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Design and Experimental Evaluation of a Peptide Antagonist against Amyloid β(1-42) Interactions with Calmodulin and Calbindin-D28k. Int J Mol Sci 2022; 23:ijms23042289. [PMID: 35216403 PMCID: PMC8880779 DOI: 10.3390/ijms23042289] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 02/10/2022] [Accepted: 02/12/2022] [Indexed: 11/21/2022] Open
Abstract
Amyloid β1–42 (Aβ(1–42)) oligomers have been linked to the pathogenesis of Alzheimer’s disease (AD). Intracellular calcium (Ca2+) homeostasis dysregulation with subsequent alterations of neuronal excitability has been proposed to mediate Aβ neurotoxicity in AD. The Ca2+ binding proteins calmodulin (CaM) and calbindin-D28k, whose expression levels are lowered in human AD brains, have relevant roles in neuronal survival and activity. In previous works, we have shown that CaM has a high affinity for Aβ(1–42) oligomers and extensively binds internalized Aβ(1–42) in neurons. In this work, we have designed a hydrophobic peptide of 10 amino acid residues: VFAFAMAFML (amidated-C-terminus amino acid) mimicking the interacting domain of CaM with Aβ (1–42), using a combined strategy based on the experimental results obtained for Aβ(1–42) binding to CaM and in silico docking analysis. The increase in the fluorescence intensity of Aβ(1–42) HiLyteTM-Fluor555 has been used to monitor the kinetics of complex formation with CaM and with calbindin-D28k. The complexation between nanomolar concentrations of Aβ(1–42) and calbindin-D28k is also a novel finding reported in this work. We found that the synthetic peptide VFAFAMAFML (amidated-C-terminus amino acid) is a potent inhibitor of the formation of Aβ(1–42):CaM and of Aβ(1–42):calbindin-D28k complexes.
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Fischer N, Johnson Chacko L, Majerus A, Potrusil T, Riechelmann H, Schmutzhard J, Schrott-Fischer A, Glueckert R. Age-Dependent Calcium-Binding Protein Expression in the Spiral Ganglion and Hearing Performance of C57BL/6J and 129/SvJ Mice. ORL J Otorhinolaryngol Relat Spec 2019; 81:138-154. [PMID: 31170714 DOI: 10.1159/000499472] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 03/08/2019] [Indexed: 11/19/2022]
Abstract
BACKGROUND/AIMS Calcium-binding proteins in neurons buffer intracellular free Ca2+ ions, which interact with proteins controlling enzymatic and ion channel activity. The heterogeneous distribution of calretinin, calbindin, and parvalbumin influences calcium homeostasis, and calcium-related neuronal processes play an important role in neuronal aging and degeneration. This study evaluated age-related changes in calretinin, calbindin, and parvalbumin immune reactivity in spiral ganglion cells. METHODS A total of 16 C57BL/6J and 16 129/SvJ mice at different ages (2, 4, 7, and 12 months) were included in the study. Hearing thresholds were assessed using auditory brainstem response before inner ears were excised for further evaluation. Semiquantitative immunohistochemistry for the aforementioned calcium-binding proteins was performed at the cellular level. RESULTS The hearing thresholds of C57BL/6J and 129/SvJ mice increased significantly by 7 months of age. The average immune reactivity of calbin-din as well as the relative number of positive cells increased significantly with aging, but no significant alterations in calretinin or parvalbumin were observed. CONCLUSIONS Upregulation of calbindin could serve as a protection to compensate for functional deficits that occur with aging. Expression of both calretinin and parvalbumin seem to be stabilizing factors in murine inner ears up to the age of 12 months in C57BL/6J and 129/SvJ mice.
