the text. Using RNAseq the authors provide in support of immune proteasome expressed in b-cells under basal conditions. How was RNAseq used to quantify mRNA levels? There is also some concern with the MS analysis of cross-linked proteasomes via immunoprecipitation approaches. It is not clear how the crosslinking on intact cells crosslinks the proteasome found in the cytoplasm (Fig 2). Some controls could be helpful with this analysis to support the authors conclusions. There is also concern regarding “non-toxic” concentrations of IL-1. It is not clear that mouse or human islets are sensitive to IL-1 alone and therefor all concentrations of IL-1 are non-toxic. It is suggested that the text be modified to low and high concentrations to be more consistent with the biological action. Also- the merits of a 10 day exposure are not clear- what is the time- and concentration-dependence of IL-1 on immune proteasome subunit expression? Quantification of RNAseq? How is it possible to determine a p-value on these studies (Table 3) and how was quantification performed. Number of cells expressing the targets or the level of expression (i.e. number of reads?). Further, was this confirmed by PCR? Also, was this one isolation of islets and the n represent the number of cells sequenced, or were multiple isolations performed for each single cell sequence? Reviewer #2: The authors describe the constitutive expression of intermediate proteasomes in pancreatic beta cells. This expression is upregulated by interleukin 1b (IL1b). Mining of available RNA-seq data of single cells from pancreatic islets of healthy individuals and analysis of human and mouse islets, INS-1E (insulinoma), A20 (lymphoma) and Jurkat (leukemic cells) cells, revealed high expression of the inducible proteasome subunits in immune cells and low but consistent expression in the pancreatic cells. By LC-MS/MS analysis, proteasomes from INS-1E cells were classified either as standard (s-proteasomes) or beta5i-containing (14%) but no proteasomes were detected with the beta1i and beta2i subunits. With the exception of the A20 cells, all other cells types tested had proteasomes exhibiting mainly chymotrypsin-like activity (50-60%) followed by trypsin- and caspase-like activity. Incubation of human/mouse islets with ONX-0914 – an inhibitor of beta5i – led to reduction in chymotrypsin-like activity. Moreover, IL-1b upregulated the expression of the inducible subunits beta-1 (b1i), -2 (b2i) and -5 (b5i) and the proteasome activity in beta cells. The findings are important as our knowledge of the proteasome activities in beta cells is still fairly limited. The authors provide a comprehensive picture of proteasome composition, especially with respect to the inducible subunits, in beta cells. Overall, the study is technically sound and the results support the conclusions. Statistical analysis of the data has been performed. I only have a few minor comments: 1. The authors should address the discrepancy in the level of chymotrypsin-like activity in the proteasomes of beta cells and Jurkat cells vs. A20 cells (lines 305-307). This is only mentioned in passing in the discussion (line 452). 2. Reporting the viability of cells (e.g. in figure 5) would be helpful to better assess the reported effects and the effect of treatment on the cells or islets. ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: No Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files to be viewed.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0222432.r001
Revision 1
26 Nov 2019 Author Response PONE-D-19-24067 The intermediate proteasome is constitutively expressed in pancreatic beta cells and upregulated by stimulatory, non-toxic concentrations of interleukin 1 b Response to Reviewers: Reviewer #1: This is a descriptive study that examines the expression of subunits of the immune proteasome in pancreatic islets. The authors have used previously published RNAseq evidence to suggest that components of the immune proteasome are expressed at the mRNA level in b-cells and other islet endocrine cells. Overall the study is consistent with other reports showing immune proteasome expression under various conditions with new information suggestive that long exposures with low concentrations of IL-1 are capable of stimulating subunit expression. There are a number of concerns that could be addressed or clarified in the text. Using RNAseq the authors provide in support of immune proteasome expressed in b-cells under basal conditions. How was RNAseq used to quantify mRNA levels? Two types of RNAseq data are included in the manuscript. Fig.1A presents human single cell sequencing data and Table 3 presents bulk mouse pancreatic islet RNA sequencing data. Quantification of single-cell RNA sequencing of human pancreatic islets was performed through data analysis with bcbio-nextgen toolkit (https://bcbio-nextgen.readthedocs.io/en/latest/), followed by the Salmon algorithm (Patro, Duggal et al. 2017) for quantitation of mRNA