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Jing J. The Relevance, Predictability, and Utility of Annexin A5 for Human Physiopathology. Int J Mol Sci 2024; 25:2865. [PMID: 38474114 PMCID: PMC10932194 DOI: 10.3390/ijms25052865] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 02/20/2024] [Accepted: 02/26/2024] [Indexed: 03/14/2024] Open
Abstract
As an important functional protein molecule in the human body, human annexin A5 (hAnxA5) is widely found in human cells and body fluids. hAnxA5, the smallest type of annexin, performs a variety of biological functions by reversibly and specifically binding phosphatidylserine (PS) in a calcium-dependent manner and plays an important role in many human physiological and pathological processes. The free state hAnxA5 exists in the form of monomers and usually forms a polymer in a specific self-assembly manner when exerting biological activity. This review systematically discusses the current knowledge and understanding of hAnxA5 from three perspectives: physiopathological relevance, diagnostic value, and therapeutic utility. hAnxA5 affects the occurrence and development of many physiopathological processes. Moreover, hAnxA5 can be used independently or in combination as a biomarker of physiopathological phenomena for the diagnosis of certain diseases. Importantly, based on the properties of hAnxA5, many novel drug candidates have been designed and prepared for application in actual medical practice. However, there are also some gaps and shortcomings in hAnxA5 research. This in-depth study will not only expand the understanding of structural and functional relationships but also promote the application of hAnxA5 in the field of biomedicine.
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Affiliation(s)
- Jian Jing
- Beijing Key Laboratory of Biotechnology and Genetic Engineering, College of Life Sciences, Beijing Normal University, Beijing 100875, China
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Kim H, Kim HY, Lee EY, Choi BK, Jang H, Choi Y. A Quenched Annexin V-Fluorophore for the Real-Time Fluorescence Imaging of Apoptotic Processes In Vitro and In Vivo. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2020; 7:2002988. [PMID: 33344139 PMCID: PMC7740095 DOI: 10.1002/advs.202002988] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 09/19/2020] [Indexed: 05/14/2023]
Abstract
Annexin-based probes have long been used to study apoptotic cell death, which is of key importance to many areas of biological research, drug discovery, and clinical applications. Although apoptosis is a dynamic biological event with cell-to-cell variations, current annexin-based probes are impractical for monitoring apoptosis in real-time. Herein, a quenched annexin V-near-infrared fluorophore conjugate (Q-annexin V) is reported as the first OFF-ON annexin protein-based molecular sensor for real-time near-infrared fluorescence imaging of apoptosis. Q-annexin V is non-fluorescent in the extracellular region, due to photoinduced electron transfer interactions between the conjugated dye and amino acid quenchers (tryptophan and tyrosine). The probe becomes highly fluorescent when bound to phosphatidylserines on the outer layer of cell membranes during apoptosis, thereby enabling apoptosis to be monitored in real-time in 2D and 3D cell structures. In particular, Q-annexin V shows superior utility for in vivo apoptosis fluorescence imaging in animal models of cisplatin-induced acute kidney injury and cancer immune therapy, compared to the conventional polarity-sensitive pSIVA-IANBD or annexin V-Alexa647 conjugates.
