Negative regulation of Vps34 by Cdk mediated phosphorylation - PubMed (original) (raw)

Negative regulation of Vps34 by Cdk mediated phosphorylation

Tsuyoshi Furuya et al. Mol Cell. 2010.

Abstract

Vacuolar protein sorting 34 (Vps34) complexes, the class III PtdIns3 kinase, specifically phosphorylate the D3 position of PtdIns to produce PtdIns3P. Vps34 is involved in the control of multiple key intracellular membrane trafficking pathways including endocytic sorting and autophagy. In mammalian cells, Vps34 interacts with Beclin 1, an ortholog of Atg6 in yeast, to regulate the production of PtdIns3P and autophagy. We show that Vps34 is phosphorylated on Thr159 by Cdk1, which negatively regulates its interaction with Beclin 1 during mitosis. Cdk5/p25, a neuronal Cdk shown to play a role in Alzheimer's disease, can also phosphorylate Thr159 of Vps34. Phosphorylation of Vps34 on Thr159 inhibits its interaction with Beclin 1. We propose that phosphorylation of Thr159 in Vps34 is a key regulatory mechanism that controls the class III PtdIns3 kinase activity in cell-cycle progression, development, and human diseases including neurodegeneration and cancers.

Copyright 2010 Elsevier Inc. All rights reserved.

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Figures

Figure 1

Figure 1

The levels of autophagy and PtdIns3P are decreased during mitosis. (A) Asynchronously growing H4 cells stably expressing LC3-GFP were counterstained with Hoechst dye to visualize nuclei and fixed with 4% paraformaldehyde. The Z-series were acquired at 60X magnification on a wide field microscope and deconvolved. Maximum projection images are shown. The levels of autophagy were assessed in interphase and mitotic cells by quantifying the translocation of LC3-GFP from diffuse cytosolic to punctate autophagosomal location from the pictures and expressed as a ratio of LC3-GFP intensity in autophagosomal (spot signal) versus cytosolic (diffused signal) location per cell. The data represent an analysis of 13 mitotic and 28 interphase cells from 2 independent experiments. P=0.04(*). (B) Asynchronously growing H4 cells stably expressing FYVE-dsRed were counterstained with DAPI to visualize nuclei and fixed with 4% paraformaldehyde. The Z-series were acquired on a wide field microscope at 60X magnification and deconvolved. Maximum projection images are shown. The levels of PtdIns3P were assessed in interphase versus mitotic cells by quantifying the amount of FYVE-dsRed from the pictures and expressed as number of FYVE-dsRed spots per cell. The data represent an analysis of 14 mitotic and 20 interphase cells from 2 independent experiments. P=0.0007(***).

Figure 2

Figure 2

Vps34 is phosphorylated by Cdk1. (A) Equal amounts of purified flag tagged Vps34 WT or T159A protein complexes were incubated with active Cdk1/cyclin B1 complex in an in vitro phosphorylation assay with [γ-32P]-ATP in the absence or presence of alsterpaullon (0.1 μM), and phosphorylation of Vps34 protein was detected by autoradiography after proteins were resolved on SDS-PAGE. The ratios of 32P-signal vs. anti-flag signal were indicated below. (B) Equal amounts of purified flag tagged Vps34 WT complexes were incubated with active Cdk1/cyclin B1 complex in an in vitro phosphorylation assay with ATP in the absence or presence of roscovitine (1 μM). The samples were either mock treated or phosphatase treated as indicated. Phosphorylation of Vps34 protein was detected with anti-pThr159 Vps34 antibody by western blotting. (C) Flag-Vps34 was incubated with mitotic extract after two rounds of Cdk1 depletion using anti-Cdk1 or mock depleted asynchronous or mitotic 293T extracts using a control antibody. The amount of residual Cdk1 was measured by western blotting. Phosphorylation of Vps34 was measured by western blotting with anti-pThr159 Vps34 antibody.

