Defining the Domain Arrangement of the Mammalian Target of Rapamycin Complex Component Rictor Protein

Abstract

Mammalian target of rapamycin (mTOR) complexes play a pivotal role in the cell. Raptor and Rictor proteins interact with mTOR to form two distinct complexes, mTORC1 and mTORC2, respectively. While the domain structure of Raptor is known, current bioinformatics tools failed to classify the domains in Rictor. Here we focus on identifying specific domains in Rictor by searching for conserved regions. We scanned the pdb structural database and constructed three protein domain datasets. Next we carried out multiple pairwise sequence alignments of the proteins in the domain dataset. By analyzing the z-scores of Rictor sequence similarity to protein sequences in the dataset, we assigned the structural and functional domains of Rictor. We found that, like Raptor, Rictor also has HEAT and WD40 domains, which could be the common motif binding to mTORC. Rictor may also have pleckstrin homology domains, which mediate cellular localization and transmit signals to downstream targets, as well as a domain that is homologous to 50S protein L17 and human 39S protein L17. This putative ribosome binding domain could mediate mTORC2-ribosome interaction.

Disruption of the RICTOR/mTORC2 complex enhances the response of head and neck squamous cell carcinoma cells to PI3K inhibition

“…The protein domain structure of RICTOR and mTORC2 has only recently been elucidated in humans; as exon 5 (residues 88–130) occurs near the beginning of the large RICTOR gene and is contained within the N‐terminal armadillo (ARM) repeat cluster that is known to interact with mTOR, we hypothesized that disrupting this region may impair mTORC2 activity (Fig. ; Chen et al , ; Zhou et al , ).…”

“…Following deletion of RICTOR exon 5, the interaction between RICTOR and mTOR was abolished, despite the detection of substantial levels of RICTOR. This observation identifies the region encoded by exon 5 as essential for the interaction of RICTOR with mTOR and therefore essential to the formation of mTORC2 (Zhou et al , ). As a specific interdependence between RICTOR and the SIN1 subunit of mTORC2 has been described, an examination of the changes in SIN1 expression and binding following RICTOR deletion in our cell lines may inform the specific roles of these subunits in relation to each other (Oh and Jacinto, ).…”

“…S2) beginning of the large RICTOR gene and is contained within the N-terminal armadillo (ARM) repeat cluster that is known to interact with mTOR, we hypothesized that disrupting this region may impair mTORC2 activity ( Fig. S3; Chen et al, 2018;Zhou et al, 2015). The predicted deletion products for our CRISPR/ Cas9 model are shown in Fig.…”

Cryo-EM structure of human mTOR complex 2

“…Rictor has an Nterminal armadillo (ARM) repeat cluster (~900 residues), followed by a large unstructured region. 28 We next performed cross-linking mass spectrometry (XL-MS) analysis using the purified mTORC2 complex ( Fig. 1b and Supplementary information, Table S1).…”

“…Secondary structure prediction indicates that the helical elements are likely to be derived mainly from the N-terminal portion of Rictor, which is composed of ARM and/or HEAT repeat domain clusters. 28 We therefore built model of Rictor as poly-Alanine chains (880 residues) into this EM density (Supplementary information, Figure S5c and e).…”