CELL VESICLE: CHARACTERISTICS, TYPES AND FUNCTIONS - BIOLOGY - 2025

The cellular vesicle is a vehicle for intracellular and extracellular communication, in which molecules synthesized in the cell, such as neurotransmitters, hormones, proteins, lipids and nucleic acids, are packaged. These molecules are called cargo. The chemical nature of the charge depends on the type of gallbladder and its function.

The general morphology of a vesicle consists of a lipid bilayer, which forms a closed sac, and whose lumen is watery. The size of the vesicles can vary. For example, in the acinar cells of the pancreas it ranges from 200 to 1200 nm, while in neurons it ranges from 30 to 50 nm.

Source: Mariana Ruiz Villarreal derivative work: Gregor_0492

In eukaryotes, different cellular processes occur in specific organelles. However, it is necessary to exchange molecules between organelles, or to send molecules out into the extracellular space. Because of this, a system is needed that allows the cargo to be transported to its correct destination. This function is fulfilled by the vesicles.

Characteristics of cell vesicles

There are different types of vesicular transport with their respective characteristics. However, there are generalities such as sprouting, which is directed by a layer or coated with proteins, such as clathrin; and binding specificity, which is dependent on transmembrane proteins, or SNARE.

Vesicular transport includes exocytosis and endocytosis, transport between organelles, and the release of extracellular vesicles. In all cases, it involves the continuous formation of shoots, and the cleavage and fusion of transport vesicles.

Exocytosis consists of the fusion of a vesicle with the plasma membrane to release the vesicular contents. There are three modes of exocytosis: 1) complete collapse fusion; 2) kiss and run; and 3) compound exocytosis.

Endocytosis consists of the recovery of the plasma membrane, which prevents cellular inflammation. There are different mechanisms of endocytosis.

In vesicular transport between organelles, the newly synthesized proteins found in the lumen of the endoplasmic reticulum are transported to the Golgi apparatus. From this organelle, the vesicles depart towards the endomembrane system and the plasma membrane.

Extracellular vesicles, found in prokaryotes and eukaryotes, are responsible for carrying molecules from one cell to another.

Types of cell vesicles

Endocytic vesicles

They serve to introduce molecules into the cell or to recycle membrane components. These vesicles may or may not be covered by a layer of proteins. The proteins that coat the surface of the gallbladder are clathrin and caveolin.

Clathrin-coated endocytic vesicles are responsible for the internalization of pathogens, such as influenza viruses among others, membrane proteins, and extracellular receptors and ligands. Caveolin-coated vesicles mediate entry of viruses, fungi, bacteria, and prions.

Exocytic vesicles

Through a stimulus, secretory cells (neurons or other cells) release their content through exocytocis.

Membrane fusion during exocytosis occurs through two steps: 1) binding of the exocytic vesicle to the membrane acceptor; and 2) fusion of the lipid bilayers. The Rab, GTPases, and SNARE proteins, among others, participate in these steps.

Transport vesicles between organelles

COPII-coated vesicles are transported from the endoplasmic reticulum to the Golgi apparatus. Transport from the Golgi apparatus to the vacuole involves two pathways: ALP (alkaline phosphatase) to the vacuole; endosomes via the carboxypeptidase Y and S pathway (CPY and CPS).

Vesicle function

Vesicles of the secretory pathway have a wide variety of functions, among which are the secretion of the following substances: insulin from pancreatic cells, neuropeptides and neurotransmitters, hormones, and substances involved in the immune response.

One of the best known functions is the release of secretory proteins from the pancreas. For example, chymotrypsinogen, a zymogen, is released by fusion of vesicles to the membrane, as a result of hormonal stimulation.

Extracellular vesicles (VE) are of two types: exosomes and ectosomes. Both are differentiated by their composition, which determines their function. Exosomes possess tetraspanin, integrin, proteoglycan, and ICAMI. Ectosomes possess receptors, glycoproteins, metalloproteins, and nucleic acids.

The functions of EVs include maintenance of cell homeostasis, regulation of cell function, and intercellular communication. The latter function requires the transport of proteins, RNA (mRNA, miRNA, antisense RNA), and DNA sequences.

Fusion of EVs to the target cell membrane can affect the regulation of gene expression by transcription factors, signaling proteins, and many enzymes. The EVs released by stem cells play an important role in organ repair and protection against disease.

Diseases

The normal physiological functioning of cells depends, among several factors, on the transport of vesicles and their fusion. For example, type 2 diabetes is characterized by defects in insulin secretion and translocation mediated by glucose transporters.

EVs play an important role in many diseases. In cancer, EVs increase the resistance of chemotherapeutic drugs, mediated by miRNA, EVs have a critical effect on neurodegeneration. In Alzheimer's diseases and multiple sclerosis, the degenerative effect depends on multiple molecules, such as miRNA, gangliosides, and proteins.

In cardiac cells, exosomes and ectosomes allow communication between cells, and furthermore, they affect the development of atheroclerotic plaque in vessels by inducing inflammation, proliferation, thrombosis, and vasoactive response.

In allergy and inflammation processes, the miRNAs of EVs regulate these processes through paracrine effects.

Vesicles in different organisms

Special attention has been paid to the EVs of protozoa. This is because EVs play an important role between parasite and host interaction.

Some of the parasites whose VE have been studied are Trypanosoma brucei, Trypanosoma cruzi, Leishmania spp., Plasmodium spp., And Toxoplasma spp.

EVs have also been observed in gram positive and negative bacteria, including Corynebacterium and Moraxellaceae. In the mucosa of the respiratory tract, outer membrane vesicles (OMVs) bind to lipid domains in alveolar epithelial cells. From there, OMVs modulate the inflammatory response.

References

1. Aaron, T. Place, Maria S. Sverdlov, Oleg Chaga, and Richard D. Minshall. 2009. Antioxidants and Redox Signaling, 11: 1301.
2. Feyder, S., De Craene, JO, Séverine, B., Bertazzi, DL, and Friant, S. 2015. Membrane Trafficking in the Yeast Saccharomyces cerevisiae Model. Int. J. Mol. Sci., 16: 1509-1525.
3. Fujita, Y., Yoshiota, Y., Saburolto, Junaraya, Kuwano, K. and Ochiya, T. 2014. Intercellular Communication by Extracellular Vesicles and Their MicroRNAs in Asthma. Clinical Therapeutics, 36: 873–881.
4. Lodish, H., Berk, A., Zipurski, SL, Matsudaria, P., Baltimore, D., Darnell, J. 2003. Cellular and molecular biology. Editorial Medica Panamericana, Buenos Aires, Bogotá, Caracas, Madrid, Mexico, Sāo Paulo.
5. Parkar, NS, Akpa, BS, Nitsche, LC, Wedgewood, LE, Place, AT, Sverdlov, MS, Chaga, O., and Minshall, RD 2009. Vesicle Formation and Endocytosis: Function, Machinery, Mechanisms, and Modeling.
6. Schmid, SL and Damke, H. 1995. Coated vesicles: diversity of form and function. The FASEB Journal, 9: 1445–1453.
7. Wu, LG, Hamid, E., Shin, W., Chiang, HC 2014. Exocytosis and Endocytosis: Modes, Functions, and Coupling Mechanisms. Annu. Rev. Physiol., 76: 301-331.
8. Yáñez, Mo, Siljander, PRM et al. 2015. Biological properties of extracellular vesicles and their physiological functions. Journal of Extracellular Vesicles, 4: 1–60.