Journal of Neuroscience Research, 79(1C2), 180C184. phosphorylation of PKC and AMPA receptor subunit GluA2 in astrocytes, and these effects were diminished by SU1498 or calphostin C, a PKC inhibitor. With the pHluorin assay, we observed that VEGF significantly increased membrane insertion and expression of GluA2, but not GluA1, in astrocytes. Moreover, siRNA\produced knockdown of GluA2 expression in astrocytes reversed the inhibitory effect of VEGF on glutamate\induced calcium influx. Together, our results suggest that VEGF reduces glutamate\induced calcium influx in astrocytes via enhancing PKC\mediated GluA2 phosphorylation, which in turn promotes the membrane insertion and expression of GluA2 and causes AMPA receptors to switch from calcium\permeable to calcium\impermeable receptors, thereby inhibiting astrocytic calcium influx. The present study reveals that excitatory neurotransmitter glutamate\mediated astrocytic calcium influx can be regulated by vascular biological factor via activation of AMPA receptor GluA2 subunit and uncovers a novel coupling mechanism between astrocytes and endothelial cells within the neurovascular unit. for 5 min. For the extraction of total cellular proteins, cells were homogenized in cold lysis buffer (Beyotime Biotechnology, Nantong, China) with protease inhibitor cocktail for 30?min (Roche, Basel, Switzerland). The supernatant containing total cellular proteins was collected after centrifuged at 16,000for 15?min. For the extraction of membrane proteins, Mem\PER? Plus Membrane Protein Extraction Kit (Thermo PLX8394 Fisher Scientific, Waltham, MA) was used according to the manufacturer’s instructions. Experiments were performed on ice and all centrifugations or mixings were performed at 4C. The concentrations of total cellular proteins and membrane proteins were measured by the BCA protein assay kit (Beyotime Biotechnology, Nantong, China) according to the manufacturer’s instructions. 2.3.3. Western blot Equal amounts (20?g) of proteins from each group were electrophoresed on 10% or 12% SDS\PAGE Rabbit Polyclonal to WIPF1 gels and then transferred to polyvinyl difluoride (PVDF) membranes (Bio\Rad, Berkeley, CA). After blocked by 10% milk in PLX8394 Tris\buffered saline (TBST, pH 7.4) containing 10 mM Tris, 150?mM NaCl, 0.1% Tween 20 at room temperature for 2 hr, the membranes were incubated with rabbit anti\GluA1 (1:500 dilution), rabbit anti\GluA2 (1:2,000 dilution) or rabbit anti\p\PKC (1:500 dilution) at 4C overnight. After washed in TBST, membranes were incubated with HRP\conjugated anti\rabbit IgG (1:3,000 dilution) for 1 hr at room temperature. Then peroxidase activity was visualized by Western blot luminescent reagent (Western lightning plus ECL, PerkinElmer, Akron, OH) and X\OMAT film. For normalization, membranes were stripped and washed overnight. Then membranes were reprobed with rabbit anti\pan\cadherin (1:2,000 dilution) or rabbit anti\PKC (1:2,000 dilution). Optical densities of immune\stained bands were scanned with a scanner (Scan Maker i900, Microtek, Shanghai, China) and analyzed with an image processing and analysis system (Image J 1.48 software, NIH, Bethesda, MD). 2.3.4. Immunoprecipitation For immunoprecipitation in total cellular proteins, PLX8394 200?g of proteins from each group were incubated with 0.5 g following antibodies at 4C overnight in lysis buffer (Beyotime Biotechnology, Nantong, China) with protease inhibitor cocktail: rabbit anti\Flk1, rabbit anti\Flt1, rabbit anti\GluA2, rabbit anti\PKC, and rabbit IgG. Then incubated the proteinCantibody complex substances with 40?L protein A sepharose CL\4B beads (GE Healthcare, Abingdon, UK) at 4C for 4 hr. Beads were then washed three times in cold lysis buffer with slight mixing and proteins were eluted by a final volume 40?L 2 ?SDS sample buffer (Beyotime Biotechnology, Nantong, China). After boiled for 5 min, samples were electrophoresed and transferred to the PVDF membranes as described in Western blot. After blocked by 5% BSA in TBST at room temperature for 2 hr, membranes were incubated with interested primary antibodies at 4C overnight. For immunoprecipitation of anti\Flk1 or anti\Flt1, membranes were immunoblotted with anti\phosphotyrosine (1:1,000 dilution) and then reprobed with rabbit anti\Flk1 (1:1,000 dilution) or rabbit anti\Flt1 (1:200 dilution). For immunoprecipitation of anti\GluA2, the membrane was immunoblotted with rabbit anti\phosphoserine (1:1,000 dilution) or rabbit anti\Flk1 and reprobed with rabbit anti\GluA2 (1:2,000 dilution). For immunoprecipitation of anti\PKC, the membrane was immunoblotted with rabbit anti\Flk1 or rabbit anti\GluA2 and then reprobed with rabbit anti\PKC (1:1,000 dilution). Ten percent amount of proteins for immunoprecipitation from each group was electrophoresed and immunoblotted with antibodies against Flk1, Flt1, GluA1, GluA2, or PKC to verify equal expression of target proteins between samples. 2.4. Immunocytochemistry For triple labeling of GFAPCFlk1\GluA2, quiescent astrocytes cultured on coverslips were fixed with 4% paraformaldehyde dissolved in PBS after washed thoroughly in cold PBS. After washed in PBS for three times, cells were incubated in a blocking solution (0.3% Triton X\100 and 10% fetal calf serum dissolved in PBS) for 1 hr at 37C. Then cells were stained with goat anti\Flk1 (1:200 dilution) at 4C overnight and then anti\goat IgG\Alexa Fluor.