Thursday, August 28, 2008
Tuesday, August 19, 2008
Annexin A5
From Wikipedia, the free encyclopedia
Jump to: navigation, search
edit
Annexin A5
PDB rendering based on 1a8a.
Available structures: 1a8a, 1a8b, 1anw, 1anx, 1avh, 1avr, 1bc0, 1bc1, 1bc3, 1bcw, 1bcy, 1bcz, 1g5n, 1hak, 1hvd, 1hve, 1hvf, 1hvg, 1n41, 1n42, 1n44, 1sav, 2ie6, 2ie7, 2ran
Identifiers
Symbol(s)
ANXA5; ANX5; ENX2; PP4
External IDs
OMIM: 131230 MGI: 106008 HomoloGene: 20312
[show]Gene ontology
Molecular Function:
• phospholipase inhibitor activity• calcium ion binding• protein binding• calcium-dependent phospholipid binding
Cellular Component:
• intracellular• cytoplasm
Biological Process:
• anti-apoptosis• signal transduction• blood coagulation• negative regulation of coagulation
RNA expression pattern
More reference expression data
Orthologs
Human
Mouse
Entrez
308
11747
Ensembl
ENSG00000164111
ENSMUSG00000027712
Uniprot
P08758
Q3U5Q1
Refseq
NM_001154 (mRNA)NP_001145 (protein)
NM_009673 (mRNA)NP_033803 (protein)
Location
Chr 4: 122.81 - 122.84 Mb
Chr 3: 36.64 - 36.66 Mb
Pubmed search
[1]
[2]
Annexin A5 (or annexin V) is a cellular protein in the annexin group. The function of the protein is unknown, however annexin A5 has been proposed to play a role in the inhibition of blood coagulation by competing for phosphatidylserine binding sites with prothrombin and also to inhibit the activity of phospholipase A1 also by competing for phosphatidylserine binding sites. These properties have been found by in vitro experiments (in a test tube) and they have not been confirmed by experiments with laboratory animals.
Contents[hide]
1 Annexin A5 in pathology
2 Laboratory use of annexin A5
3 References
4 Further reading
5 External links
//
[edit] Annexin A5 in pathology
Antibodies directed against annexin A5 are the cause of a syndrome called the antiphospholipid syndrome.
Annexin A5 forms a shield around negatively-charged phospholipid molecules. The formation of an annexin A5 shield blocks the entry of phospholipids into coagulation (clotting) reactions. In the antiphospholipid antibody syndrome, the formation of the shield is disrupted by antibodies. Without the shield, there is an increased quantity of phospholipid molecules on cell membranes, speeding up coagulation reactions and causing the blood-clotting characteristic of the antiphospholipid antibody syndrome.
[edit] Laboratory use of annexin A5
Annexin A5 is used as a probe in the annexin A5 affinity assay to detect cells that have expressed phosphatidylserine on the cell surface, a feature found in apoptosis as well as other forms of cell death.[1][2]
[edit] References
^ Koopman G, Reutelingsperger CP, Kuijten GAM et al. (1994). "Annexin V for flow cytometric detection of phosphatidylserine expression on B cells undergoing apoptosis". Blood 84 (5): 1415–20. PMID 8068938.
^ Vermes I, Haanen C, Steffens-Nakken H, Reutelingsperger C (1995). "A novel assay for apoptosis—flow cytometric detection of phosphatidylserine expression on early apoptotic cells using fluorescein labelled Annexin V". J Immunol Methods 184 (1): 39. doi:10.1016/0022-1759(95)00072-I. PMID 7622868.
[edit] Further reading
Cederholm A, Frostegård J (2007). "Annexin A5 as a novel player in prevention of atherothrombosis in SLE and in the general population.". Ann. N. Y. Acad. Sci. 1108: 96–103. PMID 17893975.
Schlaepfer DD, Jones J, Haigler HT (1992). "Inhibition of protein kinase C by annexin V.". Biochemistry 31 (6): 1886–91. PMID 1310621.
Huber R, Berendes R, Burger A, et al. (1992). "Crystal and molecular structure of human annexin V after refinement. Implications for structure, membrane binding and ion channel formation of the annexin family of proteins.". J. Mol. Biol. 223 (3): 683–704. PMID 1311770.
