PMC

(A) Images of dendrites from EGFP-expressing neurons at 7–12 DIV before and after the addition of vehicle, MG132, or lactacystin at t = 0 (black arrow). Yellow arrows indicate new spines. (B) MG132 (10 μM) decreased the rate of spine outgrowth (green bar; 34 spines, 5 cells) as compared to vehicle control (black bar; 68 spines, 6 cells; p < 0.05). (C) Lactacystin (10 μM) decreased the rate of spine outgrowth (light green bar; 33 spines, 6 cells) as compared to vehicle control (black bar; 131 spines, 8 cells; p < 0.01). Doubling the concentration of lactacystin (20 μM) inhibited spine outgrowth to a comparable extent (dark green bar; 25 spines, 6 cells; p < 0.001). (D) New spine growth was significantly reduced within 5 min after addition of lactacystin (10 μM) and remained significantly reduced for all subsequent time points (p < 0.05). Error bars represent SEM.

(A) Images of dendrites from hippocampal neurons transfected with EGFP, EGFP + Rpt6-WT, or EGFP + Rpt6-S120A at 9–10 DIV before and after the addition of vehicle or bicuculline at t = 0 (black arrow). Yellow arrows indicate new spines. (B) Transfection with Rpt6-WT (gray bar; 121 spines, 7 cells; p < 0.05) did not interfere with the bicuculline-induced increase in spine outgrowth (blue bar; 149 spines, 8 cells; p < 0.05) relative to vehicle-treated controls (black bar; 73 spines, 7 cells). In contrast, Rpt6-S120A transfection reduced spine outgrowth in bicuculline-treated cells (green bar; 56 spines, 7 cells; p < 0.001) relative to vehicle-treated controls. (C) Transfection with Rpt6-S120A decreased the rate of spine outgrowth (gray bar; 32 spines, 6 cells) as compared to cells transfected with EGFP alone (black bar; 74 spines, 6 cells; p < 0.01). Treatment of Rpt6-S120A transfected neurons with lactacystin (light green bar; 33 spines, 6 cells, p = 0.48) or with CPP (dark green bar; 44 spines, 7 cells, p = 0.24) did not further reduce rates of spine outgrowth over that observed for untreated S120A transfected cells. Error bars represent SEM.

(A) Images of dendrites from EGFP-expressing hippocampal neurons at 7–10 DIV before and after the addition of myristoylated PKI 14–22 (20 μM), Rp-cAMPS (5 μM), or KN-93 (30 μM) at t = 0 (black arrow). Yellow arrows indicate new spines. (B) Inhibition of PKA with PKI 14–22 (dark gray bar; 58 spines, 7 cells; p = 0.9) or Rp-cAMPS (light gray bar; 66 spines, 7 cells; p = 0.4) did not alter rates of spine outgrowth relative to vehicle-treated controls (black bar; 54 spines, 7 cells). In contrast, inhibition of CaMKs with KN-93 decreased spine outgrowth (light green bar; 40 spines, 7 cells; p < 0.001) but did not further decrease spine outgrowth in cells transfected with Rpt6-S120A (dark green bar; 34 spines, 7 cells; p = 0.6). (C) Images of dendrites from EGFP-expressing WT or GluN2B L1298A/R1300Q knockin (GluN2B KI) mouse neurons at 8–11 DIV, before and after treatment with vehicle, bicuculline (30 μM), or lactacystin (10 μM) at t = 0 (black arrow). Yellow arrows indicate new spines. (D) In neurons from WT mice, treatment with bicuculline increased spine outgrowth (solid blue bar; 76 spines, 5 cells; p = 0.01) relative to vehicle-treated controls (solid black bar; 40 spines, 4 cells), while lactacystin decreased spine outgrowth (solid green bar; 16 spines, 5 cells) relative to controls (solid black bar; 54 spines, 5 cells). In contrast, in neurons from GluN2B KI mice, neither bicuculline (open blue bar; 41 spines, 5 cells; p = 0.6) nor lactacystin (open green bar; 42 spines, 5 cells; p = 0.8) altered spine outgrowth relative to vehicle-treated controls (open black bar; 45 spines, 5 cells). Error bars represent SEM.

(A) Images of dendrites from EGFP-expressing neurons at 5–10 DIV before and after the addition of vehicle or bicuculline (30 μM) at t = 0 (black arrow). Yellow arrows indicate new spines. (B) Elevated neural activity in response to bicuculline increased the rate of new spine addition (blue bar; 116 spines, 6 cells) as compared to vehicle control (black bar; 68 spines, 6 cells; p < 0.01). Inhibiting the proteasome with MG132 blocked the bicu-culline-induced increase in spine outgrowth and decreased baseline new spine growth (light green bar; 46 spines, 7 cells; p < 0.05) to a level similar to that in the presence of MG132 alone (dark green bar; data from ; p = 0.4). (C) Schematic of uncaging-induced spine outgrowth. A new spine (red arrow) was induced by focal photolysis of MNI-caged glutamate (red dot) adjacent to a section of dendrite devoid of spines. (D) Images of dendrites from EGFP-expressing neurons at 7–8 DIV before and after focal photolysis of MNI-glutamate (red dots) at t = 0 (black arrow). Red arrows indicate new spines. (E) Uncaging-induced spine outgrowth (blue bar; 16 successes out of 44 trials on 15 cells) was significantly reduced in the presence of lactacystin (10 μM; green bar; 6 successes out of 40 trials on 12 cells; p < 0.05). (F) Images of dendrites from EGFP-expressing neurons at 7–11 DIV before and after the addition of CPP (30 μM) or CPP + lactacystin (10 μM) at t = 0 (black arrow). Yellow arrows indicate new spines. (G) The rate of new spine addition decreased in the presence of CPP (light green bar; 39 spines, 8 cells) as compared to vehicle control (black bar; 105 spines, 8 cells; p < 0.001). No further decrease in spine outgrowth was observed with simultaneous blockade of the proteasome with lactacystin (dark green bar; 45 spines, 7 cells; p = 0.4). Error bars represent SEM.