Microvesicles
Encyclopedia
Microvesicles are fragments of plasma membrane ranging from 50 nm to 1000 nm shed from almost all cell types. Microvesicles play a role in intercellular communication and can deliver mRNA
, miRNA, and proteins between cells. They have been implicated in the process of cancer tumor immune suppression, metastasis, tumor-stroma interactions and angiogenesis
along with having a role in tissue regeneration. They originate directly from the plasma membrane of the cell and reflect the antigenic content of the cells from which they originate.
; an outward-directed pump, or floppase; and a lipid scramblase
,
responsible for non-specific redistribution of lipids across the membrane.
After cell stimulation, including apoptosis, a subsequent cytosolic Ca2+ increase promotes the loss of phospholipid asymmetry of the plasma membrane, subsequent phosphatidylserine exposure and a transient phospholipidic imbalance between the external leaflet at the expense of the inner leaflet leading to blebbing of the plasma membrane and microvesicles release.
Messenger RNA
Messenger RNA is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes. Here, the nucleic acid polymer is translated into a polymer of amino acids: a protein...
, miRNA, and proteins between cells. They have been implicated in the process of cancer tumor immune suppression, metastasis, tumor-stroma interactions and angiogenesis
Angiogenesis
Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over terminology, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for the formation of new blood...
along with having a role in tissue regeneration. They originate directly from the plasma membrane of the cell and reflect the antigenic content of the cells from which they originate.
Mechanism of shedding of MV
Under physiologic conditions, the plasma membrane of cells has an asymmetric distribution of phospholipids. Aminophospholipids, phosphatidylserine and phosphatidilethanolammine are specifically sequestered in the inner leaflet of the membrane. The transbilayer lipid distribution is under the control of three phospholipidic pumps: an inward-directed pump, or flippaseFlippase
Flippases are a family of transmembrane lipid transporter enzymes located in the membrane responsible for aiding the movement of phospholipid molecules between the two leaflets that compose a cell's membrane...
; an outward-directed pump, or floppase; and a lipid scramblase
Scramblase
Scramblase is a protein responsible for the translocation of phospholipids between the two monolayers of a lipid bilayer of a cell membrane. In humans, phospholipid scramblases constitute a family of five homologous proteins that are named as hPLSCR1–hPLSCR5. Scramblases are members of the...
,
responsible for non-specific redistribution of lipids across the membrane.
After cell stimulation, including apoptosis, a subsequent cytosolic Ca2+ increase promotes the loss of phospholipid asymmetry of the plasma membrane, subsequent phosphatidylserine exposure and a transient phospholipidic imbalance between the external leaflet at the expense of the inner leaflet leading to blebbing of the plasma membrane and microvesicles release.