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Identification of a biologically functional novel IL-1 beta-specific receptor on adult rat hepatocytes
T Kohira1, K Matsumoto, A Ichihara
1Division of Biochemistry, Osaka University Medical School.
Cellular receptors for interleukin-1 (IL-1) bind both IL-1 alpha and IL-1 beta with the same affinity, and both IL-1 alpha and IL-1 beta have the same potential in most IL-1-related biological responses, despite their low amino acid sequence homology (26%). Here, we identified and partially characterized a biologically functional novel IL-1 receptor, which specifically binds IL-1 beta but not IL-1 alpha, present on adult rat hepatocytes. Scatchard analysis of the binding of 125I-IL-1 beta to isolated adult rat hepatocytes showed that rat hepatocytes express a high affinity receptor for IL-1 beta with a Kd value of 9.6 x 10(-10) M at 1,200 sites/cell, whereas there was no specific binding of 125I-IL-1 alpha at least up to 10 ng/ml. Specific binding of 125I-IL-1 beta to hepatocytes was competitively inhibited by unlabeled IL-1 beta, but not by IL-1 alpha. Cross-linking of 125I-IL-1 beta to plasma membranes of hepatocytes indicated that the receptor for IL-1 beta has an apparent molecular mass of 80-100 kDa. Moreover, the formation of a cross-linked complex between 125I-IL-1 beta and the receptor was specifically inhibited by unlabeled IL-1 beta, but not by IL-1 alpha. Finally, DNA synthesis of adult rat hepatocytes was specifically inhibited by IL-1 beta, but not by IL-1 alpha, in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)
Cellular receptors for interleukin-1 (IL-1) bind both IL-1 alpha and IL-1 beta with the same affinity, and both IL-1 alpha and IL-1 beta have the same potential in most IL-1-related biological responses, despite their low amino acid sequence homology (26%). Here, we identified and partially characterized a biologically functional novel IL-1 receptor, which specifically binds IL-1 beta but not IL-1 alpha, present on adult rat hepatocytes. Scatchard analysis of the binding of 125I-IL-1 beta to isolated adult rat hepatocytes showed that rat hepatocytes express a high affinity receptor for IL-1 beta with a Kd value of 9.6 x 10(-10) M at 1,200 sites/cell, whereas there was no specific binding of 125I-IL-1 alpha at least up to 10 ng/ml. Specific binding of 125I-IL-1 beta to hepatocytes was competitively inhibited by unlabeled IL-1 beta, but not by IL-1 alpha. Cross-linking of 125I-IL-1 beta to plasma membranes of hepatocytes indicated that the receptor for IL-1 beta has an apparent molecular mass of 80-100 kDa. Moreover, the formation of a cross-linked complex between 125I-IL-1 beta and the receptor was specifically inhibited by unlabeled IL-1 beta, but not by IL-1 alpha. Finally, DNA synthesis of adult rat hepatocytes was specifically inhibited by IL-1 beta, but not by IL-1 alpha, in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)