Hepatocyte insulin receptor is a calmodulin binding protein and is functionally inhibited by calmidazolium
Insulin-induced autophosphorylation of the insulin receptor and changes in intracellular Ca/sup + +/ have been proposed as possible mediators of insulin action in target tissues. The authors have investigated the association of the 17kD calcium binding protein calmodulin with the insulin receptor solubilized from rat liver plasma membranes. Insulin receptors solubilized in 0.1% Triton X-100 exhibited strong binding to calmodulin-agarose affinity columns in the presence of 100..mu..M calcium and could be eluded with 100..mu..M ethelene glycol-bis (amino ethel ether) Tetra Acetic Acid (EGTA) with an 80% yield in insulin binding activity. In addition, /sup 125/I-Calmodulin was shown to bind to wheat germ agglutinin purified solubilized receptors, was specifically inhibited by EGTA (100 ..mu..M) and/or calmidazolium (10 ..mu..M) and was found to be insulin-dependent (max 10/sup -10/ M insulin). SDS-polyacrylamide gel electrophoresis data suggests that /sup 125/I-calmodulin may be associated with the 92 kD beta-subunit of the insulin receptor, consistent with the cytoplasmic domain of this subunit. While they have confirmed previous reports that the addition of calcium and calmodulin to solubilized insulin receptors preparations produces no demonstrable change in receptor phosphorylation, the addition of the calmodulin inhibitor calmidazolium did show more than 50% inhibition of insulin stimulated receptor phosphorylation, suggesting that a domain of the calmodulin molecule may be very tightly associated with the insulin receptor. These results indicate that calmodulin binds tightly and specifically to the insulin receptor of the hepatocyte and is insulin dependent. The findings also suggest that this interaction may be functionally significant in mediating insulin-induced receptor phosphorylation as well as other insulin actions. Thus, calmodulin may play a major role as an intracellular contributor to insulin action.
- Research Organization:
- Univ. of South Florida, Tampa
- OSTI ID:
- 6985878
- Report Number(s):
- CONF-8606151-; TRN: 86-039109
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Vol. 45:6; Conference: 76. annual meeting of the Federation of American Society for Experimental Biology, Washington, DC, USA, 8 Jun 1986
- Country of Publication:
- United States
- Language:
- English
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INSULIN
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RECEPTORS
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PHOSPHORYLATION
AFFINITY
CALCIUM COMPOUNDS
CATIONS
CELL MEMBRANES
INHIBITION
IODINE 125
LIVER
LIVER CELLS
RATS
TRACER TECHNIQUES
ALKALINE EARTH METAL COMPOUNDS
ANIMAL CELLS
ANIMALS
BETA DECAY RADIOISOTOPES
BODY
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CHARGED PARTICLES
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
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GLANDS
HORMONES
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
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ISOTOPE APPLICATIONS
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KINETICS
MAMMALS
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NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
ORGANS
PEPTIDE HORMONES
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RODENTS
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550201* - Biochemistry- Tracer Techniques