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Structural and functional analysis of the role of the chaperonin CCT in mTOR complex assembly
Author(s) -
Willardson Barry M.,
Cuellar Jorge,
Ludlam Grant,
Tensmeyer Nicole C.,
Aoba Takuma,
Dhavale Madhura,
Santiago César,
Bueno-Carrasco Teresa,
Mann Michael J.,
Plimpton Rebecca L.,
Makaju Aman,
Franklin Sarah
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.04354
Subject(s) - chaperonin , mtorc2 , mtorc1 , mechanistic target of rapamycin , pi3k/akt/mtor pathway , kinase , autophagy , microbiology and biotechnology , biology , chemistry , protein folding , signal transduction , biochemistry , apoptosis
The mechanistic target of rapamycin (mTOR) kinase forms two multi‐protein signaling complexes, mTORC1 and mTORC2, which are master regulators of cell growth, metabolism, survival and autophagy. Two of the subunits of these complexes are mLST8 and Raptor, β‐propeller proteins that stabilize the mTOR kinase and recruit substrates, respectively. Here we report that the eukaryotic chaperonin CCT plays a key role in mTORC assembly and signaling by folding both mLST8 and Raptor. A high resolution (4.0 Å) cryo‐EM structure of the human mLST8‐CCT intermediate isolated directly from cells shows mLST8 in a near‐native state bound to CCT deep within the folding chamber between the two CCT rings, and interacting mainly with the disordered N‐ and C‐termini of specific CCT subunits of both rings. These findings describe a unique function of CCT in mTORC assembly and a distinct binding site in CCT for mLST8, far from those found for similar β‐propeller proteins. Support or Funding Information This research was supported by the grant BFU2016‐75984 (AEI/FEDER, EU) and the Madrid Regional Government (grant S2013/MIT2807) to JMV as well as the US National Institutes of Health grant EY012287 to BMW and fellowships from the Brigham Young University Simmons Center for Cancer Research to WGL, NCT, TA and MD.