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Affiliation(s)
- Natalie Fischer
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | - Lejo Johnson Chacko
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | - Alexandra Majerus
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | - Thomas Potrusil
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | - Herbert Riechelmann
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | - Joachim Schmutzhard
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria
| | | | - Rudolf Glueckert
- Department of Otorhinolaryngology, Medical University Innsbruck, Innsbruck, Austria.,Department of Otorhinolaryngology, Tirol Kliniken, University Clinics of Innsbruck, Innsbruck, Austria
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Kook SY, Jeong H, Kang MJ, Park R, Shin HJ, Han SH, Son SM, Song H, Baik SH, Moon M, Yi EC, Hwang D, Mook-Jung I. Crucial role of calbindin-D28k in the pathogenesis of Alzheimer's disease mouse model. Cell Death Differ 2014; 21:1575-87. [PMID: 24853300 PMCID: PMC4158683 DOI: 10.1038/cdd.2014.67] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Revised: 03/03/2014] [Accepted: 04/04/2014] [Indexed: 01/22/2023] Open
Abstract
Calbindin-D28k (CB), one of the major calcium-binding and buffering proteins, has a critical role in preventing a neuronal death as well as maintaining calcium homeostasis. Although marked reductions of CB expression have been observed in the brains of mice and humans with Alzheimer disease (AD), it is unknown whether these changes contribute to AD-related dysfunction. To determine the pathogenic importance of CB depletions in AD models, we crossed 5 familial AD mutations (5XFAD; Tg) mice with CB knock-out (CBKO) mice and generated a novel line CBKO·5XFAD (CBKOTg) mice. We first identified the change of signaling pathways and differentially expressed proteins globally by removing CB in Tg mice using mass spectrometry and antibody microarray. Immunohistochemistry showed that CBKOTg mice had significant neuronal loss in the subiculum area without changing the magnitude (number) of amyloid β-peptide (Aβ) plaques deposition and elicited significant apoptotic features and mitochondrial dysfunction compared with Tg mice. Moreover, CBKOTg mice reduced levels of phosphorylated mitogen-activated protein kinase (extracellular signal-regulated kinase) 1/2 and cAMP response element-binding protein at Ser-133 and synaptic molecules such as N-methyl-D-aspartate receptor 1 (NMDA receptor 1), NMDA receptor 2A, PSD-95 and synaptophysin in the subiculum compared with Tg mice. Importantly, this is the first experimental evidence that removal of CB from amyloid precursor protein/presenilin transgenic mice aggravates AD pathogenesis, suggesting that CB has a critical role in AD pathogenesis.
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Affiliation(s)
- S-Y Kook
- Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Korea
| | - H Jeong
- School of Interdisciplinary Bioscience and Bioengineering, Department of Chemical Engineering, POSTECH, Pohang, Korea
| | - M J Kang
- Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology and College of Medicine or College of Pharmacy, Seoul National University, Seoul, Korea
| | - R Park
- Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Korea
| | - H J Shin
- Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Korea
| | - S-H Han
- Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Korea
| | - S M Son
- Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Korea
| | - H Song
- Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Korea
| | - S H Baik
- Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Korea
| | - M Moon
- Molecular Neurobiology Laboratory, Department of Psychiatry and Mclean Hospital, Harvard Medical School, Belmont, MA, USA
| | - E C Yi
- Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology and College of Medicine or College of Pharmacy, Seoul National University, Seoul, Korea
| | - D Hwang
- 1] School of Interdisciplinary Bioscience and Bioengineering, Department of Chemical Engineering, POSTECH, Pohang, Korea [2] Department of New Biology and Center for Plant Aging Research, Institute for Basic Science, DGIST, Daegu, Korea
| | - I Mook-Jung
- Department of Biochemistry and Biomedical Sciences, Seoul National University, College of Medicine, Seoul, Korea
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Xu JH, Yang ZB, Wang H, Tang FR. Co-localization of L-type voltage dependent calcium channel alpha 1D subunit (Ca(v)1.3) and calbindin (CB) in the mouse central nervous system. Neurosci Lett 2014; 561:80-5. [PMID: 24394909 DOI: 10.1016/j.neulet.2013.12.057] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 12/16/2013] [Accepted: 12/23/2013] [Indexed: 11/28/2022]
Abstract
Previous study has shown that the co-localization of calbindin (CB) with L-type voltage dependent Ca(2+) channel (VDCC) alpha 1C subunit (Ca(v)1.2) in the rat insulinoma 1046-38 (RIN) beta cells may play an important regulatory role in Ca(2+) influx and exocytosis of insulin granules. In the present study, L-type voltage dependent Ca(2+) channel (VDCC) and calbindin (CB) were demonstrated in different regions of the mouse central nervous system (CNS). Double labeling immunofluorescence staining showed a co-localization of Ca(v)1.3 and CB. The co-localization of Ca(v)1.3 and CB in certain brain regions such as the hippocampus suggests their important roles in neuroplasticity. The relative high percentages of co-localization of Ca(v)1.3 with CB in the laminae II of the dorsal horn of the spinal cord indicate that the regulation mechanism of nociceptive transmission may be related with both VDCC and Ca(2+) binding protein.
