1
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Marsch P, Rajagopal N, Nangia S. Biophysics of claudin proteins in tight junction architecture: Three decades of progress. Biophys J 2024:S0006-3495(24)00393-X. [PMID: 38859584 DOI: 10.1016/j.bpj.2024.06.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 05/19/2024] [Accepted: 06/07/2024] [Indexed: 06/12/2024] Open
Abstract
Tight junctions are cell-cell adhesion complexes that act as gatekeepers of the paracellular space. Formed by several transmembrane proteins, the claudin family performs the primary gate-keeping function. The claudin proteins form charge and size-selective diffusion barriers to maintain homeostasis across endothelial and epithelial tissue. Of the 27 known claudins in mammals, some are known to seal the paracellular space, while others provide selective permeability. The differences in permeability arise due to the varying expression levels of claudins in each tissue. The tight junctions are observed as strands in freeze-fracture electron monographs; however, at the molecular level, tight junction strands form when multiple claudin proteins assemble laterally (cis assembly) within a cell and head-on (trans assembly) with claudins of the adjacent cell in a zipper-like architecture, closing the gap between the neighboring cells. The disruption of tight junctions caused by changing claudin expression levels or mutations can lead to diseases. Therefore, knowledge of the molecular architecture of the tight junctions and how that is tied to tissue-specific function is critical for fighting diseases. Here, we review the current understanding of the tight junctions accrued over the last three decades from experimental and computational biophysics perspectives.
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Affiliation(s)
- Patrick Marsch
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York
| | - Nandhini Rajagopal
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York
| | - Shikha Nangia
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York.
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2
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Raya-Sandino A, Lozada-Soto KM, Rajagopal N, Garcia-Hernandez V, Luissint AC, Brazil JC, Cui G, Koval M, Parkos CA, Nangia S, Nusrat A. Claudin-23 reshapes epithelial tight junction architecture to regulate barrier function. Nat Commun 2023; 14:6214. [PMID: 37798277 PMCID: PMC10556055 DOI: 10.1038/s41467-023-41999-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Accepted: 09/26/2023] [Indexed: 10/07/2023] Open
Abstract
Claudin family tight junction proteins form charge- and size-selective paracellular channels that regulate epithelial barrier function. In the gastrointestinal tract, barrier heterogeneity is attributed to differential claudin expression. Here, we show that claudin-23 (CLDN23) is enriched in luminal intestinal epithelial cells where it strengthens the epithelial barrier. Complementary approaches reveal that CLDN23 regulates paracellular ion and macromolecule permeability by associating with CLDN3 and CLDN4 and regulating their distribution in tight junctions. Computational modeling suggests that CLDN23 forms heteromeric and heterotypic complexes with CLDN3 and CLDN4 that have unique pore architecture and overall net charge. These computational simulation analyses further suggest that pore properties are interaction-dependent, since differently organized complexes with the same claudin stoichiometry form pores with unique architecture. Our findings provide insight into tight junction organization and propose a model whereby different claudins combine to form multiple distinct complexes that modify epithelial barrier function by altering tight junction structure.
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Affiliation(s)
- Arturo Raya-Sandino
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA
| | | | - Nandhini Rajagopal
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, NY, USA
| | | | - Anny-Claude Luissint
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Jennifer C Brazil
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Guiying Cui
- Department of Pediatrics, Emory + Children's Center for Cystic Fibrosis and Airways Disease Research, Emory University School of Medicine, Atlanta, GA, USA
| | - Michael Koval
- Departments of Medicine and Cell Biology, Emory University School of Medicine, Atlanta, GA, USA
| | - Charles A Parkos
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Shikha Nangia
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, NY, USA.
| | - Asma Nusrat
- Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, USA.
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3
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McGuinness S, Li P, Li Y, Fuladi S, Konar S, Sajjadi S, Sidahmed M, Li Y, Shen L, Araghi FK, Weber CR. Molecular dynamics analyses of CLDN15 pore size and charge selectivity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.16.553400. [PMID: 37645840 PMCID: PMC10461993 DOI: 10.1101/2023.08.16.553400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
The Claudin-15 (CLDN15) channel is important for nutrient, electrolyte, and water transport in the gastrointestinal tract. We used cell culture studies and molecular dynamics simulations to elucidate its structure and permeability mechanisms. We provide a model that underscores the crucial role of the D55 residue in the CLDN15 selectivity filter, which interacts with permeating cations. Our studies demonstrated the mechanisms whereby the size and charge of the D55 residue influence paracellular permeability. By altering D55 to larger, negatively charged glutamic acid (E) or similarly sized neutral asparagine (N), we observed changes in pore size and selectivity, respectively. D55E mutation decreased pore size, favoring small ion permeability without affecting charge selectivity, while D55N mutation led to reduced charge selectivity without markedly altering size selectivity. These findings shed light on the complex interplay of size and charge selectivity of CLDN15 channels. This knowledge can inform the development of strategies to modulate the function of CLDN15 and similar channels, which has implications for tight junction modulation in health and disease.
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4
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Berselli A, Alberini G, Benfenati F, Maragliano L. The impact of pathogenic and artificial mutations on Claudin-5 selectivity from molecular dynamics simulations. Comput Struct Biotechnol J 2023; 21:2640-2653. [PMID: 37138900 PMCID: PMC10149405 DOI: 10.1016/j.csbj.2023.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Revised: 04/03/2023] [Accepted: 04/03/2023] [Indexed: 05/05/2023] Open
Abstract
Tight-junctions (TJs) are multi-protein complexes between adjacent endothelial or epithelial cells. In the blood-brain-barrier (BBB), they seal the paracellular space and the Claudin-5 (Cldn5) protein forms their backbone. Despite the fundamental role in brain homeostasis, little is known on Cldn5-based TJ assemblies. Different structural models were suggested, with Cldn5 protomers generating paracellular pores that restrict the passage of ions and small molecules. Recently, the first Cldn5 pathogenic mutation, G60R, was identified and shown to induce Cl--selective channels and Na+ barriers in BBB TJs, providing an excellent opportunity to validate the structural models. Here, we used molecular dynamics to study the permeation of ions and water through two distinct G60R-Cldn5 paracellular architectures. Only the so-called Pore I reproduces the functional modification observed in experiments, displaying a free energy (FE) minimum for Cl- and a barrier for Na+ consistent with anionic selectivity. We also studied the artificial Q57D and Q63D mutations in the constriction region, Q57 being conserved in Cldns except for cation permeable homologs. In both cases, we obtain FE profiles consistent with facilitated passage of cations. Our calculations provide the first in-silico description of a Cldn5 pathogenic mutation, further assessing the TJ Pore I model and yielding new insight on BBB's paracellular selectivity.
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Affiliation(s)
- Alessandro Berselli
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy
- Department of Experimental Medicine, Università degli Studi di Genova, Viale Benedetto XV, 3, 16132, Genova, Italy
| | - Giulio Alberini
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy
- IRCCS Ospedale Policlinico San Martino, Largo Rosanna Benzi, 10, 16132, Genova, Italy
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy
- IRCCS Ospedale Policlinico San Martino, Largo Rosanna Benzi, 10, 16132, Genova, Italy
- Corresponding authors at: Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy.
| | - Luca Maragliano
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131, Ancona, Italy
- Corresponding authors at: Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy.
