Immunological Demonstration of the Accumulation of Insulin, but not Insulin Receptors, in Nuclei of Insulin-Treated Cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 86; no. 17; pp. 6640 - 6644
• Main Authors: Soler, Alejandro Peralta, Thompson, Kathleen A., Smith, Robert M., Jarett, Leonard
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.09.1989; National Acad Sciences
• Subjects: 550201 - Biochemistry- Tracer Techniques; AMINO ACIDS; Aminoacids, peptides. Hormones. Neuropeptides; Analytical, structural and metabolic biochemistry; ANIMAL CELLS; ANIMALS; Antibodies; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; BIOCHEMISTRY; Biological and medical sciences; CARBOXYLIC ACIDS; CELL CONSTITUENTS; CELL MEMBRANES; Cell nucleus; Cells; Cells, Cultured; Cellular immunity; CHEMISTRY; CHROMATIN; CONNECTIVE TISSUE CELLS; CYTOCHEMISTRY; DAYS LIVING RADIOISOTOPES; DISEASES; DOSE-RESPONSE RELATIONSHIPS; ELECTRON CAPTURE RADIOISOTOPES; ELECTRON MICROSCOPY; FIBROBLASTS; Fundamental and applied biological sciences. Psychology; GENE REGULATION; Genes - drug effects; Hepatocellular carcinoma; Hepatocytes; HEPATOMAS; Heterochromatin; HORMONES; HYDROXY ACIDS; Immunohistochemistry; INSULIN; Insulin - immunology; Insulin - metabolism; Insulin - pharmacology; INTERMEDIATE MASS NUCLEI; IODINE 125; IODINE ISOTOPES; ISOTOPES; Kinetics; LABELLED COMPOUNDS; Liver - cytology; Liver - drug effects; Liver - metabolism; Liver Neoplasms, Experimental - metabolism; MAMMALS; MEMBRANE PROTEINS; MEMBRANES; Mice; MICROSCOPY; Microscopy, Electron; NEOPLASMS; NUCLEI; ODD-EVEN NUCLEI; ORGANIC ACIDS; ORGANIC COMPOUNDS; PEPTIDE HORMONES; PROTEINS; RADIOISOTOPES; RATS; Receptor, Insulin - genetics; Receptor, Insulin - immunology; Receptor, Insulin - metabolism; RECEPTORS; RODENTS; SOMATIC CELLS; TEMPERATURE DEPENDENCE; Thermodynamics; TIME DEPENDENCE; TRANSCRIPTION; Transfection; TUMOR CELLS; TYROSINE; UPTAKE; VERTEBRATES; Rat; Cell nucleus; Rodentia; Cytochemistry; Gene expression; Electron microscopy; Insulin; Immunological method; Protein hormone; Vertebrata; Regulation(control); Mammalia; Cell line; Gel filtration; Immunoblotting assay; Biological receptor
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.86.17.6640

Although insulin is known to regulate nuclear-related processes, such as cell growth and gene transcription, the mechanisms involved are poorly understood. Previous studies suggested that translocation of insulin or its receptor to cell nuclei might be involved in some of these processes. The present investigation demonstrated that intact insulin, but not the insulin receptor, accumulated in nuclei of insulin-treated cells. Cell fractionation studies demonstrated that the nuclear accumulation of 125I-labeled insulin was time-, temperature-, and insulin-concentration-dependent. Electron microscopic immunocytochemistry demonstrated that the insulin that accumulated in the nucleus was immunologically intact and associated with the heterochromatin. Only 1% of the 125I-labeled insulin extracted from isolated nuclei was eluted from a Sephadex G-50 column as 125I-labeled tyrosine. Plasma membrane insulin receptors were not detected in the nucleus by immuno electron microscopy or when wheat germ agglutinin-purified extracts of the nuclei were subjected to PAGE, electrotransfer, and immunoblotting with anti-insulin receptor antibodies. These results suggested that internalized insulin dissociated from its receptor and accumulated in the nucleus without its membrane receptor. We propose that some of insulin's effects on nuclear function may be caused by the translocation of the intact and biologically active hormone to the nucleus and its binding to nuclear components in the heterochromatin.