The molecular, cellular and pathophysiological roles of iRhom pseudoproteases

iRhom proteins are catalytically inactive relatives of rhomboid intramembrane proteases. There is a rapidly growing body of evidence that these pseudoenzymes have a central function in regulating inflammatory and growth factor signalling and consequent roles in many diseases. iRhom pseudoproteases have evolved new domains from their proteolytic ancestors, which are integral to their modular regulation and functions. Although we cannot yet conclude the full extent of their molecular and cellular mechanisms, there is a clearly emerging theme that they regulate the stability and trafficking of other membrane proteins. In the best understood case, iRhoms act as regulatory cofactors of the ADAM17 protease, controlling its function of shedding cytokines and growth factors. It seems likely that as the involvement of iRhoms in human diseases is increasingly recognized, they will become the focus of pharmaceutical interest, and here we discuss what is known about their molecular mechanisms and relevance in known pathologies.

1. In the abstract, the authors write that the function of ADAM17 is shedding of cytokines and growth factors. ADAM17 is also an important sheddase of many receptors and adhesion proteins. This could be mentioned here. 2. On p3, the authors describe the different phenotypes of iRhom1 knock-out mice. Do the authors have a possible explanation for the observed variation on phenotypes? 3. On p5, the authors describe the role on iRhom2 in the trafficking of ADAM17 from the ER to the Golgi, where ADAM17 is processed by furin proteases. In contrast to the statement of the authors, this furin cleavage does not lead to activation of ADAM17. This statement should be rephrased. 4. On p12, the authors describe the transcriptional activation of iRhoms. They might want to include a short statement on the structure of the promoters of the iRhom genes, which might illustrate which pathways are likely to affect transcription of iRhom genes. 5. Some references (20,21,33,39,65,67,70) are imcomplete and should be amended. 6. In the inset of Fig. 1, the authors might want to indicate the iRhom homology domain (IRHD). 7. As far as this reviewer understands, the data summarized in Fig. 5

Comments to the Author
The iRhom pseudoproteases are emerging as important regulators of the metalloprotease ADAM17, which has a critical role in the body's first line of defence against infection (via shedding of TNFalpha) and repair (via shedding of EGF receptor ligands). This exciting story has developed over the last six years through a number of high-impact publications, and this is in part down to the work of the authors of this review, who have played a major role in initiating this field. Their well-written and timely review provides an introduction to iRhoms and related proteins, describes their role in protein turnover and trafficking of client proteins (including ADAM17 and others), mechanisms of iRhom function, roles in disease, and a thoughtful conclusion that nicely emphasises the current knowledge gaps and areas of future research priority. The five figures and two tables are helpful inclusions.
My specific comments are as follows.
1. The current lack of clarity concerning the phenotype of iRhom1 knockout mice is mentioned a couple of times in the review. It would be useful if the authors could comment on why they think that the two publications on this show different phenotypes, particularly as they are responsible for one of the papers.
2. It would be useful if an extra sentence or two could be added to explain the mechanisms of action of the two iRhom client proteins STING and VISA. At present, their introductions are somewhat vague.
3. On a couple of occasions, the relative conservation between regions of iRhom1 and 2 are described, but using rather vague terms such as "least conserved" and "most highly conserved". It would be useful if the authors could add the precise percentage amino acid identities of the different regions shown on Figure 4, by comparing the human iRhom1 and 2 sequences.
4. In Table 1, it would avoid confusion if "TACE" was changed to "ADAM17", because the latter is used in the main text. Table 2, the arthritis reference 14 should be changed to 62. Also, as a minor point, the breast cancer and neurological disease rows do not really need "(i)", because there is only one phenotype listed.

