Human hepatocyte-stimulating factor-III and interleukin-6 are structurally and immunologically distinct but regulate the production of the same acute phase plasma proteins.
Human squamous carcinoma (COLO-16) cells synthesize and secrete hepatocyte-stimulating factor-III (HSF-III), a glycoprotein with Mr = 39,000, which stimulates the synthesis of several acute phase plasma proteins in human hepatoma (HepG2) cells. The qualitative response of HepG2 cells to HSF-III is essentially the same as that elicited by human recombinant interleukin-6 (IL-6). Although similar in hepatocyte-stimulating activity, HSF-III and IL-6 are distinct molecules which differ not only in size and charge but also in immunologic properties: no cross-recognition of HSF-III and IL-6 occurs using neutralizing antibodies against IL-6 and HSF-III, respectively. In addition, Northern blot hybridization of IL-6 cDNA to mRNA from COLO-16 cells revealed no detectable IL-6 message. HSF-III does not compete for binding to the IL-6 receptors suggesting that HepG2 cells carry receptors specific for each hormone. Both receptor types may trigger similar intracellular processes explaining the identical regulation of acute phase protein expression.
Baumann
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Department of Molecular and Cellular Biology, Roswell Park Memorial Institute, Buffalo, New York 14263.
Won
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Jahreis
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D000209:Acute-Phase Proteins / Q000096:biosynthesis* / Q000097:blood; D001667:Binding, Competitive; D006528:Carcinoma, Hepatocellular / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000378:metabolism; D005340:Fibrinogen / Q000096:biosynthesis; D006242:Haptoglobins / Q000096:biosynthesis; D006801:Humans; D015850:Interleukin-6; D007378:Interleukins / Q000235:genetics / Q000494:pharmacology*; D007700:Kinetics; D008113:Liver Neoplasms / Q000378:metabolism; D008970:Molecular Weight; D009000:Monocytes; D009693:Nucleic Acid Hybridization; D011506:Proteins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000032:analysis; D011971:Receptors, Immunologic / Q000378:metabolism; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D000209:Acute-Phase Proteins; D006242:Haptoglobins; D015850:Interleukin-6; D007378:Interleukins; D011506:Proteins; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D019947:Receptors, Interleukin-6; D011994:Recombinant Proteins; D005340:Fibrinogen