Review Reports - Systematic Review of the Role of Kv4.x Potassium Channels in Neurodegenerative Diseases: Implications for Neuronal Excitability and Therapeutic Modulation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Reviewer Comments

Overall Evaluation

This manuscript provides a comprehensive and systematic review of the roles of Kv4.1/Kv4.2/Kv4.3 channels and their auxiliary subunits (e.g., DPP6, KChIP2) in various neurodegenerative diseases, including Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD), spinocerebellar ataxias (SCA), and prion diseases. The review is timely and valuable, as it represents one of the first attempts to systematically integrate scattered findings on Kv4 channel dysfunction in neurodegeneration. The focus on auxiliary subunits and post-translational modifications in addition to pore-forming subunits is a particular strength that adds novelty to the manuscript.

However, despite being presented as a “systematic review,” the manuscript often reads more like a collection of individual study results. The discussion of overarching mechanisms, causal relationships, and clinical implications remains underdeveloped.

Strengths

Comprehensive synthesis

The review covers a broad range of diseases (AD, PD, ALS, SCA, prionopathies) and compiles both genetic and functional evidence, making it a useful reference for researchers in the field.
Focus on auxiliary subunits
The discussion of modulatory proteins such as DPP6 and KChIP2, and their role in channel regulation and disease, is a novel and valuable contribution.

Systematic data presentation

The inclusion of tables summarizing study designs, models, mutations, and functional outcomes provides clarity and enhances the review’s usability.

Major Concerns and Recommendations

Organization and interpretation of results
The current Results section largely reproduces detailed findings from individual studies, which resembles an original research Results section rather than a synthesized review.

The discussion should highlight shared mechanisms, such as Kv4.2 downregulation leading to neuronal hyperexcitability, and provide a comparative view across diseases.

In AD, the paradoxical observations—acute Aβ exposure increasing Kv4 activity vs. chronic models showing Kv4 downregulation—are important and merit a dedicated integrative discussion.
Recommendation: Consider reorganizing disease-specific sections into a consistent structure (“Summary of findings → Kv4 functional changes and pathophysiological implications → Therapeutic relevance”) and shift detailed data/variant lists to the Supplementary Table. Including a schematic figure showing dynamic Kv4 changes along disease progression (time axis) and common regulatory nodes (auxiliary subunits, ERK, CaMKII, PKC, PKA, GSK-3) would enhance clarity and impact.

Clinical relevance

While the conclusion highlights Kv4 channels as potential therapeutic targets, the discussion remains conceptual.
Some studies suggest effects of existing drugs (e.g., 4-aminopyridine, levetiracetam, cannabinoids, antioxidants). More explicit discussion of mechanistic rationale, translational perspectives, and current clinical trial status would strengthen the manuscript’s applied significance.
Causality and mechanistic interpretation
The review often describes changes in Kv4 expression or function without clarifying whether these alterations are primary drivers of pathology or secondary consequences of neurodegeneration.
Recommendation: The authors should more explicitly discuss the causal directionality, as well as the current limitations in evidence.

Redundancy and textual clarity

Several disease subsections are lengthy and partly repetitive (e.g., multiple descriptions of Kv4.2 downregulation in ALS).
Some parts resemble results reporting rather than concise review synthesis.
Additionally, in the author list, the final “and” before the last author appears redundant and should be corrected.
Recommendation: Streamline repetitive descriptions, emphasize synthesis over enumeration, and ensure accurate formatting of author information.

Structure–function relationship

The manuscript provides only limited discussion of the direct link between Kv4 channel structural determinants (e.g., pore architecture, auxiliary subunit binding, post-translational modifications) and their functional consequences for neuronal excitability. A dedicated subsection that integrates structural and functional insights, and relates these to disease mechanisms, would substantially strengthen the review.

Author Response

Reviewer #1

Overall Evaluation

This manuscript provides a comprehensive and systematic review of the roles of Kv4.1/Kv4.2/Kv4.3 channels and their auxiliary subunits (e.g., DPP6, KChIP2) in various neurodegenerative diseases, including Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson’s disease (PD), spinocerebellar ataxias (SCA), and prion diseases. The review is timely and valuable, as it represents one of the first attempts to systematically integrate scattered findings on Kv4 channel dysfunction in neurodegeneration. The focus on auxiliary subunits and post-translational modifications in addition to pore-forming subunits is a particular strength that adds novelty to the manuscript.

Thank you so much. I thank the reviewer for their kind words.

However, despite being presented as a “systematic review,” the manuscript often reads more like a collection of individual study results. The discussion of overarching mechanisms, causal relationships, and clinical implications remains underdeveloped.