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Affiliation(s)
- Jie Hua Xu
- Department of Anatomy and Histology, Xi'an Jiaotong University College of Medicine, Xi'an 710061, People's Republic of China
| | - Zhen Bang Yang
- Department of Orthopedics, The First Hospital of Yulin, Yulin 71900, People's Republic of China
| | - Hui Wang
- Department of Anatomy and Histology, Xi'an Jiaotong University College of Medicine, Xi'an 710061, People's Republic of China; Center for Human Assisted Reproduction, Maternity and Child Healthcare Hospital of Shaanxi Province, Xi'an, Shaanxi 710003, People's Republic of China
| | - Feng-Ru Tang
- Temasek Laboratories, National University of Singapore, Singapore, Singapore; Medical School of Yangtze University, People's Republic of China.
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The use of transgenic mouse models to reveal the functions of Ca2+ buffer proteins in excitable cells. Biochim Biophys Acta Gen Subj 2012; 1820:1294-303. [DOI: 10.1016/j.bbagen.2011.11.008] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 11/14/2011] [Accepted: 11/15/2011] [Indexed: 12/19/2022]
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Westerink RHS, Beekwilder JP, Wadman WJ. Differential alterations of synaptic plasticity in dentate gyrus and CA1 hippocampal area of Calbindin-D28K knockout mice. Brain Res 2012; 1450:1-10. [PMID: 22405690 DOI: 10.1016/j.brainres.2012.02.036] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 02/14/2012] [Accepted: 02/14/2012] [Indexed: 12/15/2022]
Abstract
Regulation of the intracellular calcium concentration ([Ca(2+)](i)) is of critical importance for synaptic function. Therefore, neurons buffer [Ca(2+)](i) using intracellular Ca(2+)-binding proteins (CaBPs). Previous evidence suggests that Calbindin-D(28K) (CB), an abundantly expressed endogenous fast CaBP, plays an important role in neuronal survival, motor coordination, spatial learning paradigms and some forms of synaptic plasticity. In the present study, the role of CB in synaptic transmission and plasticity was further investigated using extracellular recordings of synaptic activity in cell- and dendritic layers of dentate gyrus (DG) and CA1 area in hippocampal slices from wild-type, heterozygous and homozygous CB knockout mice. The results demonstrate a consistent failure to maintain long-term potentiation (LTP) in hippocampal DG and CA1 area of knockout mice. Compared to wild-type mice, the paired-pulse ratio of EPSPs recorded in DG is significantly lower in slices from knockout mice, whereas it is significantly higher in CA1 area. The amplitude of the population spike recorded in CA1 area of wild-type mice steadily increases following tetanic stimulation, whereas it steadily decreases in knockout mice. The combined results demonstrate that the absence of CB results in an impairment of LTP maintenance in both hippocampal DG and CA1 area, whereas paired-pulse facilitation and cellular excitability in CA1 area are differentially affected. These results support the role of CB as a critical determinant for several forms of synaptic plasticity in hippocampal DG and CA1 area. It is hypothesized that CB functions as a postsynaptic Ca(2+) buffer as well as a presynaptic Ca(2+) sensor.
