title: Secretion of urocortin I by human glioblastoma cell lines, possibly via the constitutive pathway.
abstract: Corticotropin-releasing factor (CRF) and its family of peptides, i.e., urocortins (UCNs), play a critical role in systemic and peripheral stress-response systems and are widely expressed not only in normal tissues but also in various types of cancer cells. Given limited understanding of the mechanism of UCN I secretion, we investigated the UCN I secretory pathway in human neural stem cells (HNSCs) and in two glioblastoma cell lines, e.g., A172 and U-138 MG. Immunoreactivities for CRF receptors were detected in A172 glioblastoma cells, but not in HNSCs or U-138 glioblastoma cells, while UCN I immunoreactivity was detected in A172 and U-138 MG glioblastoma cell lines by both light field and electron microscopy. Interestingly, electron microscopy revealed UCN I immunoreactivtiy in vesicle-like structures in the plasma membrane of the glioblastoma cells. Tracking of a hybrid fluorescent protein containing a UCN I signal peptide expressed in A172 human glioblastoma cells revealed that fluorescence in secretory granules could be decreased by cycloheximide (100μg/ml), indicating that the forward transport of secretory granules containing fluorescent protein was not altered by the inhibition of protein synthesis by cycloheximide. Retrograde transport and the fusion of fluorescent granules in A172 human glioblastoma cells was induced by brefeldin A (10μg/ml), indicating that UCN I secretory granules may be transported via the constitutive pathway. Based on these results, it appears that UCN I is secreted from human glioblastoma cells by exocytosis through constitutive secretory granules, indicating that transcription of UCN I mRNA may be correlated to secretion of UCN I protein.
authors.affiliation: Division of Molecular Cell Biology, Core Research Facilities for Basic Science, Research Center for Medical Sciences, The Jikei University School of Medicine, Tokyo 105-8461, Japan. Electronic address: ikedak@jikei.ac.jp.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Ikeda
authors.affiliation: Division of Molecular Cell Biology, Core Research Facilities for Basic Science, Research Center for Medical Sciences, The Jikei University School of Medicine, Tokyo 105-8461, Japan.
authors.forename: Kouki
authors.initials: K
authors.lastname: Fujioka
authors.affiliation: Division of Molecular Cell Biology, Core Research Facilities for Basic Science, Research Center for Medical Sciences, The Jikei University School of Medicine, Tokyo 105-8461, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tachibana
authors.affiliation: Medical Research Institute, Chung-Ang University College of Medicine, Seoul, Republic of Korea; Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, BC, Canada V6T 2B5.
authors.forename: Seung U
authors.initials: SU
authors.lastname: Kim
authors.affiliation: Division of Diabetes and Endocrinology, Department of Internal Medicine, The Jikei University School of Medicine, Tokyo 105-8461, Japan.
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Tojo
authors.affiliation: Division of Molecular Cell Biology, Core Research Facilities for Basic Science, Research Center for Medical Sciences, The Jikei University School of Medicine, Tokyo 105-8461, Japan.
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Manome
mesh_terms: D045744:Cell Line, Tumor; D015870:Gene Expression; D005909:Glioblastoma / Q000378:metabolism*; D006801:Humans; D018019:Receptors, Corticotropin-Releasing Hormone / Q000378:metabolism; D055571:Secretory Pathway; D054832:Urocortins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018019:Receptors, Corticotropin-Releasing Hormone; C576814:UCN protein, human; D054832:Urocortins
keywords: Constitutive secretion; Fluorescent protein; Protein tracking; Urocortin I