Identification of IGF-1 receptors in primitive vertebrates.
This is the first report of the existence of insulin-like growth factor (IGF-1) receptors in three representatives of lower vertebrates: the osteichtyes, chondrichtyes and cyclostomi. Competitive binding studies and affinity labelling of brain membranes from Cottus scorpius (sea scorpion), Raja clavata (ray) and Myxine glutinosa (atlantic hagfish) identified a mammalian type 1 or IGF-1 receptor by its binding specificity and the molecular size of its alpha-subunit. IGF-1 and IGF-2 are almost equally potent in displacing receptor-bound 125I-IGF-1 or 125I-IGF-2, and the proteins labeled with both tracers have a molecular size of 100,000-120,000 under reducing conditions. There was no evidence for the presence of a mammalian type 2 or IGF-2/mannose 6-phosphate receptor in brains of Cottus, Raja or Myxine. In all three species the binding of 125I-IGF-1 and 125I-IGF-2 was significantly higher in brain compared with liver and gastrointestinal tract, and the IGF-1 receptor could only be identified with certainty in Raja liver. It is concluded that the brain of three lower vertebrates express mammalian IGF-1 receptors, whereas IGF-2-mannose 6-phosphate receptors could not be detected.
Drakenberg
K
K
Department of Pathology, Karolinska Institute, Stockholm, Sweden.
Sara
V R
VR
Falkmer
S
S
Gammeltoft
S
S
Maake
C
C
Reinecke
M
M
D000345:Affinity Labels; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D004064:Digestive System / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005399:Fishes / Q000378:metabolism*; D006196:Hagfishes / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008970:Molecular Weight; D017526:Receptor, IGF Type 1 / Q000378:metabolism* / Q000502:physiology; D012860:Skates, Fish / Q000378:metabolism*; D013002:Somatomedins / Q000378:metabolism; D013045:Species Specificity
D000345:Affinity Labels; D013002:Somatomedins; D017526:Receptor, IGF Type 1