IndraLab
Statements
"Here, we show that a functional TOS motif is required for 4E-BP1 to bind to raptor (a recently identified mTOR-interacting protein), for 4E-BP1 to be efficiently phosphorylated in vitro by themTOR/raptor complex, and for 4E-BP1 to be phosphorylated in vivo at all identified mTOR-regulated sites. mTOR/raptor regulated phosphorylation is necessary for 4E-BPs efficient release from the translational initiation factor eIF4E. We find that the TOS motif is absolutely required for efficient phosphorylation of 4E-BP1 at all the identified mTOR-regulated sites, namely, Thr37/46, Ser65, and Thr70 in vivo."
sparser
"Over expression of eIF4E can lead to increased cell proliferation, transformation and tumorigenesis. xref 4E-BP1, known as PHAS-1, normally binds eIF4E, inhibiting cap-dependent translation and is phosphorylated in vivo on multiple residues; phosphorylation by mTOR on Thr37 and Thr46 of human 4E-BP1 may be very important for subsequent phosphorylation. xref EIF4E protein levels were unchanged with the progression of cell series ( xref )."
reach
"Gels were transferred to nitrocellulose membranes and incubated with antibodies, diluted 1:1000 unless otherwise stated, directed to phosphorylated Ser2448 of mTOR, LAMP1, 4E-BP1, phosphorylated Thr 37 and Thr 46 of 4E-BP1, GAPDH, p70S6K, LAMP2 diluted 1:100 and beta-actin diluted 1:2000."
"These results indicate that arg, leu, and gln act coordinately to stimulate proliferation of ptr cells through activation of the mtor-rps6k-rps6-eif4ebp1 signal transduction pathway. Specifically as part of mtorc1, mtor directly phosphorylates the ribosomal protein s6 kinases (s6k1 and s6k2) and the eukaryotic initiation factor 4e (eif4e)-binding proteins (4e-bp1 and 4e-bp2), both of which control specific steps in the initiation of cap-dependent translation"
"Here, we show that a functional TOS motif is required for 4E-BP1 to bind to raptor (a recently identified mTOR-interacting protein), for 4E-BP1 to be efficiently phosphorylated in vitro by themTOR/raptor complex, and for 4E-BP1 to be phosphorylated in vivo at all identified mTOR-regulated sites. mTOR/raptor regulated phosphorylation is necessary for 4E-BPs efficient release from the translational initiation factor eIF4E. We find that the TOS motif is absolutely required for efficient phosphorylation of 4E-BP1 at all the identified mTOR-regulated sites, namely, Thr37/46, Ser65, and Thr70 in vivo."
sparser
"We propose that meiotic phosphorylation of 4E-BP1 on Ser65 and Thr70 by mTOR acts to stimulate cap-dependent translation as the oocyte proceeds though meiosis (particularly after NEBD) and that specific localization of the key cap-dependent translation regulatory factors, xref is essential for the translation of specific mRNAs at the spindle area to ensure errorless meiotic progression."
"PHAS-I in adipocytes and HEK293 cells is phosphorylated in the following five sites, all of which conform to a (S/T)P motif (9, 10): Thr-36, Thr-45, Ser-64, Thr-69, and Ser-82. Thr-45 and Ser-64 flank the eIF4E-binding motif (7, 8), and phosphorylation of either site blocks eIF4E binding in vitro (10, 11). Insulin stimulates the phosphorylation of Thr-36, Thr-45, Ser-64, and Thr-69 in both fat cells and HEK293 cells, and incubating cells with rapamycin decreases the phosphorylation of these sites.Immunoprecipitated epitope-tagged mammalian target of rapamycin (mTOR) phosphorylated Thr-36/45. mTOR also phosphorylated Thr-69 and Ser-64 but only when purified immune complexes were incubated with the activating antibody, mTAb1."
"Mtorc1 promotes protein synthesis by phosphorylating the eukaryotic initiation factor 4e (eif4e)- binding protein 1 (4e-bp1) and the p70 ribosomal s6 kinase 1 (s6k1). Raft1 phosphorylation of 4e-bp1 on thr-36 and thr-45 blocks its association with the cap-binding protein, eif-4e,in vitro. in response to insulin and nutrients, mtorc1, consisting of mtor, raptor (regulatory-associated protein of mtor), and mlst8, is activated and phosphorylates eukaryotic initiation factor 4e-binding protein (4ebp) and p70 s6 kinase to promote protein synthesis and cell size."
"Specifically as part of mTORC1, mTOR directly phosphorylates the ribo- somal protein S6 kinases (S6K1 and S6K2) and the eukaryotic initiation factor 4E (eIF4E)-binding proteins (4E-BP1 and 4E-BP2), both of which control specific steps in the initiation of cap-dependent translation"
rlimsp
"Both (S/T)P sites, such as Thr36, Thr45, and Thr69 in PHAS-I and the h(S/T)h site (where h is a hydrophobic amino acid) Thr389 in p70(S6K), were phosphorylated. Rapamycin-FKBP12 inhibited mTOR activity. Surprisingly, the extent of inhibition depended on the substrate. Moreover, mutating Ser2035 in the rapamycin-binding domain (FRB) not only decreased rapamycin sensitivity as expected but also dramatically affected the sites phosphorylated by mTOR."
