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. Author manuscript; available in PMC: 2017 Sep 1.
Published in final edited form as: Histol Histopathol. 2016 Mar 9;31(9):961–968. doi: 10.14670/HH-11-753

Figure 1. Functional domains of mTOR and the binding partners that confer mTORC1 and mTORC2 signaling complexes.

Figure 1

mTOR per se is a Ser/Thr protein kinase as noted by the two lobes KD called the KD N-lobe and the KD C-lobe. It has 20 tandem HEAT repeat domains near its N-terminus, to be followed by FAT domain, FRB domain, LBE domain and FATC domain at its C-terminus. The critical binding partner to create mTORC1 is Raptor, which together with mLST8, PRAS40, DEPTOR and FKBP12 that bind to the corresponding domains in mTOR constitute the rapamycin sensitive mTORC1. The critical binding partner to create mTORC2 is Rictor, which together with SIN1, mLST8, DEPTOR and Protor1/2 which bind to the corresponding domains in mTOR constitute the rapamycin insensitive mTORC2. Based on recent studies in the testis, the signaling proteins and pathways that modulate Sertoli cell BTB dynamics are also shown (see text for details). It is noted that the signaling pathways depicted herein are highly simplified and based on recent studies in the testis, readers should seek additional information in recent reviews from other investigators in the field, which are cited in text. Abbreviations used: Akt; transforming retrovirus Akt8, an onocogene, also known as PKB; Arp2/3 complex, actin-related protein 2/3 complex; ATM, Ataxia telangiectasia mutated containing Ser/Thr protein kinase intrinsic activity; C-lobe, C-terminal lobe; DEP, Dishevelled, Egl-10 and Pleckstrin; DEPTOR, DEP domain-containing mTOR-interacting protein; EF3, elongating factor 3; FAT domain, FRAP, ATM, TRAP domain; FATC, FAT domain at the C-terminus; FKBP12, FK506/rapamycin-binding protein; HEAT, Huntington, EF3, PP2A, TOR1; FRAP, FKBP rapamycin associated protein; FRB, FKBP132 rapamycin binding; KD, kinase domain; LBE, binding site for mLST8; mLST8, mammalian lethal with SEC thirteen 8, also known as mTOR associated protein LST8 homolog; N-lobe, N-terminal lobe; PKB, protein kinase B; PKC-α, protein kinase C-α; PP2A, protein phosphatase 2A; PRAS40, proline-rich Akt/PKB substrate 40 kDa; Protor1/2, protein observed with Rictor 1 and 2; Rac1, Ras-related C3 botulinum toxin substrate 1, a small GTPase; Raptor, regulatory-associated protein of mTOR; Rictor, rapamycin-insensitive companion of mTOR, a scaffolding protein; rpS6, ribosomal protein S6; SAPK, stress-activated protein kinase; SIN1, SAPK-interacting protein 1; TOR1, yeast kinase target of rapamycin 1; TRAP, thrombospondin-related anonymous protein.