Colony-stimulating factors (CSFs) are secreted
glycoprotein
Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycos ...
s that bind to receptor proteins on the surfaces of
hemopoietic stem cells, thereby activating
intracellular signaling pathways that can cause the cells to
proliferate and
differentiate into a specific kind of
blood cell (usually
white blood cells. For red blood cell formation, see
erythropoietin
Erythropoietin (; EPO), also known as erythropoetin, haematopoietin, or haemopoietin, is a glycoprotein cytokine secreted mainly by the kidneys in response to cellular hypoxia; it stimulates red blood cell production (erythropoiesis) in the bo ...
).
They may be synthesized and administered exogenously. However, such molecules can at a latter stage be detected, since they differ slightly from the endogenous ones in, e.g., features of
post-translational modification.
Etymology
The name "colony-stimulating factors" comes from the method by which they were discovered.
Hematopoietic stem cells were cultured (see
cell culture
Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This te ...
) on a so-called semisolid matrix, which prevents cells from moving around, so that, if a single cell starts proliferating, all of the cells derived from it will remain clustered around the spot in the matrix where the first cell was originally located. These are referred to as "colonies". Therefore, it was possible to add various substances to cultures of hemopoietic stem cells and then examine which kinds of colonies (if any) were "stimulated" by them.
The substance that was found to stimulate formation of colonies of
macrophages, for instance, was called
macrophage colony-stimulating factor, for granulocytes, granulocyte colony-stimulating factor, and so on.
Mechanism
The colony-stimulating factors are soluble (permeable), in contrast to other, membrane-bound substances of the
hematopoietic microenvironment. This is sometimes used as the definition of CSFs. They transduce by
paracrine,
endocrine
The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neu ...
, or
autocrine signaling.
Examples
Colony-stimulating factors include:
* –
macrophage colony-stimulating factor
* –
Granulocyte macrophage colony-stimulating factors (also called GM-CSF and
sargramostim)
* –
Granulocyte colony-stimulating factors (also called G-CSF and
filgrastim)
*
Interleukin 3
* Synthetic –
Promegapoietin
Clinical uses
* Bone marrow stimulation
* Stem cell mobilization
References
External links
*
Cytokines
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