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5
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Claudin-10b cation channels in tight junction strands: Octameric-interlocked pore barrels constitute paracellular channels with low water permeability. Comput Struct Biotechnol J 2023; 21:1711-1727. [PMID: 36874155 PMCID: PMC9977872 DOI: 10.1016/j.csbj.2023.02.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 02/03/2023] [Accepted: 02/04/2023] [Indexed: 02/15/2023] Open
Abstract
Claudin proteins constitute the backbone of tight junctions (TJs) regulating paracellular permeability for solutes and water. The molecular mechanism of claudin polymerization and paracellular channel formation is unclear. However, a joined double-rows architecture of claudin strands has been supported by experimental and modeling data. Here, we compared two variants of this architectural model for the related but functionally distinct cation channel-forming claudin-10b and claudin-15: tetrameric-locked-barrel vs octameric-interlocked-barrels model. Homology modeling and molecular dynamics simulations of double-membrane embedded dodecamers indicate that claudin-10b and claudin-15 share the same joined double-rows architecture of TJ-strands. For both, the results indicate octameric-interlocked-barrels: Sidewise unsealed tetrameric pore scaffolds interlocked with adjacent pores via the β1β2 loop of the extracellular segment (ECS) 1. This loop mediates hydrophobic clustering and, together with ECS2, cis- and trans-interaction between claudins of the adjacent tetrameric pore scaffolds. In addition, the β1β2 loop contributes to lining of the ion conduction pathway. The charge-distribution along the pore differs between claudin-10b and claudin-15 and is suggested to be a key determinant for the cation- and water permeabilities that differ between the two claudins. In the claudin-10b simulations, similar as for claudin-15, the conserved D56 in the pore center is the main cation interaction site. In contrast to claudin-15 channels, the claudin-10b-specific D36, K64 and E153 are suggested to cause jamming of cations that prevents efficient water passage. In sum, we provide novel mechanistic information about polymerization of classic claudins, formation of embedded channels and thus regulation of paracellular transport across epithelia.
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6
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Fuladi S, McGuinness S, Shen L, Weber CR, Khalili-Araghi F. Molecular mechanism of claudin-15 strand flexibility: A computational study. J Gen Physiol 2022; 154:213632. [PMID: 36318156 PMCID: PMC9629798 DOI: 10.1085/jgp.202213116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 07/30/2022] [Accepted: 10/05/2022] [Indexed: 11/09/2022] Open
Abstract
Claudins are one of the major components of tight junctions that play a key role in the formation and maintenance of the epithelial barrier function. Tight junction strands are dynamic and capable of adapting their structure in response to large-scale tissue rearrangement and cellular movement. Here, we present molecular dynamics simulations of claudin-15 strands of up to 225 nm in length in two parallel lipid membranes and characterize their mechanical properties. The persistence length of claudin-15 strands is comparable with those obtained from analyses of freeze-fracture electron microscopy. Our results indicate that lateral flexibility of claudin strands is due to an interplay of three sets of interfacial interaction networks between two antiparallel double rows of claudins in the membranes. In this model, claudins are assembled into interlocking tetrameric ion channels along the strand that slide with respect to each other as the strands curve over submicrometer-length scales. These results suggest a novel molecular mechanism underlying claudin-15 strand flexibility. It also sheds light on intermolecular interactions and their role in maintaining epithelial barrier function.
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Affiliation(s)
- Shadi Fuladi
- Department of Physics, University of Illinois, Chicago, IL
| | - Sarah McGuinness
- Department of Bioengineering, University of Illinois, Chicago, IL
| | - Le Shen
- Department of Surgery, The University of Chicago, Chicago, IL
| | | | - Fatemeh Khalili-Araghi
- Department of Physics, University of Illinois, Chicago, IL,Correspondence to Fatemeh Khalili-Araghi:
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7
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Berselli A, Benfenati F, Maragliano L, Alberini G. Multiscale modelling of claudin-based assemblies: a magnifying glass for novel structures of biological interfaces. Comput Struct Biotechnol J 2022; 20:5984-6010. [DOI: 10.1016/j.csbj.2022.10.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 10/24/2022] [Accepted: 10/24/2022] [Indexed: 11/03/2022] Open
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8
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Berselli A, Alberini G, Benfenati F, Maragliano L. Computational study of ion permeation through claudin-4 paracellular channels. Ann N Y Acad Sci 2022; 1516:162-174. [PMID: 35811406 PMCID: PMC9796105 DOI: 10.1111/nyas.14856] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Claudins (Cldns) form a large family of protein homologs that are essential for the assembly of paracellular tight junctions (TJs), where they form channels or barriers with tissue-specific selectivity for permeants. In contrast to several family members whose physiological role has been identified, the function of claudin 4 (Cldn4) remains elusive, despite experimental evidence suggesting that it can form anion-selective TJ channels in the renal epithelium. Computational approaches have recently been employed to elucidate the molecular basis of Cldns' function, and hence could help in clarifying the role of Cldn4. In this work, we use structural modeling and all-atom molecular dynamics simulations to transfer two previously introduced structural models of Cldn-based paracellular complexes to Cldn4 to reproduce a paracellular anion channel. Free energy calculations for ionic transport through the pores allow us to establish the thermodynamic properties driving the ion-selectivity of the structures. While one model shows a cavity permeable to chloride and repulsive to cations, the other forms barrier to the passage of all the major physiological ions. Furthermore, our results confirm the charge selectivity role of the residue Lys65 in the first extracellular loop of the protein, rationalizing Cldn4 control of paracellular permeability.
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Affiliation(s)
- Alessandro Berselli
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe)Istituto Italiano di TecnologiaGenovaItaly,Department of Experimental MedicineUniversità degli Studi di GenovaGenovaItaly
| | - Giulio Alberini
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe)Istituto Italiano di TecnologiaGenovaItaly,IRCCS Ospedale Policlinico San MartinoGenovaItaly
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe)Istituto Italiano di TecnologiaGenovaItaly,IRCCS Ospedale Policlinico San MartinoGenovaItaly
| | - Luca Maragliano
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe)Istituto Italiano di TecnologiaGenovaItaly,Department of Life and Environmental SciencesPolytechnic University of MarcheAnconaItaly
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9
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Fuladi S, McGuinness S, Khalili-Araghi F. Role of TM3 in claudin-15 strand flexibility: A molecular dynamics study. Front Mol Biosci 2022; 9:964877. [PMID: 36250014 PMCID: PMC9557151 DOI: 10.3389/fmolb.2022.964877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Accepted: 08/22/2022] [Indexed: 11/13/2022] Open
Abstract
Claudins are cell-cell adhesion proteins within tight junctions that connect epithelial cells together. Claudins polymerize into a network of strand-like structures within the membrane of adjoining cells and create ion channels that control paracellular permeability to water and small molecules. Tight junction morphology and barrier function is tissue specific and regulated by claudin subtypes. Here, we present a molecular dynamics study of claudin-15 strands within lipid membranes and the role of a single-point mutation (A134P) on the third transmembrane helix (TM3) of claudin-15 in determining the morphology of the strand. Our results indicate that the A134P mutation significantly affects the lateral flexibility of the strands, increasing the persistence length of claudin-15 strands by a factor of three. Analyses of claudin-claudin contact in our μsecond-long trajectories show that the mutation does not alter the intermolecular contacts (interfaces) between claudins. However, the dynamics and frequency of interfacial contacts are significantly affected. The A134P mutation introduces a kink in TM3 of claudin-15 similar to the one observed in claudin-3 crystal structure. The kink on TM3 skews the rotational flexibility of the claudins in the strands and limits their fluctuation in one direction. This asymmetric movement in the context of the double rows reduces the lateral flexibility of the strand and leads to higher persistence lengths of the mutant.
