Differences between migrasome, a 'new organelle', and exosome

Abstract

The migrasome is a new organelle discovered by Professor Yu Li in 2015. When cells migrate, the membranous organelles that appear at the end of the retraction fibres are migrasomes. With the migration of cells, the retraction fibres which connect migrasomes and cells finally break. The migrasomes detach from the cell and are released into the extracellular space or directly absorbed by the recipient cell. The cytoplasmic contents are first transported to the migrasome and then released from the cell through the migrasome. This release mechanism, which depends on cell migration, is named 'migracytosis'. The main components of the migrasome are extracellular vesicles after they leave the cell, which are easy to remind people of the current hot topic of exosomes. Exosomes are extracellular vesicles wrapped by the lipid bimolecular layer. With extensive research, exosomes have solved many disease problems. This review summarizes the differences between migrasomes and exosomes in size, composition, property and function, extraction method and regulation mechanism for generation and release. At the same time, it also prospects for the current hotspot of migrasomes, hoping to provide literature support for further research on the generation and release mechanism of migrasomes and their clinical application in the future.

Keywords: exosomes; extracellular vesicles; migracytosis; migrasomes; organelle.

FIGURE 1

The composition of migrasomes and exosomes is different. (A) Composition of exosomes and migrasomes. (B) Differences and commonalities between exosomes and migrasomes in terms of components.

FIGURE 2

The functions of migrasomes and exosomes are different. (A) Five functions of exosomes: ① Exosomes act as ligands and directly bind to receptors on the surface of recipient cells. ② Exosomes can also only undertake the task of nucleic acids and proteins. ③ Exosomes transport waste products from cell damage to maintain a stable environment. ④ Exosomes can promote the generation of new cellular motion paths, such as cell migration. ⑤ Exosomes secreted by tumour cells contain factors that bind to their own receptors, such as TGFβ1, which can promote the growth of tumour cells. (B) Three functions of migrasomes: ① Migrasomes carry signalling molecules. When migrasomes leave the cells, they are lysed, and the signalling molecules are released and then bind to receptors on the surface of recipient cells. ② Migrasomes can dispose of damaged mitochondria. Damaged mitochondria are transported to the migrasomes. Three proteins, KIF5B, Drp1 and Myo19, are required for this process. KIF5B transports mitochondria to the plasma membrane, Myo19 tightly binds mitochondria to cortical actin, and Drp1 mediates final fission. ③ Migrasomes can mediate the transverse transfer of contents between cells, such as proteins and nucleic acids. Cell contents are first transported to the migrasomes and then released from the cell by the migrasome. Finally, cell contents and migrasomes are phagocytosed by recipient cells.

FIGURE 3

The extraction methods for migrasomes and exosomes. (A) Density gradient centrifugation for exosomes. (B) Density gradient centrifugation for migrasomes. (C) Isolation of migrasomes by centrifugation and filtration.