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 residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
that in humans is encoded by the ''MFGE8''
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
.
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 7–13 nm in diameter, a beta sheet (β-sheet) secondary structure (known as cross-β) and ability to be stained by particular dyes, such as Congo red. In the huma ...
fragment of MFGE8 known as medin accumulates in the aorta with
aging.
MFGE8 in the vasculature of adults can induce recovery from
ischemia by facilitating
angiogenesis.
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 ap ...
(PS) binding domain, as well as an
Arginine-
Glycine
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid ( carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinog ...
-
Aspartic acid motif, which enables the binding to
integrins
Integrins are transmembrane receptors that facilitate 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
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes ( morphology) and death. These changes incl ...
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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