(A) Gel mobility shift of SynGAP induced by cotransfected wild-type (WT) or constitutively active (CA) Plk2 in COS-7 cells, but not by kinase-dead (KD) Plk2 or Plk2 N/C-terminal fragments. (B) Gel mobility shift of PDZGEF1 by cotransfected CA Plk2 but not KD Plk2. (C) RasGRF1 was cotransfected with KD or CA Plk2 in COS-7 cells, treated with MG132 (25 μM, 16 h) or vehicle (DMSO), and lysates immunoblotted as shown at right of blots. (D) COS-7 cells were transfected with SPAR and KD or CA Plk2. Cotransfected liprin was used as internal negative control and transfection/loading control. (E) Proteins as indicated at top were immunoprecipitated 24 h after transfection and recovery examined by immunoblotting. In, input; IP, immunoprecipitation. (F) Immunoprecipitates from (E) were incubated with ³²P-γ-ATP and purified KD or CA Plk2 (except in last lane, containing CA Plk2 only). Black dots indicate expected sizes of indicated proteins. Autophosphorylated CA Plk2 (auto) was marked with asterisks. Liprin and GFP were used as negative controls. Note right-most panel was run on higher percentage gel to resolve GFP. (G) Mouse brain lysates (Input) were immunoprecipitated with rabbit anti-Plk2 antibody (7382) or IgG control and immunoblotted for Ras/Rap regulators as indicated. (H–J) COS-7 cells were transfected as indicated at top of blots, with IP performed as shown at bottom and western blotting for transfected proteins as indicated at right of each blot. KD Plk2 was used in (J) to prevent loss of RasGRF1 by active Plk2. Input, 10% of lysate used for each IP. All MW in kDa.

(A–B) Cultured hippocampal neurons (20–23 DIV) were treated with PTX (100 μM, 20 h) or vehicle and immunolabeled for RasGRF1 and SPAR. MAP2 staining is shown to outline dendrites. Scale, 20 μm. (C) Quantification of integrated intensity of RasGRF1 and SPAR (n=10). (D and E) Neurons were transfected with pEGFP, WT Plk2, or KD Plk2 for 3 days followed by immunostaining for RasGRF1 and SPAR. Scale, 10 μm. (F) Quantification of integrated intensity of RasGRF1 and SPAR in proximal dendrites (n=10). (G) Hippocampal cultures were infected with Sindbis virus expressing GFP, WT Plk2 or KD Plk2, treated with PTX, then immunostained for RasGRF1, SPAR, and PSD-95. Scale, 10 μm. (H) Quantification of integrated intensity from (G) in proximal dendrites (n=10–11). (I) Neurons were treated with PTX in the presence of Plk inhibitor BI2536 (75 nM, 20 h) or vehicle as indicated, and then immunostained for RasGRF1, SPAR, and PSD-95. Scale, 10 μm. (J) Quantification of integrated intensity from (I) in proximal dendrites (n=10). (K) Hippocampal neurons were transfected with Plk2-shRNA or control (pLL3.7) vector. After 48 h, cells were treated with PTX or vehicle and immunolabeled for RasGRF1, SPAR and PSD-95. Scale, 10 μm. (L) Quantification of integrated intensity from (K) (n=10). *p<0.05, **p<0.01, ***p<0.001 for all graphs.

(A) COS-7 cells were transfected as indicated at top of blot. Cell lysates were incubated with GST-Raf1-RBD to precipitate active Ras, followed by immunoblotting (IB) as indicated. (B) Quantification of active Ras normalized to total Ras (n=6). (C) Lysates of COS-7 cells transfected as indicated at top were incubated with GST-RalGDS-RBD to precipitate active Rap, followed by IB analysis. (D) Quantification of active Rap2 normalized to total Rap2 (n=6). (E) Active Ras and Rap pulldown assays in cultured hippocampal neurons. Cells (19–21 DIV) were infected with Sindbis virus expressing GFP, WT Plk2, or KD Plk2. GST-Raf1-RBD and GST-RalGDS-RBD were used to pull down active Ras and Rap, respectively. (F) Quantification of active H-Ras and Rap2 normalized to total expression (n=5 and 7, respectively). (G) Relative fold change in Rap vs Ras activity. (H) Hippocampal neurons were stimulated with PTX in the presence or absence of BI2536. Active Ras and Rap pulldown assays were performed with GST-Raf1-RBD and GST-RalGDS-RBD. (I) Quantification of active H-Ras and Rap2 normalized to total expression (n=3–4). (J) Relative fold change in Rap vs Ras activity. *p<0.05, **p<0.01, ***p<0.001 for all graphs.

(A–E) Cultured hippocampal neurons (21 DIV) were transfected with control vector (pLL3.7) containing CMV-EGFP, Plk2-shRNA, or Plk2-shRNA plus rescue construct. After 48 h, cells were treated with PTX or vehicle, and immunolabeled against GFP. Scale, 5 μm. (F) Quantification of spine density (n=10–11, *p<0.05, **p<0.01). (G) Cumulative frequency plot of spine head area (n=262–357 spines; Kolmogorov–Smirnov (K–S) test; Table S1). (H–K) Neurons were transfected with EGFP plasmid. After 48 h, cells were treated with or without PTX in the presence of BI2536 or vehicle, and then immunostained for GFP. Scale, 5 μm. (L) Quantification of spine density (n=12, ***p<0.001). (M) Cumulative frequency plot of spine head width (n=200 spines; K–S test; Table S1).

