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Sudarikova A, Vasileva V, Sultanova R, Ilatovskaya D. Recent advances in understanding ion transport mechanisms in polycystic kidney disease. Clin Sci (Lond) 2021; 135:2521-2540. [PMID: 34751394 PMCID: PMC8589009 DOI: 10.1042/cs20210370] [Citation(s) in RCA: 9] [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: 04/05/2021] [Revised: 10/15/2021] [Accepted: 10/26/2021] [Indexed: 12/18/2022]
Abstract
This review focuses on the most recent advances in the understanding of the electrolyte transport-related mechanisms important for the development of severe inherited renal disorders, autosomal dominant (AD) and recessive (AR) forms of polycystic kidney disease (PKD). We provide here a basic overview of the origins and clinical aspects of ARPKD and ADPKD and discuss the implications of electrolyte transport in cystogenesis. Special attention is devoted to intracellular calcium handling by the cystic cells, with a focus on polycystins and fibrocystin, as well as other calcium level regulators, such as transient receptor potential vanilloid type 4 (TRPV4) channels, ciliary machinery, and purinergic receptor remodeling. Sodium transport is reviewed with a focus on the epithelial sodium channel (ENaC), and the role of chloride-dependent fluid secretion in cystic fluid accumulation is discussed. In addition, we highlight the emerging promising concepts in the field, such as potassium transport, and suggest some new avenues for research related to electrolyte handling.
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Affiliation(s)
| | | | - Regina F. Sultanova
- Saint-Petersburg State Chemical Pharmaceutical University, St. Petersburg, Russia
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Piiadov V, Ares de Araújo E, Oliveira Neto M, Craievich AF, Polikarpov I. SAXSMoW 2.0: Online calculator of the molecular weight of proteins in dilute solution from experimental SAXS data measured on a relative scale. Protein Sci 2018; 28:454-463. [PMID: 30371978 DOI: 10.1002/pro.3528] [Citation(s) in RCA: 105] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 10/05/2018] [Accepted: 10/08/2018] [Indexed: 11/07/2022]
Abstract
Knowledge of molecular weight, oligomeric states, and quaternary arrangements of proteins in solution is fundamental for understanding their molecular functions and activities. We describe here a program SAXSMoW 2.0 for robust and quick determination of molecular weight and oligomeric state of proteins in dilute solution, starting from a single experimental small-angle scattering intensity curve, I(q), measured on a relative scale. The first version of this calculator has been widely used during the last decade and applied to analyze experimental SAXS data of many proteins and protein complexes. SAXSMoW 2.0 exhibits new features which allow for the direct input of experimental intensity curves and also automatic modes for quick determinations of the radius of gyration, volume, and molecular weight. The new program was extensively tested by applying it to many experimental SAXS curves downloaded from the open databases, corresponding to proteins with different shapes and molecular weights ranging from ~10 kDa up to about ~500 kDa and different shapes from globular to elongated. These tests reveal that the use of SAXSMoW 2.0 allows for determinations of molecular weights of proteins in dilute solution with a median discrepancy of about 12% for globular proteins. In case of elongated molecules, discrepancy value can be significantly higher. Our tests show discrepancies of approximately 21% for the proteins with molecular shape aspect ratios up to 18.
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Affiliation(s)
- Vassili Piiadov
- Institute of Physics of São Carlos, University of São Paulo, São Carlos, São Paulo, Brazil
| | - Evandro Ares de Araújo
- Institute of Physics of São Carlos, University of São Paulo, São Carlos, São Paulo, Brazil
| | - Mario Oliveira Neto
- Institute of Biosciences, University Estadual Paulista, Botucatu, São Paulo, Brazil
| | | | - Igor Polikarpov
- Institute of Physics of São Carlos, University of São Paulo, São Carlos, São Paulo, Brazil
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Mukherjee S, Mondal S, Deshmukh AA, Gopal B, Bagchi B. What Gives an Insulin Hexamer Its Unique Shape and Stability? Role of Ten Confined Water Molecules. J Phys Chem B 2018; 122:1631-1637. [DOI: 10.1021/acs.jpcb.8b00453] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Saumyak Mukherjee
- Solid
State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India
| | - Sayantan Mondal
- Solid
State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India
| | | | | | - Biman Bagchi
- Solid
State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India
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Busch T, Köttgen M, Hofherr A. TRPP2 ion channels: Critical regulators of organ morphogenesis in health and disease. Cell Calcium 2017; 66:25-32. [PMID: 28807147 DOI: 10.1016/j.ceca.2017.05.005] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 05/08/2017] [Accepted: 05/08/2017] [Indexed: 12/31/2022]
Abstract
Ion channels control the membrane potential and mediate transport of ions across membranes. Archetypical physiological functions of ion channels include processes such as regulation of neuronal excitability, muscle contraction, or transepithelial ion transport. In that regard, transient receptor potential ion channel polycystin 2 (TRPP2) is remarkable, because it controls complex morphogenetic processes such as the establishment of properly shaped epithelial tubules and left-right-asymmetry of organs. The fascinating question of how an ion channel regulates morphogenesis has since captivated the attention of scientists in different disciplines. Four loosely connected key insights on different levels of biological complexity ranging from protein to whole organism have framed our understanding of TRPP2 physiology: 1) TRPP2 is a non-selective cation channel; 2) TRPP2 is part of a receptor-ion channel complex; 3) TRPP2 localizes to primary cilia; and 4) TRPP2 is required for organ morphogenesis. In this review, we will discuss the current knowledge in these key areas and highlight some of the challenges ahead.