Kirsch T, Pfäffle M (1992). "Selective binding of anchorin CII (annexin V) to type II and X collagen and to chondrocalcin (C-propeptide of type II collagen). Implications for anchoring function between matrix vesicles and matrix proteins.". FEBS Lett. 310 (2): 143–7. PMID 1397263.
Dawson SJ, White LA (1992). "Treatment of Haemophilus aphrophilus endocarditis with ciprofloxacin.". J. Infect. 24 (3): 317–20. PMID 1602151.
Tait JF, Frankenberry DA, Shiang R, et al. (1992). "Chromosomal localization of the human gene for annexin V (placental anticoagulant protein I) to 4q26----q28.". Cytogenet. Cell Genet. 57 (4): 187–92. PMID 1683830.
Huber R, Römisch J, Paques EP (1991). "The crystal and molecular structure of human annexin V, an anticoagulant protein that binds to calcium and membranes.". EMBO J. 9 (12): 3867–74. PMID 2147412.
Huber R, Schneider M, Mayr I, et al. (1991). "The calcium binding sites in human annexin V by crystal structure analysis at 2.0 A resolution. Implications for membrane binding and calcium channel activity.". FEBS Lett. 275 (1-2): 15–21. PMID 2148156.
Maurer-Fogy I, Reutelingsperger CP, Pieters J, et al. (1988). "Cloning and expression of cDNA for human vascular anticoagulant, a Ca2+-dependent phospholipid-binding protein.". Eur. J. Biochem. 174 (4): 585–92. PMID 2455636.
Rothhut B, Coméra C, Cortial S, et al. (1990). "A 32 kDa lipocortin from human mononuclear cells appears to be identical with the placental inhibitor of blood coagulation.". Biochem. J. 263 (3): 929–35. PMID 2532007.
Schlaepfer DD, Mehlman T, Burgess WH, Haigler HT (1987). "Structural and functional characterization of endonexin II, a calcium- and phospholipid-binding protein.". Proc. Natl. Acad. Sci. U.S.A. 84 (17): 6078–82. PMID 2957692.
Funakoshi T, Heimark RL, Hendrickson LE, et al. (1987). "Human placental anticoagulant protein: isolation and characterization.". Biochemistry 26 (17): 5572–8. PMID 2960376.
Iwasaki A, Suda M, Nakao H, et al. (1988). "Structure and expression of cDNA for an inhibitor of blood coagulation isolated from human placenta: a new lipocortin-like protein.". J. Biochem. 102 (5): 1261–73. PMID 2963810.
Funakoshi T, Hendrickson LE, McMullen BA, Fujikawa K (1988). "Primary structure of human placental anticoagulant protein.". Biochemistry 26 (25): 8087–92. PMID 2964863.
Kaplan R, Jaye M, Burgess WH, et al. (1988). "Cloning and expression of cDNA for human endonexin II, a Ca2+ and phospholipid binding protein.". J. Biol. Chem. 263 (17): 8037–43. PMID 2967291.
Grundmann U, Abel KJ, Bohn H, et al. (1988). "Characterization of cDNA encoding human placental anticoagulant protein (PP4): homology with the lipocortin family.". Proc. Natl. Acad. Sci. U.S.A. 85 (11): 3708–12. PMID 2967495.
Pepinsky RB, Tizard R, Mattaliano RJ, et al. (1988). "Five distinct calcium and phospholipid binding proteins share homology with lipocortin I.". J. Biol. Chem. 263 (22): 10799–811. PMID 2968983.
Ahn NG, Teller DC, Bienkowski MJ, et al. (1989). "Sedimentation equilibrium analysis of five lipocortin-related phospholipase A2 inhibitors from human placenta. Evidence against a mechanistically relevant association between enzyme and inhibitor.". J. Biol. Chem. 263 (35): 18657–63. PMID 2974032.
Demange P, Voges D, Benz J, et al. (1994). "Annexin V: the key to understanding ion selectivity and voltage regulation?". Trends Biochem. Sci. 19 (7): 272–6. PMID 7519374.
Fernández MP, Morgan RO, Fernández MR, Carcedo MT (1994). "The gene encoding human annexin V has a TATA-less promoter with a high G+C content.". Gene 149 (2): 253–60. PMID 7958998.
