Growth factor (biology)

A biological growth factor is a signaling ligand that modulates cell growth, cell proliferation, cell differentiation or cell survival. Many are proteins recognized by cell-surface receptors. The resulting response depends on which receptors and intracellular pathways the target cell contains.

For example, epidermal growth factor engages the epidermal growth factor receptor, while FGF8 acts through FGF receptors. These interactions can alter gene expression through signal transduction. The ligand and its receptor are separate molecular components, so their distribution jointly determines where a signal can act.^[ref]

Neuregulin 1 is a signaling protein ligand acting through ErbB receptors. The human NRG1 gene produces several protein isoforms through alternative promoter usage and alternative splicing; these products differ in their structure and tissue distribution.^[ref]

Its developmental roles include ventricular trabeculation. A targeted mutation in mice revealed that loss of neuregulin 1 disrupts normal development of several organ systems, providing experimental evidence of requirement rather than expression alone.^[ref]

A fibroblast growth factor is a member of a signalling-protein family whose receptor interactions regulate processes including cell proliferation, survival and cell differentiation. Many members act through FGF receptors, a class of receptor tyrosine kinases. The historical family name does not limit their targets to fibroblasts. ^[ref]

FGF8 provides a developmental example: localized production, receptor distribution and surrounding regulatory interactions help determine where cells respond. A signal's spatial effect depends on more than its concentration at the source. Detecting FGF expression therefore identifies a potential signalling input, while receptor activation and a subsequent change in cell fate require separate evidence.

FGF8, or fibroblast growth factor 8, is a signaling protein in the fibroblast growth factor family. It acts through FGF receptors, connecting extracellular ligand recognition to intracellular signal transduction.

The human FGF8 gene has alternatively spliced transcripts. Studies of the corresponding mouse and chick genes connect its expression with limb and midbrain development, gastrulation and other aspects of morphogenesis. These spatial and temporal roles make it a useful example of how a biological growth factor contributes to embryonic development.^[ref]

PDGF means platelet-derived growth factor, a family of signaling protein ligands for PDGFR. Members form protein dimers, including the classical AA, AB and BB combinations.^[ref] Ligand binding can bring two receptors together and activate their receptor tyrosine kinase activity.^[ref]

Release from platelets links PDGF to local tissue responses after injury. Nearby connective-tissue cells can respond by entering cell proliferation.^[ref]

Epidermal growth factor is a protein ligand for the epidermal growth factor receptor.

Binding can promote receptor activation and downstream phosphorylation pathways affecting growth and cell differentiation. Ligand availability, receptor abundance and intracellular pathway state jointly determine the response; receptor binding alone does not guarantee completed cell division. ^[ref]

An oocyte-derived signalling protein that activates the epidermal growth factor receptor in neighbouring Drosophila melanogaster follicle cells, helping establish ovarian polarity.

A mammalian biological growth factor encoded by the Igf2 gene. Parent-of-origin-dependent expression in mice makes it an important experimental system for genomic imprinting.