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Affiliation(s)
- Tilman Busch
- Renal Division, Department of Medicine, Faculty of Medicine, University of Freiburg, Hugstetter Straße 55, 79106 Freiburg, Germany
| | - Michael Köttgen
- Renal Division, Department of Medicine, Faculty of Medicine, University of Freiburg, Hugstetter Straße 55, 79106 Freiburg, Germany.
| | - Alexis Hofherr
- Renal Division, Department of Medicine, Faculty of Medicine, University of Freiburg, Hugstetter Straße 55, 79106 Freiburg, Germany.
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Yang Y, Ehrlich BE. Structural studies of the C-terminal tail of polycystin-2 (PC2) reveal insights into the mechanisms used for the functional regulation of PC2. J Physiol 2016; 594:4141-9. [PMID: 26857659 DOI: 10.1113/jp270933] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 01/21/2016] [Indexed: 01/17/2023] Open
Abstract
Mutations in polycystin-2 (PC2) lead to autosomal dominant polycystic kidney disease (ADPKD). The molecular mechanism linking mutations in PC2 and the pathogenesis of ADPKD is not well understood. Therefore, understanding the functional regulation of PC2 and its interaction with other proteins under both physiological and pathogenic conditions is important for elucidating the disease mechanism and identifying potential molecular targets for treatment. Normally, PC2 functions as a calcium-permeable channel whose activity is regulated by calcium binding to the C-terminal domain of PC2 (PC2 Cterm). The PC2 Cterm is also involved in the PC2 channel assembly and hetero-oligomerization with other binding partners in cells. Different functional domains of the PC2 Cterm have been studied using structural approaches. Within the PC2 Cterm, there is a calcium-binding EF-hand domain, crucial for the calcium-dependent activity of the PC2 channel. Downstream of the EF-hand domain lies a coiled-coil region, which is involved in the assembly and hetero-interaction of the PC2 protein. The PC2 Cterm can form an oligomer, mediated by the coiled-coil region. Although PC2 Cterm has been extensively studied for its relationship with ADPKD and its importance in PC2 regulation, there are misunderstandings with respect to the definition of the domain topology within the PC2 Cterm and the functional role of each domain. Here, we review previous studies that connect the molecular properties of the domains of PC2 Cterm to distinct aspects of PC2 functions and regulation.
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Affiliation(s)
- Yifei Yang
- Department of Laboratory Medicine, Yale University, New Haven, CT, 06520, USA.,Department of Pharmacology, Yale University, New Haven, CT, 06520, USA
| | - Barbara E Ehrlich
- Department of Pharmacology, Yale University, New Haven, CT, 06520, USA.,Department of Cellular and Molecular Physiology, Yale University, New Haven, CT, 06520, USA
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Yang Y, Keeler C, Kuo IY, Lolis EJ, Ehrlich BE, Hodsdon ME. Oligomerization of the polycystin-2 C-terminal tail and effects on its Ca2+-binding properties. J Biol Chem 2015; 290:10544-54. [PMID: 25716316 PMCID: PMC4400361 DOI: 10.1074/jbc.m115.641803] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Indexed: 02/05/2023] Open
Abstract
Polycystin-2 (PC2) belongs to the transient receptor potential (TRP) family and forms a Ca2+-regulated channel. The C-terminal cytoplasmic tail of human PC2 (HPC2 Cterm) is important for PC2 channel assembly and regulation. In this study, we characterized the oligomeric states and Ca2+-binding profiles in the C-terminal tail using biophysical approaches. Specifically, we determined that HPC2 Cterm forms a trimer in solution with and without Ca2+ bound, although TRP channels are believed to be tetramers. We found that there is only one Ca2+-binding site in the HPC2 Cterm, located within its EF-hand domain. However, the Ca2+ binding affinity of the HPC2 Cterm trimer is greatly enhanced relative to the intrinsic binding affinity of the isolated EF-hand domain. We also employed the sea urchin PC2 (SUPC2) as a model for biophysical and structural characterization. The sea urchin C-terminal construct (SUPC2 Ccore) also forms trimers in solution, independent of Ca2+ binding. In contrast to the human PC2, the SUPC2 Ccore contains two cooperative Ca2+-binding sites within its EF-hand domain. Consequently, trimerization does not further improve the affinity of Ca2+ binding in the SUPC2 Ccore relative to the isolated EF-hand domain. Using NMR, we localized the Ca2+-binding sites in the SUPC2 Ccore and characterized the conformational changes in its EF-hand domain due to trimer formation. Our study provides a structural basis for understanding the Ca2+-dependent regulation of the PC2 channel by its cytosolic C-terminal domain. The improved methodology also serves as a good strategy to characterize other Ca2+-binding proteins.
