Scoping Pleiotropy of CK2 in Musculoskeletal Disorders for a Novel Targeting Approach

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript of Pandit et al. is potentially an interesting review to summarize several features of protein kinase CK2 in relation to musculoskeletal disorders, also giving a perspective on different kinase targeting strategies. However, in this version the manuscript is difficult to read and understand. A thorough review of the manuscript by rewriting various paragraphs taking into account the following points is strongly recommended to make the manuscript publishable in the journal.

 

1)     Often, the terminology used is not appropriate, and concepts relating to the kinase are not strictly correct. As examples, the term “multiformity” in the title is not appropriate to define the complexity of CK2. In the abstract, the use of “Casein kinase II” is obsolete, please name the kinase as “protein kinase CK2”. The “new approach” for the kinase targeting should be explained.

What do the authors mean by “versatile kinase”? Furthermore, the authors define CK2 as a “master regulator of biochemical processes”. This definition seems too strong for the kinase that usually acts as a “lateral player” of diverse pathways, but overall, it is not clear which are the biochemical processes mentioned by the authors.

Please, the authors may explain what they mean by a “lucrative strategy” in relation to CK2  targeting in musculoskeletal diseases. Please, review the text between lines 67 and 70, because the content is not clear.

How can authors define a mechanism of action of ATP-competitive inhibitors “generalized rather than disease specific”? Generally, drugs such as kinase inhibitors are not designed for a specific disease, but to inhibit a specific target involved in a disease of interest, and it is not the case of only ATP-competitive inhibitors such as CX-4945, because the CIGB300 peptide was not designed for specific disorders, but to potentially target different CK2 substrates that could be important in multiple diseases.

It is not correct to use the terms “heterogenous” and “homogenous” in relation to the CK2 subunits that form the CK2 holoenzyme.

 

2)     Some parts of the manuscript seem a summary of salient points of diverse publications, sometimes not even explained, which are not very connected to each other. For examples, see lines 51-65, 285-295, 303-385.

3)     Section 4 is a simplified summary of a huge number of CK2 inhibitors. Since this review is focused on musculoskeletal disorders, it should be better to focus this section on the CK2 inhibitors used to treat these diseases and the potential use of other CK2 inhibitors that could be used, reporting and discussing the data obtained by various studies.

 

4)     Please, a better description of Fig. 5 should be done to make the figure clearer to the readers.

Comments on the Quality of English Language

Please see the above section.

Author Response

The authors are grateful for the valuable feedback and suggestions. We have revised the content of the review to improve the organization. Arrangement of the sections is now done to explain the significance of CK2 in musculoskeletal disorders initially and then it’s the molecular function. In the next section, we discuss the intricacies of CK2-substrate interactions. This section is followed by a summary of small molecular inhibitors of CK2 and their mechanism of action. Here, we have discussed a few examples of inhibition of CK2 in musculoskeletal disorders. In the final section, we discussed the concept behind the design of biomimetic peptides. We have discussed instances of two biomimetic peptides undergoing investigation for their use in Osteoarthritis and Osteoporosis, respectively.  The bibliography is updated by finding the most recent and relevant literature on the topics covered. We consulted a professional English language expert to edit the text for correct grammar.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

In the manuscript, the authors set out to analyse the involvement and possibility of exploiting different CK2 subunits as pharmacological targets in the treatment of musculoskeletal disorders. Although the topic may be of great interest, the authors were not able to argue the different aspects in a clear and scientifically sounding way. The different topics were treated in a confused and superficial manner, often failing to support the statements made with correct and timely cited bibliography. The first two paragraphs sound like a list of concepts that are not commented on. The rest of the review would also need to be completely reorganised/rewritten in order to make the different topics clearer. The reading of the manuscript is made even heavier by a grammatically incorrect use of English language that requires a deep and careful editing.

Comments on the Quality of English Language  

 

English language and style is very poor and needs a deep and extensive editing. Sometimes it is very difficult to identify subject and/or object in the sentence as well as follow the correct meaning of some statements. I suggest a careful check of English language and style after a complete rewriting process of the manuscript

Author Response

We have removed the term multiformity from the title. It is replaced with ‘Pleiotropy’. We intended to showcase the complexity of CK2 and used this widely accepted term for that purpose.

The acronym and name of the kinase, which is obsolete, have been corrected. We thank the reviewers for bringing it to our notice.

The new approach involves understanding important CK2-substrate interactions for pathological changes and using interfering peptides to correct those. We have explained the term ‘new approach’ in more detail.

What do the authors mean by “versatile kinase”? Furthermore, the authors define CK2 as a “master regulator of biochemical processes.” This definition seems too strong for the kinase that usually acts as a “lateral player” of diverse pathways, but overall, it is not clear which are the biochemical processes mentioned by the authors.

The versatility of CK2 is explained with the help of a summarized list in the introduction (lines 29-42). We have corrected the previous definition of kinase as a master regulator to the lateral player. We have enlisted biochemical pathways that CK2 regulates.

