Showing papers by "Masato Kasuga published in 1986"
TL;DR: Two high molecular weight heat shock proteins, HSP90 and HSP100, were separately purified from extracts of cultured cells of a mouse lymphoma cell line and each of the purified HSPs was shown to coprecipitate with rabbit skeletal muscle actin under actin-polymerizing conditions.
Abstract: Two high molecular weight heat shock proteins, HSP90 (Mr, 90,000) and HSP100 (Mr, 100,000), were separately purified from extracts of cultured cells of a mouse lymphoma cell line, L5178Y. Both of the HSPs exist in homodimeric form under physiological conditions. Their physicochemical properties are quite similar to each other. Each of the purified HSPs was shown to coprecipitate with rabbit skeletal muscle actin under actin-polymerizing conditions. Both HSP90 and HSP100 increased the low-shear viscosity of filamentous actin solutions in a dose-dependent manner, which suggests that these HSPs cross-link actin filaments. Although some molecular properties and the effects described above on actin solution of HSP90 and HSP100 resemble those of alpha-actinin, the HSPs were distinguished from alpha-actinin by various means, including visualization of molecular shapes by electron microscopy with the aid of the low-angle rotary shadowing technique. Immunofluorescence staining by specific antisera against HSP90 revealed that HSP90 was localized in ruffling membranes in addition to the cytoplasmic space.
331 citations
TL;DR: Although the specific values of IGF-I binding to erythrocytes were decreased or increased in parallel with those of insulin, the degrees of decrease or increase were much smaller, suggesting that the expression of insulin receptors and that of IGF -I receptors are discordant.
Abstract: The scarcity of purified materials has prevented studies of the mechanism of insulin-like growth factor I (IGF-I) action. Recently, an IGF-I analog, Thr59-IGF-I, was synthesized by recombinant DNA technology. We found that this analog had binding characteristics similar to those of natural IGF-I in the radioreceptor assay system. We used this analog to characterize human erythrocyte IGF-I receptors as follows. Erythrocytes from 33 normal subjects specifically bound 6.9 +/- 0.7% (mean +/- SD)/2.8 X 10(9) cells/ml. Scatchard analysis of the binding data showed that the total number of receptors per erythrocyte was 13, and the affinity constant was 1.26 X 10(9) M-1, similar to that of other human IGF-I receptors previously reported. We also examined IGF-I receptors in patients with insulin receptor abnormalities. Although the specific values of IGF-I binding to erythrocytes were decreased or increased in parallel with those of insulin, the degrees of decrease or increase were much smaller. This suggests that the expression of insulin receptors and that of IGF-I receptors are discordant.
19 citations