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Myosin phosphatase interacts with and dephosphorylates the retinoblastoma protein in THP-1 leukemic cells: Its inhibition is involved in the attenuation of daunorubicin-induced cell death by calyculin-A
- Source :
- Cellular Signalling. 20:2059-2070
- Publication Year :
- 2008
- Publisher :
- Elsevier BV, 2008.
-
Abstract
- Reversible phosphorylation of the retinoblastoma protein (pRb) is an important regulatory mechanism in cell cycle progression. The role of protein phosphatases is less understood in this process, especially concerning the regulatory/targeting subunits involved. It is shown that pretreatment of THP-1 leukemic cells with calyculin-A (CL-A), a cell-permeable phosphatase inhibitor, attenuated daunorubicin (DNR)-induced cell death and resulted in increased pRb phosphorylation and protection against proteolytic degradation. Protein phosphatase-1 catalytic subunits (PP1c) dephosphorylated the phosphorylated C-terminal fragment of pRb (pRb-C) slightly, whereas when PP1c was complexed to myosin phosphatase target subunit-1 (MYPT1) in myosin phosphatase (MP) holoenzyme dephosphorylation was stimulated. The pRb-C phosphatase activity of MP was partially inhibited by anti-MYPT11–296 implicating MYPT1 in targeting PP1c to pRb. MYPT1 became phosphorylated on both inhibitory sites (Thr695 and Thr850) upon CL-A treatment of THP-1 cells resulting in the inhibition of MP activity. MYPT1 and pRb coprecipitated from cell lysates by immunoprecipitation with either anti-MYPT1 or anti-pRb antibodies implying that pRb–MYPT1 interaction occurred at cellular levels. Surface plasmon resonance-based experiments confirmed binding of pRb-C to both PP1c and MYPT1. In control and DNR-treated cells, MYPT1 and pRb were predominantly localized in the nucleus exhibiting partial colocalization as revealed by immunofluorescence using confocal microscopy. Upon CL-A treatment, nucleo-cytoplasmic shuttling of both MYPT1 and pRb, but not PP1c, was observed. The above data imply that MP, with the targeting role of MYPT1, may regulate the phosphorylation level of pRb, thereby it may be involved in the control of cell cycle progression and in the mediation of chemoresistance of leukemic cells.
- Subjects :
- Programmed cell death
Cell Survival
Immunoprecipitation
Phosphatase
Retinoblastoma Protein
Cell Line
Dephosphorylation
Myosin-Light-Chain Phosphatase
Protein Phosphatase 1
Myosin
Humans
Elméleti orvostudományok
Phosphorylation
Oxazoles
neoplasms
Leukemia
Cell Death
biology
Caspase 3
Daunorubicin
Retinoblastoma protein
Protein phosphatase 1
Orvostudományok
Cell Biology
Surface Plasmon Resonance
Molecular biology
Protein Subunits
Protein Transport
biology.protein
Marine Toxins
Protein Processing, Post-Translational
Protein Binding
Subcellular Fractions
Subjects
Details
- ISSN :
- 08986568
- Volume :
- 20
- Database :
- OpenAIRE
- Journal :
- Cellular Signalling
- Accession number :
- edsair.doi.dedup.....fcf995627bc9656dfa42d5f13d50e85f
- Full Text :
- https://doi.org/10.1016/j.cellsig.2008.07.018