Please, the authors may explain what they mean by a “lucrative strategy” in relation to CK2  targeting in musculoskeletal diseases. Please, review the text between lines 67 and 70, because the content is not clear.

We have removed the word lucrative strategy. The content between lines 67-70 is explained in more detail.

How can authors define a mechanism of action of ATP-competitive inhibitors “generalized rather than disease specific”? Generally, drugs such as kinase inhibitors are not designed for a specific disease, but to inhibit a specific target involved in a disease of interest, and it is not the case of only ATP-competitive inhibitors such as CX-4945, because the CIGB300 peptide was not designed for specific disorders, but to potentially target different CK2 substrates that could be important in multiple diseases.

These statements are changed. We intended to explain the difference between inhibition of CK2 catalytic activity and specific substrate interactions with CK2.

It is not correct to use the terms “heterogenous” and “homogenous” in relation to the CK2 subunits that form the CK2 holoenzyme.

We agree these terms have been removed.

2)     Some parts of the manuscript seem a summary of salient points of diverse publications, sometimes not even explained, which are not very connected to each other. For examples, see lines 51-65, 285-295, 303-385.

We have expanded the explanation for these sections.

For lines 51-65, in the previous version, this paragraph was intended to explain the role of metabolic dysregulation in musculoskeletal disorders. We have re-arranged this part of the review. The study of CK2 in musculoskeletal disorders and its regulatory role in metabolic regulation is explained with examples and explanation in the introduction.

For lines 285-295, This paragraph was intended to explain the mechanism of action of dual substrate inhibitors. In the previous version of the review, there was a lack of explanation about why other kinases are targeted with CK2. Now, we have added details about that part and rearranged the paragraph.

For lines 303-385, the content within these lines in the previous version discussed the implication of CK2 in musculoskeletal diseases. However, a general description of pathological changes was not given. This has made the understanding of the role of CK2 in these disorders difficult. In the current version, we have explained the general features of each disease. This has helped us better explain the dysregulation of CK2 as a cause for the symptoms of these diseases.

3)     Section 4 is a simplified summary of a huge number of CK2 inhibitors. Since this review is focused on musculoskeletal disorders, it should be better to focus this section on the CK2 inhibitors used to treat these diseases and the potential use of other CK2 inhibitors that could be used, reporting and discussing the data obtained by various studies.

We are thankful to the reviewer for their suggestion. We have added examples of CK2 inhibition in musculoskeletal disorders, specifically in this section. However, there are fewer examples where CK2 inhibitors are used to treat these disorders.

4)     Please, a better description of Fig. 5 should be done to make the figure clearer to the readers.

We have changed the description for Fig. 5.  This figure summarizes the current advances in CK2 inhibitors and the aspects to be addressed by upcoming drugs targeting CK2-substrate interactions.

We have removed Figure 1 from the previous version. It was removed due to re-arrangement of the sections and repetitive nature of the data included in figure.

We added the following content to make the review more comprehensive. We thank the reviewer again for their valuable suggestions, which helped us make these additions.

Line 83-92: We discuss the meaning of the ‘Novel’ approach. In this review, we are discussing two examples of biomimetic peptides that target specific CK2-substrate interactions. These peptides re-direct cellular pathways to restore homeostasis within the affected cells. These peptides are undergoing investigation for their use in the treatment of Osteoarthritis and Osteoporosis. This approach is introduced as a disease-modifying approach within these lines in the introduction.

Lines102-107: We have discussed the mechanism of action of small molecular CK2 inhibitors in section 3. Here, in these lines, is a justification for discussing the mechanism of action. It is for the possibility of re-purposing CK2 inhibitors for the treatment of musculoskeletal disorders.

Lines 115-144: We have introduced role of CK2 in musculoskeletal system specifically. The concept of interrelatedness of metabolic processes and implication of their dysregulation is explained in brief.

Lines 146-164: Pathological changes in Rheumatoid arthritis (RA), which are relevant to the function of CK2, are explained. This helped explain the implications of CK2 in RA.

Lines 174-184: Pathological changes in Osteoarthritis (OA), which are relevant to the function of CK2, are explained. This helped explain the implications of CK2 in OA.

Lines 215-232: The process of Bone fracture healing is described. Defects in fracture healing due to senescence are explained. This helped explain the dysregulation of CK2 in senescence and defects in bone healing.

Lines 326-332: The molecular structure of CK2 is explained. In section 2, we have discussed the function of Ck2 and the role of individual subunits. A brief description of the molecular structure of CK2 has helped us provide a background.

Lines 365-383 : The role of the CK2α subunit in skeletal muscle development is explained with the help of an example. This is an additional example for section 2.2, where the role of CK2 subunits is discussed.

Lines 437: CK2 inhibitor Silmitasertib (CX-4945) is a highly specific inhibitor of CK2. In the previous version, we had not included this information.

