Regulation of Mammalian STE20-like Kinase 2 (MST2) by Protein Phosphorylation/Dephosphorylation and Proteolysis
Mammalian STE20-like kinase 2 (MST2), a member of the STE20-like kinase family, has been shown in previous studies to undergo proteolytic activation by caspase-3 during cell apoptosis. A few studies have also implicated protein phosphorylation reactions in MST2 regulation. In this study, we examined...
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Published in | The Journal of biological chemistry Vol. 278; no. 14; pp. 11760 - 11767 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
United States
American Society for Biochemistry and Molecular Biology
04.04.2003
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Subjects | |
Online Access | Get full text |
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Summary: | Mammalian STE20-like kinase 2 (MST2), a member of the STE20-like kinase family, has been shown in previous studies to undergo
proteolytic activation by caspase-3 during cell apoptosis. A few studies have also implicated protein phosphorylation reactions
in MST2 regulation. In this study, we examined the mechanism of MST2 regulation with an emphasis on the relationship between
caspase-3 cleavage and protein phosphorylation. Both the full-length MST2 and the caspase-3-truncated form of MST2 overexpressed
in 293T cells exist in a phosphorylated state. On the other hand, the endogenous full-length MST2 from rat thymus or from
proliferating cells is mainly unphosphorylated whereas the caspase-3-truncated endogenous MST2 from apoptotic cells is highly
phosphorylated. Cell transfection studies using mutant MST2 constructs indicate that MST2 depends on the autophosphorylation
of a unique threonine residue, Thr 180 , for kinase activity. The autophosphorylation reaction shows strong dependence on MST2 concentration suggesting that it is
an intermolecular reaction. While both the full-length MST2 and the caspase-3-truncated form of MST2 undergo autophosphorylation,
the two forms of the phosphorylated MST2 display marked difference in susceptibility to protein phosphatases. The full-length
phospho-MST2 is rapidly dephosphorylated by protein phosphatase 1 or protein phosphatase 2A whereas the truncated MST2 is
remarkably resistant to the dephosphorylation. Based on the present results, a novel molecular mechanism for MST2 regulation
in apoptotic cells is postulated. In normal cells, because of the low concentration and the ready reversal of the autophosphorylation
by protein phosphatases, MST2 is present mainly in the unphosphorylated and inactive state. During cell apoptosis, MST2 is
cleaved by caspase-3 and undergoes irreversible autophosphorylation, thus resulting in the accumulation of active MST2. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.M211085200 |