[edit] External links
MeSH Annexin+A5
[show]
v • d • eCarrier protein: calcium-binding proteins
Intracellular calcium-sensing proteins
Calmodulin - Calnexin - Calreticulin - Gelsolin - neuronal (Hippocalcin, Neurocalcin, Recoverin)
Other
Annexin (A1, A2, A5) - Vitamin D-dependent calcium-binding protein/Calbindin - Calexcitin - Calsequestrin - Fibulin - Matrix gla protein - Osteocalcin - Osteonectin - S-100 - Synaptotagmin - Troponin C
This membrane protein-related article is a stub. You can help Wikipedia by expanding it.
Retrieved from "http://en.wikipedia.org/wiki/Annexin_A5"
Categories: Genes on chromosome 4 Human proteins Peripheral membrane proteins Membrane protein stubs
From Wikipedia, the free encyclopedia
Jump to: navigation, search
edit
Annexin A5
PDB rendering based on 1a8a.
Available structures: 1a8a, 1a8b, 1anw, 1anx, 1avh, 1avr, 1bc0, 1bc1, 1bc3, 1bcw, 1bcy, 1bcz, 1g5n, 1hak, 1hvd, 1hve, 1hvf, 1hvg, 1n41, 1n42, 1n44, 1sav, 2ie6, 2ie7, 2ran
Identifiers
Symbol(s)
ANXA5; ANX5; ENX2; PP4
External IDs
OMIM: 131230 MGI: 106008 HomoloGene: 20312
[show]Gene ontology
Molecular Function:
• phospholipase inhibitor activity• calcium ion binding• protein binding• calcium-dependent phospholipid binding
Cellular Component:
• intracellular• cytoplasm
Biological Process:
• anti-apoptosis• signal transduction• blood coagulation• negative regulation of coagulation
RNA expression pattern
More reference expression data
Orthologs
Human
Mouse
Entrez
308
11747
Ensembl
ENSG00000164111
ENSMUSG00000027712
Uniprot
P08758
Q3U5Q1
Refseq
NM_001154 (mRNA)NP_001145 (protein)
NM_009673 (mRNA)NP_033803 (protein)
Location
Chr 4: 122.81 - 122.84 Mb
Chr 3: 36.64 - 36.66 Mb
Pubmed search
[1]
[2]
Annexin A5 (or annexin V) is a cellular protein in the annexin group. The function of the protein is unknown, however annexin A5 has been proposed to play a role in the inhibition of blood coagulation by competing for phosphatidylserine binding sites with prothrombin and also to inhibit the activity of phospholipase A1 also by competing for phosphatidylserine binding sites. These properties have been found by in vitro experiments (in a test tube) and they have not been confirmed by experiments with laboratory animals.
Contents[hide]
1 Annexin A5 in pathology
2 Laboratory use of annexin A5
3 References
4 Further reading
5 External links
//
[edit] Annexin A5 in pathology
Antibodies directed against annexin A5 are the cause of a syndrome called the antiphospholipid syndrome.
Annexin A5 forms a shield around negatively-charged phospholipid molecules. The formation of an annexin A5 shield blocks the entry of phospholipids into coagulation (clotting) reactions. In the antiphospholipid antibody syndrome, the formation of the shield is disrupted by antibodies. Without the shield, there is an increased quantity of phospholipid molecules on cell membranes, speeding up coagulation reactions and causing the blood-clotting characteristic of the antiphospholipid antibody syndrome.
[edit] Laboratory use of annexin A5
Annexin A5 is used as a probe in the annexin A5 affinity assay to detect cells that have expressed phosphatidylserine on the cell surface, a feature found in apoptosis as well as other forms of cell death.[1][2]
[edit] References
^ Koopman G, Reutelingsperger CP, Kuijten GAM et al. (1994). "Annexin V for flow cytometric detection of phosphatidylserine expression on B cells undergoing apoptosis". Blood 84 (5): 1415–20. PMID 8068938.
^ Vermes I, Haanen C, Steffens-Nakken H, Reutelingsperger C (1995). "A novel assay for apoptosis—flow cytometric detection of phosphatidylserine expression on early apoptotic cells using fluorescein labelled Annexin V". J Immunol Methods 184 (1): 39. doi:10.1016/0022-1759(95)00072-I. PMID 7622868.