counts. Data is then expressed as log2 of counts per million (CPM). The original use of data and more analysis details are included in, cited in the Material and Methods section, reference (Segerstolpe, Palasantza et al. 2016). Material and Method section has been amended to reflect changes. Table 3 and its description (as well as manuscript text at the lane 203-216; all lane references refer to marked copy of the manuscript) has been modified to underlie the fact that data comes from bulk mouse islet sequencing (see below). Quantification of RNAseq? How is it possible to determine a p-value on these studies (Table 3) and how was quantification performed. Number of cells expressing the targets or the level of expression (i.e. number of reads?). Further, was this confirmed by PCR? Also, was this one isolation of islets and the n represent the number of cells sequenced, or were multiple isolations performed for each single cell sequence? We thank the Reviewer for raising this issue as it made us realize that the data should be reported in a different and more detailed way. Currently the data reports on in RPKM for the specific genes of 3 independent experiments as well as their means and is analyzed by Student’s paired t-test. The conclusions remain the same. As mentioned in the material and methods section Table 3 reports on whole islets bulk RNAseq and was obtained from 3 separate isolations of islets from several mice per condition. The method of quantification is described in detail and a reference to the original publication is provided. The expression of six genes reported in this study have not been validated by PCR but multiple other genes in the original study were for ex. insulin, Mafa, Pdx-1 and Ucn3. Text changes can be found in lanes 203-216, 354-355 and overhauled Table 3 at lane 346. There is also some concern with the MS analysis of cross-linked proteasomes via immunoprecipitation approaches. It is not clear how the crosslinking on intact cells crosslinks the proteasome found in the cytoplasm (Fig 2). Some controls could be helpful with this analysis to support the authors conclusions. Co-author Marie-Pierre Bousquet’s group has set the original protocol to in vivo crosslink proteins on intact cells of various origins and then to very efficiently immmunopurify proteasome complexes after cell lysis. They have shown that this crosslinking strategy helps stabilizing Proteasome Interacting Proteins (PIPs), in particular important proteasome regulators, like the 19S and PA28 activators, and enables to characterize the whole diversity of proteasome complexes. In their 1st publication (Bousquet-Dubouch MP et al., Mol. Cell. Proteomics, 2009), the comparison of crosslinked cells and non-crosslinked cells (used as a control) has clearly demonstrated the benefit of formaldehyde crosslinking step on the efficacy of recovery of proteasome subunits and PIPs. Since then, the protocol has been successfully applied to study proteasome complexes in different subcellular compartments in leukemic cells (Fabre B. et al, Mol. Cell. Proteomics, 2013) and in cells and tissues of various origins (Fabre B. et al, J. Proteome Res., 2014; Fabre B. et al, Mol. Sys. Biol., 2015). Material and method section has been amended to include the original publication for the protocol reference (lane 234). There is also concern regarding “non-toxic” concentrations of IL-1. It is not clear that mouse or human islets are sensitive to IL-1 alone and therefor all concentrations of IL-1 are non-toxic. It is suggested that the text be modified to low and high concentrations to be more consistent with the biological action. We agree with the reviewer and have corrected the text accordingly. Also- the merits of a 10 day exposure are not clear- what is the time- and concentration-dependence of IL-1 on immune proteasome subunit expression? We thank the Reviewer for raising this issue. The rational for doing the 10 days exposure to low doses of IL-1 was to mimic and better resemble the low-grade inflammation observed in diabetes. Although, even 24h exposure to IL-1 induces significant changes in proteasome subunit expression and activity the longer exposure, more characteristic for diabetes pathology could result in a loss of inducible subunits expression and induction of other detrimental to beta cells processes. However as reported in our collaborators publication (Ibarra et al. Mol Cell Endocrinol. 