28-Jan-2019
Dear Professor Freeman, We are pleased to inform you that your manuscript RSOB-19-0003 entitled "The molecular, cellular and pathophysiological roles of iRhom pseudoproteases" has been accepted by the Editor for publication in Open Biology. The reviewer(s) have recommended publication, but also suggest some minor revisions to your manuscript. Therefore, we invite you to respond to the reviewer(s)' comments and revise your manuscript.
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3) Electronic supplementary material: this should be contained in a separate file from the main text and meet our ESM criteria (see http://royalsocietypublishing.org/instructions-authors#question5). All supplementary materials accompanying an accepted article will be treated as in their final form. They will be published alongside the paper on the journal website and posted on the online figshare repository. Files on figshare will be made available approximately one week before the accompanying article so that the supplementary material can be attributed a unique DOI.
Online supplementary material will also carry the title and description provided during submission, so please ensure these are accurate and informative. Note that the Royal Society will not edit or typeset supplementary material and it will be hosted as provided. Please ensure that the supplementary material includes the paper details (authors, title, journal name, article DOI Comments to the Author(s) The review article by Dulloo et al reviews the current knowledge of the molecular, cellular and pathophysiological role of iRhom pseudoproteases. The group of Prof. Freeman has been instrumental in uncovering the various activities of iRhom proteins and the authors did a magnificent job in summarizing these findings of the past 20 years. iRhoms are crucially needed for the trafficking and activation of the important ADAM17 protease, which governs at least three important pathways, namely the TNFa, IL-6 and EGF-R signaling pathways. These pathways are involved in the regulation of inflammation, infection, metabolism and cancer. In addition, there are additional clients of iRhoms, which are not very well studied yet, and which will possible change the direction of the field considerably. All important aspects of iRhom biology are nicely covered in the review.
The review article is very well written and it will appear timely since more and more aspects of inflammation and cancer research seem to involve iRhom activities.
There are some points, the authors might want to consider.
1. In the abstract, the authors write that the function of ADAM17 is shedding of cytokines and growth factors. ADAM17 is also an important sheddase of many receptors and adhesion proteins. This could be mentioned here.
2. On p3, the authors describe the different phenotypes of iRhom1 knock-out mice. Do the authors have a possible explanation for the observed variation on phenotypes? 3. On p5, the authors describe the role on iRhom2 in the trafficking of ADAM17 from the ER to the Golgi, where ADAM17 is processed by furin proteases. In contrast to the statement of the authors, this furin cleavage does not lead to activation of ADAM17. This statement should be rephrased. 4. On p12, the authors describe the transcriptional activation of iRhoms. They might want to include a short statement on the structure of the promoters of the iRhom genes, which might illustrate which pathways are likely to affect transcription of iRhom genes. 5. Some references (20,21,33,39,65,67,70) are imcomplete and should be amended. 6. In the inset of Fig. 1, the authors might want to indicate the iRhom homology domain (IRHD). 7. As far as this reviewer understands, the data summarized in Fig. 5 are not from Cavadas et al but rather from Oikonomidi et al. This should be corrected.

Referee: 2
Comments to the Author(s) The iRhom pseudoproteases are emerging as important regulators of the metalloprotease ADAM17, which has a critical role in the body's first line of defence against infection (via shedding of TNFalpha) and repair (via shedding of EGF receptor ligands). This exciting story has developed over the last six years through a number of high-impact publications, and this is in part down to the work of the authors of this review, who have played a major role in initiating this field. Their well-written and timely review provides an introduction to iRhoms and related proteins, describes their role in protein turnover and trafficking of client proteins (including ADAM17 and others), mechanisms of iRhom function, roles in disease, and a thoughtful conclusion that nicely emphasises the current knowledge gaps and areas of future research priority. The five figures and two tables are helpful inclusions.
My specific comments are as follows.
1. The current lack of clarity concerning the phenotype of iRhom1 knockout mice is mentioned a couple of times in the review. It would be useful if the authors could comment on why they think that the two publications on this show different phenotypes, particularly as they are responsible for one of the papers.
2. It would be useful if an extra sentence or two could be added to explain the mechanisms of action of the two iRhom client proteins STING and VISA. At present, their introductions are somewhat vague.
3. On a couple of occasions, the relative conservation between regions of iRhom1 and 2 are described, but using rather vague terms such as "least conserved" and "most highly conserved". It would be useful if the authors could add the precise percentage amino acid identities of the different regions shown on Figure 4, by comparing the human iRhom1 and 2 sequences.
4. In Table 1, it would avoid confusion if "TACE" was changed to "ADAM17", because the latter is used in the main text. Table 2, the arthritis reference 14 should be changed to 62. Also, as a minor point, the breast cancer and neurological disease rows do not really need "(i)", because there is only one phenotype listed.

19-Feb-2019
Dear Professor Freeman, We are pleased to inform you that your manuscript entitled "The molecular, cellular and pathophysiological roles of iRhom pseudoproteases" has been accepted by the Editor for publication in Open Biology.
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