Selective deletion of zinc transporter 3 in amacrine cells promotes retinal ganglion cell survival and optic nerve regeneration after injury

Vision depends on accurate signal conduction from the retina to the brain through the optic nerve,an important part of the central nervous system that consists of bundles of axons originating from retinal ganglion cells.The mammalian optic nerve,an important part of the central nervous system,cannot regenerate once it is injured,leading to permanent vision loss.To date,there is no clinical treatment that can regenerate the optic nerve and restore vision.Our previous study found that the mobile zinc(Zn^(2+))level increased rapidly after optic nerve injury in the retina,specifically in the vesicles of the inner plexiform layer.Furthermore,chelating Zn^(2+)significantly promoted axonal regeneration with a long-term effect.In this study,we conditionally knocked out zinc transporter 3(ZnT3)in amacrine cells or retinal ganglion cells to construct two transgenic mouse lines(VGAT^(Cre)ZnT3^(fl/fl)and VGLUT2^(Cre)ZnT3^(fl/fl),respectively).We obtained direct evidence that the rapidly increased mobile Zn^(2+)in response to injury was from amacrine cells.We also found that selective deletion of ZnT3 in amacrine cells promoted retinal ganglion cell survival and axonal regeneration after optic nerve crush injury,improved retinal ganglion cell function,and promoted vision recovery.Sequencing analysis of reginal ganglion cells revealed that inhibiting the release of presynaptic Zn^(2+)affected the transcription of key genes related to the survival of retinal ganglion cells in postsynaptic neurons,regulated the synaptic connection between amacrine cells and retinal ganglion cells,and affected the fate of retinal ganglion cells.These results suggest that amacrine cells release Zn^(2+)to trigger transcriptomic changes related to neuronal growth and survival in reginal ganglion cells,thereby influencing the synaptic plasticity of retinal networks.These results make the theory of zinc-dependent retinal ganglion cell death more accurate and complete and provide new insights into the complex interactions between retinal cell networks.

Bioinformatics Analysis of Zinc Transporter from Baoding Alfalfa

[Objective] This study aimed to perform the bioinformatics analysis of Zinc transporter （ZnT） from Baoding Alfalfa. [Method] Based on the amino acid sequence, the physical and chemical properties, hydrophilicity/hydrophobicity, secondary structure of ZnT from Baoding alfalfa were predicted by a series of bioinformatics software. And the transmembrane domains were predicted by using different online tools. [Result] ZnT is a hydrophobic protein containing 408 amino acids with the theoretical pl of 5.94, and it has 7 potential transmembrane hydrophobic regions. In the sec- ondary structure, co-helix （Hh） accounted for 48.04%, extended strand （Ee） for 9.56%, random coil （Cc） for 42.40%, which was accored with the characteristic of transmembrane protein. [Conclusion] mZnT is a member of CDF family, responsible for transporting Zn^2＋ out of the cell membrane to reduce the concentration and toxicity of Zn^2＋.

Effects of physical exercise on the developmental expression of hippocampal zinc transporter 1 and glutamate receptor subunit 2, and on cognitive function in a rat model of recurrent neonatal seizure

