Regulation of mitogen-activated protein kinase activation by protein kinases A and C in a cell-free system
Autor: | B, VanRenterghem, M D, Browning, J L, Maller |
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Rok vydání: | 1994 |
Předmět: | |
Zdroj: | The Journal of biological chemistry. 269(40) |
ISSN: | 0021-9258 |
Popis: | Previously pp60v-src, cyclin A, p39mos, and maturation-promoting factor (composed of Cdc2 and cyclin B) have been shown to activate mitogen-activated protein kinase (MAPK) and MAPK kinase (MEK) in cell-free extracts of Xenopus oocytes. The pp60v-src pathway is dependent on a functional Ras signal whereas the cyclin/maturation-promoting factor pathway is not. Here we show that protein kinase C (PKC) is also able to stimulate MAPK in a Ras-dependent manner, but PKC is not necessary for signaling by pp60v-src. In addition, preincubation of extracts with cAMP-dependent protein kinase (PKA) blocks stimulation of MAPK by cyclin, p21V12ras, PKC, or pp60v-src, by at least 50%, but stimulation by c-Mos is unaffected. Furthermore, inhibition of endogenous PKA by the heat-stable PKA inhibitor is sufficient to stimulate MAPK activity in these extracts in the absence of protein synthesis and without dependence on a functional Ras protein. These results suggest that independent pp60v-src and PKC pathways converge at Ras and that PKA acts to block MAPK activation by both Ras-dependent and -independent signals. |
Databáze: | OpenAIRE |
Externí odkaz: |
Abstrakt: | Previously pp60v-src, cyclin A, p39mos, and maturation-promoting factor (composed of Cdc2 and cyclin B) have been shown to activate mitogen-activated protein kinase (MAPK) and MAPK kinase (MEK) in cell-free extracts of Xenopus oocytes. The pp60v-src pathway is dependent on a functional Ras signal whereas the cyclin/maturation-promoting factor pathway is not. Here we show that protein kinase C (PKC) is also able to stimulate MAPK in a Ras-dependent manner, but PKC is not necessary for signaling by pp60v-src. In addition, preincubation of extracts with cAMP-dependent protein kinase (PKA) blocks stimulation of MAPK by cyclin, p21V12ras, PKC, or pp60v-src, by at least 50%, but stimulation by c-Mos is unaffected. Furthermore, inhibition of endogenous PKA by the heat-stable PKA inhibitor is sufficient to stimulate MAPK activity in these extracts in the absence of protein synthesis and without dependence on a functional Ras protein. These results suggest that independent pp60v-src and PKC pathways converge at Ras and that PKA acts to block MAPK activation by both Ras-dependent and -independent signals. |
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ISSN: | 00219258 |