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Affiliation(s)
- Shadi Fuladi
- Department of Physics, University of Illinois at Chicago, Chicago, IL, United States
| | - Sarah McGuinness
- Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, United States
| | - Fatemeh Khalili-Araghi
- Department of Physics, University of Illinois at Chicago, Chicago, IL, United States
- *Correspondence: Fatemeh Khalili-Araghi,
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10
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Rajagopal N, Nangia S. Unique structural features of claudin‐5 and claudin‐15 lead to functionally distinct tight junction strand architecture. Ann N Y Acad Sci 2022; 1517:225-233. [DOI: 10.1111/nyas.14891] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Nandhini Rajagopal
- Department of Biomedical and Chemical Engineering Syracuse University Syracuse New York USA
| | - Shikha Nangia
- Department of Biomedical and Chemical Engineering Syracuse University Syracuse New York USA
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11
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Berselli A, Alberini G, Benfenati F, Maragliano L. Computational Assessment of Different Structural Models for Claudin-5 Complexes in Blood-Brain Barrier Tight Junctions. ACS Chem Neurosci 2022; 13:2140-2153. [PMID: 35816296 PMCID: PMC9976285 DOI: 10.1021/acschemneuro.2c00139] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The blood-brain barrier (BBB) strictly regulates the exchange of ions and molecules between the blood and the central nervous system. Tight junctions (TJs) are multimeric structures that control the transport through the paracellular spaces between the adjacent brain endothelial cells of the BBB. Claudin-5 (Cldn5) proteins are essential for TJ formation and assemble into multiprotein complexes via cis-interactions within the same cell membrane and trans-interactions across two contiguous cells. Despite the relevant biological function of Cldn5 proteins and their role as targets of brain drug delivery strategies, the molecular details of their assembly within TJs are still unclear. Two different structural models have been recently introduced, in which Cldn5 dimers belonging to opposite cells join to generate paracellular pores. However, a comparison of these models in terms of ionic transport features is still lacking. In this work, we used molecular dynamics simulations and free energy (FE) calculations to assess the two Cldn5 pore models and investigate the thermodynamic properties of water and physiological ions permeating through them. Despite different FE profiles, both structures present single/multiple FE barriers to ionic permeation, while being permissive to water flux. These results reveal that both models are compatible with the physiological role of Cldn5 TJ strands. By identifying the protein-protein surface at the core of TJ Cldn5 assemblies, our computational investigation provides a basis for the rational design of synthetic peptides and other molecules capable of opening paracellular pores in the BBB.
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Affiliation(s)
- Alessandro Berselli
- Center
for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, Genova 16132, Italy,Department
of Experimental Medicine, Università
Degli Studi di Genova, Viale Benedetto XV, 3, Genova 16132, Italy
| | - Giulio Alberini
- Center
for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, Genova 16132, Italy,IRCCS
Ospedale Policlinico San Martino, Largo Rosanna Benzi, 10, Genova 16132, Italy
| | - Fabio Benfenati
- Center
for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, Genova 16132, Italy,IRCCS
Ospedale Policlinico San Martino, Largo Rosanna Benzi, 10, Genova 16132, Italy,
| | - Luca Maragliano
- Center
for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, Genova 16132, Italy,Department
of Life and Environmental Sciences, Polytechnic
University of Marche, Via Brecce Bianche, Ancona 60131, Italy,
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12
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Hashimoto Y, Poirier K, Boddaert N, Hubert L, Aubart M, Kaminska A, Alison M, Desguerre I, Munnich A, Campbell M. Recurrent de novo mutations in CLDN5 induce an anion-selective blood-brain barrier and alternating hemiplegia. Brain 2022; 145:3374-3382. [PMID: 35714222 PMCID: PMC9586545 DOI: 10.1093/brain/awac215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 05/19/2022] [Accepted: 05/26/2022] [Indexed: 11/16/2022] Open
Abstract
Claudin-5 is the most enriched tight junction protein at the blood–brain barrier. Perturbations in its levels of expression have been observed across numerous neurological and neuropsychiatric conditions; however, pathogenic variants in the coding sequence of the gene have never been reported previously. Here, we report the identification of a novel de novo mutation (c.178G>A) in the CLDN5 gene in two unrelated cases of alternating hemiplegia with microcephaly. This mutation (G60R) lies within the first extracellular loop of claudin-5 and based on protein modelling and sequence alignment, we predicted it would modify claudin-5 to become an anion-selective junctional component as opposed to a purely barrier-forming protein. Generation of stably transfected cell lines expressing wild-type or G60R claudin-5 showed that the tight junctions could still form in the presence of the G60R mutation but that the barrier against small molecules was clearly attenuated and displayed higher Cl− ion permeability and lower Na+ permeability. While this study strongly suggests that CLDN5 associated alternating hemiplegia is a channelopathy, it is also the first study to identify the conversion of the blood–brain barrier to an anion-selective channel mediated by a dominant acting variant in CLDN5.
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Affiliation(s)
- Yosuke Hashimoto
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
| | - Karine Poirier
- INSERM UMR1163, Institut Imagine, Université Paris Cité, F-75015, Paris France
| | - Nathalie Boddaert
- Department of pediatric radiology, Hospital Necker Enfants Malades, France
| | - Laurence Hubert
- INSERM UMR1163, Institut Imagine, Université Paris Cité, F-75015, Paris France
| | - Melodie Aubart
- Departments of pediatric neurology and medical genetics, Hospital Necker-Enfants Malades, Université Paris Cité, F-75015, Paris France
| | - Anna Kaminska
- Departments of pediatric neurology and medical genetics, Hospital Necker-Enfants Malades, Université Paris Cité, F-75015, Paris France
| | - Marianne Alison
- Department of pediatric radiology, Hospital Robert Debré, Université Paris Cité, F-75015, Paris France
| | - Isabelle Desguerre
- Departments of pediatric neurology and medical genetics, Hospital Necker-Enfants Malades, Université Paris Cité, F-75015, Paris France
| | - Arnold Munnich
- INSERM UMR1163, Institut Imagine, Université Paris Cité, F-75015, Paris France.,Departments of pediatric neurology and medical genetics, Hospital Necker-Enfants Malades, Université Paris Cité, F-75015, Paris France
| | - Matthew Campbell
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
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13
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Hempel C, Rosenthal R, Fromm A, Krug SM, Fromm M, Günzel D, Piontek J. Tight junction channels claudin-10b and claudin-15: Functional mapping of pore-lining residues. Ann N Y Acad Sci 2022; 1515:129-142. [PMID: 35650657 DOI: 10.1111/nyas.14794] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Although functional and structural models for paracellular channels formed by claudins have been reported, mechanisms regulating charge and size selectivity of these channels are unknown in detail. Here, claudin-15 and claudin-10b cation channels showing high-sequence similarity but differing channel properties were analyzed. Mutants of pore-lining residues were expressed in MDCK-C7 cells. In claudin-15, proposed ion interaction sites (D55 and E64) conserved between both claudins were neutralized. D55N and E64Q substitutions decreased ion permeabilities, and D55N/E64Q had partly additive effects. D55N increased cation dehydration capability and decreased pore diameter. Additionally, residues differing between claudin-15 and -10b close to pore center were analyzed. Claudin-10b-mimicking W63K affected neither assembly nor function of claudin-15 channels. In contrast, in claudin-10b, corresponding (claudin-15b-mimicking) K64W and K64M substitutions disturbed integration into tight junction and slightly altered relative permeabilities for differently sized monovalent cations. Removal of claudin-10b-specific negative charge (D36A substitution) was without effect. The data suggest that a common tetra-aspartate ring (D55/D56) in pore center of claudin-15/-10b channels directly attracts cations, while E64/D65 may be at least partly shielded by W63/K64. Charge at position W63/K64 affects assembly and properties for claudin-10b but not for claudin-15 channels. Our findings add to the mechanistic understanding of the determinants of paracellular cation permeability.