BACKGROUND： Developmental seizures are pathologically characterized by regenerative sprouting of hippocampal mossy fibers rich in Zn^2＋. Zn^2＋ metabolism in the mossy fiber pathway, and Zn^2＋ accumulation in presynaptic membrane vesicles, are dependent on zinc transporter 1 （ZnT1） and glutamate receptor subunit 2 （GluR2）. OBJECTIVE： To investigate the effects of long-term recurrent neonatal seizure, in the presence and absence of physical exercise, on the developmental expression of hippocampal zinc transporter 1 （ZnT1） and GluR2, and on cognitive function in rats. DESIGN, TIME AND SETTING： Based on behavioral examination and molecular biological research, a randomized, controlled animal experiment was performed at the Department of Neurobiology, Medical College of Soochow University, between January 2007 and April 2008. MATERIALS： Twenty-one 6-day-old Sprague Dawley rats of either gender were employed in this study. ZnT1 mRNA in situ hybridization kit was provided by Tianjin Haoyang Biological Manufacture Co.,Ltd., China. Rabbit anti-GluR2 was purchased from Santa Cruz Biotech, Inc, USA. METHODS： Rats were randomly divided into a recurrent seizure group （n = 11） and a control group （n = 10）. In the recurrent seizure group, 30-minute seizure was induced by flurothyl gas inhalation for a total of 6 consecutive days. Rats from the control group underwent experimental procedures similar to the recurrent seizure group, with the exception of flurothyl gas inhalation. Thirty minutes of treadmill exercise was performed daily by all rats at postnatal days 51–56. MAIN OUTCOME MEASURES： At postnatal day 82, rat hippocampal tissue was harvested for analysis of hippocampal ZnT1 and GluR2 expression by in situ hybridization and immunohistochemistry, respectively. Rat learning and memory capabilities were examined using the Y-maze test. RESULTS： In the recurrent seizure group, the gray scale value of ZnT1 in situ hybridization positive neurons in the hippocampal CA3 region was significantly greater （P 〈 0.05）, while the gray scale value of GluR2 immunoreactive neurons in the hippocampal hilus and dentate gyrus was significantly lower （P 〈 0.05）, than in the control group. At postnatal days 29–35, numbers of trials to criteria for successful learning were greater in the recurrent seizure group than in the control group （P 〈 0.05）; at postnatal days 61–67, the numbers of trials to criteria for successful learning were similar between the two groups （P 〉 0.05）. At postnatal days 29–35 and 61–67, there was no significant difference in memory capability between the recurrent seizure and control groups （P 〉 0.05）. CONCLUSION： Physical exercise likely improves the learning deficits caused by recurrent neonatal seizure in rats during brain development by modulating ZnT1 and GluR2 expression.

A Pleiotropic Drug Resistance Family Protein Gene Is Required for Rice Growth, Seed Development and Zinc Homeostasis

Zinc(Zn) is an essential mineral element for plant growth and development. Zn deficiency in crops frequently occurs in many types of soils. It is therefore crucial to identify genetic resources linking Zn acquisition traits and development of crops with improved Zn-use efficiency for sustainable crop production. In this study, we functionally identified a rice uncharacterized ABCG(ATP-binding cassette G-subfamily) gene encoding a PDR20(pleiotropic drug resistance 20) metal transporter for mediation of rice growth, seed development and Zn accumulation. OsPDR20 was localized to the plasma membrane, but it was not transcriptionally induced under Zn deficiency, rather was sufficiently up-regulated under high level of Zn stress. Yeast(Saccharomyces cerevisiae) transformed with OsPDR20 displayed a relatively lower Zn accumulation with attenuated cellular growth, suggesting that OsPDR20 had an activity for Zn transport. Knocking-down OsPDR20 by RNA interference(RNAi) compromised rice growth with shorter plant height and decreased biomass in rice plantlets grown under hydroponic media. Zn concentration in the roots of OsPDR20 knocked-down rice lines declined under Zn deficiency, while they remained unchanged compared with the wild type under normal Zn supply. A rice lifelong field trial demonstrated that OsPDR20 mutation impaired the capacity of seed development, with shortened panicle and seed length, compromised spikelet fertility, and reduced grain number per plant or grain weight per unit area. Interestingly, OsPDR20 mutation elevated the accumulation of Zn in husk and brown rice over the wild type. Overall, this study pointed out that OsPDR20 is fundamentally required for rice growth and seed development through Zn transport and homeostasis.

Zinc dysregulation in cancers and its potential as a therapeutic target

Zinc is an essential element and serves as a structural or catalytic component in many proteins.Two families of transporters are involved in maintaining cellular zinc homeostasis:the ZIP(SLC39A)family that facilitates zinc influx into the cytoplasm,and the ZnT(SLC30A)family that facilitates zinc efflux from the cytoplasm.Zinc dyshomeostasis caused by the dysfunction of zinc transporters can contribute to the initiation or progression of various cancers,including prostate cancer,breast cancer,and pancreatic cancer.In addition,intracellular zinc fluctuations lead to the disturbance of certain signaling pathways involved in the malignant properties of cancer cells.This review briefly summarizes our current understanding of zinc dyshomeostasis in cancer,and discusses the potential roles of zinc or zinc transporters in cancer therapy.

