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Cibelli A, Mola MG, Saracino E, Barile B, Abbrescia P, Mogni G, Spray DC, Scemes E, Rossi A, Spennato D, Svelto M, Frigeri A, Benfenati V, Nicchia GP. Aquaporin-4 and transient receptor potential vanilloid 4 balance in early postnatal neurodevelopment. Glia 2024; 72:938-959. [PMID: 38362923 DOI: 10.1002/glia.24512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Revised: 01/15/2024] [Accepted: 01/19/2024] [Indexed: 02/17/2024]
Abstract
In the adult brain, the water channel aquaporin-4 (AQP4) is expressed in astrocyte endfoot, in supramolecular assemblies, called "Orthogonal Arrays of Particles" (OAPs) together with the transient receptor potential vanilloid 4 (TRPV4), finely regulating the cell volume. The present study aimed at investigating the contribution of AQP4 and TRPV4 to CNS early postnatal development using WT and AQP4 KO brain and retina and neuronal stem cells (NSCs), as an in vitro model of astrocyte differentiation. Western blot analysis showed that, differently from AQP4 and the glial cell markers, TRPV4 was downregulated during CNS development and NSC differentiation. Blue native/SDS-PAGE revealed that AQP4 progressively organized into OAPs throughout the entire differentiation process. Fluorescence quenching assay indicated that the speed of cell volume changes was time-related to NSC differentiation and functional to their migratory ability. Calcium imaging showed that the amplitude of TRPV4 Ca2+ transient is lower, and the dynamics are changed during differentiation and suppressed in AQP4 KO NSCs. Overall, these findings suggest that early postnatal neurodevelopment is subjected to temporally modulated water and Ca2+ dynamics likely to be those sustaining the biochemical and physiological mechanisms responsible for astrocyte differentiation during brain and retinal development.
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Affiliation(s)
- Antonio Cibelli
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Emanuela Saracino
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Barbara Barile
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Pasqua Abbrescia
- Department of Translational Biomedicine and Neuroscience, University of Bari Aldo Moro-Medical School, Bari, Italy
| | - Guido Mogni
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - David C Spray
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Eliana Scemes
- Department of Cell Biology and Anatomy, NY Medical College, Valhalla, New York, USA
| | - Andrea Rossi
- Genome Engineering and Model Development Lab (GEMD), IUF-Leibniz Research Institute for Environmental Medicine, Düsseldorf, Germany
| | - Diletta Spennato
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Frigeri
- Department of Translational Biomedicine and Neuroscience, University of Bari Aldo Moro-Medical School, Bari, Italy
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Valentina Benfenati
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
| | - Grazia Paola Nicchia
- Department of Biosciences, Biotechnology and Environment, University of Bari Aldo Moro, Bari, Italy
- Institute for Organic Synthesis and Photoreactivity (ISOF), National Research Council of Italy (CNR), Bologna, Italy
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, USA
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Pati R, Palazzo C, Valente O, Abbrescia P, Messina R, Surdo NC, Lefkimmiatis K, Signorelli F, Nicchia GP, Frigeri A. The Readthrough Isoform AQP4ex Is Constitutively Phosphorylated in the Perivascular Astrocyte Endfeet of Human Brain. Biomolecules 2022; 12:633. [PMID: 35625560 PMCID: PMC9138620 DOI: 10.3390/biom12050633] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 04/17/2022] [Accepted: 04/22/2022] [Indexed: 02/03/2023] Open
Abstract
AQP4ex is a recently discovered isoform of AQP4 generated by a translational readthrough mechanism. It is strongly expressed at the astrocyte perivascular endfeet as a component of the supramolecular membrane complex, commonly called orthogonal array of particles (OAP), together with the canonical isoforms M1 and M23 of AQP4. Previous site-directed mutagenesis experiments suggested the potential role of serine331 and serine335, located in the extended peptide of AQP4ex, in water channel activity by phosphorylation. In the present study we evaluated the effective phosphorylation of human AQP4ex. A small scale bioinformatic analysis indicated that only Ser335 is conserved in human, mouse and rat AQP4ex. The phosphorylation site of Ser335 was assessed through generation of phospho-specific antibodies in rabbits. Antibody specificity was first evaluated in binding phosphorylated peptide versus its unphosphorylated analog by ELISA, which was further confirmed by site-directed mutagenesis experiments. Western blot and immunofluorescence experiments revealed strong expression of phosphorylated AQP4ex (p-AQP4ex) in human brain and localization at the perivascular astrocyte endfeet in supramolecular assemblies identified by BN/PAGE experiments. All together, these data reveal, for the first time, the existence of a phosphorylated form of AQP4, at Ser335 in the extended sequence exclusive of AQP4ex. Therefore, we anticipate an important physiological role of p-AQP4ex in human brain water homeostasis.
