AMPK phosphosite profiling by label-free mass spectrometry reveals a multitude of mTORC1-regulated substrates
Ontology highlight
ABSTRACT: The metabolic kinase AMPK regulates transcription in response to nutrient status. AMPK is highly phosphorylated at position Ser184 in the regulatory beta2-subunit, however it's function is unknown. Our preliminary data indicate AMPK dephosphorylated at beta2-Ser184 has elevated nuclear activity and down-regulates apoptotic pathways in response to environmental insult. Here we compare transcriptomes of HEK293T cells expressing either endogenous level beta2 WT or the non-phosphorylatable mutant beta2-Ser182Ala, to gain insight into functional effects of elevated nuclear AMPK activity
Project description:Cells respond to mitochondrial energetic stress with rapid activation of the AMP-activated protein kinase (AMPK), which acutely inhibits anabolism and stimulates catabolism. AMPK also induces sustained transcriptional reprogramming of metabolism. The TFEB transcription factor is a major effector of AMPK signals, inducing lysosome genes following energetic stress. Yet the molecular mechanism underlying how AMPK activates TFEB remains unresolved. We demonstrate here that AMPK directly phosphorylates five conserved serine residues in FNIP1, which suppresses the function of the FLCN/FNIP1 RagC GAP complex, in turn controlling TFEB lysosomal localization. We demonstrate that FNIP1 phosphorylation is required for AMPK to induce nuclear translocation of TFEB, which is fully separable from AMPK control of canonical mTORC1 signaling. Using a non-phosphorylatable allele of FNIP1, we show that in parallel to lysosomal biogenesis, AMPK induces mitochondrial biogenesis via TFEB-dependent induction of PGC1a mRNA. This signaling from mitochondrial stress is also independent of amino-acid control of the Rags and TFEB, which still proceed normally in cells bearing the AMPK-non phosphorylatable allele of FNIP1. Taken together, mitochondrial energetic stress triggers AMPK/FNIP1-dependent TFEB nuclear translocation, inducing transcriptional waves of lysosomal and mitochondrial biogenesis.
Project description:The nutrient-sensitive protein kinases AMPK and mTORC1 form a fundamental negative feedback loop that governs cell growth and proliferation. mTORC1 phosphorylates α2-S345 in the AMPK αβγ heterotrimer to suppress its activity and promote cell proliferation under nutrient stress conditions. Whether AMPK contains other functional mTORC1 substrates is unknown. Using mass spectrometry, we generated precise stoichiometry profiles of phosphorylation sites across all twelve AMPK complexes expressed in proliferating human cells and identified seven sites displaying sensitivity to pharmacological mTORC1 inhibition. These included the abundantly phosphorylated residues β1-S182 and β2-S184, which were confirmed as mTORC1 substrates on purified AMPK, and four residues in the unique γ2 N-terminal extension. β-S182/184 phosphorylation was elevated in α1-containing complexes relative to α2, an effect attributed to the α-subunit serine/threonine-rich loop. Mutation of β1-S182 to non-phosphorylatable Ala had no effect on basal and ligand-stimulated AMPK activity; however, β2-S184A mutation increased nuclear AMPK activity, enhanced cell proliferation under nutrient stress and altered expression of genes implicated in glucose metabolism and Akt signalling. Our results indicate that mTORC1 directly or indirectly phosphorylates multiple AMPK residues that may contribute to metabolic rewiring in cancerous cells.
Project description:Upon replication stress, the Mec1ATR kinase triggers the downregulation of transcription, reducing the level of RNA polymerase on chromatin to facilitate replication fork progression. We identify a hydroxyurea-induced phosphorylation site at Mec1-S1991 that contributes to the eviction of RNAPII and RNAPIII during replication stress. The non-phosphorylatable mec1-S1991A mutant reduces replication fork progression genome-wide and compromises survival on hydroxyurea. This defect can be suppressed by destabilizing chromatin-bound RNAPII with a Rpb3-TAP fusion, suggesting that lethality arises from replication-transcription conflicts. Coincident with a failure to repress gene expression, highly transcribed genes like GAL1 persist at nuclear pores in mec1-S1991A cells. Consistently, we find pore proteins and several components controlling RNAPII and RNAPIII transcription are phosphorylated in a Mec1-dependent manner, suggesting that Mec1-S1991 phosphorylation limits conflicts between replication and either RNA polymerase complex. We further show that Mec1 contributes to reduced RNAPII occupancy on chromatin during an unperturbed S phase.
Project description:Upon replication stress, the Mec1ATR kinase triggers the downregulation of transcription, reducing the level of RNA polymerase on chromatin to facilitate replication fork progression. We identify a hydroxyurea-induced phosphorylation site at Mec1-S1991 that contributes to the eviction of RNAPII and RNAPIII during replication stress. The non-phosphorylatable mec1-S1991A mutant reduces replication fork progression genome-wide and compromises survival on hydroxyurea. This defect can be suppressed by destabilizing chromatin-bound RNAPII with a Rpb3-TAP fusion, suggesting that lethality arises from replication-transcription conflicts. Coincident with a failure to repress gene expression, highly transcribed genes like GAL1 persist at nuclear pores in mec1-S1991A cells. Consistently, we find pore proteins and several components controlling RNAPII and RNAPIII transcription are phosphorylated in a Mec1-dependent manner, suggesting that Mec1-S1991 phosphorylation limits conflicts between replication and either RNA polymerase complex. We further show that Mec1 contributes to reduced RNAPII occupancy on chromatin during an unperturbed S phase.
