Signal transduction | cell communication pathway

Introduction to Signal Transduction Pathway

In this section, the speaker introduces the topic of signal transduction pathway and explains why it is important for cell communication.

What is a Signal Transduction Pathway?

• A signal transduction pathway is a process where a signaling molecule interacts with some portion of the cell outside and brings this signal inside the cell, ultimately changing the transcription of different genes and production of different proteins in response to that chemical element or chemical molecule.

• Cells work together collaboratively to establish specific functions in our body. Environmental factors can affect how cells behave, and signal transduction pathways help cells respond to these factors.

• There are two types of activity possible: either it is the activity of cell growth and division or the activity of cell death.

Components of Signal Transduction Pathway

• The components include:

• Signaling molecule

• Signal receptor

• Enzymes or any kind of other protein factors associated with the cell inside the cell actually that is a signal conveyor

• Signal transducers

• Transcription factors

How Does Signal Transduction Work?

• The signaling molecule interacts with some region of the cell which is present outside (signal receptor). This interaction provides internal changes in the receptor that can directly influence signal transducers sometimes or sometimes that can also relate with some signal conveyors that are also associated somewhere in the membrane membrane of the cell. Finally, through that signal conveyor, it provides signals to activate signal transducers.

Proteins and Signal Transduction Pathways

In this section, the speaker explains how proteins can have different functions related to growth or death. They discuss signal transduction pathways and the different components involved in conveying signals within cells.

Signal Transduction Pathway Components

• Signaling molecules interact with cell surface receptors to convey signals.

• Signals are conveyed either directly or indirectly to signal transducers.

• Multiple levels of signal transducers are present, starting with second messengers that activate downstream transducers.

• Transcription factors are activated by signal transducers and help with gene transcription and translation.

Insulin as an Example

• Insulin is a signaling molecule that interacts with insulin receptors on cell surfaces.

• Insulin tells cells to uptake glucose from the bloodstream, which helps control blood glucose levels.

• Glucose transporters are produced in response to insulin signals and embedded in cell membranes for glucose uptake.

• This pathway is an example of a growth-associated pathway.

Hydrophilic vs. Hydrophobic Signaling Molecules

• Signaling molecules can be hydrophilic (like insulin) or hydrophobic (like steroid hormones).

• Hydrophilic molecules mediate responses by standing outside cells, while hydrophobic molecules take direct entry inside cells (even into nuclei).

Signal Receptors

This section discusses the different types of signal receptors and their components.

Types of Signal Receptors

• Signal receptors can be voltage-gated, ion-gated, enzyme-linked or enzyme-coupled.

• Enzyme-linked receptors have a cytosolic domain with enzymatic activity that phosphorylates transducers to activate kinase proteins.

• Seven transmembrane receptors are another type of receptor that interacts with G-protein. An example is the G-protein coupled receptor (GPCR).

Signaling Molecules

• The signaling molecules that interact with GPCR and G-protein related interactions are mostly growth factors such as epidermal growth factor (EGF), platelet-derived growth factor (PDGF).

• Secondary messengers inside the cell lead to transcription and translation of specific proteins that help in cell cycle progression.

Signal Conveyors

This section discusses signal conveyors, adapters, and signal transducers.

Signal Conveyors

• In most cases, signal conveyors are G-proteins. In some cases, adapters help signal receptors properly interact with the signal conveyor or even second changers.

• Grb-2 acts as an adapter for interaction between receptor tyrosine kinase and Ras molecule in the middle.

Signal Transducers

• Signaling molecules generated inside the cell are called signal transducers.

Signal Amplification

In this section, the speaker explains how signal amplification works in cell signaling.

Signal Transduction Pathway

• The interaction between the GPC and EGFR provides a signal inside the cell that activates multiple signal transducers.

• Multiple signal transducers activate transcription factors, which transcribe more DNA into RNA.

• Each RNA is translated multiple times to produce a large number of proteins.

Transcription Factors

• Signal transducers influence transcription factors to be activated by modifications like phosphorylations or deactivating inhibitors.

• Activated transcription factors enter the nucleus and interact with specific regions of DNA to produce mRNA.

• Translation of mRNA produces proteins that help cells progress through different phases.

Cross-linking of Cell Signaling Processes

• Cell signaling processes are cross-linked, allowing intermediates to interact with nearby cell signaling pathways and activate or modulate them depending on the time.

• The balance between growth and death pathways is mediated by multiple cell signaling pathways together by cross-linking with each other.