title: The eta isoform of protein kinase C is localized on rough endoplasmic reticulum.
abstract: The eta isoform of protein kinase C, isolated from a cDNA library of mouse skin, has unique tissue and cellular distributions. It is predominantly expressed in epithelia of the skin, digestive tract, and respiratory tract in close association with epithelial differentiation. We report here that this isoform is localized on the rough endoplasmic reticulum in transiently expressing COS1 cells and constitutively expressing keratinocytes. By the use of polyclonal antibodies raised against peptides of the diverse D1 and D2/D3 regions, we found that immunofluorescent signals were strongest in the cytoplasm around the nucleus and became weaker toward the peripheral cytoplasm. Under immunoelectron microscopic examination, electron-dense signals were located on the rough endoplasmic reticulum and on the outer nuclear membrane which is continuous with the endoplasmic reticulum membrane. However, no signals were detected in the nucleus, inner nuclear membrane, smooth endoplasmic reticulum, Golgi apparatus, mitochondria, or plasma membrane. Treatment of the cells in situ with detergents suggested association of the isoform of protein kinase C with intracellular structures. By immunoblotting, a distinct single band with an M(r) of 80,000 was detected in whole-cell lysate and in rough microsomal and crude nuclear fractions, all of which contain outer nuclear membrane and/or rough endoplasmic reticulum. We further demonstrated the absence of a nuclear localization signal in the pseudosubstrate sequence. The present observation is not consistent with the report of Greif et al. (H. Greif, J. Ben-Chaim, T. Shimon, E. Bechor, H. Eldar, and E. Livneh, Mol. Cell. Biol. 12:1304-1311, 1992).
authors.affiliation: Department of Cancer Cell Research, University of Tokyo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Chida
authors.forename: H
authors.initials: H
authors.lastname: Sagara
authors.forename: Y
authors.initials: Y
authors.lastname: Suzuki
authors.forename: A
authors.initials: A
authors.lastname: Murakami
authors.forename: S
authors.initials: S
authors.lastname: Osada
authors.forename: S
authors.initials: S
authors.lastname: Ohno
authors.forename: K
authors.initials: K
authors.lastname: Hirosawa
authors.forename: T
authors.initials: T
authors.lastname: Kuroki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D002294:Carcinoma, Squamous Cell; D002460:Cell Line; D002522:Chlorocebus aethiops; D004591:Electrophoresis, Polyacrylamide Gel; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D006801:Humans; D015151:Immunoblotting; D007527:Isoenzymes / Q000032:analysis / Q000096:biosynthesis*; D007668:Kidney; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D011493:Protein Kinase C / Q000032:analysis / Q000096:biosynthesis*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D000906:Antibodies; D007527:Isoenzymes; D010455:Peptides; D011493:Protein Kinase C