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Affiliation(s)
- Hyunjin Kim
- Research InstituteNational Cancer Center323 Ilsan‐roGoyangGyeonggi10408Republic of Korea
| | - Hee Yeon Kim
- Research InstituteNational Cancer Center323 Ilsan‐roGoyangGyeonggi10408Republic of Korea
| | - Eun Young Lee
- Research InstituteNational Cancer Center323 Ilsan‐roGoyangGyeonggi10408Republic of Korea
| | - Boem Kyu Choi
- Research InstituteNational Cancer Center323 Ilsan‐roGoyangGyeonggi10408Republic of Korea
| | - Hyonchol Jang
- Research InstituteNational Cancer Center323 Ilsan‐roGoyangGyeonggi10408Republic of Korea
- Department of Cancer Biomedical ScienceNational Cancer Center Graduate School of Cancer Science and Policy323 Ilsan‐roGoyangGyeonggi10408Republic of Korea
| | - Yongdoo Choi
- Research InstituteNational Cancer Center323 Ilsan‐roGoyangGyeonggi10408Republic of Korea
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Fernández-Lizarbe S, Lecona E, Santiago-Gómez A, Olmo N, Lizarbe MA, Turnay J. Structural and lipid-binding characterization of human annexin A13a reveals strong differences with its long A13b isoform. Biol Chem 2017; 398:359-371. [PMID: 27676605 DOI: 10.1515/hsz-2016-0242] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 09/22/2016] [Indexed: 01/26/2023]
Abstract
Annexin A13 is the founder member of the vertebrate family of annexins, which are comprised of a tetrad of unique conserved domains responsible for calcium-dependent binding to membranes. Its expression is restricted to epithelial intestinal and kidney cells. Alternative splicing in the N-terminal region generates two isoforms, A13a and A13b, differing in a deletion of 41 residues in the former. We have confirmed the expression of both isoforms in human colon adenocarcinoma cells at the mRNA and protein levels. We have cloned, expressed, and purified human annexin A13a for the first time to analyze its structural characteristics. Its secondary structure and thermal stability differs greatly from the A13b isoform. The only tryptophan residue (Trp186) is buried in the protein core in the absence of calcium but is exposed to the solvent after calcium binding even though circular dichroism spectra are quite similar. Non-myristoylated annexin A13a binds in a calcium-dependent manner to acidic phospholipids but not to neutral or raft-like liposomes. Calcium requirements for binding to phosphatidylserine are around 6-fold lower than those required by the A13b isoform. This fact could account for the different subcellular localization of both annexins as binding to basolateral membranes seems to be calcium-dependent and myristoylation-independent.
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Chen Z, Mao Y, Yang J, Zhang T, Zhao L, Yu K, Zheng M, Jiang H, Yang H. Characterizing the binding of annexin V to a lipid bilayer using molecular dynamics simulations. Proteins 2013; 82:312-22. [DOI: 10.1002/prot.24389] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 07/07/2013] [Accepted: 08/01/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Zhuxi Chen
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
| | - Yanyan Mao
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
| | - Jing Yang
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
| | - Tao Zhang
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
| | - Lifen Zhao
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
| | - Kunqian Yu
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
| | - Mingyue Zheng
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
| | - Hualiang Jiang
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
| | - Huaiyu Yang
- Drug Discovery and Design Center; State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 China
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Clark GB, Morgan RO, Fernandez MP, Roux SJ. Evolutionary adaptation of plant annexins has diversified their molecular structures, interactions and functional roles. THE NEW PHYTOLOGIST 2012; 196:695-712. [PMID: 22994944 DOI: 10.1111/j.1469-8137.2012.04308.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 07/29/2012] [Indexed: 05/04/2023]
Abstract
Annexins are an homologous, structurally related superfamily of proteins known to associate with membrane lipid and cytoskeletal components. Their involvement in membrane organization, vesicle trafficking and signaling is fundamental to cellular processes such as growth, differentiation, secretion and repair. Annexins exist in some prokaryotes and all eukaryotic phyla within which plant annexins represent a monophyletic clade of homologs descended from green algae. Genomic, proteomic and transcriptomic approaches have provided data on the diversity, cellular localization and expression patterns of different plant annexins. The availability of 35 complete plant genomes has enabled systematic comparative analysis to determine phylogenetic relationships, characterize structures and observe functional specificity between and within individual subfamilies. Short amino termini and selective erosion of the canonical type 2 calcium coordinating sites in domains 2 and 3 are typical of plant annexins. The convergent evolution of alternate functional motifs such as 'KGD', redox-sensitive Cys and hydrophobic Trp/Phe residues argues for their functional relevance and contribution to mechanistic diversity in plant annexins. This review examines recent findings and advances in plant annexin research with special focus on their structural diversity, cellular and molecular interactions and their potential integrated functions in the broader context of physiological responses.
