mTOR Complexes

The mechanistic target of rapamycin (mTOR) is a critical kinase in cellular growth and metabolism regulation, functioning through two distinct complexes known as mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2). These complexes play pivotal roles in integrating inputs from various upstream signals, including nutrients, growth factors, and cellular energy levels, to control downstream processes affecting cell growth, survival, and metabolism.

mTOR Complex 1 (mTORC1) is the more extensively studied of the two and is sensitive to rapamycin, an immunosuppressive drug from which mTOR gets its name. mTORC1 regulates protein synthesis, a fundamental aspect of cell growth, by phosphorylating S6 kinase (S6K) and the eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1). These phosphorylations lead to an increase in translation of specific mRNAs, particularly those encoding components of the protein synthesis machinery and metabolic enzymes. mTORC1 is also involved in lipid synthesis, autophagy inhibition, and lysosome biogenesis. It responds to nutrient availability (particularly amino acids), energy status (via AMPK), and growth factors (via the PI3K/Akt pathway).

mTOR Complex 2 (mTORC2), which is not sensitive to short-term treatment with rapamycin, has a role in regulating the cytoskeleton and activating Akt by phosphorylating it at a key serine residue (Ser473). Akt, in turn, is a critical mediator of growth factor signaling, promoting survival and growth. mTORC2 also influences ion transport and cellular metabolism and has been implicated in the regulation of glucose and lipid metabolism through different substrates.

Both complexes are composed of the mTOR kinase itself, but they have distinct regulatory and associated subunits that determine their substrate specificity and localization. For mTORC1, regulatory-associated protein of mTOR (RAPTOR) is a defining component, which helps recruit substrates for mTORC1. In contrast, rapamycin-insensitive companion of mTOR (RICTOR) is essential for mTORC2 activity and substrate specificity. The regulation of mTORC1 and mTORC2 involves multiple feedback loops and cross-talk with other signaling pathways, which adds complexity to their roles in cellular physiology. For example, prolonged activation of mTORC1 can lead to the inhibition of PI3K/Akt signaling through S6K-mediated phosphorylation and inhibition of insulin receptor substrate (IRS), which can contribute to insulin resistance in peripheral tissues.

Figure 1 Biological processes regulated by mTOR complexes and downstream effector pathways. (Centonze, 2022)

Representative Targets of mTOR Complexes

mTOR

mTOR is a highly conserved serine/threonine kinase that serves as a central regulator of cellular metabolism, growth, and survival. This protein is a core component of two distinct complexes: mTORC1 and mTORC2, each of which has unique substrates and biological functions. mTORC1 is sensitive to rapamycin and primarily regulates protein synthesis, cell growth, autophagy, and metabolism through its ability to sense and integrate diverse nutritional and environmental cues, including growth factors, energy status, oxygen levels, and amino acid availability. In contrast, mTORC2, which is less sensitive to rapamycin, plays a key role in regulating the cytoskeleton, cell survival, and lipid metabolism. The mTOR pathway is pivotal for its role in promoting anabolic processes such as lipid and protein synthesis while inhibiting catabolic processes like autophagy, making it crucial for cell growth and proliferation. Dysregulation of mTOR signaling is linked to a variety of diseases, including cancer, obesity, type 2 diabetes, and neurodegenerative disorders. In cancer, for example, hyperactivation of mTOR can drive tumor growth and resistance to therapy by enhancing protein synthesis and cell proliferation. Conversely, inhibition of mTOR has been shown to extend lifespan and reduce symptoms in various models of age-related disease.

Recommended Rabbit Anti-mTOR mAb (CAT#: ZG-0473U)

Figure 2 Rabbit Anti-Phospho-MTOR (S2481) Antibody (ZG-0473U) in IF. Immunofluorescence staining of Hela cells with ZG-0473U at 1:100, counter-stained with DAPI. The cells were fixed in 4% formaldehyde, permeabilized using 0.2% Triton X-100 and blocked in 10% normal Goat Serum. The cells were then incubated with the antibody overnight at 4°C. The secondary antibody was Alexa Fluor 488-congugated Goat Anti-Rabbit IgG (H+L).

