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Evidence for induction by thyroid hormone of cytosolic proteins which control mitochondrial protein synthesis
Abstract:
The effect of thyroid hormone on the generation of modulators of mitochondrial protein synthesis was investigated. The modulators were present in the 150,000 X g supernatant (S-150) prepared from Wistar rat liver and kidney. In young rats (50 g BW), a stimulator was found in liver, and an inhibitory modulator was present in kidney tissue. Generation of these modulators was stimulated by T4 administration to the animals. In aged rats (200 g BW), the production of an inhibitory modulator in both liver and kidney was stimulated by thyroid hormone administration. Both the stimulatory and inhibitory modulators were inactivated by pretreatment with trypsin. The mol wt of these modulators was estimated by gel filtration study, and for both the stimulatory and inhibitory modulator proteins was approximately 10,000. The results suggested that thyroid hormone regulates mitochondrial protein synthesis through the stimulation of synthesis of mitochondrial protein synthesis modulators and that the tissue-specific modulators (stimulatory in liver and inhibitory in kidney) can be produced in young animals. In aged animals, however, it is postulated that thyroid hormone stimulates biosynthesis of an inhibitory modulator in both liver and kidney.
Insights
Thyroid hormone influences mitochondrial protein synthesis by regulating specific modulators. These modulators, stimulatory in young rat liver and inhibitory in kidney, become inhibitory in both tissues in aged rats.
Area of Science:
- Biochemistry
- Endocrinology
- Molecular Biology
Background:
- Thyroid hormones are crucial regulators of metabolism.
- Mitochondrial protein synthesis is essential for cellular energy production.
- The role of thyroid hormone in modulating mitochondrial protein synthesis is not fully understood.
Purpose of the Study:
- To investigate the effect of thyroid hormone on the generation of modulators of mitochondrial protein synthesis.
- To characterize these modulators in young and aged Wistar rats.
- To determine the tissue-specific roles of these modulators.
Main Methods:
- Preparation of 150,000 x g supernatant (S-150) from Wistar rat liver and kidney.
- Administration of thyroxine (T4) to young and aged rats.
- Enzymatic inactivation with trypsin and molecular weight estimation by gel filtration.
Main Results:
- In young rats, liver S-150 contained a stimulatory modulator, while kidney S-150 had an inhibitory modulator; T4 administration stimulated their generation.
- In aged rats, thyroid hormone administration stimulated the production of an inhibitory modulator in both liver and kidney.
- Both stimulatory and inhibitory modulators were trypsin-inactivated and had an approximate molecular weight of 10,000.
Conclusions:
- Thyroid hormone regulates mitochondrial protein synthesis by modulating the synthesis of specific protein modulators.
- Tissue-specific modulators (stimulatory in liver, inhibitory in kidney) are produced in young animals.
- In aged animals, thyroid hormone appears to stimulate the biosynthesis of an inhibitory modulator in both liver and kidney.