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Affiliation(s)
- Caroline Hempel
- Clinical Physiology/Nutritional Medicine, Medizinische Klinik für Gastroenterologie, Infektiologie und Rheumatologie, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Rita Rosenthal
- Clinical Physiology/Nutritional Medicine, Medizinische Klinik für Gastroenterologie, Infektiologie und Rheumatologie, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Anja Fromm
- Clinical Physiology/Nutritional Medicine, Medizinische Klinik für Gastroenterologie, Infektiologie und Rheumatologie, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Susanne M Krug
- Clinical Physiology/Nutritional Medicine, Medizinische Klinik für Gastroenterologie, Infektiologie und Rheumatologie, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Michael Fromm
- Clinical Physiology/Nutritional Medicine, Medizinische Klinik für Gastroenterologie, Infektiologie und Rheumatologie, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Dorothee Günzel
- Clinical Physiology/Nutritional Medicine, Medizinische Klinik für Gastroenterologie, Infektiologie und Rheumatologie, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jörg Piontek
- Clinical Physiology/Nutritional Medicine, Medizinische Klinik für Gastroenterologie, Infektiologie und Rheumatologie, Charité - Universitätsmedizin Berlin, Berlin, Germany
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14
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Lin YC, Luo YL. Unifying Single-Channel Permeability From Rare-Event Sampling and Steady-State Flux. Front Mol Biosci 2022; 9:860933. [PMID: 35495625 PMCID: PMC9043130 DOI: 10.3389/fmolb.2022.860933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 03/07/2022] [Indexed: 11/18/2022] Open
Abstract
Various all-atom molecular dynamics (MD) simulation methods have been developed to compute free energies and crossing rates of ions and small molecules through ion channels. However, a systemic comparison across different methods is scarce. Using a carbon nanotube as a model of small conductance ion channel, we computed the single-channel permeability for potassium ion using umbrella sampling, Markovian milestoning, and steady-state flux under applied voltage. We show that a slightly modified inhomogeneous solubility-diffusion equation yields a single-channel permeability consistent with the mean first passage time (MFPT) based method. For milestoning, applying cylindrical and spherical bulk boundary conditions yield consistent MFPT if factoring in the effective bulk concentration. The sensitivity of the MFPT to the output frequency of collective variables is highlighted using the convergence and symmetricity of the inward and outward MFPT profiles. The consistent transport kinetic results from all three methods demonstrated the robustness of MD-based methods in computing ion channel permeation. The advantages and disadvantages of each technique are discussed, focusing on the future applications of milestoning in more complex systems.
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15
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Guardiani C, Cecconi F, Chiodo L, Cottone G, Malgaretti P, Maragliano L, Barabash ML, Camisasca G, Ceccarelli M, Corry B, Roth R, Giacomello A, Roux B. Computational methods and theory for ion channel research. ADVANCES IN PHYSICS: X 2022; 7:2080587. [PMID: 35874965 PMCID: PMC9302924 DOI: 10.1080/23746149.2022.2080587] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 05/15/2022] [Indexed: 06/15/2023] Open
Abstract
Ion channels are fundamental biological devices that act as gates in order to ensure selective ion transport across cellular membranes; their operation constitutes the molecular mechanism through which basic biological functions, such as nerve signal transmission and muscle contraction, are carried out. Here, we review recent results in the field of computational research on ion channels, covering theoretical advances, state-of-the-art simulation approaches, and frontline modeling techniques. We also report on few selected applications of continuum and atomistic methods to characterize the mechanisms of permeation, selectivity, and gating in biological and model channels.
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Affiliation(s)
- C. Guardiani
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Rome, Italy
| | - F. Cecconi
- CNR - Istituto dei Sistemi Complessi, Rome, Italy and Istituto Nazionale di Fisica Nucleare, INFN, Roma1 section. 00185, Roma, Italy
| | - L. Chiodo
- Department of Engineering, Campus Bio-Medico University, Rome, Italy
| | - G. Cottone
- Department of Physics and Chemistry-Emilio Segrè, University of Palermo, Palermo, Italy
| | - P. Malgaretti
- Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich, Erlangen, Germany
| | - L. Maragliano
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy, and Center for Synaptic Neuroscience and Technology, Istituto Italiano di Tecnologia, Genova, Italy
| | - M. L. Barabash
- Department of Materials Science and Nanoengineering, Rice University, Houston, TX 77005, USA
| | - G. Camisasca
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Rome, Italy
- Dipartimento di Fisica, Università Roma Tre, Rome, Italy
| | - M. Ceccarelli
- Department of Physics and CNR-IOM, University of Cagliari, Monserrato 09042-IT, Italy
| | - B. Corry
- Research School of Biology, The Australian National University, Canberra, ACT 2600, Australia
| | - R. Roth
- Institut Für Theoretische Physik, Eberhard Karls Universität Tübingen, Tübingen, Germany
| | - A. Giacomello
- Dipartimento di Ingegneria Meccanica e Aerospaziale, Sapienza Università di Roma, Rome, Italy
| | - B. Roux
- Department of Biochemistry & Molecular Biology, University of Chicago, Chicago IL, USA
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16
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Wilson CG, Aarons L, Augustijns P, Brouwers J, Darwich AS, De Waal T, Garbacz G, Hansmann S, Hoc D, Ivanova A, Koziolek M, Reppas C, Schick P, Vertzoni M, García-Horsman JA. Integration of advanced methods and models to study drug absorption and related processes: An UNGAP perspective. Eur J Pharm Sci 2021; 172:106100. [PMID: 34936937 DOI: 10.1016/j.ejps.2021.106100] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 12/14/2021] [Accepted: 12/16/2021] [Indexed: 01/09/2023]
Abstract
This collection of contributions from the European Network on Understanding Gastrointestinal Absorption-related Processes (UNGAP) community assembly aims to provide information on some of the current and newer methods employed to study the behaviour of medicines. It is the product of interactions in the immediate pre-Covid period when UNGAP members were able to meet and set up workshops and to discuss progress across the disciplines. UNGAP activities are divided into work packages that cover special treatment populations, absorption processes in different regions of the gut, the development of advanced formulations and the integration of food and pharmaceutical scientists in the food-drug interface. This involves both new and established technical approaches in which we have attempted to define best practice and highlight areas where further research is needed. Over the last months we have been able to reflect on some of the key innovative approaches which we were tasked with mapping, including theoretical, in silico, in vitro, in vivo and ex vivo, preclinical and clinical approaches. This is the product of some of us in a snapshot of where UNGAP has travelled and what aspects of innovative technologies are important. It is not a comprehensive review of all methods used in research to study drug dissolution and absorption, but provides an ample panorama of current and advanced methods generally and potentially useful in this area. This collection starts from a consideration of advances in a priori approaches: an understanding of the molecular properties of the compound to predict biological characteristics relevant to absorption. The next four sections discuss a major activity in the UNGAP initiative, the pursuit of more representative conditions to study lumenal dissolution of drug formulations developed independently by academic teams. They are important because they illustrate examples of in vitro simulation systems that have begun to provide a useful understanding of formulation behaviour in the upper GI tract for industry. The Leuven team highlights the importance of the physiology of the digestive tract, as they describe the relevance of gastric and intestinal fluids on the behaviour of drugs along the tract. This provides the introduction to microdosing as an early tool to study drug disposition. Microdosing in oncology is starting to use gamma-emitting tracers, which provides a link through SPECT to the next section on nuclear medicine. The last two papers link the modelling approaches used by the pharmaceutical industry, in silico to Pop-PK linking to Darwich and Aarons, who provide discussion on pharmacometric modelling, completing the loop of molecule to man.