"exogenously provided PA stimulated the activation of the mTORsubs trate S6 kinase and phosphorylation of another mTORsubs trate eukaryotic initiation factor 4E binding protein-1 (4E-BP1) in HEK293 cells. The effect of PA was sensitive to rapamycin (3, 8) and was dependent on the presence of amino acids (3). The amino acid dependence indicated that the effect of PA was physiologic. Subsequently, Blenis group similarly showed that PA stimulated S6 kinase activity in HEK293 cells (9). The ability of PA to stimulate S6 kinase was suppressed by coexpression of TSC1/2, also suggesting that the PA-induced S6 kinase activity was physiologic. PA was also shown to activate mTORin macrophages in an Akt-dependent manner"
"The mechanism involves the ability of this integrin to stimulate the phosphorylation and inactivation of 4E-binding protein (4E-BP1), a translational repressor that inhibits the function of eukaryotic translation initiation factor 4E (eIF-4E). The regulation of 4E-BP1 phosphorylation by alpha 6 beta 4 derives from the ability of this integrin to activate the PI-3K-Akt pathway and, consequently, the rapamycin-sensitive kinase mTOR that can phosphorylate 4E-BP1."
"In addition to stimulating p70S6 kinase mediated protein translation, activation of mTOR inhibits PHAS1 (phosphorylated heat- and acid-stable protein 1) (also known as 4EBP), which is a negative regulator of the translation initiation factor eIF4E Mutations in PHAS1 that inhibit interaction with Raptor also inhibit mTOR mediated phosphorylation of PHAS1"
"Activation of mTOR by insulin results in phosphorylation of downstream targets, e.g. 4E-BP1, S6K1 and ribosomal protein S6, resulting in activation of the mRNA-binding steps in translation initiation. Activation of the phosphatidylinositol 3-kinase-mammalian target of rapamycin signalling pathway by amino acids Although it is clear that amino acids, and in particular leucine, enhance phosphorylation of proteins downstream of mTOR, e.g. 4E-BP1 and S6K1, and indeed require mTOR to be active in order to be effective, whether or not they directly regulate mTOR activity is undecided."
rlimsp
"Mutational analysis of sites in the translational regulator, PHAS-I, that are selectively phosphorylated by mTOR. Results obtained with PHAS-I proteins having Ser to Ala mutations in the five known phosphorylation sites indicate that mTOR preferentially phosphorylates Thr36 and Thr45."
"Specifically as part of mTORC1, mTOR directly phosphorylates the ribo- somal protein S6 kinases (S6K1 and S6K2) and the eukaryotic initiation factor 4E (eIF4E)-binding proteins (4E-BP1 and 4E-BP2), both of which control specific steps in the initiation of cap-dependent translation"
"Mtorc1 promotes protein synthesis by phosphorylating the eukaryotic initiation factor 4e (eif4e)- binding protein 1 (4e-bp1) and the p70 ribosomal s6 kinase 1 (s6k1). Raft1 phosphorylation of 4e-bp1 on thr-36 and thr-45 blocks its association with the cap-binding protein, eif-4e,in vitro. in response to insulin and nutrients, mtorc1, consisting of mtor, raptor (regulatory-associated protein of mtor), and mlst8, is activated and phosphorylates eukaryotic initiation factor 4e-binding protein (4ebp) and p70 s6 kinase to promote protein synthesis and cell size."
sparser
"MTOR phosphorylated PHAS-I on serine and threonine residues in vitro, and these modifications inhibited the binding of PHAS-I to eIF-4E. These studies define a role for mTOR in translational control and offer further insights into the mechanism whereby rapamycin inhibits G1-phase progression in mammalian cells."
sparser
"MTOR phosphorylated PHAS-I on serine and threonine residues in vitro, and these modifications inhibited the binding of PHAS-I to eIF-4E. These studies define a role for mTOR in translational control and offer further insights into the mechanism whereby rapamycin inhibits G1-phase progression in mammalian cells."
reach
"Activated mTOR regulates mRNA translation, ribosomal biosynthesis, protein translation initiation, and other important physiological functions in podocytes in diabetic individuals by phosphorylating the ribosomal S6 kinase 1 (40S ribosomal 6 kinase 1, S6K1) and the eukaryotic initiation factor 4E binding protein 1 (4EBP1) [12,13], which reduce autophagy."
reach
"Our results showed that the protein expression of p-mTOR, mTOR-mediated phosphorylation of 4E-binding protein 4 (4E-BP1), p70 ribosomal S6 protein kinase 1 (S6K1) as well as phosphatidylinositide 3-kinase (p-PI3K) pathways were amplified in the superficial dorsal horn of the spinal cord of bone cancer rats compared with control rats."
"The rapamycin-sensitive component in the 4E-BP1 phosphorylation pathway is FRAP/mTOR (FKBP12-rapamycin associated protein/mammalian target of rapamycin), also known as RAFT1 (rapamycin and 12-kD FK506 binding protein target 1), a member of the PIK (phosphoinositide kinase-related) family of kinases. (from full text) A recombinant FRAP/mTOR protein and a FRAP/mTOR immunoprecipitate were utilized in in vitro kinase assays to phosphorylate 4E-BP1. Phosphopeptide mapping of the in vitro-labeled protein yielded two 4E-BP1 phosphopeptides that comigrated with phosphopeptides produced in vivo. Mass spectrometry analysis indicated that these peptides contain phosphorylated Thr-37 and Thr-46. Thr-37 and Thr-46 are efficiently phosphorylated in vitro by FRAP/mTOR when 4E-BP1 is bound to eIF4E."