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The AMBRA1 E3 ligase adaptor regulates Cyclin D protein stability [U937 cells]

ABSTRACT: The initiation of cell division is a fundamental process that integrates a large number of intra- and extra-cellular inputs. In mammalian cells, D-type cyclins (Cyclin D) couple these inputs to the decision to initiate DNA replication. Increased levels of Cyclin D promote cell cycle progression by activating cyclin-dependent kinases 4 and 6 (CDK4/6). Accordingly, increased levels and activity of Cyclin D and their associated kinases are strongly linked to unchecked cell proliferation and tumor development. Despite this central role of Cyclin D in cell cycle progression, the mechanisms regulating their levels remain incompletely understood. Here we describe AMBRA1 as the main regulator of Cyclin D protein degradation. We first identify AMBRA1 as the top candidate in a genome-wide CRISPR/Cas9 loss-of-function screen investigating the genetic basis of resistance to chemical CDK4/6 inhibition. AMBRA1 loss results in high protein levels of Cyclin D in cells and in mice. AMBRA1 loss further promotes lung cancer development in a mouse model, and low levels of AMBRA1 correlate with worse survival in lung cancer patients. Mechanistically, AMBRA1 acts as a substrate receptor for the Cullin 4 E3 ligase complex to promote ubiquitylation and proteasomal degradation of the three Cyclin D family members. Thus, AMBRA1 regulates Cyclin D protein levels and contributes to the development of cancer as well as the response of cancer cells to CDK4/6 inhibitors.

ORGANISM(S): Homo sapiens

PROVIDER: GSE146588 | GEO | 2021/02/05

REPOSITORIES: GEO

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The AMBRA1 E3 ligase adaptor regulates Cyclin D protein stability [U2OS cells]

Project description:The initiation of cell division is a fundamental process that integrates a large number of intra- and extra-cellular inputs. In mammalian cells, D-type cyclins (Cyclin D) couple these inputs to the decision to initiate DNA replication. Increased levels of Cyclin D promote cell cycle progression by activating cyclin-dependent kinases 4 and 6 (CDK4/6). Accordingly, increased levels and activity of Cyclin D and their associated kinases are strongly linked to unchecked cell proliferation and tumor development. Despite this central role of Cyclin D in cell cycle progression, the mechanisms regulating their levels remain incompletely understood. Here we describe AMBRA1 as the main regulator of Cyclin D protein degradation. We first identify AMBRA1 as the top candidate in a genome-wide CRISPR/Cas9 loss-of-function screen investigating the genetic basis of resistance to chemical CDK4/6 inhibition. AMBRA1 loss results in high protein levels of Cyclin D in cells and in mice. AMBRA1 loss further promotes lung cancer development in a mouse model, and low levels of AMBRA1 correlate with worse survival in lung cancer patients. Mechanistically, AMBRA1 acts as a substrate receptor for the Cullin 4 E3 ligase complex to promote ubiquitylation and proteasomal degradation of the three Cyclin D family members. Thus, AMBRA1 regulates Cyclin D protein levels and contributes to the development of cancer as well as the response of cancer cells to CDK4/6 inhibitors.

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The AMBRA1 E3 ligase adaptor regulates the stability of cyclin D

Project description:The initiation of cell division integrates a large number of intra- and extracellular inputs. D-type cyclins (hereafter, cyclin D) couple these inputs to the initiation of DNA replication1. Increased levels of cyclin D promote cell division by activating cyclin-dependent kinases 4 and 6 (hereafter, CDK4/6), which in turn phosphorylate and inactivate the retinoblastoma tumour suppressor. Accordingly, increased levels and activity of cyclin D-CDK4/6 complexes are strongly linked to unchecked cell proliferation and cancer2,3. However, the mechanisms that regulate levels of cyclin D are incompletely understood4,5. Here we show that autophagy and beclin 1 regulator 1 (AMBRA1) is the main regulator of the degradation of cyclin D. We identified AMBRA1 in a genome-wide screen to investigate the genetic basis of the response to CDK4/6 inhibition. Loss of AMBRA1 results in high levels of cyclin D in cells and in mice, which promotes proliferation and decreases sensitivity to CDK4/6 inhibition. Mechanistically, AMBRA1 mediates ubiquitylation and proteasomal degradation of cyclin D as a substrate receptor for the cullin 4 E3 ligase complex. Loss of AMBRA1 enhances the growth of lung adenocarcinoma in a mouse model, and low levels of AMBRA1 correlate with worse survival in patients with lung adenocarcinoma. Thus, AMBRA1 regulates cellular levels of cyclin D, and contributes to cancer development and the response of cancer cells to CDK4/6 inhibitors.

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The AMBRA1 E3 ligase adaptor regulates Cyclin D protein stability

Project description:Here we describe AMBRA1 as the main regulator of Cyclin D protein degradation. We first identify AMBRA1 as the top candidate in a genome-wide CRISPR/Cas9 loss-of-function screen investigating the genetic basis of resistance to chemical CDK4/6 inhibition. AMBRA1 loss results in high protein levels of CyclinÂ D in cells and in mice. AMBRA1 loss further promotes lung cancer development in a mouse model, and low levels of AMBRA1 correlate with worse survival in lung cancer patients. Mechanistically, AMBRA1 acts as a substrate receptor for the Cullin 4 E3 ligase complex to promote ubiquitylation and proteasomal degradation of the three CyclinÂ D family members. Thus, AMBRA1 regulates Cyclin D protein levels and contributes to the development of cancer as well as the response of cancer cells to CDK4/6 inhibitors.

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Rb and the APC/C coactivator FZR1 determine CDK4/6-Cyclin D requirement in C. elegans and human cancer cells

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Structure of the DDB1-AMBRA1 E3 ligase receptor complex linked to cell cycle regulation

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