[edit] Further reading
Cederholm A, Frostegård J (2007). "Annexin A5 as a novel player in prevention of atherothrombosis in SLE and in the general population.". Ann. N. Y. Acad. Sci. 1108: 96–103. PMID 17893975.
Schlaepfer DD, Jones J, Haigler HT (1992). "Inhibition of protein kinase C by annexin V.". Biochemistry 31 (6): 1886–91. PMID 1310621.
Huber R, Berendes R, Burger A, et al. (1992). "Crystal and molecular structure of human annexin V after refinement. Implications for structure, membrane binding and ion channel formation of the annexin family of proteins.". J. Mol. Biol. 223 (3): 683–704. PMID 1311770.
Kirsch T, Pfäffle M (1992). "Selective binding of anchorin CII (annexin V) to type II and X collagen and to chondrocalcin (C-propeptide of type II collagen). Implications for anchoring function between matrix vesicles and matrix proteins.". FEBS Lett. 310 (2): 143–7. PMID 1397263.
Dawson SJ, White LA (1992). "Treatment of Haemophilus aphrophilus endocarditis with ciprofloxacin.". J. Infect. 24 (3): 317–20. PMID 1602151.
Tait JF, Frankenberry DA, Shiang R, et al. (1992). "Chromosomal localization of the human gene for annexin V (placental anticoagulant protein I) to 4q26----q28.". Cytogenet. Cell Genet. 57 (4): 187–92. PMID 1683830.
Huber R, Römisch J, Paques EP (1991). "The crystal and molecular structure of human annexin V, an anticoagulant protein that binds to calcium and membranes.". EMBO J. 9 (12): 3867–74. PMID 2147412.
Huber R, Schneider M, Mayr I, et al. (1991). "The calcium binding sites in human annexin V by crystal structure analysis at 2.0 A resolution. Implications for membrane binding and calcium channel activity.". FEBS Lett. 275 (1-2): 15–21. PMID 2148156.
Maurer-Fogy I, Reutelingsperger CP, Pieters J, et al. (1988). "Cloning and expression of cDNA for human vascular anticoagulant, a Ca2+-dependent phospholipid-binding protein.". Eur. J. Biochem. 174 (4): 585–92. PMID 2455636.
Rothhut B, Coméra C, Cortial S, et al. (1990). "A 32 kDa lipocortin from human mononuclear cells appears to be identical with the placental inhibitor of blood coagulation.". Biochem. J. 263 (3): 929–35. PMID 2532007.
Schlaepfer DD, Mehlman T, Burgess WH, Haigler HT (1987). "Structural and functional characterization of endonexin II, a calcium- and phospholipid-binding protein.". Proc. Natl. Acad. Sci. U.S.A. 84 (17): 6078–82. PMID 2957692.
Funakoshi T, Heimark RL, Hendrickson LE, et al. (1987). "Human placental anticoagulant protein: isolation and characterization.". Biochemistry 26 (17): 5572–8. PMID 2960376.
Iwasaki A, Suda M, Nakao H, et al. (1988). "Structure and expression of cDNA for an inhibitor of blood coagulation isolated from human placenta: a new lipocortin-like protein.". J. Biochem. 102 (5): 1261–73. PMID 2963810.
Funakoshi T, Hendrickson LE, McMullen BA, Fujikawa K (1988). "Primary structure of human placental anticoagulant protein.". Biochemistry 26 (25): 8087–92. PMID 2964863.
Kaplan R, Jaye M, Burgess WH, et al. (1988). "Cloning and expression of cDNA for human endonexin II, a Ca2+ and phospholipid binding protein.". J. Biol. Chem. 263 (17): 8037–43. PMID 2967291.
Grundmann U, Abel KJ, Bohn H, et al. (1988). "Characterization of cDNA encoding human placental anticoagulant protein (PP4): homology with the lipocortin family.". Proc. Natl. Acad. Sci. U.S.A. 85 (11): 3708–12. PMID 2967495.
Pepinsky RB, Tizard R, Mattaliano RJ, et al. (1988). "Five distinct calcium and phospholipid binding proteins share homology with lipocortin I.". J. Biol. Chem. 263 (22): 10799–811. PMID 2968983.