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Affiliation(s)
- Yifei Yang
- From the Departments of Laboratory Medicine, Pharmacology, and
| | | | | | | | - Barbara E Ehrlich
- Pharmacology, and Cellular and Molecular Physiology, School of Medicine, Yale University, New Haven, Connecticut 06520
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Cyst growth, polycystins, and primary cilia in autosomal dominant polycystic kidney disease. Kidney Res Clin Pract 2014; 33:73-8. [PMID: 26877954 PMCID: PMC4714135 DOI: 10.1016/j.krcp.2014.05.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 05/12/2014] [Accepted: 05/12/2014] [Indexed: 12/15/2022] Open
Abstract
The primary cilium of renal epithelia acts as a transducer of extracellular stimuli. Polycystin (PC)1 is the protein encoded by the PKD1 gene that is responsible for the most common and severe form of autosomal dominant polycystic kidney disease (ADPKD). PC1 forms a complex with PC2 via their respective carboxy-terminal tails. Both proteins are expressed in the primary cilia. Mutations in either gene affect the normal architecture of renal tubules, giving rise to ADPKD. PC1 has been proposed as a receptor that modulates calcium signals via the PC2 channel protein. The effect of PC1 dosage has been described as the rate-limiting modulator of cystic disease. Reduced levels of PC1 or disruption of the balance in PC1/PC2 level can lead to the clinical features of ADPKD, without complete inactivation. Recent data show that ADPKD resulting from inactivation of polycystins can be markedly slowed if structurally intact cilia are also disrupted at the same time. Despite the fact that no single model or mechanism from these has been able to describe exclusively the pathogenesis of cystic kidney disease, these findings suggest the existence of a novel cilia-dependent, cyst-promoting pathway that is normally repressed by polycystin function. The results enable us to rethink our current understanding of genetics and cilia signaling pathways of ADPKD.
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Fedeles SV, Gallagher AR, Somlo S. Polycystin-1: a master regulator of intersecting cystic pathways. Trends Mol Med 2014; 20:251-60. [PMID: 24491980 DOI: 10.1016/j.molmed.2014.01.004] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Revised: 01/04/2014] [Accepted: 01/07/2014] [Indexed: 12/13/2022]
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is the most common potentially lethal monogenic disorder, with more than 12 million cases worldwide. The two causative genes for ADPKD, PKD1 and PKD2, encode protein products polycystin-1 (PC1) and polycystin-2 (PC2 or TRPP2), respectively. Recent data have shed light on the role of PC1 in regulating the severity of the cystic phenotypes in ADPKD, autosomal recessive polycystic kidney disease (ARPKD), and isolated autosomal dominant polycystic liver disease (ADPLD). These studies showed that the rate for cyst growth was a regulated trait, a process that can be either sped up or slowed down by alterations in functional PC1. These findings redefine the previous understanding that cyst formation occurs as an 'on-off' process. Here, we review these and other related studies with an emphasis on their translational implications for polycystic diseases.
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Affiliation(s)
- Sorin V Fedeles
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA.
| | - Anna-Rachel Gallagher
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
| | - Stefan Somlo
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA; Department of Genetics, Yale University School of Medicine, New Haven, CT, USA.
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Affiliation(s)
- Ivana Y Kuo
- Departments of †Pharmacology and ‡Cellular and Molecular Physiology School of Medicine, Yale University , 333 Cedar Street, New Haven, Connecticut 06520
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