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Affiliation(s)
- R H S Westerink
- Neurotoxicology Research Group, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands.
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CHOI JH, HWANG IK, YOO KY, YI SS, PARK OK, LEE CH, YOON YS, WON MH. Reduction of Calbindin D-28k-Immunoreactive Neurons in the Dog Dentate Gyrus. J Vet Med Sci 2009; 71:1125-8. [DOI: 10.1292/jvms.71.1125] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Jung Hoon CHOI
- Department of Anatomy and Neurobiology, and Institute of Neurodegeneration and Neuroregeneration, Hallym University
| | - In Koo HWANG
- Department of Anatomy and Cell Biology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University
| | - Ki-Yeon YOO
- Department of Anatomy and Neurobiology, and Institute of Neurodegeneration and Neuroregeneration, Hallym University
| | - Sun Shin YI
- Department of Anatomy and Cell Biology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University
| | - Ok Kyu PARK
- Department of Anatomy and Neurobiology, and Institute of Neurodegeneration and Neuroregeneration, Hallym University
| | - Choong Hyun LEE
- Department of Anatomy and Neurobiology, and Institute of Neurodegeneration and Neuroregeneration, Hallym University
| | - Yeo Sung YOON
- Department of Anatomy and Cell Biology, College of Veterinary Medicine and BK21 Program for Veterinary Science, Seoul National University
| | - Moo-Ho WON
- Department of Anatomy and Neurobiology, and Institute of Neurodegeneration and Neuroregeneration, Hallym University
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Westerink RHS, Rook MB, Beekwilder JP, Wadman WJ. Dual role of calbindin-D28Kin vesicular catecholamine release from mouse chromaffin cells. J Neurochem 2006; 99:628-40. [PMID: 16824046 DOI: 10.1111/j.1471-4159.2006.04099.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Calbindin-D(28K) is suggested to play a postsynaptic role in neurotransmission and in the regulation of the intracellular Ca(2+) concentration. However, it is still unclear whether calbindin-D(28K) has a role in the regulation of exocytosis, either as Ca(2+) buffer or as Ca(2+) sensor. Amperometric recordings of catecholamine exocytosis from wild-type and calbindin-D(28K) knockout mouse chromaffin cells reveal a strong reduction in the number of released vesicles, as well as in the amount of neurotransmitter released per fusion event in knockout cells. However, Ca(2+) current recordings and Ca(2+) imaging experiments, including video-rate confocal laser scanning microscopy, revealed that the intracellular Ca(2+) dynamics are remarkably similar in wild-type and knockout cells. The combined results demonstrate that calbindin-D(28K) plays an important and dual role in exocytosis, affecting both release frequency and quantal size, apparently without strong effects on intracellular Ca(2+) dynamics. Consequently, the possibility that calbindin-D(28K) functions not only as a Ca(2+) buffer but also as a modulator of vesicular catecholamine release is discussed.
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Affiliation(s)
- R H S Westerink
- Cellular and Molecular Toxicology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, the Netherlands.
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Palop JJ, Jones B, Kekonius L, Chin J, Yu GQ, Raber J, Masliah E, Mucke L. Neuronal depletion of calcium-dependent proteins in the dentate gyrus is tightly linked to Alzheimer's disease-related cognitive deficits. Proc Natl Acad Sci U S A 2003; 100:9572-7. [PMID: 12881482 PMCID: PMC170959 DOI: 10.1073/pnas.1133381100] [Citation(s) in RCA: 311] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transgenic mice expressing human amyloid precursor proteins (hAPP) and amyloid-beta peptides (Abeta) in neurons develop phenotypic alterations resembling Alzheimer's disease (AD). The mechanisms underlying cognitive deficits in AD and hAPP mice are largely unknown. We have identified two molecular alterations that accurately reflect AD-related cognitive impairments. Learning deficits in mice expressing familial AD-mutant hAPP correlated strongly with decreased levels of the calcium-binding protein calbindin-D28k (CB) and the calcium-dependent immediate early gene product c-Fos in granule cells of the dentate gyrus, a brain region critically involved in learning and memory. These molecular alterations were age-dependent and correlated with the relative abundance of Abeta1-42 but not with the amount of Abeta deposited in amyloid plaques. CB reductions in the dentate gyrus primarily reflected a decrease in neuronal CB levels rather than a loss of CB-producing neurons. CB levels were also markedly reduced in granule cells of humans with AD, even though these neurons are relatively resistant to AD-related cell death. Thus, neuronal populations resisting cell death in AD and hAPP mice can still be drastically altered at the molecular level. The tight link between Abeta-induced cognitive deficits and neuronal depletion of CB and c-Fos suggests an involvement of calcium-dependent pathways in AD-related cognitive decline and could facilitate the preclinical evaluation of novel AD treatments.
