mTOR Methods and Protocols
Since its discovery, the mammalian target of rapamycin (mTOR) has been shown to regulate many critical molecular processes in eukaryotes such as metabolism, growth, survival, aging, synaptic plasticity, memory, and immunity. In mTOR: Methods and Protocols
- PDF / 311,279 Bytes
- 14 Pages / 504.57 x 720 pts Page_size
- 40 Downloads / 160 Views
1. Identification of mTOR When the antifungal drug rapamycin was isolated from the soil bacterium Streptomyces hygroscopicus on Easter Island (Rapa Nui) in the 1970s, nobody could have imagined back in those days that this drug would be fundamental for the identification of a signaling network that regulates so many different aspects of cellular life (1). Initially, rapamycin was developed as antifungal agent, but soon afterward it was found that rapamycin possesses immunosuppressive and antiproliferative properties (2). Yeast genetic screens discovered that rapamycin inhibits two genes called target of rapamycin 1 and 2 (TOR1 and TOR2) and later the mammalian homolog mammalian Thomas Weichhart (ed.), mTOR: Methods and Protocols, Methods in Molecular Biology, vol. 821, DOI 10.1007/978-1-61779-430-8_1, © Springer Science+Business Media, LLC 2012
1
2
T. Weichhart Wnt
Insulin/ IGF-1 TLR ligands IRS-1 P
LKB1
Cellular stress
PI3K PIP3
P
AMP PIP2
Akt
P
AMPK
GSK3
PTEN
P
PDK1
mTORC2 mTOR Rictor SIN1 mLST8
+
amino acids
P
P
Ribosome
P
TSC2 TSC1
Rag GTPases mTORC1
FKBP12
P 4E-BP1
Rheb GDP TCTP
mTOR Raptor mLST8 PRAS40
Rapamycin
+
Rheb GTP
P p70S6K
protein synthesis & cell growth
Fig. 1. The current understanding of mTOR signaling. All pathway members, which are discussed in the text, are shown. Please note that additional proteins in the mTOR pathway have been described that are comprehensively reviewed by Zoncu et al. (3) or Yang and Guan (1).
(or mechanistic) TOR (mTOR; also known as FRAP1 or RAFT1) was identified (1). Rapamycin does not directly inhibit mTOR, but instead binds the FK506-binding protein 12 (FKBP12), and it is this complex, which inhibits mTOR (Fig. 1) (1). mTOR is a signaling kinase that affects broad aspects of cellular functions, including metabolism, growth, survival, aging, synaptic plasticity, immunity, and memory (3). It is an atypical serine-threonine protein kinase belonging to the phosphatidylinositol kinase-related kinase (PIKK) family with a predicted molecular weight of 290 kDa. mTOR is the catalytic subunit of two distinct complexes called mTOR complex 1 (mTORC1) and mTORC2.
2. The mTOR Signaling Pathway The mTOR signaling pathway is highly conserved from yeast to humans and is activated by a variety of divergent stimuli. mTOR senses cellular energy levels by monitoring cellular ATP:AMP levels via the AMP-activated protein kinase (AMPK), growth factors such
1
Mammalian Target of Rapamycin: A Signaling Kinase…
3
as insulin and insulin-like growth factor 1 (IGF-1) via the insulin receptor and the IGF-1 receptor respectively, amino acids via Rag GTPases, and signals from the Wnt family via glycogen synthase kinase 3 (GSK3) (1, 4). In the immune system, stimulation of antigen receptors (T and B cell receptors), cytokine receptors (e.g., Interleukin [IL]-2 receptor), or toll-like receptors (TLRs) (1, 5–8) all lead to the activation of mTOR (Fig. 1). As the archetypical and best-documented example, triggering of the insulin receptor activates tyrosine kinas
Data Loading...