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Affiliation(s)
- Roberta Pati
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (R.P.); (C.P.); (O.V.); (P.A.); (R.M.); (F.S.)
| | - Claudia Palazzo
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (R.P.); (C.P.); (O.V.); (P.A.); (R.M.); (F.S.)
| | - Onofrio Valente
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (R.P.); (C.P.); (O.V.); (P.A.); (R.M.); (F.S.)
| | - Pasqua Abbrescia
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (R.P.); (C.P.); (O.V.); (P.A.); (R.M.); (F.S.)
| | - Raffaella Messina
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (R.P.); (C.P.); (O.V.); (P.A.); (R.M.); (F.S.)
| | - Nicoletta Concetta Surdo
- Foundation for Advanced Biomedical Research, Veneto Institute of Molecular Medicine, 35129 Padova, Italy; (N.C.S.); (K.L.)
- Neuroscience Institute, National Research Council of Italy (CNR), 35129 Padova, Italy
| | - Konstantinos Lefkimmiatis
- Foundation for Advanced Biomedical Research, Veneto Institute of Molecular Medicine, 35129 Padova, Italy; (N.C.S.); (K.L.)
- Department of Molecular Medicine, University of Pavia, 27100 Pavia, Italy
| | - Francesco Signorelli
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (R.P.); (C.P.); (O.V.); (P.A.); (R.M.); (F.S.)
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnology and Biopharmaceutics, University of Bari Aldo Moro, 70124 Bari, Italy;
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 840 Kennedy Center, Bronx, NY 10461, USA
| | - Antonio Frigeri
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (R.P.); (C.P.); (O.V.); (P.A.); (R.M.); (F.S.)
- Dominick P. Purpura Department of Neuroscience, Albert Einstein College of Medicine, 840 Kennedy Center, Bronx, NY 10461, USA
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Valente O, Messina R, Ingravallo G, Bellitti E, Zimatore DS, de Gennaro L, Abbrescia P, Pati R, Palazzo C, Nicchia GP, Trojano M, Signorelli F, Frigeri A. Alteration of the translational readthrough isoform AQP4ex induces redistribution and downregulation of AQP4 in human glioblastoma. Cell Mol Life Sci 2022; 79:140. [PMID: 35187599 PMCID: PMC8858924 DOI: 10.1007/s00018-021-04123-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 12/21/2021] [Accepted: 12/29/2021] [Indexed: 11/03/2022]
Abstract
AbstractGlioblastoma multiforme (GBM) is characterized by a remarkable cellular and molecular heterogeneity that make the behavior of this tumor highly variable and resistant to therapy. In addition, the most serious clinical complication of GBM and other brain tumors is the development of vasogenic edema which dramatically increase the intracranial pressure. In the present study we evaluate the expression, supramolecular organization and spatial distribution of AQP4 and AQP4ex, the new readthrough isoform of AQP4, in relationship with the degree of vasogenic brain edema and tumor progression. To this purpose, tissue samples from regions of tumor core, peritumoral and non-infiltrated tissues of each GBM patient (n = 31) were analyzed. Immunofluorescence experiments revealed that the expression of AQP4ex was almost absent in tumoral regions while the canonical AQP4 isoforms appear mostly delocalized. In peritumoral tissues, AQP4 expression was found altered in those perivascular astrocyte processes where AQP4ex appeared reduced and partially delocalized. Protein expression levels measured by immunoblot showed that global AQP4 was reduced mainly in the tumor core. Notably, the relative amount of AQP4ex was more severely reduced starting from the peritumoral region. BN-PAGE experiments showed that the supramolecular organization of AQP4 is only partially affected in GBM. Edema assessment by magnetic resonance imaging revealed that the level of AQP4ex downregulation correlated with edema severity. Finally, the degree of BBB alteration, measured with sodium fluorescein content in GBM biopsies, correlated with the edema index and AQP4ex downregulation. Altogether these data suggest that the AQP4ex isoform is critical in the triggering event of progressive downregulation and mislocalization of AQP4 in GBM, which may affect the integrity of the BBB and contributes to accumulation of edema in the peritumoral tissue. Thus, AQP4ex could be considered as a potential early biomarker of GBM progression.
