scholarly journals Disruption of the lens circulation causes calcium accumulation and precipitates in connexin mutant mice

2018 ◽  
Vol 314 (4) ◽  
pp. C492-C503 ◽  
Author(s):  
Junyuan Gao ◽  
Peter J. Minogue ◽  
Eric C. Beyer ◽  
Richard T. Mathias ◽  
Viviana M. Berthoud
Keyword(s):  
Autosomal Dominant ◽  
Circulation System ◽  
Lens Fiber ◽  
Cataract Formation ◽  
Wild Type ◽  
Mice Model ◽  
Internal Circulation ◽  
Alizarin Red ◽  
Fiber Cells ◽  
Junction Coupling

The lens is an avascular organ whose function and survival depend on an internal circulation system. Cx46fs380 mice model a human autosomal dominant cataract caused by a mutant lens connexin. In these mice, fiber cell connexin levels and gap junction coupling are severely decreased. The present studies were conducted to examine components of the lens circulation system that might be altered and contribute to the pathogenesis of cataracts. Lenses from wild-type mice and Cx46fs380 heterozygotes and homozygotes were studied at 2 months of age. Cx46fs380-expressing lens fiber cells were depolarized. Cx46fs380 lenses had increased intracellular hydrostatic pressure and concentrations of Na+ and Ca2+. The activity of epithelial Na+-K+-ATPase was decreased in Cx46fs380 lenses. All of these changes were more severe in homozygous than in heterozygous Cx46fs380 lenses. Cx46fs380 cataracts were stained by Alizarin red, a dye used to detect insoluble Ca2+. These data suggest that the lens internal circulation was disrupted by expression of Cx46fs380, leading to several consequences including accumulation of Ca2+ to levels so high that precipitates formed. Similar Ca2+-containing precipitates may contribute to cataract formation due to other genetic or acquired etiologies.

scholarly journals Connexin Mutants Compromise the Lens Circulation and Cause Cataracts through Biomineralization

2020 ◽  
Vol 21 (16) ◽  
pp. 5822
Author(s):  
Viviana M. Berthoud ◽  
Junyuan Gao ◽  
Peter J. Minogue ◽  
Oscar Jara ◽  
Richard T. Mathias ◽  
...  
Keyword(s):  
Gap Junction ◽  
Lens Fiber ◽  
Lens Fiber Cell ◽  
Alizarin Red ◽  
General Process ◽  
Fiber Cells ◽  
Gap Junctional Communication ◽  
Junctional Communication ◽  
Gap Junctional ◽  
Junction Proteins

Gap junction-mediated intercellular communication facilitates the circulation of ions, small molecules, and metabolites in the avascular eye lens. Mutants of the lens fiber cell gap junction proteins, connexin46 (Cx46) and connexin50 (Cx50), cause cataracts in people and in mice. Studies in mouse models have begun to elucidate the mechanisms by which these mutants lead to cataracts. The expression of the dominant mutants causes severe decreases in connexin levels, reducing the gap junctional communication between lens fiber cells and compromising the lens circulation. The impairment of the lens circulation results in several changes, including the accumulation of Ca2+ in central lens regions, leading to the formation of precipitates that stain with Alizarin red. The cataract morphology and the distribution of Alizarin red-stained material are similar, suggesting that the cataracts result from biomineralization within the organ. In this review, we suggest that this may be a general process for the formation of cataracts of different etiologies.

scholarly journals Regulation of Connexin Gap Junctions and Hemichannels by Calcium and Calcium Binding Protein Calmodulin

2020 ◽  
Vol 21 (21) ◽  
pp. 8194
Author(s):  
Zhengping Hu ◽  
Manuel A. Riquelme ◽  
Sumin Gu ◽  
Jean X. Jiang
Keyword(s):  
Gap Junctions ◽  
Calcium Binding ◽  
Lens Fiber ◽  
Site Mutation ◽  
Fiber Cells ◽  
Channel Function ◽  
Research Findings ◽  
Cataract Development ◽  
Junction Coupling ◽  
Extracellular Environment

