Soluble Megalin Is Accumulated in the Lumen of the Rat Endolymphatic Sac

• Ishida Tetsuya

  Department of Histology and Cell Biology, School of Medicine, Kagawa University

• Hatae Tanenori

  Department of Histology and Cell Biology, School of Medicine, Kagawa University

• Nishi Nozomu

  Department of Endocrinology, School of Medicine, Kagawa University

• Araki Nobukazu

  Department of Histology and Cell Biology, School of Medicine, Kagawa University

抄録

The endolymphatic sac (ES) is believed to play an important role in maintaining homeostasis in the inner ear by the absorption and endocytosis of endolymph. Megalin is a 600-kDa multiligand endocytic receptor expressed in certain types of absorptive epithelia including kidney proximal tubules. We analyzed the immunoreactivity for megalin in rat ES by immunofluorescence, immunogold electron microscopy, and immunoblotting. With immunostaining, the luminal substances of the ES were strongly stained for megalin. Megalin was also localized in luminal macrophage-like cells and both types of epithelial cell (mitochondria-rich cells and ribosome-rich cells). In these cells, the megalin was localized in the lumen of endosomes, but was not membrane associated. This localization pattern indicates that the megalin in these cells is not a membrane receptor, but merely one of the constituents that are endocytosed from the lumen of the ES. Immunoblotting indicated that the megalin in the ES is a 210-kDa molecule lacking a cytoplasmic domain. This suggests that the megalin in the ES may be a soluble form, different from the 600-kDa membrane-bound receptor expressed in kidneys. Taken together, it is likely that the megalin in the ES lumen is a soluble component and may be endocytosed by the ES epithelial cells. Furthermore, we found that the tectorial membrane, an acellular structure in the cochlea, gave a strong megalin immunoreaction. Since the cochlea is connected to the ES, the megalin may be transported alone or with the components of the tectorial membrane from the cochlea to the ES lumen through longitudinal flow.<br>

収録刊行物

• Cell Structure and Function

  Cell Structure and Function 31 (2), 77-85, 2006

  日本細胞生物学会

キーワード

• megalin
• endolymphatic sac
• tectorial membrane
• cubilin
• endocytosis

詳細情報

• CRID: 1390001204695269888
• NII論文ID: 130004137508
• NII論文ID: 40015510802
• NII書誌ID: AA0060007X
• DOI: 10.1247/csf.06013
• ISSN: 13473700
• ISSN: 03867196
• NDL書誌ID: 8837814
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I8837814
• Web Site: http://www.jstage.jst.go.jp/article/csf/31/2/31_2_77/_pdf
• Web Site: https://search.jamas.or.jp/link/ui/2007217544
• 本文言語コード: en
• データソース種別:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可