Figure 3

Figure 3

Vps34 is phosphorylated in the mitotic phase. (A) Treatment of proliferating 293T, H4 and HeLa cells with nocodazole for indicated amount of times led to a gradual increase of Vps34 Thr159 phosphorylation as detected by western blotting using anti-pT159 antibody. Anti-tubulin was used as a loading control. (B) HeLa cells were arrested in mitosis using 200ng/ml nocodazole for 16 hours. Two different cdk1 inhibitors, alsterpaullone (1μM) and roscovitine (10μM), reduced nocodazole induced Vps34 Thr159 phosphorylation were added as indicated, Phosphorylation of Vps34 was detected by western blotting using anti-pT159 antibody. (C) H4 and HeLa cells were treated with nocodazole for 16 hours and the lysates were analyzed by western blotting with anti-pT159 antibody with or without λ phosphatase treatment as indicated. (D, E) HeLa cells were harvested after serum addition to induce synchronous cell cycle re-entering after 3 days of serum deprivation (D) or release from double thymidine block (E). The total lysates were analyzed at the indicated time points by western blotting with anti-cyclin B1 and anti-pT159 antibody. (F, G) Asynchronously proliferating HeLa cells were fixed by paraformaldehyde and immunostained with anti-Vps34 (F) or affinity purified anti-pThr159 Vps34 (G) antibodies and DAPI. Vps34, phosphorylated Vps34, DAPI and merged images were shown in each stage of the cell cycle. These images were magnified from Supplemental Figure 1A and 1B. Bar, 10μm.

Figure 4

Figure 4

Vps34 is phosphorylated by Cdk5/p25. (A) Vps34 was immunoprecipitated using anti-flag antibody from 293T cells transfected with flag-Vps34 vector and incubated in the absence or with different amounts of Cdk5/p25 complex and [γ-32P] ATP. The mixtures were resolved with 8% SDS/PAGE and subjected to autoradiography. Relative ratios of the γ-32P signals divided by the amount of protein are indicated. (B) A schematic representation of phosphorylation sites on Vps34. The upperside shows phosphorylation sites detected without incubation with Cdk5/p25. The underside shows two additional phosphorylation sites detected only after incubation with Cdk5/p25. (C) Lysates from H4 cells expressing Cdk5/p25 were either untreated or treated with lambda protein phosphatase (λPP) prior to western blotting with anti-pThr159 Vps34 and total Vps34 antibodies. (D) 293T cells were transfected with indicated expression constructs of Vps34 with or without that of Cdk5/p25. The immunoprecipitants with anti-flag antibody were analyzed by western blotting using anti-pThr159 Vps34 and anti-flag antibodies. (E) H4 cells were transfected with Cdk5/p25 vectors with or without 10uM roscovitine (Ros). After 20h, the whole cells lysates were analyzed by western blotting using anti-pThr159 Vps34 and total Vps34 antibodies. (F) Western blotting analysis of CK-p25 Tg mouse forebrain lysates after induced for 2 or 5 weeks (Tg-On) or not induced (control) (Tg-Off) using anti-pT159 Vps34, total Vps34, anti-p35 and anti-tubulin (as a loading control).

Figure 5

Figure 5

Cdk5/p25 disrupts Beclin 1/Vps34 complex (A) 293T cells were transfected with flag-Vps34 and GFP-Beclin 1 with or without Cdk5/p25 expression vectors. Flag-Vps34 was immunoprecipitated with anti-flag antibody from the lysates. The immunoprecipitates were blotted with anti-GFP antibody, and subsequently probed with anti-flag, p35 and cdk5 antibodies. (B) HA-Vps34, flag-Beclin 1 with or without Cdk5/p25 expression vectors were transfected into 293T cells. The protein complexes were immunoprecipitated using anti-flag antibody and analyzed by western blotting using anti-HA antibody. (C) H4 cells were transfected with or without p25 expression vector. Beclin 1 was immunoprecipitated with anti-Beclin 1 antibody from the lysates. The immunoprecipitates were analyzed by western blotting using anti-Vps34 antibody. (D) HeLa cells were synchronized in mitotic phase with nocodazole. Beclin 1 was immunoprecipitated with anti-Beclin 1 antibody from lysates. The immunoprecipitates were analyzed by western blotting using anti-Vps34 and pThr159 Vps34 antibodise. (E) 293T cells were transfected with flag tagged Vps34 wt, mutant T159A, T668A and GFP-Beclin 1 with or without Cdk5/p25 expression vectors. Flag-Vps34 was immunoprecipitated with anti-flag antibody from the lysates. The immunocomplexes were analyzed by western blotting using anti-GFP and flag antibodies. (F) 293T cells were transfected with flag tagged Beclin 1 with HA tagged Vps34 wt, mutant T159A and T668A with or without Cdk5/p25 expression vectors. Flag-Beclin 1 was immunoprecipitated with anti-flag antibody from the lysates. The immunocomplexes were analyzed using anti-HA and flag antibodies. Western blotting of total lysates using anti-HA, anti-flag, anti-Cdk5 and anti-p35 are loading controls.