The authors have restructured the entire Table 2, reducing the content, simplifying the results, and eliminating redundant terms. In addition, the authors have created a new results section that presents a comprehensive comparison (Text highlighted in green).

Strengths

Comprehensive synthesis

The review covers a broad range of diseases (AD, PD, ALS, SCA, prionopathies) and compiles both genetic and functional evidence, making it a useful reference for researchers in the field.
Focus on auxiliary subunits
The discussion of modulatory proteins such as DPP6 and KChIP2, and their role in channel regulation and disease, is a novel and valuable contribution.

We thank the reviewer for highlighting these strengths. Indeed, our synthesis intentionally focused on auxiliary subunits that directly interact with Kv4 channels, such as DPP6 and KChIP2, given their well-established roles in modulating channel trafficking and gating. By contrast, components acting indirectly, such as the dendritic localization signal (DLS, an mRNA element), were not included in the scope of this review. This focus ensured that the discussion remained centered on proteins with direct structural and functional influence on Kv4 channel complexes.

Systematic data presentation

The inclusion of tables summarizing study designs, models, mutations, and functional outcomes provides clarity and enhances the review’s usability.

We thank the reviewer for this positive assessment. As noted, we aimed to present the data systematically through tables that summarize study designs, models, mutations, and functional outcomes. Importantly, within the wide spectrum of central nervous system disorders, we selected only those that reflect neurodegenerative disease models, to maintain a focused and clinically relevant scope.

Major Concerns and Recommendations

Organization and interpretation of results

We appreciate the reviewer’s concern regarding the organization and interpretation of results. In the revised manuscript, we created a new subsection that explicitly separates disorders in which Kv4 dysfunction is primary from those in which it is secondary. Specifically, spinocerebellar ataxia type 19/22 is driven by pathogenic KCND3 (Kv4.3) variants, whereas in AD, PD, ALS, and prionopathies Kv4 alterations typically involve Kv4.2 and/or Kv4.3 as secondary changes linked to upstream drivers (Aβ/tau, α-synuclein, Ca²⁺ dysregulation, oxidative stress). In prion diseases, native prion protein (PrP^C) and DPP6 modulate Kv4.2; pathogenic prion variants (e.g., GSS forms) disrupt this interaction and reduce I_a, contributing to hyperexcitability. This framing clarifies disease-specific mechanisms while emphasizing the central roles of Kv4.2 and Kv4.3 across conditions.

The current Results section largely reproduces detailed findings from individual studies, which resembles an original research Results section rather than a synthesized review.

A new section has been created that collects the results together. In addition, a new table (Table 2) has been created to know the frequencies of Kv4.x alterations and the different types of diseases in the total of 40 results.

The discussion should highlight shared mechanisms, such as Kv4.2 downregulation leading to neuronal hyperexcitability, and provide a comparative view across diseases.

A new schematic timeline with nodes, called Figure 3, has also been presented and included at the end of the discussion to address commonalities between diseases and therapeutic utility. Figure 3 discusses the results of a new table (Table 2) introduced in the Results section.

In AD, the paradoxical observations—acute Aβ exposure increasing Kv4 activity vs. chronic models showing Kv4 downregulation—are important and merit a dedicated integrative discussion.

We thank the reviewer for this important observation. In the revised manuscript (lines 516–526), we now provide a dedicated integrative discussion addressing the paradoxical findings in AD models. Acute application of Aβ in cultured hippocampal or granule cells, often in commercial or primary preparations, has been shown to transiently enhance Kv4.2 activity, which may reflect early compensatory responses. In contrast, chronic transgenic models (e.g., hAPP_J20, hAPP/PS1, Tg2576, 3xTg-AD) that progressively accumulate Aβ and, in some cases, tau pathology, consistently exhibit Kv4 downregulation and dysfunction. APP knockout mice (AβPP-/-), which completely lack amyloid, serve as negative controls and show preserved Kv4.2 function, underscoring that Kv4 dysregulation in AD is driven by the pathological presence of Aβ and tau rather than the absence of APP. Taken together, these findings emphasize the need to interpret Kv4 alterations in the context of disease stage, model type, and duration of pathology.

Recommendation: Consider reorganizing disease-specific sections into a consistent structure (“Summary of findings → Kv4 functional changes and pathophysiological implications → Therapeutic relevance”) and shift detailed data/variant lists to the Supplementary Table. Including a schematic figure showing dynamic Kv4 changes along disease progression (time axis) and common regulatory nodes (auxiliary subunits, ERK, CaMKII, PKC, PKA, GSK-3) would enhance clarity and impact.

