Milk fat globule-EGF factor 8 protein (Mfge8), also known as lactadherin, is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
that in humans is encoded by the ''MFGE8''
gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
.
Species distribution
Mfge8 is a secreted protein found in vertebrates, including mammals as well as birds.
Function
MFGE8 may function as a cell adhesion protein to connect smooth muscle to elastic fibers in arteries.
An
amyloid
Amyloids are aggregates of proteins characterised by a fibrillar morphology of typically 7–13 nm in diameter, a β-sheet secondary structure (known as cross-β) and ability to be stained by particular dyes, such as Congo red. In the human ...
fragment of MFGE8 known as medin accumulates in the aorta with
aging
Ageing (or aging in American English) is the process of becoming Old age, older until death. The term refers mainly to humans, many other animals, and fungi; whereas for example, bacteria, perennial plants and some simple animals are potentiall ...
.
MFGE8 in the vasculature of adults can induce recovery from
ischemia
Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems ...
by facilitating
angiogenesis
Angiogenesis is the physiological process through which new blood vessels form from pre-existing vessels, formed in the earlier stage of vasculogenesis. Angiogenesis continues the growth of the vasculature mainly by processes of sprouting and ...
.
It has been suggested that antagonizing MFGE8-induced angiogenesis could be a way of fighting cancer.
MFGE8 contains a
phosphatidylserine
Phosphatidylserine (abbreviated Ptd-L-Ser or PS) is a phospholipid and is a component of the cell membrane. It plays a key role in cell cycle signaling, specifically in relation to apoptosis. It is a key pathway for viruses to enter cells via a ...
(PS) binding domain, as well as an
arginine-glycine-aspartic acid motif, which enables the binding to
integrins
Integrins are transmembrane receptors that help cell–cell and cell– extracellular matrix (ECM) adhesion. Upon ligand binding, integrins activate signal transduction pathways that mediate cellular signals such as regulation of the cell cycle, ...
. MFGE8 binds PS, which is exposed on the surface of
apoptotic cells.
Opsonization
Opsonins are extracellular proteins that, when bound to substances or cells, induce phagocytes to phagocytose the substances or cells with the opsonins bound. Thus, opsonins act as tags to label things in the body that should be phagocytosed (i.e. ...
of the apoptotic cells and binding to integrins on the surface of
phagocytic cells, mediates the engulfment of the dead cell.
References
Further reading
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