2019) prolonged exposure of mouse islets to IL-1 resulted in decrease of glucose stimulated insulin secretion but did not reduce cellular insulin content, did not induce endoplasmic reticulum stress or cell death and inducible subunits expression was maintained. This experiment provides a time perspective underlying the relevance of the observed short- and long-term subunits induction to the pathology of diabetes. We have modified the manuscript text at lane 502-511. Reviewer #2: The authors describe the constitutive expression of intermediate proteasomes in pancreatic beta cells. This expression is upregulated by interleukin 1b (IL1b). Mining of available RNA-seq data of single cells from pancreatic islets of healthy individuals and analysis of human and mouse islets, INS-1E (insulinoma), A20 (lymphoma) and Jurkat (leukemic cells) cells, revealed high expression of the inducible proteasome subunits in immune cells and low but consistent expression in the pancreatic cells. By LC-MS/MS analysis, proteasomes from INS-1E cells were classified either as standard (s-proteasomes) or beta5i-containing (14%) but no proteasomes were detected with the beta1i and beta2i subunits. With the exception of the A20 cells, all other cells types tested had proteasomes exhibiting mainly chymotrypsin-like activity (50-60%) followed by trypsin- and caspase-like activity. Incubation of human/mouse islets with ONX-0914 – an inhibitor of beta5i – led to reduction in chymotrypsin-like activity. Moreover, IL-1b upregulated the expression of the inducible subunits beta-1 (b1i), -2 (b2i) and -5 (b5i) and the proteasome activity in beta cells. The findings are important as our knowledge of the proteasome activities in beta cells is still fairly limited. The authors provide a comprehensive picture of proteasome composition, especially with respect to the inducible subunits, in beta cells. Overall, the study is technically sound and the results support the conclusions. Statistical analysis of the data has been performed. I only have a few minor comments: 1. The authors should address the discrepancy in the level of chymotrypsin-like activity in the proteasomes of beta cells and Jurkat cells vs. A20 cells (lines 305-307). This is only mentioned in passing in the discussion (line 452). We have made changes to the manuscript to clearly underlie observed discrepancies and pointed to their possible sources although we have to admit that at this stage we do not understand the observed proteasome profile in A20 cells (lane 466-477). The proteasome activity and/or substrate specific activity can be regulated on multiple levels and the issue has been recently reviewed in Kors et al. Front. Mol. Biosci., 16 July 2019, https://doi.org/10.3389/fmolb.2019.00048, although, again, it does not provide a clear explanation of our observation. 2. Reporting the viability of cells (e.g. in figure 5) would be helpful to better assess the reported effects and the effect of treatment on the cells or islets. We agree with the Reviewer and have added data on mouse islets and INS1-E cell viability to the S1 figure and made appropriate changes in the manuscript text (lane 367-368) adding also references from previously published work e.g. Ibarra et al. Mol Cell Endocrinol. 2019 PMID: 31362031 Fig. 1E. References Patro, R., G. Duggal, M. I. Love, R. A. Irizarry and C. Kingsford (2017). "Salmon provides fast and bias-aware quantification of transcript expression." Nat Methods 14(4): 417-419. Segerstolpe, A., A. Palasantza, P. Eliasson, E. M. Andersson, A. C. Andreasson, X. Sun, S. Picelli, A. Sabirsh, M. Clausen, M. K. Bjursell, D. M. Smith, M. Kasper, C. Ammala and R. Sandberg (2016). "Single-Cell Transcriptome Profiling of Human Pancreatic Islets in Health and Type 2 Diabetes." Cell Metab 24(4): 593-607. Attachments Attachment Submitted filename: Response to Reviewers Khilji et al.docx https://doi.org/10.1371/journal.pone.0222432.r002
2 Jan 2020 Decision Letter - Corentin Cras-Méneur, Editor PONE-D-19-24067R1 The intermediate proteasome is constitutively expressed in pancreatic beta cells and upregulated by stimulatory, low concentrations of interleukin 1 b PLOS ONE Dear Prof. Marzec, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. While most of the comments in the manuscript have been addressed according to the comments made by the reviewers, two points remain to be clarified in the text for the manuscript to be accepted. We would appreciate receiving your revised manuscript by Feb 16 2020 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols Please include the following items when submitting your revised manuscript: A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'. Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out. We look forward to receiving your revised manuscript. Kind regards, Corentin Cras-Méneur, Ph.D. Academic Editor PLOS ONE Additional Editor Comments (if provided): The revised version of the manuscript addresses most of the comments raised by the original reviewers. There are only two points that remained to be clarified in the manuscript: • The authors need to mention and justify that Normal distribution needs too be assumed for the use of parametric tests. • The authors need to emphasize and discuss in the text that the replicates are technical replicates (3 isolations) and not biological replicates. [Note: HTML markup is below. Please do not edit.] [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files to be viewed.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0222432.r003
Revision 2