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Affiliation(s)
- Clive G Wilson
- Strathclyde Institute of Pharmacy & Biomedical Sciences, Glasgow, U.K.
| | | | | | | | | | | | | | | | | | | | - Mirko Koziolek
- NCE Formulation Sciences, Abbvie Deutschland GmbH & Co. KG, Germany
| | | | - Philipp Schick
- Department of Biopharmaceutics and Pharmaceutical Technology, Center of Drug Absorption and Transport, University of Greifswald, Germany
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17
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Ray D, Stone SE, Andricioaei I. Markovian Weighted Ensemble Milestoning (M-WEM): Long-Time Kinetics from Short Trajectories. J Chem Theory Comput 2021; 18:79-95. [PMID: 34910499 DOI: 10.1021/acs.jctc.1c00803] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We introduce a rare-event sampling scheme, named Markovian Weighted Ensemble Milestoning (M-WEM), which inlays a weighted ensemble framework within a Markovian milestoning theory to efficiently calculate thermodynamic and kinetic properties of long-time-scale biomolecular processes from short atomistic molecular dynamics simulations. M-WEM is tested on the Müller-Brown potential model, the conformational switching in alanine dipeptide, and the millisecond time-scale protein-ligand unbinding in a trypsin-benzamidine complex. Not only can M-WEM predict the kinetics of these processes with quantitative accuracy but it also allows for a scheme to reconstruct a multidimensional free-energy landscape along additional degrees of freedom, which are not part of the milestoning progress coordinate. For the ligand-receptor system, the experimental residence time, association and dissociation kinetics, and binding free energy could be reproduced using M-WEM within a simulation time of a few hundreds of nanoseconds, which is a fraction of the computational cost of other currently available methods, and close to 4 orders of magnitude less than the experimental residence time. Due to the high accuracy and low computational cost, the M-WEM approach can find potential applications in kinetics and free-energy-based computational drug design.
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Affiliation(s)
- Dhiman Ray
- Department of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - Sharon Emily Stone
- Department of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - Ioan Andricioaei
- Department of Chemistry, University of California Irvine, Irvine, California 92697, United States.,Department of Physics and Astronomy, University of California Irvine, Irvine, California 92697, United States
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18
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Affiliation(s)
- Benoît Roux
- Department of Biochemistry and Molecular Biology and Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, Illinois 60637, United States
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19
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Jiang W, Lin YC, Botello-Smith W, Contreras JE, Harris AL, Maragliano L, Luo YL. Free energy and kinetics of cAMP permeation through connexin26 via applied voltage and milestoning. Biophys J 2021; 120:2969-2983. [PMID: 34214529 DOI: 10.1016/j.bpj.2021.06.024] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 04/08/2021] [Accepted: 06/17/2021] [Indexed: 11/18/2022] Open
Abstract
The connexin family is a diverse group of highly regulated wide-pore channels permeable to biological signaling molecules. Despite the critical roles of connexins in mediating selective molecular signaling in health and disease, the basis of molecular permeation through these pores remains unclear. Here, we report the thermodynamics and kinetics of binding and transport of a second messenger, adenosine-3',5'-cyclophosphate (cAMP), through a connexin26 hemichannel (Cx26). First, inward and outward fluxes of cAMP molecules solvated in KCl solution were obtained from 4 μs of ± 200 mV simulations. These fluxes data yielded a single-channel permeability of cAMP and cAMP/K+ permeability ratio consistent with experimentally measured values. The results from voltage simulations were then compared with the potential of mean force (PMF) and the mean first passage times (MFPTs) of a single cAMP without voltage, obtained from a total of 16.5 μs of Voronoi-tessellated Markovian milestoning simulations. Both the voltage simulations and the milestoning simulations revealed two cAMP-binding sites, for which the binding constants KD and dissociation rates koff were computed from PMF and MFPTs. The protein dipole inside the pore produces an asymmetric PMF, reflected in unequal cAMP MFPTs in each direction once within the pore. The free energy profiles under opposite voltages were derived from the milestoning PMF and revealed the interplay between voltage and channel polarity on the total free energy. In addition, we show how these factors influence the cAMP dipole vector during permeation, and how cAMP affects the local and nonlocal pore diameter in a position-dependent manner.
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Affiliation(s)
- Wenjuan Jiang
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, California
| | - Yi-Chun Lin
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, California
| | - Wesley Botello-Smith
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, California
| | - Jorge E Contreras
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California.
| | - Andrew L Harris
- Department of Pharmacology, Physiology, and Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, New Jersey.
| | - Luca Maragliano
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy; Center for Synaptic Neuroscience and Technology, Italian Institute of Technology, Genoa, Italy.
| | - Yun Lyna Luo
- Department of Pharmaceutical Sciences, College of Pharmacy, Western University of Health Sciences, Pomona, California.
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20
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Alberini G, Benfenati F, Maragliano L. Structural Mechanism of ω-Currents in a Mutated Kv7.2 Voltage Sensor Domain from Molecular Dynamics Simulations. J Chem Inf Model 2021; 61:1354-1367. [PMID: 33570938 PMCID: PMC8023575 DOI: 10.1021/acs.jcim.0c01407] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
![]()
Activation of voltage-gated
ion channels is regulated by conformational
changes of the voltage sensor domains (VSDs), four water- and ion-impermeable
modules peripheral to the central, permeable pore domain. Anomalous
currents, defined as ω-currents, have been recorded in response
to mutations of residues on the VSD S4 helix and associated with ion
fluxes through the VSDs. In humans, gene defects in the potassium
channel Kv7.2 result in a broad range of epileptic disorders, from
benign neonatal seizures to severe epileptic encephalopathies. Experimental
evidence suggests that the R207Q mutation in S4, associated with peripheral
nerve hyperexcitability, induces ω-currents at depolarized potentials,
but the fine structural details are still elusive. In this work, we
use atom-detailed molecular dynamics simulations and a refined model
structure of the Kv7.2 VSD in the active conformation in a membrane/water
environment to study the effect of R207Q and four additional mutations
of proven clinical importance. Our results demonstrate that the R207Q
mutant shows the most pronounced increase of hydration in the internal
VSD cavity, a feature favoring the occurrence of ω-currents.