Ahn NG, Teller DC, Bienkowski MJ, et al. (1989). "Sedimentation equilibrium analysis of five lipocortin-related phospholipase A2 inhibitors from human placenta. Evidence against a mechanistically relevant association between enzyme and inhibitor.". J. Biol. Chem. 263 (35): 18657–63. PMID 2974032.
Demange P, Voges D, Benz J, et al. (1994). "Annexin V: the key to understanding ion selectivity and voltage regulation?". Trends Biochem. Sci. 19 (7): 272–6. PMID 7519374.
Fernández MP, Morgan RO, Fernández MR, Carcedo MT (1994). "The gene encoding human annexin V has a TATA-less promoter with a high G+C content.". Gene 149 (2): 253–60. PMID 7958998.
[edit] External links
MeSH Annexin+A5
[show]
v • d • eCarrier protein: calcium-binding proteins
Intracellular calcium-sensing proteins
Calmodulin - Calnexin - Calreticulin - Gelsolin - neuronal (Hippocalcin, Neurocalcin, Recoverin)
Other
Annexin (A1, A2, A5) - Vitamin D-dependent calcium-binding protein/Calbindin - Calexcitin - Calsequestrin - Fibulin - Matrix gla protein - Osteocalcin - Osteonectin - S-100 - Synaptotagmin - Troponin C
This membrane protein-related article is a stub. You can help Wikipedia by expanding it.
Retrieved from "http://en.wikipedia.org/wiki/Annexin_A5"
Categories: Genes on chromosome 4 Human proteins Peripheral membrane proteins Membrane protein stubs
Annexin-5 apoptosis assay
Annexin-5 is a member of a highly conserved protein family that bind acidic phospholipids in a calcium-dependent manner. Annexin-5 is known also as 35 kDa Calelectrin, 35-gamma Calcimedin, Anchorin C2, PAP-1 (placental anticoagulant protein-1), Calphobindin-1, Endonexin-2, Lipocortin V, VAC-alpha (vascular anticoagulant-alpha).
The protein has been shown to possess a high affinity for phosphatidylserine. Phosphatidylserine is translocated from the inner side of the plasma membrane to the outer layer when cells undergo death by apoptosis or cell necrosis and serves as one of several signals by which cell destined for death are recognized by phagocytes (see also: apoptotic bodies) (Van Engeland et al, 1998).
Cell death by apoptosis and necrosis differ from each other in that cell membranes maintain their integrity during the initial stages of apoptosis, while they become leaky during necrotic cell death. If Annexin-5 binds to the cell surface this indicates that cell death is imminent. In order to differentiate apoptosis from necrosis, a dye exclusion test with propidium iodide is performed to establish whether membrane integrity has been conserved or whether membranes have become leaky. A combination test measuring Annexin-5 binding and dye exclusion thus allows discrimination between intact cells, apoptotic cells, and necrotic cells. The test allows detection of apoptosis at early stages before gross morphological changes have occurred and has been adapted for use with flow cytometry, light and electron microscopy and can be applied to vital and fixed material (Miller, 2004; Pellicciari et al, 1997). Schellenberger et al (2002) have conjugated Annexin-5 to crosslinked iron oxide (CLIO) nanoparticles, a functionalized superparamagnetic preparation developed for target-specific magnetic resonance imaging (MRI). The resulting nanoparticles can be used to remove apoptotic cells from cell suspensions containing healthy and apoptotic cells by magnetic column chromatography and to visualize apoptotic cells by MRI.
Dillon et al (2000) have reported that detection of annexin-5 binding may not always be indicative of apotosis. Phosphatidylserine exposed on the majority of B-cells in vivo does not reflect early apoptosis, but, instead, plays a role in receptor-mediated signaling events.
For other assays allowing detection of apoptotic cells see also: apoptosis assays. Kawaminami et al (1998) have reported that the withdrawal of ovarian hormones induces huge castration cells in the anterior pituitary gland. These cells express annexin-5. Annexin-5 is detected also in follicular epithelial cells and parafollicular cells of the thyroid gland, adrenocortical cells of the zona fasciculata and zona reticularis, luteal cells, testicular interstitial cells, and Sertoli cells. It is not detected in the pineal gland, the parathyroid gland, the islet of Langerhans, the adrenal medulla, zona glomerulosa cells, and granulosa cells. The authors have suggested that annexin-5 contributes to secretory cell functions, which may be common to endocrine cells secreting chemically different hormones.