Reviewer 3 Report

Comments and Suggestions for Authors

The abstract appears to be of potential interest to the scientific community, particularly those focused on cell biology, oncology, and musculoskeletal disorders. The abstract provides a comprehensive overview, and researchers in relevant fields may find it valuable for further investigation and exploration of therapeutic opportunities.

Concerning the introduction, the content is scientifically sound, but refining the writing style and addressing the mentioned points could improve the overall quality of the passage.

From the beginning of the introduction section:

1.      Consider rephrasing for smoother transitions between sentences. For example, the transition between the paragraph discussing Osteoporosis and the introduction of Protein kinase CK2 could be improved for better coherence.

2.      Check for sentence structure and consider breaking down long sentences into shorter ones. This can improve readability and make the information more digestible.

3.      Use consistent formatting for citations (e.g., "was studied2" could be revised to "was studied" with a proper citation format).

4.      The phrase "lateral player" is mentioned multiple times. While it may be a specific term in the context, consider providing a brief explanation or using alternative terminology to avoid potential confusion for readers who may not be familiar with the term.

From Line 45.

1.      Consider breaking down some of the longer sentences for improved readability. For example, the sentence starting with "The kinetics of holoenzyme formation..." could be divided into two sentences to enhance clarity.

2.      Ensure consistent use of terminology. In the first paragraph, the catalytic subunits are referred to as α and α', while in the second paragraph, they are mentioned as α and α’. Consistency in notation can improve clarity.

3.      Consider providing a brief explanation or definition for terms like "holoenzyme" to ensure that readers without specialized knowledge can follow the content more easily.

4.      The sentence starting with "Controlling the inhibition of CK2 activity..." is quite complex. Consider breaking it down into shorter sentences for better comprehension.

5.      In the last paragraph, consider rephrasing "Focusing on specific CK2-substrate interaction will help bring a pathology-tailored approach." for improved clarity. Specify how this approach may benefit musculoskeletal disorders.

At the end of the introductive section, the passage clearly outlines the challenges in drug development, particularly the low success rate in moving candidate molecules from preclinical studies to clinical use

Line 172. Provide number of paragraph or sub-paragraph.

In my opinion, Status of clinical application in Table 1 should be synthetized.

Same observation for Table 2.

Overall, the Discussion section is coherent and provides a comprehensive overview of the topic. However, the conclusion section together with further perspectives is missing.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

We read with interest the article by Pandit et al discussing the role of CK2 in Musculoskeletal Disorders which is timely and informative to the field of kinases.

there are a few comments, 

the paper seems to be a resubmission having the yellow highlights and they are a great fit to the sections they are added to.

one major point to take is that many sections are running with no references, which is weird and requires corrections, similarly a whole paragraph is written with one reference which raises the issue of limited referencing and plagiarism. we ask the authors to check the manuscript

 

The other comment is related to the figures which are somehow low in resolution and the writing is small, these need to be fixed. Other than this, the study runs smoothly.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The article is suitable for publication in this new version.

Comments on the Quality of English Language

English language need a minor check.

Author Response

We appreciate the valuable feedback for improving our review!

Reviewer 2 Report

Comments and Suggestions for Authors

Unfortunately, in the revised version of the manuscrit the Authors were not able to amend and improve the previous one. The upgrade made by the Authors concerns only some introductive sentence about the different pathologies but all the paragraphs still require a complete reorganization/rewriting also from a conceptual point of view.

Comments on the Quality of English Language

English language and style is very poor and needs a deep and extensive editing. Sometimes it is very difficult to identify subject and/or object in the sentence as well as follow the correct meaning of some statements. I suggest a careful check of English language and style after a complete rewriting process of the manuscript

Author Response

We appreciate the feedback and suggestions by the reviewer. These have helped us immensely to understand possible improvements.

We have carefully restructured the content of the review. We have also elaborated on the key concepts.

The English language center and writing center present on the university campus have been timely consulted during the revision of the review. We have strived our best to present the content in easy-to-understand yet scientifically appropriate language.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper proposed to this Journal is entitled “Scoping Pleiotropy of CK2 in Musculoskeletal Disorders for a Novel Targeting Approach”.

The abstract appears to be correct and well-written. It discusses the role of Protein kinase CK2 (CK2) in cellular processes, highlighting its influence on the cellular phosphoproteome and its regulation of various pathways.

Introduction provides a comprehensive overview of musculoskeletal disorders, emphasizing their impact on skeletal muscle, bone, cartilage, and connective tissue. It introduces specific disorders such as Osteoporosis (OP), Osteoarthritis (OA), and Rheumatoid arthritis (RA), highlighting their implications, chronic pain, and their status as costly co-morbidities. However, as an overall comment on the introduction, authors may condense certain sentences to maintain a concise and focused narrative.

Moreover, authors could explicitly state the significance of investigating CK2 in musculoskeletal disorders, emphasizing its potential as a target for therapeutic interventions and the need for a nuanced understanding of its complex role.

Finally, please check the consistency of references cited in the introduction.

Try to improve the focus of the written parts in Figure 1 and 2.