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de Bellis M, Cibelli A, Mola MG, Pisani F, Barile B, Mastrodonato M, Banitalebi S, Amiry-Moghaddam M, Abbrescia P, Frigeri A, Svelto M, Nicchia GP. Orthogonal arrays of particle assembly are essential for normal aquaporin-4 expression level in the brain. Glia 2020; 69:473-488. [PMID: 32946135 DOI: 10.1002/glia.23909] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 08/26/2020] [Accepted: 08/28/2020] [Indexed: 11/11/2022]
Abstract
Astrocyte endfeet are endowed with aquaporin-4 (AQP4)-based assemblies called orthogonal arrays of particles (OAPs) whose function is still unclear. To investigate the function of OAPs and of AQP4 tetramers, we have generated a novel "OAP-null" mouse model selectively lacking the OAP forming M23-AQP4 isoform. We demonstrated that AQP4 transcript levels were not reduced by using qPCR. Blue native (BN)/SDS-PAGE and Western blot performed on OAP-null brain and primary astrocyte cultures showed the complete depletion of AQP4 assemblies, the selective expression of M1-AQP4-based tetramers, and a substantial reduction in AQP4 total expression level. Fluorescence quenching and super-resolution microscopy experiments showed that AQP4 tetramers were functionally expressed in astrocyte plasma membrane and their dimensions were reduced compared to wild-type assemblies. Finally, as shown by light and electron microscopy, OAP depletion resulted in a massive reduction in AQP4 expression and a loss of perivascular AQP4 staining at astrocyte endfeet, with only sparse labeling throughout the brain areas analyzed. Our study relies on the unique property of AQP4 to form OAPs, using a novel OAP-null mouse model for the first time, to show that (a) AQP4 assembly is essential for normal AQP4 expression level in the brain and (b) most of AQP4 is organized into OAPs under physiological conditions. Therefore, AQP4 tetramers cannot be used by astrocytes as an alternative to OAPs without affecting AQP4 expression levels, which is important in the physiological and pathological conditions in which OAP aggregation/disaggregation dynamics have been implicated.
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Affiliation(s)
- Manuela de Bellis
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Cibelli
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Maria Grazia Mola
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Francesco Pisani
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Barbara Barile
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | | | - Shervin Banitalebi
- Department of Molecular Medicine, Division of Anatomy, University of Oslo, Oslo, Norway
| | | | - Pasqua Abbrescia
- School of Medicine, Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Antonio Frigeri
- School of Medicine, Department of Basic Medical Sciences, Neuroscience and Sense Organs, University of Bari Aldo Moro, Bari, Italy
| | - Maria Svelto
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
| | - Grazia Paola Nicchia
- Department of Biosciences, Biotechnologies and Biopharmaceutics, University of Bari Aldo Moro, Bari, Italy
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Palazzo C, Abbrescia P, Valente O, Nicchia GP, Banitalebi S, Amiry-Moghaddam M, Trojano M, Frigeri A. Tissue Distribution of the Readthrough Isoform of AQP4 Reveals a Dual Role of AQP4ex Limited to CNS. Int J Mol Sci 2020; 21:ijms21041531. [PMID: 32102323 PMCID: PMC7073200 DOI: 10.3390/ijms21041531] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 02/14/2020] [Accepted: 02/19/2020] [Indexed: 02/06/2023] Open
Abstract
Translational readthrough (TRT) of aquaporin-4 (AQP4) has remarkably expanded the importance of this new post-transcriptional mechanism, as well as the regulation potential of AQP4. The TRT isoform of AQP4, named AQP4ex, is central for both AQP4 polarization and water channel activity in the central nervous system (CNS). Here we evaluate the relevance of the TRT mechanism by analyzing whether AQP4ex is also expressed in peripheral tissues and whether the expression of AQP4ex is necessary for its polarized expression as it occurs in perivascular astrocyte processes. To this purpose, AQP4ex null mice were used, and analysis was performed by immunolocalization and immunoblot. The results demonstrate that AQP4ex is expressed in kidney, stomach, trachea and skeletal muscle with the same localization pattern as the canonical AQP4 isoforms. AQP4ex protein levels vary from 6% to about 13% of the total AQP4 protein levels in peripheral tissues. Immunogold electron microscopy experiments demonstrated the localization of AQP4ex at the astrocytic endfeet, and experiments conducted on AQP4ex null mice CNS confirmed that the expression of AQP4ex is necessary for anchoring of the perivascular AQP4. Without the readthrough isoform, AQP4 assemblies are mis-localized, being uniformly distributed on the astrocyte processes facing the neuropile. No alteration of AQP4 polarization was found in AQP4ex null kidney, stomach, trachea or skeletal muscle, suggesting that AQP4ex does not have a role for proper membrane localization of AQP4 in peripheral tissues. We conclude that a dual role for AQP4ex is limited to the CNS.