Annexin-5 is a member of a highly conserved protein family that bind acidic phospholipids in a calcium-dependent manner. Annexin-5 is known also as 35 kDa Calelectrin, 35-gamma Calcimedin, Anchorin C2, PAP-1 (placental anticoagulant protein-1), Calphobindin-1, Endonexin-2, Lipocortin V, VAC-alpha (vascular anticoagulant-alpha).
The protein has been shown to possess a high affinity for phosphatidylserine. Phosphatidylserine is translocated from the inner side of the plasma membrane to the outer layer when cells undergo death by apoptosis or cell necrosis and serves as one of several signals by which cell destined for death are recognized by phagocytes (see also: apoptotic bodies) (Van Engeland et al, 1998).
Cell death by apoptosis and necrosis differ from each other in that cell membranes maintain their integrity during the initial stages of apoptosis, while they become leaky during necrotic cell death. If Annexin-5 binds to the cell surface this indicates that cell death is imminent. In order to differentiate apoptosis from necrosis, a dye exclusion test with propidium iodide is performed to establish whether membrane integrity has been conserved or whether membranes have become leaky. A combination test measuring Annexin-5 binding and dye exclusion thus allows discrimination between intact cells, apoptotic cells, and necrotic cells. The test allows detection of apoptosis at early stages before gross morphological changes have occurred and has been adapted for use with flow cytometry, light and electron microscopy and can be applied to vital and fixed material (Miller, 2004; Pellicciari et al, 1997). Schellenberger et al (2002) have conjugated Annexin-5 to crosslinked iron oxide (CLIO) nanoparticles, a functionalized superparamagnetic preparation developed for target-specific magnetic resonance imaging (MRI). The resulting nanoparticles can be used to remove apoptotic cells from cell suspensions containing healthy and apoptotic cells by magnetic column chromatography and to visualize apoptotic cells by MRI.
Dillon et al (2000) have reported that detection of annexin-5 binding may not always be indicative of apotosis. Phosphatidylserine exposed on the majority of B-cells in vivo does not reflect early apoptosis, but, instead, plays a role in receptor-mediated signaling events.
For other assays allowing detection of apoptotic cells see also: apoptosis assays. Kawaminami et al (1998) have reported that the withdrawal of ovarian hormones induces huge castration cells in the anterior pituitary gland. These cells express annexin-5. Annexin-5 is detected also in follicular epithelial cells and parafollicular cells of the thyroid gland, adrenocortical cells of the zona fasciculata and zona reticularis, luteal cells, testicular interstitial cells, and Sertoli cells. It is not detected in the pineal gland, the parathyroid gland, the islet of Langerhans, the adrenal medulla, zona glomerulosa cells, and granulosa cells. The authors have suggested that annexin-5 contributes to secretory cell functions, which may be common to endocrine cells secreting chemically different hormones.
Annexin-5 apoptosis assay
Annexin-5 is a member of a highly conserved protein family that bind acidic phospholipids in a calcium-dependent manner. Annexin-5 is known also as 35 kDa Calelectrin, 35-gamma Calcimedin, Anchorin C2, PAP-1 (placental anticoagulant protein-1), Calphobindin-1, Endonexin-2, Lipocortin V, VAC-alpha (vascular anticoagulant-alpha).
The protein has been shown to possess a high affinity for phosphatidylserine. Phosphatidylserine is translocated from the inner side of the plasma membrane to the outer layer when cells undergo death by apoptosis or cell necrosis and serves as one of several signals by which cell destined for death are recognized by phagocytes (see also: apoptotic bodies) (Van Engeland et al, 1998).
Cell death by apoptosis and necrosis differ from each other in that cell membranes maintain their integrity during the initial stages of apoptosis, while they become leaky during necrotic cell death. If Annexin-5 binds to the cell surface this indicates that cell death is imminent. In order to differentiate apoptosis from necrosis, a dye exclusion test with propidium iodide is performed to establish whether membrane integrity has been conserved or whether membranes have become leaky. A combination test measuring Annexin-5 binding and dye exclusion thus allows discrimination between intact cells, apoptotic cells, and necrotic cells. The test allows detection of apoptosis at early stages before gross morphological changes have occurred and has been adapted for use with flow cytometry, light and electron microscopy and can be applied to vital and fixed material (Miller, 2004; Pellicciari et al, 1997). Schellenberger et al (2002) have conjugated Annexin-5 to crosslinked iron oxide (CLIO) nanoparticles, a functionalized superparamagnetic preparation developed for target-specific magnetic resonance imaging (MRI). The resulting nanoparticles can be used to remove apoptotic cells from cell suspensions containing healthy and apoptotic cells by magnetic column chromatography and to visualize apoptotic cells by MRI.
