GABA_A-ρ Receptors in the CNS: Their Functional, Pharmacological, and Structural Properties in Neurons and Astroglia

Round 1

Reviewer 1 Report

Reviewer Evaluation of GABA_A-ρ Receptors and their Expression in Astroglia by Rosas-Arellano and colleagues.

This short review provides a basic overview of the molecular and functional properties of GABA_A-ρ subunit containing receptors in astrocytes and neurons. I am not aware of any recent and concise reviews on this subject. The review is also quite timely because astrocytes are in the news with a recent publication of new data supporting their role in gliotransmission (see de Ceglia, R., Ledonne, A., Litvin, D.G. et al. Specialized astrocytes mediate glutamatergic gliotransmission in the CNS. Nature (2023). https://doi.org/10.1038/s41586-023-06502-w.

The paper is reasonably well written but contains some verbiage, which needs tidying up. Here are some examples of repetition in the first two paragraphs.

‘GABA …. known as pentameric proteins .. modulated by binding effector molecules such …. GABA_A receptor is an ion channel member of the pentameric ligand-gated ion channel (pLGIC) superfamily, a family of channels that opens transiently and whose inhibitory members induce the inhibition … consists of pentameric combinations coordinate differential neural inhibition …’

And in paragraph 2 we again read that ‘GABA activity is an essential inhibitory resource ..’

Lines 102-108 more repetition: ‘… involvement of GABA_A-ρ receptors in sleep-waking behavior and antinociception …. learning … and also to investigate memory enhancers … but also …. pain perception, sleep-waking behavior, learning and memory ….’

Section 3. ‘Trafficking and scaffold proteins of GABAA-ρ receptors’. It’s unclear, at least to me, if this section is describing data from neurons, glial cells or both. Could the authors please clarify this for readers.

No further comments.

Author Response

Response to reviewer 1

Thank you very much for taking the time to review our manuscript. Please find the detailed responses below and the corresponding edition highlighted in red

• This short review provides a basic overview of the molecular and functional properties of GABAA-ρ subunit containing receptors in astrocytes and neurons. I am not aware of any recent and concise reviews on this subject. The review is also quite timely because astrocytes are in the news with a recent publication of new data supporting their role in gliotransmission (see de Ceglia, R., Ledonne, A., Litvin, D.G. et al. Specialized astrocytes mediate glutamatergic gliotransmission in the CNS. Nature (2023). https://doi.org/10.1038/s41586-023-06502-w.

Thank you for your valuable input, we incorporated a brief paragraph into the discussion to update our manuscript (lines 266-269, reference 105).

• The paper is reasonably well written but contains some verbiage, which needs tidying up. Here are some examples of repetition in the first two paragraphs.GABA …. known as pentameric proteins .. modulated by binding effector molecules such …. GABAA receptor is an ion channel member of the pentameric ligand-gated ion channel (pLGIC) superfamily, a family of channels that opens transiently and whose inhibitory members induce the inhibition … consists of pentameric combinations coordinate differential neural inhibition …’And in paragraph 2 we again read that ‘GABA activity is an essential inhibitory resource ..’Lines 102-108 more repetition: ‘… involvement of GABAA-ρ receptors in sleep-waking behavior and antinociception …. learning … and also to investigate memory enhancers … but also …. pain perception, sleep-waking behavior, learning and memory ….’

Thank you for your observations, we reviewed the verbiage and tied up the edition of the manuscript, avoiding the repetitions in the mentioned paragraphs. Section 2: lines 39-42; 45-46; 61-63, 74-77; 80-83; 86-87; 90-94; 105-107.

• Section 3. ‘Trafficking and scaffold proteins of GABAA-ρ receptors’. It’s unclear, at least to me, if this section is describing data from neurons, glial cells or both. Could the authors please clarify this for readers.

We reviewed this section and added a paragraph describing data from neurons and astrocytes to clarify the information as requested by the reviewer. Thank you for your suggestion (lines 120-126).

Reviewer 2 Report

Ref: GABAA receptors and their expression in Astroglia

The purpose of this review manuscript is to inform readers about GABA_ᴬ-ρ receptors and their expression in astroglia. Additionally, it seeks to assess the current state of knowledge in the subject. The authors' specific points are missing in the abstract and introduction.

The manuscript needs a major revision.

Comments to the authors:

In certain areas as mentioned below in the comments to the authors that needs to be addressed.

1.    The abstract is laconic and does not properly articulate the aim of the review. Authors are required to revise the abstract to emphasize the significance of GABAA receptors and their associated disorders. End with conclusion of the review.

2.    Introduction: The introductory section is satisfactory up until line 29, where additional elaboration is provided regarding the structural aspects of GABAA receptors. The content that should be included in the second paragraph, along with a revised heading. Additional information regarding the significance of GABAA receptors in Astroglia and their involvement in the regulation of neuronal activity and maintenance of the excitation-inhibition balance in the brain can be included after line number 29 in the introduction.

3.    Figure 1. “Molecular structure model of the human GABAA-ρ1 receptor”: is not clear and correctly labeled.

4.    The citation for the coating reference (Hibbs and Gouaux, 2011) in Figure 1 is incomplete in the author's references section of the review manuscript.

5.    “GABAA-ρ Receptors” heading 2: Rewrite the title of heading, for example. Structural properties, Characterization, and Functions of GABAA-ρ Receptors.

