Thursday, October 29, 2020

mTOR Signaling

 Mtor is a protein found in the cell membrane which transmits signals from outside of the cell to inside. It is rather interesting how this signaling happens, as it acts like a switch that turns on and off various proteins within the cell. When mtor signaling occurs, it causes several changes to occur within the cell, for example an increase in autophagy or apoptosis which can lead to growth or destruction of cells depending on their state.

It appears that the mtor signaling pathway is an important part of cell regulation, and so mutations or changes to this protein can cause problems in growth. It also appears as though there are several different types of mtor, each with a specific purpose depending on where it's located (in the nucleus or cytoplasm) and what type of cell it is.

It also appears that mtor signaling is a mechanism of cell regulation which helps in the functioning of the cell. It can trigger responses to external signals, such as stress and toxins, which lead to changes within the cells.

One example of this is the autophagy process, which can lead to the destruction of old cells or parts within cells if they are not functioning properly. Another example is apoptosis, where unnecessary or abnormal cells are destroyed by the cell itself.

It appears that mtor signaling is very important to cell regulation, and so mutations within the protein can cause issues with this process. This often leads to problems in both growth and destruction of cells.

The fact that the mtor protein can be found in all cell types, means that this signaling affects all cells.

The most obvious conclusion here is that the Mtor pathway specifically controls protein synthesis in response to insulin. The human body takes a number of actions to maintain stable blood sugar levels. For example, when we eat food, it breaks down into glucose (a simple carbohydrate) which enters our bloodstream and goes to all cells in the body. Some cells need more energy than others at any given time. Brain cells use a lot of energy because they are highly active and performing lots of complex calculations all the time; muscle cells do not normally require much additional glucose but can increase their activity if certain hormones signal them to do so; liver cells have an extremely high capacity for converting excess carbohydrate or fat into simple sugars like glycogen (and these are stored in case future consumption should be necessary). Thus some parts of our bodies need extra fuel from within as well as outside sources.

The pancreas is a small organ that lies behind the stomach. It has two functions: it produces digestive enzymes which break down food into smaller pieces, and also insulin hormone which signals cells to absorb glucose from the blood stream when we eat.

The Mtor pathway is a major signal transduction pathway that controls protein synthesis and cell growth. It has insulin as an upstream regulator, which binds to the receptor on the cell surface and activates signaling cascades inside the cell. The same cascade also contains a number of other proteins (including S6K) which activate ribosomes in cells.

The ribosome is a complex molecular machine that translates genetic information stored in DNA into proteins. The translation of this information is achieved by matching three-letter 'words' (codons) with their corresponding amino acids.

The ribosome, activated by Mtor signalling, binds to the messenger RNA (mRNA) molecule inside the cell nucleus. The mRNA has specific places where proteins are being 'printed' onto it. This process is called translation because the information that has been transcribed from DNA into an intermediate molecule of RNA now becomes a sequence of amino acids which will eventually form a protein.

Proteins are the workhorse molecules of life. They perform a variety of tasks, from structural support to carrying information around inside cells. Protein synthesis is triggered by an increase in Mtor signaling.

The Mtor Signaling pathway is a key regulatory mechanism in the cell, turning on and off protein synthesis. It facilitates alterations in cellular metabolism through increases or decreases in the rate at which proteins are translated into functional products.

In Prokaryotes this signaling pathway has a single component, but in eukaryotic cells there are several components that compose it.

Mtor is a protein kinase, which can phosphorylate (activate) itself and other proteins. When there are enough Mtor molecules present to bind to all the available TOR sites, it activates Rheb, another GTP-binding protein.

Rheb, in turn, can bind to and activate a GTP-binding protein called Raptor. When Raptor becomes active it binds with one or more of the following four proteins:

At this point, the cell activates or suppresses protein synthesis by phosphorylating (activating) or de-phosphorylating (inactivating) another GTP-binding protein called eIF4E. When eIF4E is active it binds to mRNA and this complex can then enter the ribosome where translation into proteins begins.

When eIF4E is inactive, the complex of mRNA and eIF4E cannot enter the ribosome and protein synthesis stops. This entire process is in response to signals from other proteins that are part of a cell's internal network.

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