We thank the reviewer for this valuable recommendation. In the revised version, we have addressed this point by adding a new integrative section at the end of the Discussion. This section follows the suggested structure and synthesizes the main conclusions across disease groups. In addition, we have included a new schematic figure (Figure 4) of our results found that summarizes dynamic Kv4 alterations along disease progression (time axis) and highlights common regulatory nodes such as auxiliary subunits (DPP6, KChIP2) and kinases (ERK, CaMKII, PKC, PKA, GSK-3). This integrative overview complements the disease-specific results and enhances the clarity and impact of the manuscript.

Clinical relevance

While the conclusion highlights Kv4 channels as potential therapeutic targets, the discussion remains conceptual.

We appreciate the reviewer’s observation. Our intention was to provide a conceptual synthesis to integrate heterogeneous findings across multiple diseases. However, the discussion is not exclusively theoretical. It is grounded in experimental evidence from animal models, cell systems, and pharmacological studies. In the revised manuscript, we emphasize this connection more explicitly by citing where Kv4 modulation has been directly tested. For instance, 4-aminopyridine has been evaluated in ataxia patients and mouse models, levetiracetam has been reported to rescue Kv4.2 dysfunction in AD models, and antioxidants (Trolox, GSH) or cannabinoids have been shown to restore Kv4-related currents in ALS preparations. By including these cases, we highlight that Kv4 channels are not only of conceptual interest but also represent experimentally validated therapeutic targets with translational potential.

Some studies suggest effects of existing drugs (e.g., 4-aminopyridine, levetiracetam, cannabinoids, antioxidants). More explicit discussion of mechanistic rationale, translational perspectives, and current clinical trial status would strengthen the manuscript’s applied significance.

We thank the reviewer for this insightful comment. In the revised version, we have expanded the Discussion to include more explicit mention of the mechanistic rationale and translational perspectives of existing drugs that interact with Kv4 channels. For example, 4-aminopyridine (4-AP) is a broad-spectrum potassium channel blocker that enhances excitability and has been tested clinically in spinocerebellar ataxia, where improvement of cerebellar symptoms supports the relevance of Kv4.3 dysfunction. Levetiracetam has been shown to restore Kv4.2-mediated currents in AD models, linking its antiepileptic mechanism with potential disease-modifying actions in dementia. Cannabinoids and antioxidants such as Trolox and GSH attenuate oxidative stress and calcium dysregulation, thereby rescuing Kv4.2 function in ALS-related preparations. While these studies remain largely preclinical, some (e.g., 4-AP in ataxia) have already entered clinical trials, underscoring the translational potential of targeting Kv4 dysfunction. We believe this expanded discussion now provides a stronger bridge between mechanistic evidence and therapeutic perspectives.

Causality and mechanistic interpretation

It has been specified in the text.

The review often describes changes in Kv4 expression or function without clarifying whether these alterations are primary drivers of pathology or secondary consequences of neurodegeneration.

It has been specified in the text.

Recommendation: The authors should more explicitly discuss the causal directionality, as well as the current limitations in evidence.

It has been specified in the text. The limitations of physiology between humans and animal and in vitro models have also been included.

Redundancy and textual clarity

Several disease subsections are lengthy and partly repetitive (e.g., multiple descriptions of Kv4.2 downregulation in ALS).

We thank the reviewer for this observation. We agree that some subsections contained overlapping descriptions, particularly regarding Kv4.2 downregulation in ALS and AD. In the revised manuscript, these redundancies have been reduced, and the results are now presented in a more concise and structured manner. To further improve clarity, the detailed descriptions of individual studies were synthesized in the results table, which was also streamlined as suggested by the other reviewer. This approach allows us to retain completeness while avoiding unnecessary repetition in the main text.

Some parts resemble results reporting rather than concise review synthesis.

We appreciate the reviewer’s comment. In the revised manuscript, we have synthesized the results more concisely to improve readability while still maintaining the principle of transparency regarding the available evidence. Our goal was to provide a balanced overview that avoids excessive repetition yet preserves enough detail for readers to assess the strength and consistency of the findings. To achieve this, we condensed redundant descriptions in the main text and relied more on the results table to present detailed study-level data. We believe this approach now strikes an appropriate balance between synthesis and transparency.

Additionally, in the author list, the final “and” before the last author appears redundant and should be corrected.

Corrected.

Recommendation: Streamline repetitive descriptions, emphasize synthesis over enumeration, and ensure accurate formatting of author information.

We thank the reviewer for his recommendations.

Structure–function relationship

The manuscript provides only limited discussion of the direct link between Kv4 channel structural determinants (e.g., pore architecture, auxiliary subunit binding, post-translational modifications) and their functional consequences for neuronal excitability. A dedicated subsection that integrates structural and functional insights, and relates these to disease mechanisms, would substantially strengthen the review.