Recommended Rabbit Anti-mTOR mAb (CAT#: ZG-0474U)

Figure 3 Rabbit Anti-Phospho-MTOR (S2448) Antibody (ZG-0474U) in IHC. IHC image of ZG-0474U diluted at 1:100 and staining in paraffin-embedded human breast cancer performed on a Leica BondTM system. After dewaxing and hydration, antigen retrieval was mediated by high pressure in a citrate buffer (pH 6.0). Section was blocked with 10% normal goat serum 30min at RT. Then primary antibody (1% BSA) was incubated at 4°C overnight. The primary is detected by a biotinylated secondary antibody and visualized using an HRP conjugated SP system.

Recommended Rabbit Anti-mTOR mAb (CAT#: VS3-FY973)

Figure 4 Recombinant Rabbit Anti-MTOR (phospho Ser2448) Antibody (clone R08-7G7) in IHC-P. Immunohistochemical analysis of paraffin-embedded human lung carcinoma using Phospho-mTOR (Ser2448) Antibody. High pressure and high temperature sodium citrate pH 6.0 for antigen retrieval.

RPTOR

RPTOR, known as regulatory-associated protein of MTOR, is a component of the mTORC1. RPTOR serves as a scaffolding protein that helps assemble the mTORC1 complex and mediates its interaction with substrates and other regulatory proteins, ensuring the effective transduction of signaling pathways essential for protein synthesis, lipid metabolism, and autophagy. The importance of RPTOR in the mTORC1 pathway lies in its ability to regulate the kinase activity of mTOR based on environmental cues. For instance, when nutrients are abundant, RPTOR assists mTORC1 in promoting anabolic processes, such as protein and lipid synthesis, while inhibiting catabolic processes like autophagy. This regulatory mechanism is vital for cellular and organismal growth and plays a role in maintaining energy homeostasis. Dysregulation of RPTOR and the mTORC1 pathway is associated with a range of diseases, including cancer, obesity, type 2 diabetes, and neurodegenerative disorders. In cancer, for example, overactivation of mTORC1 due to mutations or alterations in RPTOR can lead to unchecked cellular proliferation and survival, contributing to tumor growth and resistance to conventional therapies. Similarly, in metabolic diseases, impaired regulation of mTORC1 is linked to insulin resistance and altered lipid metabolism.

RICTOR

RICTOR, short for RPTOR independent companion of MTOR, complex 2, is an essential component of the mTOR Complex 2 (mTORC2). RICTOR is critical for the assembly and function of mTORC2, facilitating its ability to respond to growth factors and other extracellular signals. RICTOR helps mTORC2 phosphorylate a range of AGC kinase family members, including AKT, SGK1, and PKC, which are pivotal for cellular processes such as cell survival, migration, and differentiation. The phosphorylation of AKT by mTORC2 at Ser473, for example, is a crucial step in activating AKT signaling, which promotes cell growth and survival, highlighting RICTOR's role in vital signaling pathways. Importantly, the function of RICTOR and mTORC2 is implicated in several human diseases, particularly cancer. Overexpression or hyperactivation of RICTOR has been observed in various cancers, leading to enhanced AKT signaling and promoting oncogenic processes such as tumor growth and metastasis. Consequently, RICTOR has emerged as a potential therapeutic target, with research focused on developing inhibitors that can selectively disrupt mTORC2 activity to suppress cancer progression. In addition to cancer, the role of RICTOR in insulin signaling and lipid metabolism links it to metabolic diseases, such as diabetes and obesity. This makes it a subject of interest not only for cancer therapy but also for the treatment of metabolic disorders.

Full List of Targets of mTOR Complexes

Tested Data-Supported Products for Targeting mTOR Complexes

CAT	Product Name	Biomarker	Assay	Image
ZG-069R	Mouse Anti-RICTOR Recombinant Antibody (ZG-069R)	RICTOR	WB
ZG-0084U	Rabbit Anti-RPTOR Recombinant Antibody (clone 1B10)	RPTOR	IHC
ZG-0473U	Rabbit Anti-Phospho-MTOR (S2481) Recombinant Antibody (clone 3H11)	MTOR	WB
ZG-0474U	Rabbit Anti-Phospho-MTOR (S2448) Recombinant Antibody (clone 1G6)	MTOR	WB
VS3-FY973	Recombinant Rabbit Anti-MTOR (phospho Ser2448) Antibody (clone R08-7G7)	MTOR	WB

For research use only. Not intended for any clinical use.