(A–F) Hippocampal neurons (21 DIV) were transfected as indicated, along with pEGFP to visualize spine morphology. After 3 days, cells were immunostained for GFP. Scale, 5 μm. (G) Quantification of spine density from (A–F) (n=10–11, *p<0.05, **p<0.01, ***p<0.001). (H) Cumulative frequency plot of spine head area (n=150–200 spines; K–S test; Table S1). (I) Summary of spine remodeling. Plk2 was compared to GFP control, while other conditions were compared to Plk2. (J–O) Cultured neurons were transfected as indicated for 3 days, followed by immunocytochemistry for GFP. Scale, 5 μm. (P) Quantification of spine density from (J–O) (n=10–11, *p<0.05, **p<0.01, ***p<0.001). (Q) Cumulative frequency plot of spine head area (n=150–250 spines; K–S test; Table S1). (R) Summary of spine remodeling. Plk2 RNAi was compared to control vector (pLL3.7), while other conditions were compared to Plk2 RNAi.

(A) Schematic of phosphomutants used: RasGRF1 (S71A), SynGAP (S390A or S783A), and quintuple PDZGEF1 mutant (5×A). (B–I) Hippocampal neurons (DIV19) were transfected with pEGFP and either WT or phosphomutant constructs. After 48 h, neurons were treated with PTX or vehicle, followed by immunostaining for GFP. Scale, 5 μm. (J) Quantification of spine density from (B–I) (n=8–11, *p<0.05, **p<0.01, ***p<0.001). (K–M) Cumulative frequency plot of spine head width (n=150–200 spines; K–S test; Table S1).

(A, B) Hippocampal neurons (DIV19) were transfected with Plk2-shRNA or control vector (pLL3.7) and treated with or without PTX in the presence of BI2536 or vehicle. Immunostaining is shown for surface GluA1 or GluA2 in proximal and distal dendrites as indicated. Scale, 5 μm. (C, D) Quantification of integrated intensity for surface GluA1 (C) and GluA2 (D) (n=10–15, *p<0.05, **p<0.01 vs. proximal control; ⁺p<0.05, ⁺⁺p<0.01 vs. distal control). (E, G) Neurons were transfected as indicated, treated with PTX or vehicle, and immunolabeled for surface GluA1 and GluA2. Scale, 5 μm. (F, H) Quantification of integrated intensity for surface GluA1 (F) and GluA2 (H) (n=10–15, *p<0.05, **p<0.01). (I, J) Neurons were transfected with pEGFP and either wild-type or phosphomutant constructs. After 48 h, neurons were treated with PTX or vehicle, followed by immunostaining for surface GluA1 and GluA2. Scale, 5 μm. (K, L) Quantification of integrated intensity for surface GluA1 (K) and GluA2 (L) (n=10–15, *p<0.05, **p<0.01, ***p<0.001 vs. GFP; ⁺p<0.05, ⁺⁺p<0.01, ⁺⁺⁺p<0.001 vs. -PTX).

(A) Schematic representation of DN-Plk2 transgene (TG) construct. Gray bar, myc-epitope tag. Black bar, TG-specific in situ hybridization probe. (B) PCR genotyping of TG mice. (C) In situ hybridization of mRNA for transgenic and endogenous Plk2. (D) Immunohistochemistry of TG and WT brain sections (higher magnification images shown at bottom). (E) Western blot analysis of forebrain extracts. Transgene band (arrow) is larger than endogenous Plk2 (arrowhead) due to additional myc epitope. (F) Pulldown of active Ras, Rap1, and Rap2 in brain lysates from WT and DN-Plk2 mice using GST-Raf1-RBD and GST-RalGDS-RBD. (G) Quantification of active Ras, Rap1 and Rap2 normalized to total expression (n=5, **p<0.01, ***p<0.001). (H) Immunoblotting of forebrain lysates from WT and DN-Plk2 mice against proteins indicated at right of blots. (I) Quantification of data from (H) normalized to β-actin or total ERK (n=5–10, *p<0.05, **p<0.01). (J) Proximal dendritic segments from hippocampal CA1 pyramidal neurons. Spines were quantified separately on apical oblique (AO) and basal (BS) dendrites. Scale, 5 μm. (K–M) Quantification of spine density (K), head width (L), and length (M) (n=6, **p<0.01; head width, K–S test, p<0.001). (N, O) Spontaneous alternation of WT and DN-Plk2 mice (n=6) in the T-maze, quantified by latency to select an arm (N) and percent alternation (O). (P, Q) Morris water maze test (n=6). Latency to find the platform (P) was recorded as index of learning, and probe test (Q) was performed 2 days after training (*p<0.05). Dashed line indicates chance level of quadrant exploration time. T, target; R, right, O, opposite, and L, left of target. (R, S) Fear conditioning. Mice were conditioned with two tone-shock pairing, then tested for contextual fear (R) at 24 h and cued fear (S) at 48 h (WT, n=10; TG, n=7; **p<0.01).