Characterisation of receptors for IGF-I and insulin; evidence for hybrid insulin/IGF-I receptor in human coronary artery endothelial cells

Growth Horm IGF Res. 2006 Aug;16(4):258-66. doi: 10.1016/j.ghir.2006.06.003. Epub 2006 Aug 17.


Objective: Coronary artery disease is a prevalent cause of morbidity and mortality in diabetes. Little is known about insulin-like growth factor-I receptors (IGF-IR) and insulin receptors (IR) in human coronary endothelium. Our aim was to characterize IGF-IR and IR in human coronary artery endothelial cells (HCAEC).

Design: Cultured human coronary artery endothelial cells were used. Gene expression was measured by quantitative real-time RT-PCR analysis and receptor affinity by ligand binding. Receptor protein, phosphorylation of IGF-IR and IR beta-subunit as well as the presence of hybrid insulin receptor/Insulin-like growth factor-I receptor (Hybrid IR/IGF-IR) was analyzed by immunoprecipitation and Western blot. Postreceptor effects of insulin and IGF-I were assed by (3)H-thymidine incorporation.

Results: The gene expression of IGF-IR was several folds higher than that of IR. and insulin receptor isoform A (IR-A) was 20-fold more expressed than insulin receptor isoform B (IR-B) in HCAEC. The specific binding of (125)I-IGF-I was higher than that of (125)I-insulin. Insulin and the new long acting insulin analog, glargine, interacted with the IGF-IR with over thousand and 100-fold less potency than IGF-I itself, whereas IGF-II had 6 times lower potency than IGF-I. Phosphorylation of the IGF-IR beta-subunit was obtained by concentrations of 10(-10)-10(-8)M IGF-I, 10(-6)M of insulin, inconsistently by 10(-8)M insulin and not at all by 10(-10)-10(-9)M insulin. The IR beta-subunit was phosphorylated by insulin and IGF-I at concentrations of 10(-9)-10(-8)M. When immunoprecipitating with specific monoclonal anti-IR or anti-IGF-IR alpha-subunit antibodies we found bands situated in slightly different positions suggesting the presence of Hybrid IR/IGF-IR. IGF-I, IGF-II and insulin (10(-9)-10(-7)M) had no significant effect on (3)H-thymidine incorporation into DNA.

Conclusions: Human coronary endothelial cells express more IGF-IR than IR, mainly IR-A, and also Hybrid IR/IGF-IR. Both IGF-I and insulin phosphorylate their receptors, but only IGF-I seems to phosphorylate Hybrid IR/IGF-IR. Our study provides experimental evidence for a possible role of IGF-IR, IR and Hybrid IR/IGF-IR in human coronary artery endothelial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Cells, Cultured
  • Coronary Vessels / cytology
  • Coronary Vessels / metabolism*
  • DNA / biosynthesis
  • Endothelial Cells / metabolism*
  • Humans
  • Immunoprecipitation / methods
  • Insulin / metabolism
  • Insulin-Like Growth Factor I / metabolism*
  • Mutant Chimeric Proteins / isolation & purification
  • Mutant Chimeric Proteins / metabolism*
  • Protein Binding
  • Radioligand Assay / methods
  • Receptor, IGF Type 1 / metabolism*
  • Receptor, Insulin / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction / methods
  • Thymidine / analysis


  • Insulin
  • Mutant Chimeric Proteins
  • Insulin-Like Growth Factor I
  • DNA
  • Receptor, IGF Type 1
  • Receptor, Insulin
  • Thymidine