Something old, something new and something borrowed: emerging paradigm of insulin-like growth factor type 1 receptor (IGF-1R) signaling regulation

Cell Mol Life Sci. 2014 Jul;71(13):2403-27. doi: 10.1007/s00018-013-1514-y. Epub 2013 Nov 26.

Abstract

The insulin-like growth factor type 1 receptor (IGF-1R) plays a key role in the development and progression of cancer; however, therapeutics targeting it have had disappointing results in the clinic. As a receptor tyrosine kinase (RTK), IGF-1R is traditionally described as an ON/OFF system, with ligand stabilizing the ON state and exclusive kinase-dependent signaling activation. Newly added to the traditional model, ubiquitin-mediated receptor downregulation and degradation was originally described as a response to ligand/receptor interaction and thus inseparable from kinase signaling activation. Yet, the classical model has proven over-simplified and insufficient to explain experimental evidence accumulated over the last decade, including kinase-independent signaling, unbalanced signaling, or dissociation between signaling and receptor downregulation. Based on the recent findings that IGF-1R "borrows" components of G-protein coupled receptor (GPCR) signaling, including β-arrestins and G-protein-related kinases, we discuss the emerging paradigm for the IGF-1R as a functional RTK/GPCR hybrid, which integrates the kinase signaling with the IGF-1R canonical GPCR characteristics. The contradictions to the classical IGF-1R signaling concept as well as the design of anti-IGF-1R therapeutics treatment are considered in the light of this paradigm shift and we advocate recognition of IGF-1R as a valid target for cancer treatment.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Arrestins / genetics
  • Arrestins / metabolism
  • Humans
  • Molecular Targeted Therapy*
  • Neoplasms / genetics*
  • Neoplasms / pathology
  • Neoplasms / therapy
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphorylation
  • Receptor, IGF Type 1 / genetics*
  • Receptor, IGF Type 1 / metabolism
  • Receptors, G-Protein-Coupled / genetics*
  • Receptors, G-Protein-Coupled / metabolism
  • Signal Transduction
  • Ubiquitin / genetics
  • beta-Arrestins

Substances

  • Arrestins
  • Receptors, G-Protein-Coupled
  • Ubiquitin
  • beta-Arrestins
  • Phosphatidylinositol 3-Kinases
  • Receptor, IGF Type 1