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Affiliation(s)
- Jorge J Palop
- Gladstone Institute of Neurological Disease and Department of Neurology, University of California, San Francisco, CA 94141, USA
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Jouvenceau A, Potier B, Poindessous-Jazat F, Dutar P, Slama A, Epelbaum J, Billard JM. Decrease in calbindin content significantly alters LTP but not NMDA receptor and calcium channel properties. Neuropharmacology 2002; 42:444-58. [PMID: 11955516 DOI: 10.1016/s0028-3908(01)00202-7] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The contribution of the cytosolic calcium binding protein calbindin D(28K) (CaBP) to the synaptic plasticity was investigated in hippocampal CA1 area of wild-type and antisense transgenic CaBP-deficient mice. We showed that long-term potentiation (LTP) induced by tetanic stimulation in CaBP-deficient mice was impaired. The fundamental biophysical properties of NMDA receptors and their number were not modified in CaBP-deficient mice. We also demonstrated that the physiological properties of calcium channels were identical between genotypes. An insufficient Ca(2+) entry through NMDA receptors or calcium channels, or a decrease in NMDA receptor density are unlikely to explain this impairment of LTP. Interestingly, we showed that the loss of LTP was not prevented by glycine but was restored in the presence of a low concentration of the NMDA receptor antagonist D-APV (5 microM) and of the calcium chelator BAPTA-AM (5 microM). Moreover, we observed a loss of LTP in the wild-type mice when the postsynaptic tetanic-induced [Ca(2+)](i) rise is excessively increased. Conversely, a weaker tetanus stimulation allowed LTP induction and maintenance in CaBP-deficient mice. These results suggest that a higher cytosol [Ca(2+)](i), due to the decrease of CaBP expression may impair LTP induction and maintenance mechanisms without affecting the mechanisms of calcium entry. Thus, CaBP plays a critical role in long term synaptic plasticity by limiting the elevation of calcium rise in the cytosol to some appropriate spatio-temporal pattern.
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Affiliation(s)
- A Jouvenceau
- Neurobiologie de la Croissance et de la Sénescence, INSERM U 549, IFR Broca-Sainte Anne, 2ter rue d'Alésia, 75014, Paris, France
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Thorns V, Licastro F, Masliah E. Locally reduced levels of acidic FGF lead to decreased expression of 28-kda calbindin and contribute to the selective vulnerability of the neurons in the entorhinal cortex in Alzheimer's disease. Neuropathology 2001; 21:203-11. [PMID: 11666017 DOI: 10.1046/j.1440-1789.2001.00399.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent studies demonstrate that a disturbed calcium-homeostasis leading to increased susceptibility to excitotoxic triggers plays a major role in the neurodegenerative process initiating in layer 2 of the entorhinal cortex (EC2) during Alzheimer's disease (AD). Thus, proteins binding free Ca++ (i.e. calbindin) and factors regulating these proteins are of great importance for the neuroprotective-neurotoxic balance in the affected brain regions. In the present combined human and in vitro study evidence is provided that altered levels of the acidic fibroblast growth factor (aFGF) and calbindin expression are concomitantly present in EC2 neurons and have interactive effects. A dramatic loss of aFGF- and calbindin-labeled EC2 neurons was found. Further analysis of the surviving EC2 neurons revealed a strong immunoreactivity to calbindin and aFGF. In vitro experiments show that aFGF regulates calbindin expression, because treatment of differentiating neurons with recombinant aFGF increases calbindin expression in a time-dependent fashion. The data imply that a reduced expression of aFGF in EC2 neurons of AD brains leads to lower levels of calbindin resulting in decreased neuroprotective capacity.