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Affiliation(s)
- Claudia Palazzo
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (C.P.); (O.V.); (M.T.)
| | - Pasqua Abbrescia
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (C.P.); (O.V.); (M.T.)
| | - Onofrio Valente
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (C.P.); (O.V.); (M.T.)
| | - Grazia Paola Nicchia
- Department of Bioscience, Biotechnology and Biopharmaceutics, University of Bari Aldo Moro, 70125 Bari, Italy;
| | - Shervin Banitalebi
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; (S.B.); (M.A.-M.)
| | - Mahmood Amiry-Moghaddam
- Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; (S.B.); (M.A.-M.)
| | - Maria Trojano
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (C.P.); (O.V.); (M.T.)
| | - Antonio Frigeri
- Department of Basic Medical Sciences, Neurosciences and Sense Organs, School of Medicine, University of Bari Aldo Moro, 70124 Bari, Italy; (C.P.); (O.V.); (M.T.)
- Correspondence:
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Palazzo C, Buccoliero C, Mola MG, Abbrescia P, Nicchia GP, Trojano M, Frigeri A. AQP4ex is crucial for the anchoring of AQP4 at the astrocyte end-feet and for neuromyelitis optica antibody binding. Acta Neuropathol Commun 2019; 7:51. [PMID: 30935410 PMCID: PMC6444679 DOI: 10.1186/s40478-019-0707-5] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 03/21/2019] [Indexed: 12/18/2022] Open
Abstract
Brain water homeostasis is essential for the appropriate control of neuronal activity. Furthermore, the encasement of the central nervous system (CNS) by a hard structure, greatly limits its tolerance for the volume changes occurring with acute brain edema, which quickly leads to severe damage or death. The recent discovery of the extended isoform of AQP4 (AQP4ex), generated by translational readthrough, revealed a potential new mechanism of water transport regulation and polarization at the blood-brain-barrier level. In the present study we used CRISPR/Cas9 technology to generate an AQP4ex−/− mouse model and evaluate the effect on the overall AQP4 expression, polarization, supramolecular organization in orthogonal arrays of particles (OAPs) and neuromyelitis optica (NMO-IgG) autoantibodies binding. AQP4ex removal did not cause a decrease in total AQP4 protein expression but completely suppressed the specific location of AQP4 at the astrocyte endfeet. Without AQP4ex, AQP4 was mislocalized and α-syntrophin expression, the selective partner for AQP4 localization, was partially altered. The supramolecular organization of AQP4 in OAPs was subtly altered. Indeed, the absence of AQP4ex reduced the size of AQP4-OAPs but the number of AQP4-OAP pools remained largely the same. More importantly, AQP4ex resulted critical for the binding of pathogenic human NMO-IgG autoantibodies to the brain. Indeed, the absence of AQP4ex completely abolished the binding of NMO-IgG at the perivascular astrocyte endfeet. This study provides the first direct evidence in vivo on the specific role of AQP4ex in AQP4 perivascular OAPs assembly and confinement and reveals AQP4ex as new and important player in neuromyelitis optica.
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