Connexins are the structural components of gap junctions and hemichannels that mediate the communication and exchange of small molecules between cells, and between the intracellular and extracellular environment, respectively. Connexin (Cx) 46 is predominately expressed in lens fiber cells, where they function in maintaining the homeostasis and transparency of the lens. Cx46 mutations are associated with impairment of channel function, which results in the development of congenital cataracts. Cx46 gap junctions and hemichannels are closely regulated by multiple mechanisms. Key regulators of Cx46 channel function include Ca2+ and calmodulin (CaM). Ca2+ plays an essential role in lens homeostasis, and its dysregulation causes cataracts. Ca2+ associated CaM is a well-established inhibitor of gap junction coupling. Recent studies suggest that elevated intracellular Ca2+ activates Cx hemichannels in lens fiber cells and Cx46 directly interacts with CaM. A Cx46 site mutation (Cx46-G143R), which is associated with congenital Coppock cataracts, shows an increased Cx46-CaM interaction and this interaction is insensitive to Ca2+, given that depletion of Ca2+ reduces the interaction between CaM and wild-type Cx46. Moreover, inhibition of CaM function greatly reduces the hemichannel activity in the Cx46 G143R mutant. These research findings suggest a new regulatory mechanism by which enhanced association of Cx46 with CaM leads to the increase in hemichannel activity and dysregulation may lead to cataract development. In this review, we will first discuss the involvement of Ca2+/CaM in lens homeostasis and pathology, and follow by providing a general overview of Ca2+/CaM in the regulation of Cx46 gap junctions. We discuss the most recent studies concerning the molecular mechanism of Ca2+/CaM in regulating Cx46 hemichannels. Finally, we will offer perspectives of the impacts of Ca2+/CaM and dysregulation on Cx46 channels and vice versa.

scholarly journals c-MAF deletion in adult C57BL/6J mice induces cataract formation and abnormal differentiation of lens fiber cells

2020 ◽  
Vol 69 (2) ◽  
pp. 242-249
Author(s):  
Mitsunori Fujino ◽  
Asuka Tagami ◽  
Masami Ojima ◽  
Seiya Mizuno ◽  
Ahmed M. Abdellatif ◽  
...  
Keyword(s):  
Lens Fiber ◽  
Cataract Formation ◽  
Fiber Cells

scholarly journals Ectopic Activation of Wnt/β-Catenin Signaling in Lens Fiber Cells Results in Cataract Formation and Aberrant Fiber Cell Differentiation

PLoS ONE ◽  
2013 ◽  
Vol 8 (10) ◽  
pp. e78279 ◽  
Author(s):  
Barbora Antosova ◽  
Jana Smolikova ◽  
Romana Borkovcova ◽  
Hynek Strnad ◽  
Jitka Lachova ◽  
...  
Keyword(s):  
Cell Differentiation ◽  
Fiber Cell ◽  
Lens Fiber ◽  
Cataract Formation ◽  
Fiber Cells ◽  
Ectopic Activation

scholarly journals Protein and Water Distribution Across Visual Axis in Mouse Lens: A Confocal Raman MicroSpectroscopic Study for Cold Cataract

2021 ◽  
Vol 9 ◽  
Author(s):  
Yao Li ◽  
Yuxing Li ◽  
Xi Liu ◽  
Yonghong He ◽  
Tian Guan
Keyword(s):  
Raman Spectra ◽  
Water Distribution ◽  
Lens Protein ◽  
Lens Fiber ◽  
Cataract Formation ◽  
Gaussian Peak ◽  
Lens Proteins ◽  
Fiber Cells ◽  
Different Temperatures ◽  
Mouse Lens

Purpose: The aims of the study were to investigate cellular mechanisms of cold cataract in young lenses of wild-type C57BL/6J (B6WT) mice treated at different temperatures and to test a hypothesis that cold cataract formation is associated with the changes in lens protein and water distribution at different regions across lens fiber cells by Raman spectroscopy (RS).Methods: RS was utilized to scan the mouse lens at different regions with/without cold cataract. Three regions with various opacification along the equatorial axis in the anterior–posterior lens section were scanned. The intensity ratio of Raman bands at 2,935 and 3,390 cm−1 (Ip/Iw) were used to evaluate lens protein and water distribution. We further determined water molecular changes through Gaussian profiles of water Raman spectra.Results: Three specific regions 1, 2, and 3, located at 790–809, 515–534, and 415–434 μm away from the lens center, of postnatal day 14 B6WT lenses, were subjected to RS analysis. At 37°C, all three regions were transparent. At 25°C, only region 3 became opaque, while at 4°C, both regions 2 and 3 showed opacity. The sum of the difference between Ip/Iw and the value of linear fitting line from scattered-line at each scanning point was considered as fluctuation degree (FD) in each region. Among different temperatures, opaque regions showed relatively higher FD values (0.63 and 0.79 for regions 2 and 3, respectively, at 4°C, and 0.53 for region 3 at 25°C), while transparent regions provided lower FD values (less than 0.27). In addition, the decrease in Gaussian peak II and the rising of Gaussian peak III and IV from water Raman spectra indicated the instability of water molecule structure in the regions with cold cataract.Conclusion: Fluctuation degrees of RS data reveal new mechanistic information about cold cataract formation, which is associated with uneven distribution of lens proteins and water across lens fiber cells. It is possible that RS data partly reveals cold temperature-induced redistribution of lens proteins such as intermediate filaments in inner fiber cells. This lens protein redistribution might be related to unstable structure of water molecules according to Gaussian profiles of water RS.