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Affiliation(s)
- Greg B Clark
- Section of Molecular Cell and Developmental Biology, University of Texas, Austin, TX, 78713, USA
| | - Reginald O Morgan
- Department of Biochemistry and Molecular Biology, Faculty of Medicine and University Institute of Biotechnology of Asturias, University of Oviedo, E-33006, Oviedo, Spain
| | - Maria-Pilar Fernandez
- Department of Biochemistry and Molecular Biology, Faculty of Medicine and University Institute of Biotechnology of Asturias, University of Oviedo, E-33006, Oviedo, Spain
| | - Stanley J Roux
- Section of Molecular Cell and Developmental Biology, University of Texas, Austin, TX, 78713, USA
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Identification, phylogenetic relationships, characterization and gene expression patterns of six different annexins of channel catfish (Ictalurus punctatus Rafinesque, 1818). Vet Immunol Immunopathol 2010; 136:176-83. [DOI: 10.1016/j.vetimm.2010.02.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 02/05/2010] [Accepted: 02/17/2010] [Indexed: 11/21/2022]
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Turnay J, Guzmán-Aránguez A, Lecona E, Barrasa JI, Olmo N, Lizarbe MA. Key role of the N-terminus of chicken annexin A5 in vesicle aggregation. Protein Sci 2009; 18:1095-106. [PMID: 19388055 PMCID: PMC2771311 DOI: 10.1002/pro.119] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Accepted: 02/27/2009] [Indexed: 11/12/2022]
Abstract
Annexins are calcium-dependent phospholipid-binding proteins involved in calcium signaling and intracellular membrane trafficking among other functions. Vesicle aggregation is a crucial event to make possible the membrane remodeling but this process is energetically unfavorable, and phospholipid membranes do not aggregate and fuse spontaneously. This issue can be circumvented by the presence of different agents such as divalent cations and/or proteins, among them some annexins. Although human annexin A5 lacks the ability to aggregate vesicles, here we demonstrate that its highly similar chicken ortholog induces aggregation of vesicles containing acidic phospholipids even at low protein and/or calcium concentration by establishment of protein dimers. Our experiments show that the ability to aggregate vesicles mainly resides in the N-terminus as truncation of the N-terminus of chicken annexin A5 significantly decreases this process and replacement of the N-terminus of human annexin A5 by that of chicken switches on aggregation; in both cases, there are no changes in the overall protein structure and only minor changes in phospholipid binding. Electrostatic repulsions between negatively charged residues in the concave face of the molecule, mainly in the N-terminus, seem to be responsible for the impairment of dimer formation in human annexin A5. Taking into account that chicken annexin A5 presents a high sequence and structural similarity with mammalian annexins absent in birds, as annexins A3 and A4, some of the physiological functions exerted by these proteins may be carried out by chicken annexin A5, even those that could require calcium-dependent membrane aggregation.
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Affiliation(s)
| | | | | | | | | | - Ma Antonia Lizarbe
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense28040-Madrid, Spain
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Zibouche M, Vincent M, Illien F, Gallay J, Ayala-Sanmartin J. The N-terminal domain of annexin 2 serves as a secondary binding site during membrane bridging. J Biol Chem 2008; 283:22121-7. [PMID: 18508775 DOI: 10.1074/jbc.m801000200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Annexin A2 (AnxA2) is a Ca(2+)- and acidic phospholipid-binding protein involved in many cellular processes. It undergoes Ca(2+)-mediated membrane bridging at neutral pH and has been demonstrated to be involved in an H(+)-mediated mechanism leading to a novel AnxA2-membrane complex structure. We used fluorescence techniques to characterize this H(+)-dependent mechanism at the molecular level; in particular, the involvement of the AnxA2 N-terminal domain. This domain was labeled at Cys-8 either with acrylodan or pyrene-maleimide fluorescent probes. Steady-state and time-resolved fluorescence analysis for acrylodan and fluorescence quenching by doxyl-labeled phospholipids revealed direct interaction between the N-terminal domain and the membrane. The absence of pyrene excimer suggested that interactions between N termini are not involved in the H(+)-mediated mechanism. These findings differ from those previously observed for the Ca(2+)-mediated mechanism. Protein titration experiments showed that the protein concentration for half-maximal membrane aggregation was twice for Ca(2+)-mediated compared with H(+)-mediated aggregation, suggesting that AnxA2 was able to bridge membranes either as a dimer or as a monomer, respectively. An N-terminally deleted AnxA2 was 2-3 times less efficient than the wild-type protein for H(+)-mediated membrane aggregation. We propose a model of AnxA2-membrane assemblies, highlighting the different roles of the N-terminal domain in the H(+)- and Ca(2+)-mediated membrane bridging mechanisms.
