What are Exosomes?

Exosomes are vesicles, or cellular components, that exist outside of a cell. They are generally understood as having been released from cells upon fusion with an intermediate endocytic compartment, or a multivesicular body (MVB).

Credit: dreamerb/Shutterstock.com

When the MVB fuses with the plasma membrane surrounding the cell, intraluminal vesicles are released into the extracellular matrix and become exosomes. Other types of vesicles found outside of cells include apoptotic bodies and ectosomes. These are distinct types of vesicles from the exosome.

History of exosomes

Extracellular vesicles were first identified~50 years ago, and were assumed to be waste products of the cell. In 1983, studies on the loss of transferrin during maturation of reticulocytes into erythrocytes led to the characterization of the exosome.

For the first time, the observation was made that MVBs can produce intraluminal vesicles (ILVs) that are then released into the extracellular space through fusion with the plasma membrane. ILVs were subsequently named exosomes.

Formation of exosomes

Exosomes derive from ILVs, but the process of formation of ILVs is not yet fully understood. There are two mechanisms believed to lead to the formation of ILVs. One is based on endosomal sorting complexes required for transport (ESCRT) machinery, which is comprised of cytosolic protein complexes recruited to endosomes.

The ESCRT machinery forms a cluster of proteins on the endosome, inducing curvature of the membrane to form ILVs. However, ILVs also form in the absence of ESCRTs, through the action of tetraspanin CD63. That mechanism has not yet been characterized.

Which cells release exosome?

Not all cells have endomembrane systems, and therefore not all are able to release exosomes. B cells, dendritic cells, and mast cells release exosomes regularly as part of their normal processes. These cells can also be stimulated to release exosomes by interactions with other cells.

Purpose of exosomes

The ultimate destiny of exosomes may be to be engulfed by an acceptor cell, or they may trigger the intended physiological response without being taken up by an acceptor cell. Acceptor cells can take up exosomes by phagocytosis or endocytosis, depending on the size of the vesicle or its cargo.

Exosomes are thought to be a form of communication between cells and transmission of molecules. Recent studies have shown that exosomes have a role in the movement of proteins, lipids, and nucleic acids contributing to disease.

They also may be useful as vectors for drugs because they are made of natural cell membranes, rather than synthetic polymers, and would be tolerated better by the host. One study showed that exosomes can carry MHC-peptide complexes recognized by T lymphocytes. Secretion of those exosomes could promote antitumor immune responses.

Exosomes and disease

Exosomes have been shown to act as vehicles for disease. They may contain cargos such as:

  • amyloid β: a neurodegenerative-associated peptide linked to Alzheimer’s disease
  • tau: a protein associated with a number of neurodegenerative diseases
  • prions: causative agent in spongiform encephalopathies
  • alpha-synuclein: implicated in Parkinson’s disease and related illnesses
  • superoxide dismutase 1: implicated in amyotrophic lateral sclerosis (ALS)

Avenues for further study

Exosomes and their role in the body are poorly understood. Much remains to be learned about the biological significance of exosomes and their role in disease. Better criteria are needed for distinguishing exosomes from other types of vesicles to avoid confusion as these questions are explored.

Further Reading

Last Updated: Feb 26, 2019

Dr. Catherine Shaffer

Written by

Dr. Catherine Shaffer

Catherine Shaffer is a freelance science and health writer from Michigan. She has written for a wide variety of trade and consumer publications on life sciences topics, particularly in the area of drug discovery and development. She holds a Ph.D. in Biological Chemistry and began her career as a laboratory researcher before transitioning to science writing. She also writes and publishes fiction, and in her free time enjoys yoga, biking, and taking care of her pets.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Shaffer, Catherine. (2019, February 26). What are Exosomes?. News-Medical. Retrieved on October 31, 2024 from https://www.news-medical.net/life-sciences/What-are-Exosomes.aspx.

  • MLA

    Shaffer, Catherine. "What are Exosomes?". News-Medical. 31 October 2024. <https://www.news-medical.net/life-sciences/What-are-Exosomes.aspx>.

  • Chicago

    Shaffer, Catherine. "What are Exosomes?". News-Medical. https://www.news-medical.net/life-sciences/What-are-Exosomes.aspx. (accessed October 31, 2024).

  • Harvard

    Shaffer, Catherine. 2019. What are Exosomes?. News-Medical, viewed 31 October 2024, https://www.news-medical.net/life-sciences/What-are-Exosomes.aspx.

Comments

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment
Post

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.

You might also like...
Allen Institute and NYSCF launch collaboration to create inclusive cellular models