Effect of Phosphate on Zinc Transport in Lou Soil

A study on the transport characteristics of zinc in lou soil with phosphate at different concentrations was carried out by the method of step input. The effects of phosphate and temperature on zinc transport were studied through analysing the diffusion-dispersion coefficients (D) and the retardation factor (R) obtained by the program CXTFIT. The results showed that D decreased and R increased with increasing concentration of phosphate so that it was difficult for zinc to break through the soil column, and zinc stopped to break through the column at high temperature. One order equation, double constant equation and the Elovich equation were all suitable for the description of zinc dynamica. Effects of phosphate and temperature on zinc transport were further confirmed by the analysis on pseudo-thermodynamic parameters of zinc transport.

Increased performance of an organic light-emitting diode by employing a zinc phthalocyanine based composite hole transport layer

We demonstrate that the electroluminescent performances of organic light-emitting diodes are significantly improved by employing a zinc phthalocyanine （ZnPc）-based composite hole transport layer （c-HTL）. The optimum ris-（8-hydroxyquinoline）aluminum （Alq3）-based organic light-emitting diode with a c-HTL exhibits a lower turn-on voltage of 2.8 V, a higher maximum current efficiency of 3.40 cd/A and a higher maximum power efficiency of 1.91 lm/W, which are superior to those of the conventional device （turn-on voltage of 3.8 V, maximum current efficiency of 2.60 cd/A, and maximum power efficiency of 1.21 lm/W）. We systematically studied the effects of different kinds of N’-diphenyl-N,N’-bis（1-naphthyl）（1,1’-biphenyl）-4,4’diamine （NPB）：ZnPc c-HTL. Meanwhile, we also investigate their mechanisms different from that in the case of using ZnPc as buffer layer. The specific analysis is based on the absorption spectra of the hole transporting material and current density–voltage characteristics of the corresponding hole-only devices.

Autophagy inhibitor 3-methyladenine regulatesthe expression of LC3, Beclin-1 and ZnTs in ratcerebral cortex following recurrent neonatal seizures

BACKGROUND： Autophagy is a homeostatic process for intracellular recycling of bulk proteins and aging organelles. Increased autophagy has now been reported in experimental models of traumatic brain injury, stroke and excitotoxicity, and in patients with Alzheimer＇s disease and critical illness. The role of autophagy in developmental epilepsy, however, is unknown. The present study was to investigate the effects of recurrent neonatal seizure, in the presence and absence of autophagy inhibitor 3-methyladenine （3-MA）, on the acute phase gene expression of ZnTs, LC3 and Beclin-1 in rat cerebral cortex and the interaction among them.METHODS： Thirty-six Sprague-Dawley neonatal rats at postnatal day 6（P6） were randomly divided into three groups： a recurrent-seizures group （RS, n=12）, a 3-MA treated-seizure group （3-MA group, each rat pretreated with 3-methyladenine before seizures, 100nmol/μl/day, i.p., n=12） and a control group （n=12）. At 1.5 and 6 hours after the last seizures, the mRNA levels of ZnT1-ZnT3, microtubule-associated protein 1A/1B light chain 3 （LC3） and beclin-1 were detected using the real-time RT-PCR method. The LC3 protein level was examined by Western blotting.RESULTS： The levels of LC3, beclin-1 and ZnT-2 transcripts in the RS group elevated signi？ cantly at 1.5 and 6 hours after the last seizures compared with those in the control and 3-MA groups. At the interval of 1.5 hours, the mRNA level of ZnT-1 increased signi？ cantly after the last seizure compared with that in the control group. There was no signi？ cant difference in the transcript levels of ZnT-3 among the three groups. Linear correlation analysis showed that the expression of the ？ ve genes in the control group exhibited a signi？ cant inter-relationship. In the 3-MA group, however, the inter-relationship was only found between beclin-1 and ZnT-1. In the RS group, the inter-relationship was not observed.CONCLUSIONS： The autophagy/lysosomal pathway is immediately activated along with the elevated expression of ZnT1 and ZnT2 in the cerebral cortex after recurrent seizures. 3-MA is involved in the regulation of the autophagy/lysosomal pathway and ZnTs by down-regulating the expression of LC3 and beclin-1.