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Turnay J, Lecona E, Fernández-Lizarbe S, Guzmán-Aránguez A, Fernández M, Olmo N, Lizarbe M. Structure-function relationship in annexin A13, the founder member of the vertebrate family of annexins. Biochem J 2005; 389:899-911. [PMID: 15813707 PMCID: PMC1180741 DOI: 10.1042/bj20041918] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Annexin A13 is considered the original progenitor of the 11 other members of vertebrate annexins, a superfamily of calcium/phospholipid-binding proteins. It is highly tissue-specific, being expressed only in intestinal and kidney epithelial cells. Alternative splicing generates two isoforms, both of which bind to rafts. In view of the lack of structural information supporting the physiological role of this annexin subfamily, we have cloned, expressed and purified human annexin A13b to investigate its structural and functional properties. The N-terminus of annexin A13b: (i) destabilizes the conserved protein core, as deduced from the low melting temperature in the absence (44 degrees C) or presence of calcium (55 degrees C), and (ii) impairs calcium-dependent binding to acidic phospholipids, requiring calcium concentrations >400 microM. Truncation of the N-terminus restores thermal stability and decreases the calcium requirement for phospholipid binding, confirming its essential role in the structure-function relationship of this annexin. Non-myristoylated annexin A13b only binds to acidic phospholipids at high calcium concentrations. We show for the first time that myristoylation of annexin A13b enables the direct binding to phosphatidylcholine, raft-like liposomes and acidic phospholipids in a calcium-independent manner. The conformational switch induced by calcium binding, from a 'closed' to an 'open' conformation with exposure of Trp227, can be mimicked by a decrease in pH, a process that may be relevant for membrane interactions. Our studies confirm that the common structural and functional characteristics that are dependent on the protein core of vertebrate annexins are likely to be common conserved features, whereas their variable N-termini confer distinct functional properties on annexins, as we report for myristoylation of annexin A13b.
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Affiliation(s)
- Javier Turnay
- *Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040-Madrid, Spain
| | - Emilio Lecona
- *Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040-Madrid, Spain
| | - Sara Fernández-Lizarbe
- *Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040-Madrid, Spain
| | - Ana Guzmán-Aránguez
- *Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040-Madrid, Spain
| | - María Pilar Fernández
- †Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Oviedo, 33006-Oviedo, Spain
| | - Nieves Olmo
- *Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040-Madrid, Spain
| | - Ma Antonia Lizarbe
- *Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Químicas, Universidad Complutense, 28040-Madrid, Spain
- To whom correspondence should be addressed (email )
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Hofmann A, Huber R. Structural Conservation and Functional Versatility: Allostery as a Common Annexin Feature. ANNEXINS 2003. [DOI: 10.1007/978-1-4419-9214-7_3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Turnay J, Olmo N, Gasset M, Iloro I, Arrondo JLR, Lizarbe MA. Calcium-dependent conformational rearrangements and protein stability in chicken annexin A5. Biophys J 2002; 83:2280-91. [PMID: 12324445 PMCID: PMC1302316 DOI: 10.1016/s0006-3495(02)73988-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The conformational rearrangements that take place after calcium binding in chicken annexin A5 and a mutant lacking residues 3-10 were analyzed, in parallel with human annexin A5, by circular dichroism (CD), infrared spectroscopy (IR), and differential scanning calorimetry. Human and chicken annexins present a slightly different shape in the far-UV CD and IR spectra, but the main secondary-structure features are quite similar (70-80% alpha-helix). However, thermal stability of human annexin is significantly lower than its chicken counterpart (approximately 8 degrees C) and equivalent to the chicken N-terminally truncated form. The N-terminal extension contributes greatly to stabilize the overall annexin A5 structure. Infrared spectroscopy reveals the presence of two populations of alpha-helical structures, the canonical alpha-helices (approximately 1650 cm(-1)) and another, at a lower wavenumber (approximately 1634 cm(-1)), probably arising from helix-helix interactions or solvated alpha-helices. Saturation with calcium induces: alterations in the environment of the unique tryptophan residue of the recombinant proteins, as detected by near-UV CD spectroscopy; more compact tertiary structures that could account for the higher thermal stabilities (8 to 12 degrees C), this effect being higher for human annexin; and an increase in canonical alpha-helix percentage by a rearrangement of nonperiodical structure or 3(10) helices together with a variation in helix-helix interactions, as shown by amide I curve-fitting and 2D-IR.
