Author/Authors :
Philippe Riou، نويسنده , , Svend Kj?r، نويسنده , , Ritu Garg، نويسنده , , Andrew Purkiss، نويسنده , , Roger George، نويسنده , , Robert J. Cain، نويسنده , , Ganka Bineva، نويسنده , , Nicolas Reymond، نويسنده , , Brad McColl، نويسنده , , Andrew J. Thompson، نويسنده , , Nicola O’Reilly، نويسنده , , Neil Q. McDonald، نويسنده , , Peter J. Parker، نويسنده , , Anne J. Ridley، نويسنده ,
Abstract :
Signaling through G proteins normally involves conformational switching between GTP- and GDP-bound states. Several Rho GTPases are also regulated by RhoGDI binding and sequestering in the cytosol. Rnd proteins are atypical constitutively GTP-bound Rho proteins, whose regulation remains elusive. Here, we report a high-affinity 14-3-3-binding site at the C terminus of Rnd3 consisting of both the Cys241-farnesyl moiety and a Rho-associated coiled coil containing protein kinase (ROCK)-dependent Ser240 phosphorylation site. 14-3-3 binding to Rnd3 also involves phosphorylation of Ser218 by ROCK and/or Ser210 by protein kinase C (PKC). The crystal structure of a phosphorylated, farnesylated Rnd3 peptide with 14-3-3 reveals a hydrophobic groove in 14-3-3 proteins accommodating the farnesyl moiety. Functionally, 14-3-3 inhibits Rnd3-induced cell rounding by translocating it from the plasma membrane to the cytosol. Rnd1, Rnd2, and geranylgeranylated Rap1A interact similarly with 14-3-3. In contrast to the canonical GTP/GDP switch that regulates most Ras superfamily members, our results reveal an unprecedented mechanism for G protein inhibition by 14-3-3 proteins.