Calmodulin-mediated gating of lens gap junction channels in vesicles

1984 ◽  
Vol 42 ◽  
pp. 134-137
Author(s):  
Camillo Peracchia ◽  
Stephen J. Girsch
Keyword(s):  
Gap Junctions ◽  
Freeze Fracture ◽  
Orthogonal Arrays ◽  
Eye Lens ◽  
Lens Fiber ◽  
Cell Coupling ◽  
Particle Spacing ◽  
Fiber Cells ◽  
Gap Junction Channels ◽  
Communicating Junctions

The fiber cells of eye lens communicate directly with each other by exchanging ions, dyes and metabolites. In most tissues this type of communication (cell coupling) is mediated by gap junctions. In the lens, the fiber cells are extensively interconnected by junctions. However, lens junctions, although morphologically similar to gap junctions, differ from them in a number of structural, biochemical and immunological features. Like gap junctions, lens junctions are regions of close cell-to-cell apposition. Unlike gap junctions, however, the extracellular gap is apparently absent in lens junctions, such that their thickness is approximately 2 nm smaller than that of typical gap junctions (Fig. 1,c). In freeze-fracture replicas, the particles of control lens junctions are more loosely packed than those of typical gap junctions (Fig. 1,a) and crystallize, when exposed to uncoupling agents such as Ca++, or H+, into pseudo-hexagonal, rhombic (Fig. 1,b) and orthogonal arrays with a particle-to-particle spacing of 6.5 nm. Because of these differences, questions have been raised about the interpretation of the lens junctions as communicating junctions, in spite of the fact that they are the only junctions interlinking lens fiber cells.

Therapeutic effect of Prdx1 on NAFLD mice may be related to the activation of Nrf-2/HO-1 pathway

2020 ◽  
Vol 26 ◽  
Author(s):  
Ru-Xue Bai ◽  
Ying-Ying Xu ◽  
Yan-Ming Chen ◽  
Geng Qin ◽  
Hui-Fen Wang ◽  
...  
Keyword(s):  
Positive Staining ◽  
Wild Type ◽  
Mice Model ◽  
Alcoholic Fatty Liver ◽  
Liver Histopathology ◽  
Final Weight ◽  
Oil Red O Staining ◽  
Alcoholic Fatty Liver Disease ◽  
Oil Red O ◽  
Liver Tissues

Objective: To investigate the effect of peroxiredoxin1 (Prdx1) on the methionine-choline deficient (MCD)- induced mice model of non-alcoholic fatty liver disease (NAFLD). Methods: Wild type (WT), transgenic Prdx1 over-expressing (TG) and Prdx1 knockout (KO) mice were fed with MCD diet to construct NAFLD model. General parameters was determined followed by detection with HE staining, oil red O staining, Immunofluorescence, Immunohistochemistry, qRT-PCR and Western blotting. The activities of MDA, GPX and SOD were also quantified. Results: Compared with WT + MCD group, mice in KO + MCD group showed the decresed final weight, food intake and the levels of glucose, insulin, total cholesterol and triglyceride, accompanying with the increased FFA, ALT and AST, as well as the aggravated liver histopathology, which was alleviated in TG + MCD group. Also, mice from KO + MCD group had increased F4/80 and CD68 positive staining with the upregulation of pro-inflammatory and fibrogenic factors in liver tissues than those from WT + MCD group, as well as the enhanced MDA and the reduced GPX and SOD, while TG + MCD group demonstrated improvements than the WT + MCD group. Nrf-2/HO-1 pathway in liver tissues from NFALD mice was inhibited, and Prdx1-/- can further reduce the expression of Nrf-2 and HO-1, while Prdx1 overexpression increased Nrf-2 and HO-1 expression. Conclusion: Prdx1 improved oxidative stress, inflammation and fibrosis in liver of NAFLD mice, which may be associate with the activation of Nrf-2/HO-1 pathway.

Abstract 336: A 14-3-3 Mode-1 Binding Motif Promotes Gap Junction Internalization During Acute Cardiac Ischemia

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
James W Smyth ◽  
Jose M Sanchez ◽  
Samy Lamouille ◽  
Ting-Ting Hong ◽  
Jacob M Vogan ◽  
...  
Keyword(s):  
Gap Junction ◽  
Protein Trafficking ◽  
Connexin 43 ◽  
Electrical Coupling ◽  
Acute Ischemia ◽  
Binding Motif ◽  
Wild Type ◽  
Gap Junction Coupling ◽  
Junction Coupling ◽  
Cell Cell