Zinc homeostasis in the metabolic syndrome and diabetes

Zinc(Zn)is an essential mineral that is required for various cellular functions.Zn dyshomeostasis always is related to certain disorders such as metabolic syndrome,diabetes and diabetic complications.The associations of Zn with metabolic syndrome,diabetes and diabetic complications,thus,stem from the multiple roles of Zn:(1)a constructive component of many important enzymes or proteins,(2)a requirement for insulin storage and secretion,(3)a direct or indirect antioxidant action,and(4)an insulin-like action.However,whether there is a clear cause-and-effect relationship of Zn with metabolic syndrome,diabetes,or diabetic complications remains unclear.In fact,it is known that Zn deficiency is a common phenomenon in diabetic patients.Chronic low intake of Zn was associated with the increased risk of diabetes and diabetes also impairs Zn metabolism.Theoretically Zn supplementation should prevent the metabolic syndrome,diabetes,and diabetic complications;however,limited available data are not always supportive of the above notion.Therefore,this review has tried to summarize these pieces of available information,possible mechanisms by which Zn prevents the metabolic syndrome,diabetes,and diabetic complications.In the final part,what are the current issues for Zn supplementation were also discussed.

Sequence Similarity and Functional Relationship Among Eukaryotic ZIP and CDF Transporters

ZIP （ZRT/IRT-like Protein） and CDF （Cation Diffusion Facilitator） are two large metal transporter families mainly transporting zinc into and out of the cytosol. Several ZIP and CDF transporters have been characterized in mammals and various model organisms, such as yeast, nematode, fruit fly, and zebrafish, and many candidate genes have been identified by genome projects. Unexpected functions of ZIP and CDF transporters have been recently reported in some model organisms, leading to major advances in our understanding of the functions of mammalian counterparts. Here, we review the recent information on the sequence similarity and functional relationship among eukaryotic ZIP and CDF transporters obtained from the representative model organisms.

Screening and identification of human Zn T8-specific single-chain variable fragment (scFv) from type 1 diabetes phage display library

Zinc transporter 8 （ZnT8） is a major autoantigen and a predictive marker in type 1 diabetes （T1D）. To investigate ZnT8-specific antibodies, a phage display library from TID was constructed and single-chain antibodies against ZnT8 were screened and identified. Human T1D single-chain variable fragment （scFv） phage display library consists of approximately 1 ~ l0s clones. After four rounds of bio-panning, seven unique clones were positive by phage ELISA. Among them, C27 and C22, which demonstrated the highest affinity to ZnT8, were expressed in Escherichia coli Topl0F＇ and then purified by affin- ity chromatography. C27 and C22 specifically bound ZnT8 N/C fusion protein and ZnT8 C terminal dimer with one Arg325Trp mutation. The specificity to human islet cells of these scFvs were further confirmed by immunohistochemistry. In conclusion, we have successfully constructed a T1D phage display antibody library and identified two ZnT8-specific scFv clones, C27 and C22. These ZnT8-specific scFvs are potential agents in immunodiagnostic and immunotherapy of T1D.

Growth and Characterization of Pencil-Like ZnO Nanowires in the Presence of a Disturbance in Boundary Layer

Pencil-like zinc oxide（ZnO） nanowire was synthesized on Si（111） substrate through a simple vapor phase method using a mixture of zinc oxide and graphite as the source material. The source inside a quartz tube created a Zn-rich vapor that facilitated the formation and growth of ZnO nanowires. Field emission scanning electron microscopic studies indicated that pencil-like ZnO nanowires had a size of the range from 50 to 150 nm in diameter and several microns in length. X-ray diffraction was used to investigate the crystal structure of ZnO nanowires. Raman scattering and photoluminescence were applied to characterize the optical properties of the pencils. The growth mechanism of the nanopencils was discussed based on the growth conditions.