Detection and Identification of Proteins Related to the Hereditary Dwarfism of the rdw Rat*

Abstract

Proteins having relations to hereditary dwarfism of the rdw rat (gene symbol: rdw) were searched for in various tissues of the rat with an improved two-dimensional gel electrophoresis technique followed by immunoblotting and microsequencing. Tissues inspected were cerebral cortex, cerebellum, brain trunk, hypothalamus, pituitary, thyroid gland, liver, testis, spleen, and thymus. Only pituitary and thyroid glands among those tissues showed abnormalities in protein contents. GH and PRL contents in the rdw pituitary were much less than in the normal one, which in the former were 1/15 and less than 1/30 times as much as in the latter, respectively, but the abnormalities in the rdw thyroid were far more serious than in the pituitary. At least 18 protein levels in the rdw thyroid were above, and 17 were below the normal. Those identified among the increased proteins were endoplasmin (GRP94), immunoglobulin heavy chain binding protein (BiP/GRP78), and heat shock protein 70 (hsp70), the contents of which respectively were 40 times, 10 times and more than 50 times as much in the rdw thyroid as in the normal tissue. Because BiP and endoplasmin are known to be ER resident proteins, and because all three belong to a chaperone protein family, accumulation of these proteins in the rdw thyroid suggests that protein folding and secreting disorders underlie the hypothyroidism of the rdw rat.

Rescue from Dwarfism by Thyroid Function Compensation in rdw Rats

“…Based on the findings of in this study, and the results of our previous studies, such as protein analysis [17], morphological findings [19], and sequencing of the entire Tg cDNA from the rdw rat [9,12], we concluded that the synthesized abnormal Tg forms a complex with the chaperons and accumulates in the ER, resulting in dramatic swelling of the ER. As a result, the rdw rat has severe hypothyroidism and dwarfism.…”

“…Subsequently, it was revealed that the expressions of mRNA (Received 28 February 2005 / Accepted 1 September 2005 Address corresponding: S. Furudate, Department of Laboratory Animal Science, Japan of growth hormone (GH) and prolactin (PRL) in the rdw rat are drastically decreased [18,21]. In addition, the GH and PRL proteins in the rdw rat are decreased to a level 1/30 to 1/100 of those of a normal rat [17,18].In the rdw rat, the thyroxine (T 4 ) levels in serum are drastically decreased [19,21,23], but the thyroid-stimu- …”

“…In addition, two-dimensional gel electrophoresis studies conducted on various tissues of the rdw rat have revealed that the rdw thyroid glands have a very serious abnormality in protein content [17]. In the rdw thyroid gland, the content of endoplasmic reticulum (ER) resident chaperons is significantly increased, and electron microscopic analysis conducted on the rdw rat determined beyond question that it has an abnormal thyroid gland, as indicated by missing secretory granules, a dilated ER, and nuclear dislocation [19].…”

Pituitary-Adrenal Functions in a Hereditary Hypothyroid (rdw) Rat

“…Previous reports have mainly examined reproductive functions [2][3][4] and the abnormalities of the thyroglobulin gene [1,9,10]. There has been no study investigating the pituitary-adrenal functions in the rdw rat, although hypothyroidism is known to cause adrenal dysfunction.…”

Gerbils of a seizure‐sensitive strain have a mitochondrial inner membrane protein with different isoelectric points from those of a seizure‐resistant strain

“…Profiles of the limited digestion of proteins by peptidases were analyzed by the method originally developed by Cleveland et al [10] with some modification [11]. We have improved this method by burying protease(s) homogeneously in stacking gels electrophoretically prior to loading gel pieces in which a protein to be analyzed was present.…”