Figure 6

Figure 6

Phosphorylation of Vps34 negatively regulates the class III PI3 kinase activity. (A) H4 cells stably expressing FYVE-dsRed were transfected with p25 expression vector. FYVE-dsRed H4 cells were stimulated for 2h with HBSS as starvation condition or with roscovitine in HBSS to inhibit Cdk5 activity. The cells were fixed with 3.7% formaldehyde and used for quantifying the number and intensity of FYVE-dsRed dots with Meta-Morph. Statistical analysis was performed by Student’s t-test. Data are Mean±Standard error. * P<0.05. (B) 293T cells were transfected with vector control (lane 1), with flag -Vps34 and GFP-Beclin 1 (lane 2 and 4), with flag-Vps34, GFP-Beclin 1 and cdk5/p25 (lane 3). The whole cell lysates were used for immunoprecipitation using anti-flag antibody followed by an assay for Vps34 lipid kinase activity. Wortmannin (10μM) was added prior to PtdIns3P kinase assay (lane 4) as a positive control. (C) 293T cells were transfected with vector control (lane 1), with flag tagged wild type Vps34 and GFP-Beclin 1 (lane 2), with flag tagged phospho-mutant T159A Vps34 and GFP-Beclin 1 (lane 3). Flag tagged Vps34 was immunoprecipitated with anti-flag antibody, and followed by an assay for Vps34 lipid kinase activity. Relative ratios of the γ-32P signal divided by the amount of protein are indicated for (B) and (C). (D) H4 cells stably expressing FYVE-dsRed were transfected with wild type or phospho-mutant T159A Vps34, with or without Beclin-1. Cells were fixed and FYVE dots were quantified as in (A). Data are Mean±Standard error. *P<0.01.

Figure 7

Figure 7

Phosphorylation of Vps34 results in the inhibition of autophagy. (A) H4 cells expressing LC3-GFP were transfected with p25 expression vector. Twenty-two hrs after the transfection, starvation was induced by culturing in HBSS only. The cells were fixed after 1 and 2 hours of starvation with 3.7% formaldehyde and the area of LC3-GFP dots were quantified using Meta-Morph. Data are Mean±Standard deviation. * P<0.05. (B) H4 cells expressing LC3-GFP were transfected with wild type or T159A Vps34 mutant. Twenty-two hrs after the transfection, starvation was induced by culturing in HBSS only. The cells were fixed after 1 and 2 hours of starvation with 3.7% formaldehyde and analyzed as in (A). * P<0.05. (C) 293T cells were transfected with different expression vectors of wt and T668A, T668D and T668E mutants in different combination and lipid kinase assays were conducted as in Figure 6. (D) 293T cells were transfected with indicated expression vectors, and lipid kinase assays were conducted as in Figure 6. Relative ratios of the γ-32P signal divided by the amount of protein as measured by the densitometry are indicated. (E) H4 cells expressing LC3-GFP were transfected with wt or mutant Vps34 expression vector with or without p25 expression vector. Twenty-two hrs after the transfection, starvation was induced by culturing in HBSS only for 2 hours. The cells were fixed with 4% paraformaldehyde and the intensity of LC3-GFP dots were quantified using Meta-Morph. Data are Mean±Standard error. *** P<0.01.

Comment in

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