Free energy and kinetics calculations of sodium permeation through
the native and mutated VSD indicate as more favorable the formation
of a cationic current in the latter. Overall, our simulations establish
a mechanistic linkage between genetic variations and their physiological
outcome, by providing a computational description that includes both
thermodynamic and kinetic features of ion permeation associated with
ω-currents.
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Affiliation(s)
- Giulio Alberini
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy.,Department of Experimental Medicine, Università degli Studi di Genova, Viale Benedetto XV, 3, 16132 Genova, Italy
| | - Fabio Benfenati
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy.,IRCCS Ospedale Policlinico San Martino, Largo Rosanna Benzi, 10, 16132 Genova, Italy
| | - Luca Maragliano
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy.,Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona, Italy
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21
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Cottone G, Chiodo L, Maragliano L. Thermodynamics and Kinetics of Ion Permeation in Wild-Type and Mutated Open Active Conformation of the Human α7 Nicotinic Receptor. J Chem Inf Model 2020; 60:5045-5056. [PMID: 32803965 PMCID: PMC8011927 DOI: 10.1021/acs.jcim.0c00549] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
![]()
Molecular
studies of human pentameric ligand-gated ion channels
(LGICs) expressed in neurons and at neuromuscular junctions are of
utmost importance in the development of therapeutic strategies for
neurological disorders. We focus here on the nicotinic acetylcholine
receptor nAChR-α7, a homopentameric channel widely expressed
in the human brain, with a proven role in a wide spectrum of disorders
including schizophrenia and Alzheimer’s disease. By exploiting
an all-atom structural model of the full (transmembrane and extracellular)
protein in the open, agonist-bound conformation we recently developed,
we evaluate the free energy and the mean first passage time of single-ion
permeation using molecular dynamics simulations and the milestoning
method with Voronoi tessellation. The results for the wild-type channel
provide the first available mapping of the potential of mean force
in the full-length α7 nAChR, reveal its expected cationic nature,
and are in good agreement with simulation data for other channels
of the LGIC family and with experimental data on nAChRs. We then investigate
the role of a specific mutation directly related to ion selectivity
in LGICs, the E-1′ → A-1′ substitution at the
cytoplasmatic selectivity filter. We find that the mutation strongly
affects sodium and chloride permeation in opposite directions, leading
to a complete inversion of selectivity, at variance with the limited
experimental results available that classify this mutant as cationic.
We thus provide structural determinants for the observed cationic-to-anionic
inversion, revealing a key role of the protonation state of residue
rings far from the mutation, in the proximity of the hydrophobic channel
gate.
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Affiliation(s)
- Grazia Cottone
- Department of Physics and Chemistry-Emilio Segrè, University of Palermo, Viale delle Scienze Ed. 17, 90128 Palermo, Italy
| | - Letizia Chiodo
- Department of Engineering, Campus Bio-Medico University of Rome, Via Á. del Portillo 21, 00128 Rome, Italy
| | - Luca Maragliano
- Center for Synaptic Neuroscience and Technology (NSYN@UniGe), Istituto Italiano di Tecnologia, Largo Rosanna Benzi, 10, 16132 Genova, Italy.,IRCCS Ospedale Policlinico San Martino, Largo Rosanna Benzi, 10, 16132 Genova, Italy
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22
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Irudayanathan FJ, Nangia S. Paracellular Gatekeeping: What Does It Take for an Ion to Pass Through a Tight Junction Pore? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6757-6764. [PMID: 32450698 DOI: 10.1021/acs.langmuir.0c00877] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Tight junction pores are physiological gatekeepers of paracellular transport in epithelial tissues. Conventionally, tight junction permeability is determined via in vitro electrophysiology measurements; however, the macroscopic readout does not provide molecular-level understanding into the mechanism of ion permeation. Insight into the factors governing selectivity across the paracellular space is just emerging. In this study, we investigated tight junction pores comprising of claudin-2 and claudin-5 proteins that are structurally similar to subnanometer radii but have measurably different in vitro ion permeabilities. To evaluate the mechanistic differences in ion transport across the pores, we computed the free-energy profiles and relative rate constants for the transport of monovalent (Na+, K+, Cl-) and divalent (Mg2+ and Ca2+) ions through the pores using replica exchange metadynamics. In claudin-2, we demonstrate how a single residue dictates selective permeability of Na+ and K+ ions. In claudin-5, we found no clear preference for anion or cation selectivity; thus, pores formed by claudin-5 are indeed barriers to ion permeation. Mutations to claudin-5 that widen the pore's steric radius did not significantly impact pore selectivity, indicating that electrostatics dominate pore selectivity. The key takeaways from this work are as follows: (a) two pores that are similar in diameter and length can have dissimilar ion conductance, (b) existence of a physical pore does not guarantee ion permeability, and (c) the electrostatic environment created by the pore-lining residues dictates the ion conductivity. These mechanistic understandings of the tight junction pores are critical for the interpretation of tight junction physiology.
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Affiliation(s)
| | - Shikha Nangia
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, New York 13244, United States
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23
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Piontek J, Krug SM, Protze J, Krause G, Fromm M. Molecular architecture and assembly of the tight junction backbone. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183279. [PMID: 32224152 DOI: 10.1016/j.bbamem.2020.183279] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 03/16/2020] [Accepted: 03/19/2020] [Indexed: 12/18/2022]
Abstract
The functional and structural concept of tight junctions has developed after discovery of claudin and TAMP proteins. Many of these proteins contribute to epi- and endothelial barrier but some, in contrast, form paracellular channels. Claudins form the backbone of tight junction (TJ) strands whereas other proteins regulate TJ dynamics. The current joined double-row model of TJ strands and channels is crucially based on the linear alignment of claudin-15 in the crystal. Molecular dynamics simulations, protein docking, mutagenesis, cellular TJ reconstitution, and electron microscopy studies largely support stability and functionality of the model. Here, we summarize in silico and in vitro data about TJ strand assembly including comparison of claudin crystal structures and alternative models. Sequence comparisons, experimental and structural data substantiate differentiation of classic and non-classic claudins differing in motifs related to strand assembly. Classic claudins seem to share a similar mechanism of strand formation. Interface variations likely contribute to TJ strand flexibility. Combined in vitro/in silico studies are expected to elucidate mechanistic keys determining TJ regulation.
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Affiliation(s)
- Jörg Piontek
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Susanne M Krug
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - Universitätsmedizin Berlin, 12203 Berlin, Germany
| | - Jonas Protze
- Leibniz-Institut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Gerd Krause
- Leibniz-Institut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Michael Fromm
- Institute of Clinical Physiology/Nutritional Medicine, Medical Department, Division of Gastroenterology, Infectiology, Rheumatology, Charité - Universitätsmedizin Berlin, 12203 Berlin, Germany.