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Affiliation(s)
- Javier Turnay
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain
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Sopkova J, Raguenes-Nicol C, Vincent M, Chevalier A, Lewit-Bentley A, Russo-Marie F, Gallay J. Ca(2+) and membrane binding to annexin 3 modulate the structure and dynamics of its N terminus and domain III. Protein Sci 2002; 11:1613-25. [PMID: 12070314 PMCID: PMC2373663 DOI: 10.1110/ps.4230102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Annexin 3 (ANX A3) represents approximately 1% of the total protein of human neutrophils and promotes tight contact between membranes of isolated specific granules in vitro leading to their aggregation. Like for other annexins, the primary molecular events of the action of this protein is likely its binding to negatively charged phospholipid membranes in a Ca(2+)-dependent manner, via Ca(2+)-binding sites located on the convex side of the highly conserved core of the molecule. The conformation and dynamics of domain III can be affected by this process, as it was shown for other members of the family. The 20 amino-acid, N-terminal segment of the protein also could be affected and also might play a role in the modulation of its binding to the membranes. The structure and dynamics of these two regions were investigated by fluorescence of the two tryptophan residues of the protein (respectively, W190 in domain III and W5 in the N-terminal segment) in the wild type and in single-tryptophan mutants. By contrast to ANX A5, which shows a closed conformation and a buried W187 residue in the absence of Ca(2+), domain III of ANX A3 exhibits an open conformation and a widely solvent-accessible W190 residue in the same conditions. This is in agreement with the three-dimensional structure of the ANX A3-E231A mutant lacking the bidentate Ca(2+) ligand in domain III. Ca(2+) in the millimolar concentration range provokes nevertheless a large mobility increase of the W190 residue, while interaction with the membranes reduces it slightly. In the N-terminal region, the W5 residue, inserted in the central pore of the protein, is weakly accessible to the solvent and less mobile than W190. Its amplitude of rotation increases upon binding of Ca(2+) and returns to its original value when interacting with membranes. Ca(2+) concentration for half binding of the W5A mutant to negatively charged membranes is approximately 0.5 mM while it increases to approximately 1 mM for the ANX A3 wild type and to approximately 3 mM for the W190 ANX A3 mutant. In addition to the expected perturbation of the W190 environment at the contact surface between the protein and the membrane bilayer, binding of the protein to Ca(2+) and to membranes modulates the flexibility of the ANX A3 hinge region at the opposite of this interface and might affect its membrane permeabilizing properties.
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Affiliation(s)
- Jana Sopkova
- L.U.R.E., Bâtiment 209D, Centre Universitaire Paris-Sud, F-91898 Orsay, France
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Abstract
Annexins are Ca2+ and phospholipid binding proteins forming an evolutionary conserved multigene family with members of the family being expressed throughout animal and plant kingdoms. Structurally, annexins are characterized by a highly alpha-helical and tightly packed protein core domain considered to represent a Ca2+-regulated membrane binding module. Many of the annexin cores have been crystallized, and their molecular structures reveal interesting features that include the architecture of the annexin-type Ca2+ binding sites and a central hydrophilic pore proposed to function as a Ca2+ channel. In addition to the conserved core, all annexins contain a second principal domain. This domain, which NH2-terminally precedes the core, is unique for a given member of the family and most likely specifies individual annexin properties in vivo. Cellular and animal knock-out models as well as dominant-negative mutants have recently been established for a number of annexins, and the effects of such manipulations are strikingly different for different members of the family. At least for some annexins, it appears that they participate in the regulation of membrane organization and membrane traffic and the regulation of ion (Ca2+) currents across membranes or Ca2+ concentrations within cells. Although annexins lack signal sequences for secretion, some members of the family have also been identified extracellularly where they can act as receptors for serum proteases on the endothelium as well as inhibitors of neutrophil migration and blood coagulation. Finally, deregulations in annexin expression and activity have been correlated with human diseases, e.g., in acute promyelocytic leukemia and the antiphospholipid antibody syndrome, and the term annexinopathies has been coined.
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Affiliation(s)
- Volker Gerke
- Institute for Medical Biochemistry, Center for Molecular Biology of Inflammation, University of Münster, Münster, Germany
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