(A) Sequence alignment of the gatekeeper site for PKA, c-Kit, EGFR, ABL,
p110-PI3Kα, and mTOR. Arrowhead marks the gatekeeper residue.
(B) Electrostatic model of the ATP-binding pocket of mTOR kinase (PDB ID code
4JSP). The I2237 position is as indicated. Atom is colored as follows: N, blue;
O, red; P, orange; S, yellow; Mg+2, green. Surface representation is
as follows: hydrophobic residue, red; neutral residue, white; hydrophilic
residue, blue.
(C) tor2-dg cells expressing WT or mutant TOR2-mTOR were
serially diluted by 10-fold and assayed for drug sensitivity on SC-leucine
plates containing BEZ235, OSI-027, or Torin2, or AZD8055, BEZ235, INK128,
PF-04691502 or PKI-587 in the presence of amphotericin B.
(D) tor2-dg cells expressing WT or mutant TOR2-mTOR were
serially diluted by 10-fold and assayed for cell growth at different
temperatures. Vector and TOR2 plasmids were used as a negative
and positive control, respectively.
(E) Summary of gatekeeper mutations and their effects on mTOR kinase function.
“+”: normal function; “−”: minor defect;
“−−”: moderate defect, and
“−−−”: severe defect.