Specific immunocytochemical localization of cathepsin E at the ruffled border membrane of active osteoclasts

Yoshimine Yoshito, Takayuki Tsukuba, Ryoko Isobe, Misa Sumi, Akifumi Akamine, Katsumasa Maeda, Kenji Yamamoto

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Abstract

The immunocytochemical localization of cathepsin E, a non-lysosomal aspartic proteinase, was investigated in rat osteoclasts using the monospecific antibody to this protein. At the light-microscopic level, the preferential immunoreactivity for cathepsin E was found at high levels in active osteoclasts in the physiological bone modeling process. Neighboring osteoblastic cells were devoid of its immunoreactivity. At the electron-microscopic level, cathepsin E was exclusively confined to the apical plasma membrane at the ruffled border of active osteoclasts and the eroded bone surface. Cathepsin E was also concentrated in some endocytotic vacuoles of various sizes in the vicinity of the ruffled border membrane, some of which appeared to be secondary lysosomes containing the phagocytosed materials. These results strongly suggest that this enzyme is involved both in the extracellular degradation of the bone organic matrix and in the intracellular breakdown of the ingested substances in osteoclasts.

Original languageEnglish
Pages (from-to)85-91
Number of pages7
JournalCell and tissue research
Volume281
Issue number1
DOIs
Publication statusPublished - Jul 1 1995

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All Science Journal Classification (ASJC) codes

  • Pathology and Forensic Medicine
  • Histology
  • Cell Biology

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