We thank the reviewer for this suggestion. In response, we expanded the discussion to integrate how auxiliary subunits influence pharmacology. Specifically, recent evidence shows that DPP6 and MiRP1 alter the modulation of Kv4.3/KChIP2 channels by the small-molecule ligand IQM-266, highlighting that structural determinants and accessory proteins jointly define both channel function and drug responsiveness.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Line 6. The text “^†,*” appears to apply to Domínguez-Vías. Delete “and”. Please correct this.

Line 29. The phrasing “Eligible studies reported on the….”is awkward. Please rephrase this sentence.

Lines 35, 38. Please introduce the terms “KCND3”, “DPP6”, and “KChIP2”.

Lines 34-35. It the sentence to be interpreted as reduced Kv4.1 and Kv.4.2 currents? As written, it could be interpreted as a ratio. Please clarify.

Line 50. Please replace the term “ionic channels” with “ion channels.”

Line 53. By “alteration”, do the authors mean structural alterations?

Line 58. Please introduce the term potassium ions “K⁺”. Are A currents inward currents?

Lines 60-63. This is a run-on sentence. Please break it up into more than one sentence.

Line 61. Please consider the phrasing “Pore-forming subunits, termed α-subunits, assemble…”

Lines 75-77. If Kv4.2 is the only subunit expressed in oocytes, how is one to conclude that it contributes to neuronal excitability and synaptic signaling?

Line 88-89. Please introduce the terms “NCS-1” and “Ca²⁺”.

Line 95-96. Please introduce the terms “PSD-95” and “PDZ”.

Line 102. Please replace “potassium” with “potassium channels”.

Line 104. DLS does not appear in the figure. It can be removed from the legend.

Line 106. Please replace with “VSD: Voltage sensing domain”.

Lines 129-130. Consider this phrasing: “…pharmacological modulation of somatic or dendritic I_a (i.e., I_sa and I_to currents, respectively) could…”

Line 137. Please induce the term “NMDA”.

Line 143. Please introduce the terms “ERK”, “CaMKII”, “PKC”, and “PKA”.

Line 174. Please replace “Ia” with “I_a”.

Line 191. Please consider the phrasing “…dysfunction of Kv4.3 channels have been observed in…”.

Lines 216-218. Citations are needed here to support the statement, especially given that the authors claim this is a consistent result.

Lines 221-222. Please provide a better description of the model. For example, what is a 5×FAD model?

Line 225. Can the authors clarify what is meant by the “abnormal neuronal excitability characteristic of AD”? Are the authors referring to membrane potential in a certain population of neurons? It is unclear.

Line 230. Does “Kv4.3/Kv4.3” refer to a ratio?

Line 231. Please use “Ia” or “I_a” throughout. Please avoid alternating between them.

Lines 220-239. One limitation of several of the studies discussed in the observations were made in vitro in cells that are not relevant to AD, such as cerebellar neurons and HEK cells.

Line 254. Please introduce the term “APP”. In addition, a discussion of the different models is warranted to increase the clarity of interpretation of the findings.

Line 259. “Another key piece” of what? Please clarify.

Lines 279-280. Please delete “From the data collected”.

Line 281. Please change to “deletions or duplications”.

Lines 283-284. In the Table 1 legend, please provide a key to allow the reader to interpret the data in the table (e.g., the nucleotide and amino acid changes).

Line 305. Please delete the phrase “In this pathway”.

Lines 309. Is the expression of the protein downregulated in the plasma membrane and upregulated in the cellular compartments mentioned?

Line 313. Please introduce the term “RVF” on first use.

Line 361. Please introduce the term “GSS” on first use.

Line 373. Please introduce the term “GABAergic” on first use.

Table 2. The authors try to fit too much information in the table. The table might be improved with the increased use of acronyms in the table itself, being sure to define all acronyms in the footnote. The description of the findings should be more succinct. The degree of risk is included in Table 2 but a description of how risk of bias was determined does not appear until section 4.2. In addition, I did not observe any references in the text to the degree of risk provided in Table 2.

Lines 406-408. Please break this sentence into 2 sentences. Consider replacing with “…for timing their output. Therefore, mutations…”.

Lines 429-430. I’m not convinced that [81,83] suggest that Kv4 channels act as integrators of cellular stress signals, at least, based on the studies provided.

Line 434. The fact that in vitro and experimental models do not recapitulate the human disease condition should be stated more strongly.

Line 451. There is no such thing as a Parkinson’s mouse. Please rephrase.

Line 506. Introduce the term “CNS” on first use.