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Affiliation(s)
- V Thorns
- Institute of Neuropathology, Medical School of Hannover, Germany.
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Nägerl UV, Novo D, Mody I, Vergara JL. Binding kinetics of calbindin-D(28k) determined by flash photolysis of caged Ca(2+). Biophys J 2000; 79:3009-18. [PMID: 11106608 PMCID: PMC1301179 DOI: 10.1016/s0006-3495(00)76537-4] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
We have used UV flash photolysis of DM-nitrophen in combination with model-based analysis of Oregon Green 488 BAPTA-5N fluorescence transients to study the kinetics of Ca(2+) binding to calbindin-D(28K). The experiments used saturated DM-nitrophen at a [Ca(2+)] of 1.5 microM. Under these conditions, UV laser flashes produced rapid steplike increases in [Ca(2+)] in the absence of calbindin-D(28K), and in its presence the decay of the flash-induced fluorescence was due solely to the Ca(2+) buffering by the protein. We developed a novel method for kinetic parameter derivation and used the synthetic Ca(2+) buffer EGTA to confirm its validity. We provide evidence that calbindin-D(28K) binds Ca(2+) in at least two distinct kinetic patterns, one arising from high-affinity sites that bind Ca(2+) with a k(on) comparable to that of EGTA (i.e., approximately 1 x 10(7) M(-1) s(-1)) and another with lower affinity and an approximately eightfold faster k(on). In view of the inability of conventional approaches to adequately resolve rapid Ca(2+) binding kinetics of Ca(2+) buffers, this method promises to be highly valuable for studying the Ca(2+) binding properties of other biologically important Ca(2+) binding proteins.
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Affiliation(s)
- U V Nägerl
- Department of IDP Neuroscience, UCLA School of Medicine, Los Angeles, California 90095, USA.
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Xiong Z, O'Hanlon D, Becker LE, Roder J, MacDonald JF, Marks A. Enhanced calcium transients in glial cells in neonatal cerebellar cultures derived from S100B null mice. Exp Cell Res 2000; 257:281-9. [PMID: 10837142 DOI: 10.1006/excr.2000.4902] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
S100B is the major low-affinity Ca(2+)-binding protein in astrocytes. In order to study the role of S100B in the maintenance of Ca(2+) homeostasis, we generated S100B null mice by a targeted inactivation of the S100B gene. Absence of S100B expression was demonstrated by Northern and Western blotting for S100B mRNA and protein, respectively, and immunoperoxidase staining of sections of various brain regions. S100B null mice were viable, fertile, and exhibited no overt behavioral abnormalities up to 12 months of age. On the basis of light microscopy and immunohistochemical staining, there were no discernable alterations in the distribution and morphology of astrocytes or neurons in sections of adult brains of these mice. Astrocytes in cerebellar cultures derived from 6-day-old S100B null mice exhibited enhanced Ca(2+) transients in response to treatment with KCl or caffeine. On the other hand, granule neurons, in the same cultures, exhibited normal Ca(2+) transients in response to treatment with KCl, caffeine, or N-methyl-d-aspartate. These results demonstrate a specific decrease in Ca(2+)-handling capacity in astrocytes derived from S100B null mice and suggest that S100B plays a role in the maintenance of Ca(2+) homeostasis in astrocytes.
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Affiliation(s)
- Z Xiong
- Department of Physiology, University of Toronto, Toronto, Ontario, M5S 1A8, Canada
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