Paracrine: What is it? Cell Signaling, Stages, Pathways, Types of Molecules and Functions

It is a type of cellular communication by chemical secretion.

Paracrine signaling is a form of cell-to-cell communication; is the process in which a cell produces a signal to induce changes in the vicinity of cells, altering the behavior of those cells.

However, the exact distance that paracrine factors can travel is not certain.

Cell signaling

Cell signaling refers to the vast communication networks that occur between and within every cell in our body.

Unlike the stable bricks that form the foundation of our homes, cells are dynamic, always-on building blocks. Cell signaling makes it possible.

Together, cells can coordinate everything from neonatal development to large cascading immune responses against bacteria or viruses.

Stages of cell signaling

At its core, however, cell-to-cell signaling can simply be described as the production of a “signal” by a cell that is then received by its “target” cell. Indeed, signal transduction is said to have three stages:

  • Reception, whereby the signal molecule binds to the receptor.
  • Transduction, which is where the chemical signal results in a series of enzyme activations.
  • Finally, the response, which is the resulting cellular response.

Cell signaling pathways

Typically, cell signaling is mechanical or biochemical and can occur locally (autocrine, paracrine) or from a distance (endocrine).

The labeling itself depends on the distance between the original cell and the target cell, and on the physical properties of the signal (“ligand”). Hydrophobic ligands have fatty properties and include steroid hormones and vitamin D 3, among others.

Following the concept similar to that of similar solutions, these molecules are able to diffuse through the plasma membrane of the target cell to bind to internal intracellular receptors.

On the other hand, hydrophilic ligands are often derived from amino acids and will bind to receptors on the cell surface; Being watery allows the signal to travel through the watery environment of our bodies without assistance.

Types of signaling molecules

Signaling molecules are currently assigned one of five classifications.

  • Intracrine ligands are produced by the target cell itself and bind to an internal receptor.
  • Autocrine ligands are finely distinct in that, although they are also manufactured by the target cell, they are first secreted and then bound to the cell as well as neighboring cells (eg immune cells).
  • Juxtacrine ligands target adjacent cells (often called “contact-dependent” signaling).
  • Paracrine ligands target cells in the vicinity of the original emitter cell (eg, neurotransmitters such as acetylcholine).
  • Lastly, endocrine cells produce hormones that have the important task of attacking distant cells and often travel through our circulatory system.

Cell signaling function and key players

As mentioned earlier, cell signaling serves a vital purpose by allowing our cells to carry out life as we know it.

Thanks to the concerted efforts of our cells through their signaling molecules, our bodies can orchestrate the many complexities that sustain life. These complexities, in effect, require a diverse collection of receptor-mediated pathways that perform their unique functions.

Intracellular receptors

A common type of signaling receptor are intracellular receptors, which are located within the cytoplasm of the cell and generally include two types.

  • Nuclear receptors are a class of protein with diverse DNA-binding domains that, when bound to steroid or thyroid hormones, form a complex that enters the nucleus and modulates the transcription of a gene.
  • IP 3 receptors are another class, found in the endoplasmic reticulum and serve important functions, such as the release of Ca 2+, which is so crucial for the contraction of our muscles and the plasticity of our neuronal cells.
Ligand-activated ion channels

Our plasma membranes encompass another type of receptor called ligand-dependent ion channels that allow hydrophilic ions to pass through the thick fatty membranes of our cells and organelles.

When bound to a neurotransmitter such as acetylcholine, ions (commonly K +, Na +, Ca 2+, or Cl -) are allowed to flow through the membrane to allow the life support function of activation to take place. neural, among many other functions.

G protein-coupled receptors

Moving into a diverse family of cell surface receptors, G-protein-coupled receptors (GPCRs) remain the largest and most diverse group of membrane receptors in eukaryotes.

They are special because they receive information from a diverse group of signals ranging from light energy to peptides and sugars.

Its mechanism of action also begins with a ligand that binds to its receptor.

However, the demarcation is that the binding of the ligand results in the activation of a G protein which can then transmit a complete cascade of enzyme and second messenger activations that carry out an incredible variety of functions such as vision, sensation, inflammation and growth.

Receptor tyrosine kinases

Receptor tyrosine kinases are another class of receptors revealed to show unforeseen diversity in their actions and activation mechanisms.

The general method of activation follows a ligand that binds to the receptor tyrosine kinase, allowing its kinase domains to dimerize. This dimerization invites phosphorylation of their tyrosine kinase domains, which, in turn, allow intracellular proteins to bind to phosphorylated sites and become “active.”

An important function of receptor tyrosine kinases is their role in mediating growth pathways (ie, epidermal growth factors).

Fibroblast growth factors). Of course, the downside to having complex signaling networks lies in the unforeseen ways that any alteration can lead to disease or unregulated growth – cancer.