mTORC1 vs mTORC2: complex-level reference

Definition

Mechanistic Target of Rapamycin (mTOR) assembles into two distinct multiprotein complexes, mTORC1 and mTORC2, distinguished by scaffold protein, upstream input sensitivity, downstream substrates, and rapamycin sensitivity. The two complexes are NOT interchangeable and should never be treated as a single 'mTOR' signal in a claim.

Complex-level reference table

Field	mTORC1	mTORC2
Scaffold protein	RPTOR (Raptor)	RICTOR
Core components	mTOR, RPTOR, mLST8, PRAS40, DEPTOR	mTOR, RICTOR, mLST8, SIN1 (MAPKAP1), PROTOR, DEPTOR
Upstream inputs	Insulin/IGF-1 -> PI3K -> AKT -> TSC1/2 -> Rheb Amino acids -> Rag GTPases / Ragulator complex Leucine -> Sestrin2 -> GATOR2/GATOR1 -> Rag Energy status (low ATP) -> AMPK -> TSC2 (inhibitory) Hypoxia -> REDD1 (inhibitory)	Growth-factor/PI3K-associated signaling (upstream input map less fully characterized than mTORC1) Ribosome association implicated in activation in some models
Downstream outputs	S6K1 (phosphorylated at Thr389) -> protein synthesis 4E-BP1 -> cap-dependent translation ULK1 -> autophagy initiation (mTORC1 activity SUPPRESSES this step) TFEB -> lysosomal/autophagy gene transcription (mTORC1 activity SUPPRESSES nuclear TFEB translocation)	AKT (phosphorylated at Ser473) SGK1 PKC-family kinases
Rapamycin sensitivity (acute)	Sensitive -- FKBP12-rapamycin complex directly binds the mTOR FRB domain within mTORC1 and inhibits its kinase output.	Largely insensitive -- mTORC2 is not directly bound by the FKBP12-rapamycin complex in most contexts.
Rapamycin sensitivity (chronic)	Sensitive, and prolonged/high-dose exposure can additionally disrupt mTORC2 assembly indirectly in some tissues/contexts.	Can become sensitive/disrupted with prolonged, high-dose rapamycin exposure in certain cell types.
Functional summary	Principal anabolic/growth control node integrating nutrient and growth-factor status; drives protein synthesis and suppresses autophagy when active.	Regulates cytoskeletal organization, metabolism, and cell-survival signaling. Biologically distinct from mTORC1 -- must not be treated as interchangeable with mTORC1 in any claim about 'mTOR activity'.

Editorial nuances

mTOR signaling is not uniformly harmful or beneficial -- context (tissue, acute vs. chronic, developmental stage) determines outcome.
mTORC1 does not equal mTORC2 -- claims about 'mTOR' without specifying complex are underspecified and should be flagged in review.
IGF-1 is not a one-directional 'lower is always better' longevity score; both excess and deficiency states have documented trade-offs in the source literature.
Autophagy is a dynamic PROCESS (flux), not a static blood biomarker -- LC3-II or p62 snapshots do not equal flux measurement.

Assay reference

Protein synthesis marker	p-S6K1 (Thr389)
mTORC2 marker	p-AKT (Ser473)
Autophagy markers (static)	LC3-II, p62/SQSTM1, ULK1 phosphorylation state, TFEB localization
Flux caveat	Static LC3-II/p62 levels are NOT equivalent to autophagic flux; flux requires lysosomal turnover assays (e.g., with/without lysosomal inhibitor).

Source tier

Tier 2 · Biological synthesis (author-cluster reviews, not primary trial data) Reference synthesis attributed in the brief to the Saxton & Sabatini; Laplante & Sabatini; and Liu & Sabatini mTOR review literature (author-cluster attribution, tier 2). Exact article-level PMID/DOI not supplied in the sourcing brief and is not fabricated here.

Version 0.1.0-poc · literature search date 2026-07-11 · editorial owner Nabus Research