6.    In section ‘4’ GABAA-ρ receptors in Astroglia: This section of the manuscript is insufficient in describing Astroglia and how it functions in neurodegenerative illnesses, as well as in describing the disorders' molecular mechanisms. The authors should expand on the role of GABA receptors in illnesses and discuss both early and more recent research to clarify the relationship between Astroglia and the GABA network.

7.    In the same section, describe how the network of GABAA receptors is expressed in Astroglia with the aid of a diagram. Or describe the molecular processes that lead to the expression of these receptors and outline the factors that might influence their stimulation.

8.    The conclusion should be revised to reflect the importance of Astroglia GABA receptors for understanding and treating neurological diseases as well as for modulating neuronal activity. It should also provide a brief summary of the major points made in the review paper. Emphasize the significance of this type of research for the future. 

The manuscript needs extensive revision for language and grammar.

Author Response

Thank you very much for taking the time to review our manuscript. Please find the detailed responses below and the corresponding edition highlighted in red.

1. The abstract is laconic and does not properly articulate the aim of the review. Authors are required to revise the abstract to emphasize the significance of GABAA receptors and their associated disorders. End with conclusion of the review.

We agree with the reviewer and have edited the abstract according to the recommendations. The significance of GABA_A-ρ receptors in E/I balance, as well as their relevance in neurodevelopment and disease are now highlighted. These points are incorporated into the aim of the review (lines 19-21).

2. Introduction: The introductory section is satisfactory up until line 29, where additional elaboration is provided regarding the structural aspects of GABAA receptors. The content that should be included in the second paragraph, along with a revised heading. Additional information regarding the significance of GABAA receptors in Astroglia and their involvement in the regulation of neuronal activity and maintenance of the excitation-inhibition balance in the brain can be included after line number 29 in the introduction.

Thank you for your comments. We now include a paragraph describing the significance of GABA-A receptors in astroglia and neuron-glia communication to achieve the required excitatory/inhibitory balance (lines 30-37). This paragraph is reinforced with the addition of figure 4 in the discussion section.

3. Figure 1. “Molecular structure model of the human GABAA-ρ1 receptor”: is not clear and correctly labeled.

Thank you, we edited the figure legend according to the recommendations.

4. The citation for the coating reference (Hibbs and Gouaux, 2011) in Figure 1 is incomplete in the author's references section of the review manuscript.

The reference for Figure was updated and correctly cited in the references: Cowgill et al., 2023. Additionally we added a new paragraph related to the recently published structure of the GABAA-ρ Receptor (lines 107-114).

5. “GABAA-ρ Receptors” heading 2: Rewrite the title of heading, for example. Structural properties, Characterization, and Functions of GABAA-ρ Receptors.

Thank you for the recommendation, we change the title of the manuscript to: “GABA_A-r RECEPTORS IN CNS: Functional, pharmacological, and structural properties in neurons and astroglia” (lines 2-3).

6. In section ‘4’ GABAA-ρ receptors in Astroglia: This section of the manuscript is insufficient in describing Astroglia and how it functions in neurodegenerative illnesses, as well as in describing the disorders' molecular mechanisms. The authors should expand on the role of GABA receptors in illnesses and discuss both early and more recent research to clarify the relationship between Astroglia and the GABA network.

We appreciate your input. We added a new paragraph to describe the role of astroglial in the GABA network at the beginning of the Discussion. Briefly, we discuss about the interneuron-astrocyte communication through GABAergic signaling, highlighting the role of astroglial GABA_A receptors in extrasynaptic tonic currents and gliotransmission (lines 229-236). We also added another paragraph and discuss about the importance of these receptors in early postnatal development and reduced expression in a preclinic model of autism. We also included a recent study exploring astroglial GABA_A-ρ receptors as therapeutical target for stroke. Finally, we close the discussion with a recent study by Ceglia et al., 2023 showing that specific populations of astrocytes (molecularly identified with scRNAseq studies) contribute to LTP-strengthening and hippocampal memories, hyperexcitation during seizures and overactivation in Parkinson disease after genetic deletion of VGLUT. Thus, the GABA_A-ρ astroglial population awaits examination to establish the precise inhibitory synapse-astrocyte organization at molecular and functional level (lines 253-270).

7. In the same section, describe how the network of GABAA receptors is expressed in Astroglia with the aid of a diagram. Or describe the molecular processes that lead to the expression of these receptors and outline the factors that might influence their stimulation.

Besides the paragraphs added to the discussion we included a new figure that summarize GABA-A subunits expressed in neurons and astrocytes. The figure also recapitulates how astrocytes.expressing GABA-A receptors modulate synaptic communication (figure legend, lines 239-251).

8. The conclusion should be revised to reflect the importance of Astroglia GABA receptors for understanding and treating neurological diseases as well as for modulating neuronal activity. It should also provide a brief summary of the major points made in the review paper. Emphasize the significance of this type of research for the future. 

The importance of astroglial GABA-A receptors is highlighted in the discussion as previously mentioned. However, we close the review with a brief conclusion recapitulating their relevance in tonic currents and neurodevelopment but mentioning that further studies are required to fully understand their role in physiology and pathology of CNS (lines 273-276).

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have satisfactorily addressed all suggestions in the revised review manuscript.

The manuscript needs editing for grammar and syntax.