Dillon et al (2000) have reported that detection of annexin-5 binding may not always be indicative of apotosis. Phosphatidylserine exposed on the majority of B-cells in vivo does not reflect early apoptosis, but, instead, plays a role in receptor-mediated signaling events.
For other assays allowing detection of apoptotic cells see also: apoptosis assays. Kawaminami et al (1998) have reported that the withdrawal of ovarian hormones induces huge castration cells in the anterior pituitary gland. These cells express annexin-5. Annexin-5 is detected also in follicular epithelial cells and parafollicular cells of the thyroid gland, adrenocortical cells of the zona fasciculata and zona reticularis, luteal cells, testicular interstitial cells, and Sertoli cells. It is not detected in the pineal gland, the parathyroid gland, the islet of Langerhans, the adrenal medulla, zona glomerulosa cells, and granulosa cells. The authors have suggested that annexin-5 contributes to secretory cell functions, which may be common to endocrine cells secreting chemically different hormones.
Annexin-5 is a member of a highly conserved protein family that bind acidic phospholipids in a calcium-dependent manner. Annexin-5 is known also as 35 kDa Calelectrin, 35-gamma Calcimedin, Anchorin C2, PAP-1 (placental anticoagulant protein-1), Calphobindin-1, Endonexin-2, Lipocortin V, VAC-alpha (vascular anticoagulant-alpha).
The protein has been shown to possess a high affinity for phosphatidylserine. Phosphatidylserine is translocated from the inner side of the plasma membrane to the outer layer when cells undergo death by apoptosis or cell necrosis and serves as one of several signals by which cell destined for death are recognized by phagocytes (see also: apoptotic bodies) (Van Engeland et al, 1998).
Cell death by apoptosis and necrosis differ from each other in that cell membranes maintain their integrity during the initial stages of apoptosis, while they become leaky during necrotic cell death. If Annexin-5 binds to the cell surface this indicates that cell death is imminent. In order to differentiate apoptosis from necrosis, a dye exclusion test with propidium iodide is performed to establish whether membrane integrity has been conserved or whether membranes have become leaky. A combination test measuring Annexin-5 binding and dye exclusion thus allows discrimination between intact cells, apoptotic cells, and necrotic cells. The test allows detection of apoptosis at early stages before gross morphological changes have occurred and has been adapted for use with flow cytometry, light and electron microscopy and can be applied to vital and fixed material (Miller, 2004; Pellicciari et al, 1997). Schellenberger et al (2002) have conjugated Annexin-5 to crosslinked iron oxide (CLIO) nanoparticles, a functionalized superparamagnetic preparation developed for target-specific magnetic resonance imaging (MRI). The resulting nanoparticles can be used to remove apoptotic cells from cell suspensions containing healthy and apoptotic cells by magnetic column chromatography and to visualize apoptotic cells by MRI.
Dillon et al (2000) have reported that detection of annexin-5 binding may not always be indicative of apotosis. Phosphatidylserine exposed on the majority of B-cells in vivo does not reflect early apoptosis, but, instead, plays a role in receptor-mediated signaling events.
For other assays allowing detection of apoptotic cells see also: apoptosis assays. Kawaminami et al (1998) have reported that the withdrawal of ovarian hormones induces huge castration cells in the anterior pituitary gland. These cells express annexin-5. Annexin-5 is detected also in follicular epithelial cells and parafollicular cells of the thyroid gland, adrenocortical cells of the zona fasciculata and zona reticularis, luteal cells, testicular interstitial cells, and Sertoli cells. It is not detected in the pineal gland, the parathyroid gland, the islet of Langerhans, the adrenal medulla, zona glomerulosa cells, and granulosa cells. The authors have suggested that annexin-5 contributes to secretory cell functions, which may be common to endocrine cells secreting chemically different hormones.
Subscribe to:
Posts (Atom)