During each heartbeat, robust cell-cell electrical coupling via connexin 43 (Cx43) gap junctions allows billions of individual cardiomyocytes to contract in synchrony. Cx43 turns over rapidly, and altered Cx43 trafficking during disease contributes to the arrhythmias of sudden cardiac death. The overall phosphorylation status of the Cx43 protein is known to regulate gap junction coupling, but the role of many residue specific phosphorylation events remains unknown. One such residue, Ser373, forms a mode-1 14-3-3 binding motif upon phosphorylation. Given that 14-3-3 proteins are known to regulate protein trafficking, we hypothesized a role for Cx43 Ser373 phosphorylation in regulation of Cx43 gap junction coupling. Using Langendorff-perfused mouse hearts we find robust phosphorylation of Cx43 at Ser373 and Ser368 after 30 min of no-flow ischemia. In human cell lines, a S373A mutation ablated Cx43/14-3-3 complexing and 35 S pulse-chase revealed Cx43 S373A also experiences a longer half-life than wild-type Cx43. Previous reports have implicated phosphorylation of Cx43 Ser368 in PKC mediated Cx43 internalization. We find that upon activation of PKC, the Cx43 S373A mutant undergoes lower and more transient levels of phosphorylation at Ser368 than wild-type Cx43. Consistent with these data, siRNA-mediated ablation of 14-3-3 expression results in enlargement of gap junction plaque formation at cell-cell borders. In conclusion, we propose that phosphorylation of Cx43 Ser373 results in 14-3-3 binding which promotes and maintains phosphorylation of Cx43 Ser368 and the subsequent internalization of gap junction channels. These results identify for the first time a specific role for 14-3-3 proteins in regulation of Cx43 internalization during acute ischemia and contribute to the development of therapies aimed at preserving or enhancing gap junction coupling in the heart.

Contrasting patterns of c-myc and N-myc expression in proliferating, quiescent, and differentiating cells of the embryonic chicken lens

Development ◽  
1992 ◽  
Vol 115 (3) ◽  
pp. 813-820
Author(s):  
L.L. Harris ◽  
J.C. Talian ◽  
P.S. Zelenka
Keyword(s):  
Cell Proliferation ◽  
Protein Product ◽  
Mrna Levels ◽  
Lens Fiber ◽  
Proliferating Cells ◽  
Fiber Cells ◽  
Embryonic Chicken ◽  
Cell Proliferation And Differentiation ◽  
Proliferation And Differentiation

The present study uses the polymerase chain reaction and in situ hybridization to examine c-myc and N-myc mRNA in the embryonic chicken lens at 6, 10, 14 and 19 days of development and compares the pattern of expression obtained with the developmental pattern of cell proliferation and differentiation. In the central epithelium, c-myc mRNA levels were proportional to the percentage of proliferating cells throughout development. N-myc mRNA expression in this region was relatively low and showed no correlation with cell proliferation. The ratio of N-myc to c-myc mRNA increased markedly with the onset of epithelial cell elongation and terminal fiber cell differentiation, although both c-myc and N-myc mRNAs continued to be expressed in postmitotic, elongating cells of the equatorial epithelium and in terminally differentiating lens fiber cells. Thus, increased expression of N-myc, a gene whose protein product may compete with c-myc protein for dimerization partners, accompanies the dissociation of c-myc expression and cell proliferation during terminal differentiation of lens fiber cells.

Cloning and functional expression of an MIP (AQP0) homolog from killifish (Fundulus heteroclitus) lens

2001 ◽  
Vol 281 (6) ◽  
pp. R1994-R2003 ◽  
Author(s):  
Leila V. Virkki ◽  
Gordon J. Cooper ◽  
Walter F. Boron
Keyword(s):  
Water Permeability ◽  
Fundulus Heteroclitus ◽  
Water Channel ◽  
Fold Increase ◽  
Functional Expression ◽  
Xenopus Laevis Oocytes ◽  
Lens Fiber ◽  
Fiber Cells ◽  
Aqp1 Expression ◽  
Very High

The major intrinsic protein (MIP) of lens fiber cells is a member of the aquaporin (AQP) water channel family. The protein is expressed at very high levels in lens fiber cells, but its physiological function is unclear. By homology to known AQPs, we have cloned a full-length cDNA encoding an MIP from the lens of killifish ( Fundulus heteroclitus). The predicted protein (263 amino acids; GenBank accession no. AF191906 ) shows 77% identity to amphibian MIPs, 70% identity to mammalian MIPs, and 46% identity to mammalian AQP1. Expression of MIPfun in Xenopus laevis oocytes causes an ∼40-fold increase in oocyte water permeability. This stimulation is comparable to that seen with AQP1 and substantially larger than that seen with other MIPs. The mercurials HgCl2 and p-chloromercuribenzenesulfonate inhibit the water permeability of MIPfun by ∼25%. MIPfun is not permeable to glycerol, urea, or formic acid but is weakly permeable to CO2.

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