21 Jan 2020 Author Response PONE-D-19-24067 The intermediate proteasome is constitutively expressed in pancreatic beta cells and upregulated by stimulatory, non-toxic concentrations of interleukin 1 b Response to Editor Comments The revised version of the manuscript addresses most of the comments raised by the original reviewers. There are only two points that remained to be clarified in the manuscript: • The authors need to mention and justify that Normal distribution needs too be assumed for the use of parametric tests. The following text has been added to Statistical analysis section of the manuscript: All samples were selected without bias and represent biological not technical variations. Distribution of islets, specifically, were randomized and independent of e.g. size and shape. As a result, samples should be homogenous and represent biological variation, and both protein expression and activity is therefore assumed to be normally distributed (43, 44). Furthermore, normality of all expression data was tested with a Shapiro-Wilk test and found normally distributed and tested using a student t-test. Meanwhile proteasome activity and cell viability data is represented by a mean value of technical replicates, and as such should be normally distributed according to the central limits theorem (45). • The authors need to emphasize and discuss in the text that the replicates are technical replicates (3 isolations) and not biological replicates. The replicates presented in all figures, irrespective if those are cells or pancreatic islets, are biological not technical replicates. Islet isolation: islets were isolated on separate days and from separate group of mice and that constitutes biological replications. Similarly, in case of human islets obtained from deceased donors, isolated islets represent biological variability (thus are replications) not a technical replicate. Proteasome studies: for each data point cells were separately cultured (minimum two weeks), plated (on different days) and collected. That procedure constitutes biological replication for cell culture experiments. Then each data set was run, in minimum, as three technical replicates and the mean of those is presented. We have amended the manuscript text to emphasize the fact that presented data is based on biological replicates. See lanes: 164-164, 287, 311 (already mentioned), 334-335, 361-362, 383, 403 (already mentioned). Attachments Attachment Submitted filename: Response to Reviewers Khilji et al Jan 21 2020.docx https://doi.org/10.1371/journal.pone.0222432.r004
22 Jan 2020 Decision Letter - Corentin Cras-Méneur, Editor The intermediate proteasome is constitutively expressed in pancreatic beta cells and upregulated by stimulatory, low concentrations of interleukin 1 b PONE-D-19-24067R2 Dear Dr. Marzec, We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements. Within one week, you will receive an e-mail containing information on the amendments required prior to publication. When all required modifications have been addressed, you will receive a formal acceptance letter and your manuscript will proceed to our production department and be scheduled for publication. Shortly after the formal acceptance letter is sent, an invoice for payment will follow. To ensure an efficient production and billing process, please log into Editorial Manager at https://www.editorialmanager.com/pone/, click the "Update My Information" link at the top of the page, and update your user information. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, you must inform our press team as soon as possible and no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. With kind regards, Corentin Cras-Méneur, Ph.D. Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0222432.r005
Formally Accepted
5 Feb 2020 Acceptance Letter - Corentin Cras-Méneur, Editor PONE-D-19-24067R2 The intermediate proteasome is constitutively expressed in pancreatic beta cells and upregulated by stimulatory, low concentrations of interleukin 1 β Dear Dr. Marzec: I am pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please notify them about your upcoming paper at this point, to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. For any other questions or concerns, please email plosone@plos.org. Thank you for submitting your work to PLOS ONE. With kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Corentin Cras-Méneur Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0222432.r006

Open letter on the publication of peer review reports

PLOS recognizes the benefits of transparency in the peer review process. Therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. Reviewers remain anonymous, unless they choose to reveal their names.

We encourage other journals to join us in this initiative. We hope that our action inspires the community, including researchers, research funders, and research institutions, to recognize the benefits of published peer review reports for all parts of the research system.

Learn more at ASAPbio .