Colony-stimulating factors (CSFs) are secretedglycoproteins that bind to receptor proteins on the surfaces of committed progenitors[1] in the bone marrow, thereby activatingintracellular signaling pathways that can cause the cells toproliferate anddifferentiate into a specific kind ofblood cell (usuallywhite blood cells. For red blood cell formation, seeerythropoietin).
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 ofpost-translational modification.
The name "colony-stimulating factors" comes from the method by which they were discovered.
Hematopoietic stem cells were cultured (seecell culture) 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 ofmacrophages, for instance, was calledmacrophage colony-stimulating factor, for granulocytes, granulocyte colony-stimulating factor, and so on.
The colony-stimulating factors are soluble (permeable), in contrast to other, membrane-bound substances of thehematopoietic microenvironment. This is sometimes used as the definition of CSFs. They transduce byparacrine,endocrine, orautocrine signaling.
Colony-stimulating factors include:
