Types of mTOR
The Mammalian/mechanistic target of rapamycin is referred to as mTOR. In the middle of the 20th century, a bacteria discovered on Easter Island yielded the immunosuppressive medicine rapamycin. The moniker mTOR was coined since one of the first impacts that rapamycin was shown to have was on TOR genes.
In reality, mTOR works as a component of a protein complex that is made up of several other proteins that are joined together and have various inhibitory and activating properties. mTORC1 and mTORC2 are two distinct mTOR complexes. They all stabilize mTOR and aid in its ability to connect to its target receptor, despite having somewhat different proteins in the complex.
The ribosomal protein S6K is activated by mTORC1, which increases protein synthesis. In addition, mTORC1 suppresses 4EBP1 activity, which typically prevents protein synthesis. Additionally, mTORC1 promotes mitochondrial biogenesis, lipid synthesis, and downregulates autophagy.
mTORC1 and mTORC2
- mTOR is a PI3K-related kinase (PIKK) family serine/threonine protein kinase that forms the catalytic component of two different protein complexes known as mTOR Complex 1 (mTORC1) and 2 (mTORC2) (mTORC2).
- The three key components of mTORC1 are mTOR, Raptor (a regulatory protein linked with mTOR), and mLST8 (mammalian lethal with Sec13 protein 8, also known as GL).
- Raptor enhances substrate recruitment to mTORC1 by binding to the TOR signaling (TOS) motif present on numerous conventional mTORC1 substrates and is needed for mTORC1 subcellular localization.
- mLST8, on the other hand, connects with the catalytic domain of mTORC1 and may maintain the kinase activation loop, while genetic studies show it is required for mTORC1 to operate properly.
- The rapamycin-FKBP12 combination binds to the FRB domain of mTOR to narrow the catalytic cleft and partially occlude substrates from the active site, according to a crystal structure of the mTOR kinase domain linked to mLST8.
mTOR Signaling Pathway
Cell signaling (cell communication in British English) is the capacity of a cell to receive, process, and transmit messages with its surroundings and with itself. Cell signaling is a basic characteristic of all prokaryotic and eukaryotic cellular life. Cell signaling can take place across short or long distances, and is thus classed as autocrine, juxtacrine, paracrine, and endocrine. Signaling molecules can be produced via a variety of biosynthetic pathways and released by passive or active transporters, as well as cell injury.
Receptors are important in cell signaling because they can sense chemical signals as well as physical inputs. Receptors are proteins that are found on the cell surface or within the cell’s interior, such as the cytoplasm, organelles, and nucleus. Additional enzymatic activity such as proteolytic cleavage, phosphorylation, methylation, and ubiquitinylation may occur as a result of these signaling pathways. Each cell is designed to respond to certain extracellular signal molecules, which serve as the foundation for development, tissue repair, immunology, and homeostasis.