Project description:Upon replication stress, the Mec1ATR kinase triggers the downregulation of transcription, reducing the level of RNA polymerase on chromatin to facilitate replication fork progression. We identify a hydroxyurea-induced phosphorylation site at Mec1-S1991 that contributes to the eviction of RNAPII and RNAPIII during replication stress. The non-phosphorylatable mec1-S1991A mutant reduces replication fork progression genome-wide and compromises survival on hydroxyurea. This defect can be suppressed by destabilizing chromatin-bound RNAPII with a Rpb3-TAP fusion, suggesting that lethality arises from replication-transcription conflicts. Coincident with a failure to repress gene expression, highly transcribed genes like GAL1 persist at nuclear pores in mec1-S1991A cells. Consistently, we find pore proteins and several components controlling RNAPII and RNAPIII transcription are phosphorylated in a Mec1-dependent manner, suggesting that Mec1-S1991 phosphorylation limits conflicts between replication and either RNA polymerase complex. We further show that Mec1 contributes to reduced RNAPII occupancy on chromatin during an unperturbed S phase.
Project description:Deletion of AMPK significantly extended the onset of leukemogenesis and depleted leukemia initiating cells (LICs). To identify how AMPK regulates LICs, we performed gene expression profiling of LICs isolated from AMPK wild type leukemic mice or AMPK-deficient leukemic mice. 4 groups were analyzed; 1) Whole leukemia (GFP+) from AMPK WT ( AMPKfl/fl) mice, 2) Whole leukemia (GFP+) from AMPK-deficient ( AMPK?/?l) mice, 3) LICs=L-GMP (GFP+,lin-,c-kit+, CD16/32+,CD34+) cells from AMPK WT ( AMPKfl/fl) mice, 4) LICs=L-GMP (GFP+,lin-,c-kit+, CD16/32+,CD34+) cells from AMPK-deficient ( AMPK?/?l) mice.
Project description:Tomida2003 - NFAT functions Calcium
Oscillation
This model is described in the article:
NFAT functions as a working
memory of Ca2+ signals in decoding Ca2+ oscillation.
Tomida T, Hirose K, Takizawa A,
Shibasaki F, Iino M.
EMBO J. 2003 Aug; 22(15):
3825-3832
Abstract:
Transcription by the nuclear factor of activated T cells
(NFAT) is regulated by the frequency of Ca(2+) oscillation.
However, why and how Ca(2+) oscillation regulates NFAT activity
remain elusive. NFAT is dephosphorylated by Ca(2+)-dependent
phosphatase calcineurin and translocates from the cytoplasm to
the nucleus to initiate transcription. We analyzed the kinetics
of dephosphorylation and translocation of NFAT. We show that
Ca(2+)-dependent dephosphorylation proceeds rapidly, while the
rephosphorylation and nuclear transport of NFAT proceed slowly.
Therefore, after brief Ca(2+) stimulation, dephosphorylated
NFAT has a lifetime of several minutes in the cytoplasm. Thus,
Ca(2+) oscillation induces a build-up of dephosphorylated NFAT
in the cytoplasm, allowing effective nuclear translocation,
provided that the oscillation interval is shorter than the
lifetime of dephosphorylated NFAT. We also show that Ca(2+)
oscillation is more cost-effective in inducing the
translocation of NFAT than continuous Ca(2+) signaling. Thus,
the lifetime of dephosphorylated NFAT functions as a working
memory of Ca(2+) signals and enables the control of NFAT
nuclear translocation by the frequency of Ca(2+) oscillation at
a reduced cost of Ca(2+) signaling.
This model is hosted on
BioModels Database
and identified by:
BIOMD0000000678.
To cite BioModels Database, please use:
Chelliah V et al. BioModels: ten-year
anniversary. Nucl. Acids Res. 2015, 43(Database
issue):D542-8.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:Cyclin-dependent kinase 12 (CDK12) interacts with Cyclin K to form a a functional nuclear kinase complex, which has been reported to phosphorylate the carboxyl-terminal domain (CTD) of RNA polymerase II (Pol II) for transcriptional regulation and co-transcriptional RNA processing. However, the precise mechanisms and targets of CDK12 action remain largely unknown. Here, we combined a chemical genetic screen and phosphoproteomic strategies and identified a landscape of nuclear CDK12 substrates, which included proteins that regulate transcription, chromatin organization, and RNA splicing. Next, we confirmed that the LEO1 subunit of the transcription elongation factor PAF1 complex (PAF1C) is a bona fide substrate of CDK12. Acute depletion of LEO1 reduces Pol II occupancy on the chromatin, while mutations of LEO1 phosphorylation sites to non-phosphorylatable alanine residues attenuated the association of PAF1C with elongating Pol II and chromatin, resulting in impaired processive transcription elongation. Furthermore, LEO1 C-terminus could interact with and be dephosphorylated by the Integrator-PP2A complex (INTAC), while acute depletion of INTAC in cells promotes the association between PAF1C and elongating Pol II on the chromatin. Together, this study provides a novel transcriptional regulatory mechanism that the CDK12-INTAC axis fine-tunes LEO1 phosphorylation for processive transcription elongation.
Project description:Deletion of AMPK significantly extended the onset of leukemogenesis and depleted leukemia initiating cells (LICs). To identify how AMPK regulates LICs, we performed gene expression profiling of LICs isolated from AMPK wild type leukemic mice or AMPK-deficient leukemic mice.