1.Add 10 volumes of HEPES-buffered sucrose (0.32 M sucrose, 4 mM HEPES pH7.4) to the tissue and homogenize in a motor driven glass-teflon homogenizer at ~900 rpm (10-15 strokes). Never use polytron. 2. Centrifuge the homogenate (Hom.) at 800-1000 x g at 4°C to remove the pelleted nuclear fraction (P1). 3. Spin resulting supernatant (S1) at 10,000 x g for 15 min (9200 rpm in SL50T rotor) to yield the crude synaptosomal pellet (P2). 4.Resuspend pellet (P2) in 10 volumes of HEPES-buffered sucrose and then respin at 10,000 x g for another 15 min to yield the washed crude synaptosomal fraction (P2?. 5. Lyse resulting pellet by hypoosmotic shock in 9 volumes ice cold H20 plus protease/phosphatase inhibitors and three strokes of a glass-teflon homogenizer 6. Rapidly adjust to 4 mM HEPES using 1 M HEPES, pH 7.4 stock solution. 7. Mix constantly in cold room for 30 min to ensure complete lysis. 8.Centrifuge lysate at 25,000 x g for 20 min (14,500 rpm in SL50T rotor) to yield a supernatant (S3, crude synaptic vesicle fraction) and a pellet (P3, lysed synaptosomal membrane fraction). 9. Resuspend P3 pellet in HEPES-buffered sucrose. 10. Using a Pasteur pipet, layer the resuspended membranes on top of a discontinuous gradient containing 0.8 to 1.0 to 1.2 M sucrose (top to bottom; equals 27%/34%/41%) in a clear tube. Don’t forget to add protease/phosphatase inhibitors to the sucrose solutions! Always use a Pasteur pipet to pour layers and add sample. 11. Centrifuge the gradient at ~150,000 x g for 2 hr in a swinging bucket rotor (30,000 rpm in SW41 Ti; 36,000 rpm in SW50.1 Ti; 42,000 rpm in TLS-55; 28,0000 rpm in SW28). 12. Recover synaptic plasma membranes in the layer between 1.0 and 1.2 M sucrose. 13. Dilute to 0.32 M sucrose by adding 2.5 volumes of 4 mM HEPES pH 7.4. 14.Pellet by centrifugation at 150,000 x g for 30 min. 42,000 rpm in 70.1 Ti; 55,000 rpm in TLA 100.3 15.Resuspend resulting pellet (SPM) in PBS (pH 7.4) or (50 mM HEPES pH 7.4, 2 mM EDTA) with protease and phosphatase inhibitors. 16. Can store at ?0°C. Postsynaptic Densities For references, see Carlin et al. (1980) and Cho et al. (1992). 1. Resuspend synaptic plasma membranes prepared as above in 3-5 ml of ice cold 50 mM HEPES pH7.4, 2 mM EDTA, plus protease/phosphatase inhibitors. Add Triton X-100 to 0.5% 2. Rotate in cold room for 15 min. 3. Centrifuge at at 32,000 x g for 20 min (22,000 rpm in 70.1 Ti; 28,000 rpm in TLA 100.3) to obtain the PSD-1T pellet. 4. Resuspend PSD-1T in 3 mL ice-cold 50 mM HEPES pH7.4, 2 mM EDTA plus protease/phosphatase inhibitors). Save 1 mL. 5. To half of the remaining resuspended pellet (~1 mL), add Triton X-100 to 0.5% and rotate in cold room again for 15 min. 6. Centrifuge at 200,000 x g for 20 min to obtain the PSD-2T pellet. 50,000 rpm in 70.1 Ti; 65,000 rpm in TLA 100.3. 7. In a separate experiment resuspend the second half of the PSD-1T pellet and incubate for 10 min in ice-cold 3% sarcosyl (same as N-lauroyl sarcosine) in 50 mM HEPES pH7.4, 2 mM EDTA, plus protease/phosphatase inhibitors. 8. Centrifuge at 200,000 x g for 1 hr to obtain the PSD-1T+S pellet. 9. All pellets can be resuspended in PBS or 50 mM HEPES pH7.4, 2 mM EDTA plus protease/phosphatase inhibitors or SDS-PAGE sample buffer. 10. For PSD-2T pellets, may need some SDS (0.2%) to dissolve completely. Synaptic Vesicle Prep 1. To prepare synaptic vesicles, prepare S3 fraction as in Synaptic Plasma Membrane Prep above. 2. Centrifuge S3 fraction at 165,000 x g for 2 hr. 55,000 rpm in TLA 100.3, 45,000 rpm in 70.1 Ti. 3. Resuspend in PBS or 50 mM HEPES pH7.4, 2 mM EDTA plus protease/phosphatase inhibitors. Pure Synaptosome Prep For crude synaptosomes, can simply use P2?fraction from the Synaptic Plasma Membrane Prep. For added purity: 1. layer P2?fraction onto 4 ml of 1.2 M sucrose. 2. Centrifuge at 230,000 x g for 15 min in swinging bucket rotor. 38,000 rpm in SW 41 Ti, 44,000 rpm in SW50.1, 52,000 rpm in TLS-55. 3. Collect gradient interphase. 4. Dilute to ~7-8 ml with ice-cold HEPES-buffered sucrose (0.32 M sucrose, 4 mM HEPES pH 7.4). 5. Layer onto 4 ml of 0.8 M sucrose. 6. Centrifuge at 230,000 x g for 15 min. 7. Pellet contains pure synaptosomes. 