Function:Participates in the FRAP1 pathway and associates in a near stoichiometric ratio with FRAP1 to form a nutrient-sensitive complex (NSC) . Plays a pivotal role as a scaffold protein in the FRAP1-signaling pathway and this interaction is essential for the catalyzed phosphorylation of EIF4EBP1. Has a positive role in nutrient-stimulated signaling to the downstream effector RPS6KB1. Under nutrient-deprived conditions , serves as a negative regulator of FRAP1 kinase activity. Regulation of the interaction with FRAP1 is a critical mechanism by which cells coordinate the rate of cell growth and maintenance of cell size with different environmental conditions. ,miscellaneous:Rapamycin destabilizes the interaction with FRAP1 regardless of nutrient availability , and its potency for dissociation is increased under nutrient-rich conditions. This action uncouples FRAP1 from its substrates , and inhibits FRAP1 signaling without altering its intrinsic catalytic activity. ,similarity:Belongs to the WD repeat RAPTOR family. ,similarity:Contains 7 WD repeats. ,subunit:Binds directly 4EBP1 and RPS6KB1 independently of its association with FRAP1. Binds preferentially to poorly or non-phosphorylated form of EIF4EBP1 , and this binding is critical to the ability of FRAP1 to catalyze phosphorylation. Complex with FRAP1 physically interacts under both leucine-rich and -poor conditions and therefore in at least two nutrient-determined states with different stability. ,tissue specificity:Highly expressed in skeletal muscle , and in a lesser extent in brain , lung , small intestine , kidney and placenta. ,
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