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24
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Tipsmark CK, Nielsen AM, Bossus MC, Ellis LV, Baun C, Andersen TL, Dreier J, Brewer JR, Madsen SS. Drinking and Water Handling in the Medaka Intestine: A Possible Role of Claudin-15 in Paracellular Absorption? Int J Mol Sci 2020; 21:ijms21051853. [PMID: 32182691 PMCID: PMC7085193 DOI: 10.3390/ijms21051853] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 03/05/2020] [Accepted: 03/06/2020] [Indexed: 12/27/2022] Open
Abstract
When euryhaline fish move between fresh water (FW) and seawater (SW), the intestine undergoes functional changes to handle imbibed SW. In Japanese medaka, the potential transcellular aquaporin-mediated conduits for water are paradoxically downregulated during SW acclimation, suggesting paracellular transport to be of principal importance in hyperosmotic conditions. In mammals, intestinal claudin-15 (CLDN15) forms paracellular channels for small cations and water, which may participate in water transport. Since two cldn15 paralogs, cldn15a and cldn15b, have previously been identified in medaka, we examined the salinity effects on their mRNA expression and immunolocalization in the intestine. In addition, we analyzed the drinking rate and intestinal water handling by adding non-absorbable radiotracers, 51-Cr-EDTA or 99-Tc-DTPA, to the water. The drinking rate was >2-fold higher in SW than FW-acclimated fish, and radiotracer experiments showed anterior accumulation in FW and posterior buildup in SW intestines. Salinity had no effect on expression of cldn15a, while cldn15b was approximately 100-fold higher in FW than SW. Despite differences in transcript dynamics, Cldn15a and Cldn15b proteins were both similarly localized in the apical tight junctions of enterocytes, co-localizing with occludin and with no apparent difference in localization and abundance between FW and SW. The stability of the Cldn15 protein suggests a physiological role in water transport in the medaka intestine.
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Affiliation(s)
- Christian K. Tipsmark
- Department of Biological Sciences, University of Arkansas, SCEN 601, Fayetteville, AR 72701, USA; (M.C.B.); (L.V.E.); (S.S.M.)
- Correspondence: ; Tel.: +1-479-575-8436
| | - Andreas M. Nielsen
- Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark;
| | - Maryline C. Bossus
- Department of Biological Sciences, University of Arkansas, SCEN 601, Fayetteville, AR 72701, USA; (M.C.B.); (L.V.E.); (S.S.M.)
- Department of Math and Sciences, Lyon College, 2300 Highland Rd, Batesville, AR 72501, USA
| | - Laura V. Ellis
- Department of Biological Sciences, University of Arkansas, SCEN 601, Fayetteville, AR 72701, USA; (M.C.B.); (L.V.E.); (S.S.M.)
| | - Christina Baun
- Department of Nuclear Medicine, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense C, Denmark; (C.B.); (T.L.A.)
| | - Thomas L. Andersen
- Department of Nuclear Medicine, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense C, Denmark; (C.B.); (T.L.A.)
| | - Jes Dreier
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark; (J.D.); (J.R.B.)
| | - Jonathan R. Brewer
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark; (J.D.); (J.R.B.)
| | - Steffen S. Madsen
- Department of Biological Sciences, University of Arkansas, SCEN 601, Fayetteville, AR 72701, USA; (M.C.B.); (L.V.E.); (S.S.M.)
- Department of Biology, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark;
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25
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Assembly of Tight Junction Strands: Claudin-10b and Claudin-3 Form Homo-Tetrameric Building Blocks that Polymerise in a Channel-Independent Manner. J Mol Biol 2020; 432:2405-2427. [DOI: 10.1016/j.jmb.2020.02.034] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 02/12/2020] [Accepted: 02/28/2020] [Indexed: 02/03/2023]
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26
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Fuladi S, Jannat RW, Shen L, Weber CR, Khalili-Araghi F. Computational Modeling of Claudin Structure and Function. Int J Mol Sci 2020; 21:ijms21030742. [PMID: 31979311 PMCID: PMC7037046 DOI: 10.3390/ijms21030742] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 01/16/2020] [Accepted: 01/16/2020] [Indexed: 12/18/2022] Open
Abstract
Tight junctions form a barrier to control passive transport of ions and small molecules across epithelia and endothelia. In addition to forming a barrier, some of claudins control transport properties of tight junctions by forming charge- and size-selective ion channels. It has been suggested claudin monomers can form or incorporate into tight junction strands to form channels. Resolving the crystallographic structure of several claudins in recent years has provided an opportunity to examine structural basis of claudins in tight junctions. Computational and theoretical modeling relying on atomic description of the pore have contributed significantly to our understanding of claudin pores and paracellular transport. In this paper, we review recent computational and mathematical modeling of claudin barrier function. We focus on dynamic modeling of global epithelial barrier function as a function of claudin pores and molecular dynamics studies of claudins leading to a functional model of claudin channels.
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Affiliation(s)
- Shadi Fuladi
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA; (S.F.); (R.-W.J.)
| | - Ridaka-Wal Jannat
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA; (S.F.); (R.-W.J.)
| | - Le Shen
- Department of Pathology, University of Chicago, Chicago, IL 60637, USA;
- Department of Surgery, University of Chicago, Chicago, IL 60637, USA
| | - Christopher R. Weber
- Department of Pathology, University of Chicago, Chicago, IL 60637, USA;
- Correspondence: (C.R.W.); (F.K.-A.)
| | - Fatemeh Khalili-Araghi
- Department of Physics, University of Illinois at Chicago, Chicago, IL 60607, USA; (S.F.); (R.-W.J.)
- Correspondence: (C.R.W.); (F.K.-A.)
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Li JN, Zhang Z, Wu GZ, Yao DB, Cui SS. Claudin-15 overexpression inhibits proliferation and promotes apoptosis of Schwann cells in vitro. Neural Regen Res 2020; 15:169-177. [PMID: 31535666 PMCID: PMC6862392 DOI: 10.4103/1673-5374.264463] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Our previous experiments have discovered that Claudin-15 was up-regulated in Schwann cells of the distal nerve stumps of rat models of sciatic nerve injury. However, how Claudin-15 affects Schwann cell function is still unknown. This study aimed to identify the effects of Claudin-15 on proliferation and apoptosis of Schwann cells cultured in vitro and explore the underlying mechanisms. Primary Schwann cells were obtained from rats. Claudin-15 in Schwann cells was knocked down using siRNA (siRNA-1 group) compared with the negative control siRNA transfection group (negative control group). Claudin-15 in Schwann cells was overexpressed using pGV230-Claudin-15 plasmid (pGV230-Claudin-15 group). The pGV230 transfection group (pGV230 group) acted as the control of the pGV230-Claudin-15 group. Cell proliferation was analyzed with EdU assay. Cell apoptosis was analyzed with flow cytometric analysis. Cell migration was analyzed with Transwell inserts. The mRNA and protein expressions were analyzed with quantitative polymerase chain reaction assay and western blot assay. The results showed that compared with the negative control group, cell proliferation rate was up-regulated; p-AKT/AKT ratio, apoptotic rate, p-c-Jun/c-Jun ratio, mRNA expression of protein kinase C alpha, Bcl-2 and Bax were down-regulated; and mRNA expression of neurotrophins basic fibroblast growth factor and neurotrophin-3 were increased in the siRNA-1 group. No significant difference was found in cell migration between the negative control and siRNA-1 groups. Compared with the pGV230 group, the cell proliferation rate was down-regulated; apoptotic rate, p-c-Jun/c-Jun ratio and c-Fos protein expression increased; mRNA expression of protein kinase C alpha and Bax decreased; and mRNA expressions of neurotrophins basic fibroblast growth factor and neurotrophin-3 were up-regulated in the pGV230-Claudin-15 group. The above results demonstrated that overexpression of Claudin-15 inhibited Schwann cell proliferation and promoted Schwann cell apoptosis in vitro. Silencing of Claudin-15 had the reverse effect and provided neuroprotective effect. This study was approved by the Experimental Animal Ethics Committee of Jilin University of China (approval No. 2016-nsfc001) on March 5, 2016.