8. For bioassays, wash and resuspend in appropriate incubation buffer: For electroporation or functional release assays: (140 mM NaCl, 5 mM KCl, 5 mM NaHCO3, 1.2 mM Na2HPO4, 1 mM MgCl2, 20 mM HEPES pH 7.4, 10 mM dextrose (added fresh), ?.8 mM CaCl2, and optional ATP regenerating system. For digitonin permeabilization: 115 mM KOAc, 25 mM HEPES, pH 7.4, 5 mM NaOAc, 0.05 mM EGTA containing 0.025% digitonin, an ATP regenerating system, and 10 mM DTT. (see Meacham, Patterson, et al., Nature Cell Biology, 2001) ATP regenerating system ?5 mM Mg-ATP, 80 mM creatine phosphate, 0.5 mg/ml creatine phosphokinase 9. Otherwise, can solubilize as desired, or subfractionate further into synaptosomal membranes and synaptic vescles by hypotonic lysis as described under Synaptic Plasma Membrane Prep. Synaptoneurosomes Advance Prep a. Get rat b. Prepare Dissection Buffer (~100 mL, see below) and oxygenate on ice. c. Prepare Incubation Buffer (see below) and place on ice and 37°C if needed. Need ~30 mL/brain. d. Put glass-glass Dounce homogenizer and 2-3 conical tubes on ice. (1 brain requires 15 mL Dounce homogenizer). e. Prepare nylon syringe filters (100 m and 50 m). To do this, cut ends off of 30 mL syringes, warp double layer of nylon mesh over end and fasten tightly with rubber and (thick rubber bands for biohazard waste work well for this). f. Prepare Millipore Mitex 10 m filter (either the #LCWP 047 or LCWP 025) by fitting to Swinnex filter holders (Millipore). Be sure to tighten these HARD. g. Get dissection tools/guillotine h. Set up protein assay 1. Rapidly dissect out brain regions of interest in ice-cold oxygenated dissection buffer (see below) (212.7 mM sucrose, 2.6 mM KCl, 1.23 mM NaH2PO4, 26 mM NaHCO3, 10 mM dextrose, 10 mM MgCl2, 0.5 mM CaCl2, saturated with 95% O2 and 5% CO2). One can optionally include 20 mM CNQX plus 100 mM AP5 if excitotoxicity is a problem. Can also substitute kynurenic acid (2 mM) for CNQX and AP5. 2. Homogenize in 10 volumes ice-cold incubation buffer: 140 mM NaCl, 5 mM KCl, 5 mM NaHCO3, 1.2 mM Na2HPO4, 1 mM MgCl2, 20 mM HEPES pH 7.4, 10 mM dextrose (added fresh), ?.8 mM CaCl2, and optional ATP regenerating system by 7 strokes with a loose pestle and 4 strokes with a tight pestle in a glass-glass tissue homogenizer (Kontes). Add protease inhibitors and phosphatase inhibitors if only using synaptoneurosomes for western. If using SN’s for bioassay, leave out protease inhibitors and phosphatase inhibitors unless testing pharmacologically. Don’t forget to add ubiquitin aldehyde for ubiquitination experiments!!! 3. SAVE ALIQUOT OF UNFILTERED BRAIN HOMOGENATE. 4. Pass homogenate over two layers of 100 mm pore nylon mesh filters (Small Parts, Inc.) pre-wetted with cold incubation buffer followed by two layers of pre-wetted 50 mm pore nylon mesh filters (optional) (Small Parts, Inc). This step is accomplished by cutting the ends of 20 mL syringes and fastening the nylon mesh tightly over using rubber bands. Homogenate is then placed in the syringe and gentle pressure applied. 5. Force homogenate through a final pass pre-wetted 10 mm pore LCWP 047 or LCWP 025 Millipore Mitex membrane filter (Millipore catalog # LCWP 047 00 and LCWP 025 00) fitted to Swinnex filter holders (Millipore). Make sure filter holder is VERY tight. 6. Collect the filtered particulate and spin at 1000 x g for 20 min at 4°C. 7. Discard supernatant. 8. Resuspend pellet in 5 volumes incubation buffer. 9. Respin at 1000 x g for 10 min at 4°C to obtain washed synaptoneurosomes. 10. Resuspend pellet in incubation buffer (~ 5 volumes) to a final protein concentration of ~ 0.5 ?1.5 mg/ml. Yield is approximately 20 mg SN/brain 11. Use synaptoneurosomes fresh for experiments (within 90 min) or freeze at ?0°C if only to be used for western blot. 12. For bioassay experiments, may also want to add an ATP regenerating system, as well as some DTT (10 mM) if the synaptoneurosomes will be permeabilized or electroporated. See above section of synaptosomes for electroporation and digitonin solutions. ATP regenerating system ?5 mM Mg-ATP, 80 mM creatine phosphate, 0.5 mg/ml creatine phosphokinase
Rotor Notes Available rotors at Duke: For our SuperT21 table top superspeed: ST-H750 (swinging bucket, ~700 ml, max 3800 x g), SLC-250T (fixed angle, ~200 ml, max 20,000 x g), SL-50T (fixed angle, ~25 ml, max 41,000 x g). For the floor model Beckman XL-90 ultracentrifuge Dept. of Neurobiology Type 70.1 Ti (fixed angle, max 450,000 x g), SW28 (swinging bucket, max 140,000 x g, 6 x 39 mL), NVT90 (near vertical, max 645,000 x g) Dept. of Neurology SW41 (swinging bucket, max 288,000 x g, 6 x 13.2 mL), SW 50.1 (swinging bucket, max 300,000 x g, 6 x 5 mL), Type 60 Ti (fixed angle, max 360,000 x g) For the Beckman tabletop ultracentrifuge in Pate’s lab TLA 100.3 (fixed angle, max 540,000 x g), TLS-55 (swinging bucket, max 255,000 x g) back to top (责任编辑：泉水) |
神经元的培养及转染(2)
时间:2006-03-16 10:00来源:ehlerslab 作者:bioguider 点击:
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