Growth Factor Receptors

Growth factor receptors are cell surface proteins that bind secreted polypeptide growth factors — such as epidermal growth factor, platelet-derived growth factor, and insulin-like growth factors — and convert that binding into intracellular signals controlling cell proliferation, survival, differentiation, and migration. Most are single-pass transmembrane proteins with intrinsic or associated kinase activity.

Definition

A growth factor receptor is a cell surface receptor that binds a specific secreted growth factor and transduces that signal — usually via an intracellular kinase activity — into programs of cell growth, division, survival, or differentiation.

Scope

The entry covers the polypeptide growth factor receptor families, the ligand-binding event that activates them, the downstream pathways they engage (notably the RAS-MAPK and PI3K-AKT cascades), and the general logic by which a growth signal at the cell surface becomes a proliferative or survival response. It treats growth factor receptors as a biochemical topic; it is not clinical guidance.

Core questions

• Which receptor families mediate responses to the major polypeptide growth factors?
• How does ligand binding activate the receptor's intracellular signaling output?
• Which downstream pathways translate a growth factor signal into proliferation or survival?
• How is growth factor signaling normally restrained, and what happens when it is not?

Key concepts

• Polypeptide growth factors as ligands
• Receptor autophosphorylation
• Adaptor and effector recruitment
• RAS-MAPK proliferative pathway
• PI3K-AKT survival pathway
• Insulin and IGF receptors
• Signal termination and receptor internalization

Key theories

Receptor activation by ligand-induced oligomerization

Binding of a growth factor reorganizes or dimerizes its receptor, juxtaposing intracellular catalytic domains so they can autophosphorylate and recruit signaling proteins, thereby coupling an external growth cue to internal kinase cascades.

Mechanisms

A secreted growth factor binds the extracellular region of its receptor, promoting dimerization or conformational reorganization that activates the receptor's cytoplasmic kinase activity. The receptor autophosphorylates on tyrosine residues, creating docking sites for adaptor proteins (such as GRB2) and enzymes containing SH2 and PTB domains. These recruit guanine-nucleotide exchange factors and lipid kinases, engaging the RAS-RAF-MEK-ERK (MAPK) cascade that drives proliferation and the PI3K-AKT axis that promotes survival and metabolism. The insulin and IGF-1 receptors are constitutive disulfide-linked dimers that use a phosphorylated docking-protein (IRS) relay. Signaling is normally restrained by phosphatases, by receptor endocytosis and degradation, and by negative-feedback loops.

Clinical relevance

Because growth factor receptors govern proliferation and survival, their constitutive activation through overexpression or mutation is a recurring feature of cancers, and several receptor families are targets of approved therapeutics. This entry describes the underlying biology and does not provide diagnostic or treatment recommendations.

History

The recognition in the 1980s that the epidermal growth factor receptor and related proteins carry intrinsic tyrosine kinase activity — and that some viral oncogenes are derived from such receptors — linked growth factor signaling to cancer and motivated the molecular dissection of the field. Subsequent work mapped the adaptor-and-cascade architecture connecting receptors to RAS-MAPK and PI3K-AKT, and detailed the distinctive insulin/IGF receptor relay.

Key figures

• Axel Ullrich
• Joseph Schlessinger
• C. Ronald Kahn
• Michael Karin

Seminal works

• ullrich-1990
• lemmon-2010
• chang-2001

Frequently asked questions

Are all growth factor receptors tyrosine kinases?

Most well-characterized polypeptide growth factor receptors are receptor tyrosine kinases or are closely coupled to kinase activity, but the broader category also includes receptors that signal through associated kinases rather than an intrinsic catalytic domain.

How does one growth factor produce both proliferation and survival signals?

An activated receptor recruits multiple effectors at once; the RAS-MAPK branch chiefly drives proliferation while the PI3K-AKT branch promotes survival and metabolism, so a single binding event can engage several outputs in parallel.