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Affiliation(s)
- Jian-Nan Li
- China-Japan Union Hospital of Jilin University, Changchun, Jilin Province, China
| | - Zhan Zhang
- China-Japan Union Hospital of Jilin University, Changchun, Jilin Province, China
| | - Guang-Zhi Wu
- China-Japan Union Hospital of Jilin University, Changchun, Jilin Province, China
| | - Deng-Bing Yao
- School of Life Sciences, Jiangsu Key Laboratory of Neuroregeneration, Co-innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu Province, China
| | - Shu-Sen Cui
- China-Japan Union Hospital of Jilin University, Changchun, Jilin Province, China
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Rosenthal R, Günzel D, Piontek J, Krug SM, Ayala‐Torres C, Hempel C, Theune D, Fromm M. Claudin-15 forms a water channel through the tight junction with distinct function compared to claudin-2. Acta Physiol (Oxf) 2020; 228:e13334. [PMID: 31188544 DOI: 10.1111/apha.13334] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 06/06/2019] [Accepted: 06/07/2019] [Indexed: 12/18/2022]
Abstract
AIM Claudin-15 is mainly expressed in the small intestine and indirectly involved in glucose absorption. Similar to claudin-2 and -10b, claudin-15 is known to form a paracellular channel for small cations. Claudin-2, but not claudin-10b, also forms water channels. Here we experimentally tested whether claudin-15 also mediates water transport and if yes, whether water transport is Na+ -coupled, as seen for claudin-2. METHODS MDCK C7 cells were stably transfected with claudin-15. Ion and water permeability were investigated in confluent monolayers of control and claudin-15-expressing cells. Water flux was induced by an osmotic or ionic gradient. RESULTS Expression of claudin-15 in MDCK cells strongly increased cation permeability. The permeability ratios for monovalent cations indicated a passage of partially hydrated ions through the claudin-15 pore. Accordingly, its pore diameter was determined to be larger than that of claudin-2 and claudin-10b. Mannitol-induced water flux was elevated in claudin-15-expressing cells compared to control cells. In contrast to the Na+ -coupled water flux of claudin-2 channels, claudin-15-mediated water flux was inhibited by Na+ flux. Consequently, water flux was increased in Na+ -free solution. Likewise, Na+ flux was decreased after induction of water flux through claudin-15. CONCLUSION Claudin-15, similar to claudin-2, forms a paracellular cation and water channel. In functional contrast to claudin-2, water and Na+ fluxes through claudin-15 inhibit each other. Claudin-15 allows Na+ to retain part of its hydration shell within the pore. This then reduces the simultaneous passage of additional water through the pore.
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Affiliation(s)
- Rita Rosenthal
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Institute of Clinical Physiology/Nutritional Medicine Charité – Universitätsmedizin Berlin Berlin Germany
| | - Dorothee Günzel
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Institute of Clinical Physiology/Nutritional Medicine Charité – Universitätsmedizin Berlin Berlin Germany
| | - Jörg Piontek
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Institute of Clinical Physiology/Nutritional Medicine Charité – Universitätsmedizin Berlin Berlin Germany
| | - Susanne M. Krug
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Institute of Clinical Physiology/Nutritional Medicine Charité – Universitätsmedizin Berlin Berlin Germany
| | - Carlos Ayala‐Torres
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Institute of Clinical Physiology/Nutritional Medicine Charité – Universitätsmedizin Berlin Berlin Germany
| | - Caroline Hempel
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Institute of Clinical Physiology/Nutritional Medicine Charité – Universitätsmedizin Berlin Berlin Germany
| | - Dian Theune
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Institute of Clinical Physiology/Nutritional Medicine Charité – Universitätsmedizin Berlin Berlin Germany
| | - Michael Fromm
- Department of Gastroenterology, Rheumatology and Infectious Diseases, Institute of Clinical Physiology/Nutritional Medicine Charité – Universitätsmedizin Berlin Berlin Germany
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Heinemann U, Schuetz A. Structural Features of Tight-Junction Proteins. Int J Mol Sci 2019; 20:E6020. [PMID: 31795346 PMCID: PMC6928914 DOI: 10.3390/ijms20236020] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Revised: 11/25/2019] [Accepted: 11/26/2019] [Indexed: 12/14/2022] Open
Abstract
Tight junctions are complex supramolecular entities composed of integral membrane proteins, membrane-associated and soluble cytoplasmic proteins engaging in an intricate and dynamic system of protein-protein interactions. Three-dimensional structures of several tight-junction proteins or their isolated domains have been determined by X-ray crystallography, nuclear magnetic resonance spectroscopy, and cryo-electron microscopy. These structures provide direct insight into molecular interactions that contribute to the formation, integrity, or function of tight junctions. In addition, the known experimental structures have allowed the modeling of ligand-binding events involving tight-junction proteins. Here, we review the published structures of tight-junction proteins. We show that these proteins are composed of a limited set of structural motifs and highlight common types of interactions between tight-junction proteins and their ligands involving these motifs.
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Affiliation(s)
- Udo Heinemann
- Macromolecular Structure and Interaction Laboratory, Max Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
| | - Anja Schuetz
- Protein Production & Characterization Platform, Max Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
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Rajagopal N, Irudayanathan FJ, Nangia S. Computational Nanoscopy of Tight Junctions at the Blood-Brain Barrier Interface. Int J Mol Sci 2019; 20:E5583. [PMID: 31717316 PMCID: PMC6888702 DOI: 10.3390/ijms20225583] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 11/05/2019] [Accepted: 11/06/2019] [Indexed: 12/16/2022] Open
Abstract
The selectivity of the blood-brain barrier (BBB) is primarily maintained by tight junctions (TJs), which act as gatekeepers of the paracellular space by blocking blood-borne toxins, drugs, and pathogens from entering the brain. The BBB presents a significant challenge in designing neurotherapeutics, so a comprehensive understanding of the TJ architecture can aid in the design of novel therapeutics. Unraveling the intricacies of TJs with conventional experimental techniques alone is challenging, but recently developed computational tools can provide a valuable molecular-level understanding of TJ architecture. We employed the computational methods toolkit to investigate claudin-5, a highly expressed TJ protein at the BBB interface. Our approach started with the prediction of claudin-5 structure, evaluation of stable dimer conformations and nanoscale assemblies, followed by the impact of lipid environments, and posttranslational modifications on these claudin-5 assemblies. These led to the study of TJ pores and barriers and finally understanding of ion and small molecule transport through the TJs. Some of these in silico, molecular-level findings, will need to be corroborated by future experiments. The resulting understanding can be advantageous towards the eventual goal of drug delivery across the BBB. This review provides key insights gleaned from a series of state-of-the-art nanoscale simulations (or computational nanoscopy studies) performed on the TJ architecture.
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Affiliation(s)
| | | | - Shikha Nangia
- Department of Biomedical and Chemical Engineering, Syracuse University, Syracuse, NY 13244, USA
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