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1.
Figure 6

Figure 6. Regulation of breast cancer cell random migration by palladin phosphorylation. From: THE ACTIN BUNDLING PROTEIN PALLADIN IS AN AKT1-SPECIFIC SUBSTRATE THAT REGULATES BREAST CANCER CELL MIGRATION.

A, MDA-MB-231 cells were infected with palladin shRNA lentiviral vector or empty vector for 48 h. Cells were then transfected with shRNA-resistant (*) HA-palladin WT* or HA-palladin S507A mutant* or control vector. Twenty-four hours after transfection, cell migration on NIH 3T3 cell-secreted ECM was monitored by time-lapse microscopy for 1 h. Representative phase-contrast images from the movies are shown. B, Quantification of the velocity of random migration in A. Data are represented as mean ± SEM. See also movies S1–4.

Y. Rebecca Chin, et al. Mol Cell. ;38(3):333-344.
2.
Figure 2

Figure 2. Phosphorylation of palladin in breast cancer cells. From: THE ACTIN BUNDLING PROTEIN PALLADIN IS AN AKT1-SPECIFIC SUBSTRATE THAT REGULATES BREAST CANCER CELL MIGRATION.

A, Analysis of palladin expression in various cell lines by immunoblotting. B, MDA-MB-231 and SKBR3 cells were transfected with HA-palladin for 9 h then serum starved for 12–16 h. Cells were then stimulated with IGF-1 (100 ng ml−1) for 20 min or EGF (20 ng ml−1) for 10 min in the presence of SN30978 (5 μM) or DMSO. Cell extracts were immunoprecipitated with anti-HA antibody followed by immunoblotting. C, Serum-starved MCF10A and BT-549 cells were stimulated with EGF (20 ng ml−1) for 10 min in the presence of wortmannin (100 nM) or SN30978 (5 μM), or DMSO. Endogenous palladin was immunoprecipitated with anti-palladin antibody and immunoblotted with α-pAkt-MOTIF antibody. D, MCF10A cells infected with empty vector or retroviral vectors expressing the indicated HA-p110α variants were serum-starved overnight. Phosphorylation of endogenous palladin was detected as described in C. All results are representative of three independent experiments.

Y. Rebecca Chin, et al. Mol Cell. ;38(3):333-344.
3.
Figure 5

Figure 5. Phosphorylation of palladin at Ser507 by Akt1 inhibits cell migration. From: THE ACTIN BUNDLING PROTEIN PALLADIN IS AN AKT1-SPECIFIC SUBSTRATE THAT REGULATES BREAST CANCER CELL MIGRATION.

A, MDA-MB-231 cells infected with palladin shRNA or empty lentiviral vectors were transfected with HA-Myr-Akt1 or control vector. 24 h after transfection cells were subjected to Transwell migration assays and lysates were immunoblotted with the indicated antibodies. B, MDA-MB-231 cells were infected with palladin shRNA lentiviral vector or empty vector. Forty-eight hours after infection cells were serum-starved overnight then stimulated with IGF-1 (100 ng ml−1) for 18 h, followed by Transwell migration assays. Total cell lysates were subjected to immunoblot analysis. C, MDA-MB-231 cells were infected with palladin shRNA and/or Akt1 shRNA lentiviral vectors, or empty vector. Forty-eight hours after infection, cells were subjected to Transwell migration assays and lysates were immunoblotted. D, MDA-MB-231 cells were infected with palladin shRNA lentiviral vector or empty vector for 48 h. Cells were then transfected with shRNA-resistant (*) HA-palladin WT* or HA-palladin S507A mutant* or control vector. 24 h after transfection cells were subjected to Transwell migration assays. Cell lysates were immunoblotted with anti-HA and anti-actin. All Transwell migration data are represented as mean ± SEM. All results are representative of three independent experiments. See also Figure S4.

Y. Rebecca Chin, et al. Mol Cell. ;38(3):333-344.
4.
Figure 7

Figure 7. Phosphorylation of palladin regulates actin organization and bundling. From: THE ACTIN BUNDLING PROTEIN PALLADIN IS AN AKT1-SPECIFIC SUBSTRATE THAT REGULATES BREAST CANCER CELL MIGRATION.

A, shRNA-resistant (*) HA-palladin WT* or HA-palladin S507A mutant* was overexpressed in MDA-MB-231 cells infected with palladin shRNA lentiviral vector or empty vector. 24 h after transfection cells were fixed and stained with anti-palladin and Alexa Fluor 488-conjugated phalloidin. B, MDA-MB-231 cells were infected and transfected as described in A. Cell lysates were incubated with F-actin, and F-actin binding (left panel) and bundling (right panel) was determined by differential centrifugation at 150,000 × g for 1.5 h and 10,000 × g for 1 h, respectively. Pellet (P) and supernatant (S) fractions were immuno-blotted with anti-HA to visualize palladin and stained with Ponceau S to reveal total F-actin protein. All results are representative of three independent experiments. See also Figure S5.

Y. Rebecca Chin, et al. Mol Cell. ;38(3):333-344.
5.
Figure 4

Figure 4. Palladin inhibits breast cancer cell invasive migration. From: THE ACTIN BUNDLING PROTEIN PALLADIN IS AN AKT1-SPECIFIC SUBSTRATE THAT REGULATES BREAST CANCER CELL MIGRATION.

