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Osmotic stress regulates the stability of cyclin D1 in a p38SAPK2-dependent manner
O Casanovas1, F Miró, J M Estanyol
1Departament de Biologia Cellular i Anatomia Patològica, Facultat de Medicina, Institut d'Investigacions Biomèdiques August Pi Sunyer, University of Barcelona, 08036 Barcelona, Spain.
Abstract:
We report here that different cell stresses regulate the stability of cyclin D1 protein. Exposition of Granta 519 cells to osmotic shock, oxidative stress, and arsenite induced the post-transcriptional down-regulation of cyclin D1. In the case of osmotic shock, this effect was completely reversed by the addition of p38(SAPK2)-specific inhibitors (SB203580 or SB220025), indicating that this effect is dependent on p38(SAPK2) activity. Moreover, the use of proteasome inhibitors prevented this down-regulation. Thus, osmotic shock induces proteasomal degradation of cyclin D1 protein by a p38(SAPK2)-dependent pathway. The effect of p38(SAPK2) on cyclin D1 stability might be mediated by direct phosphorylation at specific sites. We found that p38(SAPK2) phosphorylates cyclin D1 in vitro at Thr(286) and that this phosphorylation triggers the ubiquitination of cyclin D1. These results link for the first time a stress-induced MAP kinase pathway to cyclin D1 protein stability, and they will help to understand the molecular mechanisms by which stress transduction pathways regulate the cell cycle machinery and take control over cell proliferation.
Insights
Cell stresses like osmotic shock reduce cyclin D1 protein levels by triggering its degradation via a p38(SAPK2)-dependent pathway. This involves phosphorylation and ubiquitination, linking stress responses to cell cycle control.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cyclin D1 protein is crucial for cell cycle progression.
- Cellular stresses can impact protein stability and cell cycle regulation.
Purpose of the Study:
- To investigate how different cell stresses affect cyclin D1 protein stability.
- To elucidate the molecular mechanisms linking stress responses to cell cycle control via cyclin D1.
Main Methods:
- Exposing Granta 519 cells to various stresses (osmotic shock, oxidative stress, arsenite).
- Utilizing p38(SAPK2)-specific inhibitors (SB203580, SB220025) and proteasome inhibitors.
- Performing in vitro phosphorylation assays and ubiquitination studies.
Main Results:
- Osmotic shock, oxidative stress, and arsenite induce post-transcriptional down-regulation of cyclin D1.
- Inhibition of p38(SAPK2) or proteasomes reversed stress-induced cyclin D1 down-regulation.
- p38(SAPK2) phosphorylates cyclin D1 at Thr(286) in vitro, promoting its ubiquitination and degradation.
Conclusions:
- Osmotic shock triggers proteasomal degradation of cyclin D1 via a p38(SAPK2)-dependent pathway.
- This study establishes a novel link between stress-induced MAP kinase pathways and cyclin D1 protein stability.
- Findings provide insights into how stress pathways regulate cell cycle machinery and proliferation.