A, MDA-MB-231 cells were stimulated with IGF-1 (100 ng ml−1) for 20 min in the presence of DMSO or LY294002 (10 μM). Immunofluorescence was performed using anti-palladin antibody and Alexa Fluor 488-conjugated phalloidin. Cell nuclei were labeled with DAPI. B, MDA-MB-231, MCF7, SUM-159-PT and MCF10A cells were infected with palladin shRNA lentiviral vector or empty vector for 48 h followed by Transwell migration assays. Relative migration (y axis) = ratio of the number of migrated cells in test versus control. Error bars represent mean ± standard error of the mean (SEM). Total cell lysates were subjected to immunoblot analysis. C, MCF10A cells infected with palladin shRNA lentiviral vector or empty pLKO vector were grown in 3D cultures for 8 days. Lysates were immunoblotted with the indicated antibodies. All results are representative of three independent experiments. See also Figure S3.

Y. Rebecca Chin, et al. Mol Cell. ;38(3):333-344.
6.
Figure 1

Figure 1. Akt phosphorylates palladin at Ser507. From: THE ACTIN BUNDLING PROTEIN PALLADIN IS AN AKT1-SPECIFIC SUBSTRATE THAT REGULATES BREAST CANCER CELL MIGRATION.

A, schematic of palladin showing the position of the putative Akt consensus phosphorylation site at Ser507. Amino acid sequences of Akt motifs in other known Akt substrates are shown for comparison. The Ser507 Akt motif in palladin is evolutionarily conserved. Numbers on the left of sequences indicate the position of Ser in the Akt motif. PP, poly-proline; Ig, immunoglobulin-like domain. B, HeLa cells were transfected with HA-palladin or control vector for 9 h then serum starved for 12–16 h. Cells were then stimulated with IGF-1 (100 ng ml−1) for 20 min in the presence of wortmannin (100 nM) or Akt inhibitor SN30978 (5 μM), or DMSO. Cell extracts were immunoprecipitated with anti-HA antibody and immunoblotted with the indicated antibodies. C, HeLa cells were transfected with wild-type HA-palladin (HA-palladin WT) or HA-palladin S507A mutant or control vector for 9 h, followed by serum starving for 12–16 h. Cells were then stimulated with IGF-1 (100 ng ml−1) for 20 min. Palladin was precipitated from whole cell lysates followed by immunoblotting. D, HeLa cells were transfected with HA-palladin WT or HA-palladin S507A or control vector in serum-free media for 24 h. Anti-HA immunoprecipitates were used in in vitro assays with recombinant active Akt1 (Recom. Akt1). The kinase reaction was terminated and samples were immunoblotted. All results are representative of three independent experiments. See also Figure S1.

Y. Rebecca Chin, et al. Mol Cell. ;38(3):333-344.
7.
Figure 3

Figure 3. Palladin is an Akt1-specific substrate. From: THE ACTIN BUNDLING PROTEIN PALLADIN IS AN AKT1-SPECIFIC SUBSTRATE THAT REGULATES BREAST CANCER CELL MIGRATION.

A, HeLa, SKBR3 and MDA-MB-231 cells were transfected with HA-Myr-Akt1, HA-Myr-Akt2, or empty vector, along with GFP-palladin. 24 h after transfection cells were lysed and immunoprecipitated with anti-GFP. Whole cell lysates and immunoprecipitates were subjected to immunoblotting. B, SKBR3 cells were transfected with HA-palladin WT in serum-free medium for 24 h. Anti-HA immunoprecipitates were used as substrates in in vitro kinase assays with recombinant active Akt1 or Akt2. The kinase reaction was terminated and samples were immunoblotted. C, HeLa and SKBR3 cells were co-transfected with HA-palladin and Akt1, Akt2 or control luciferase siRNA. 36 h after transfection, HeLa and SKBR3 cells were serum starved for 12 h then treated with IGF-1 (100 ng ml−1) for 20 min and EGF (20 ng ml−1) for 10 min, respectively. BT-549 cells were infected with Akt1 or Akt2 shRNA lentiviral vector or empty vector for 72 h, followed by serum starvation and then stimulation with EGF (20 ng ml−1) for 10 min. Lysates were subjected to immunoprecipitation and immunoblot analysis. D, HeLa cells were infected with retroviral vectors expressing Akt chimeras, followed by transfection with GFP-palladin for 24 h. Cell extracts were immunoprecipitated with anti-GFP antibody and immunoblotted with the indicated antibodies. Akt has 4 domains: PH, linker, catalytic and C-terminal regulatory domain. Akt chimera 1122 contains PH and linker regions of Akt1 plus catalytic and regulatory domains of Akt2. Akt chimera 2211 contains PH and linker regions of Akt2 plus catalytic and regulatory domains of Akt1. Akt chimera 2111 contains PH domain of Akt2 plus linker, catalytic and regulatory domains of Akt1. All results are representative of three independent experiments. See also Figure S2.

Y. Rebecca Chin, et al. Mol Cell. ;38(3):333-344.

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