title: Distribution of actin filaments, non-muscle myosin, M-Ras, and extracellular signal-regulated kinase (ERK) in osteoclasts after calcitonin administration.
abstract: Scanning electron microscopy (SEM) was employed to study the effect of calcitonin on the distribution of actin filaments in osteoclasts obtained from rat tibiae. Fluorescent microscopy was also applied to examine calcitonin-induced changes in the distribution of actin filaments, non-muscle myosin, M-Ras, and extracellular signal-regulated kinase (ERK) to clarify the role of ERK in the cytoskeleton of osteoclasts. SEM of control osteoclasts revealed a ring-like structure in the peripheral region. Labeled actin filaments and non-muscle myosin were detected in the peripheral region and exhibited a ring-like pattern. Immunoreactivity indicating M-Ras and ERK was also detected in the vicinity of the actin ring. After calcitonin treatment, many osteoclasts exhibited a retracted appearance and lacked a discernible actin ring. Numerous retraction fibers were found at the edge of calcitonin-treated osteoclasts. Actin filaments and non-muscle myosin were concentrated in the cytoplasm of calcitonin-treated osteoclasts, and exhibited a filamentous pattern. Labeled M-Ras and ERK also accumulated in the central region of these osteoclasts. These findings suggest that actin-myosin interaction plays an essential role in the retraction of osteoclasts induced by calcitonin. ERK may play a role in this interaction by activating myosin light chain kinase, as previously observed in smooth muscle cells.
authors.affiliation: Department of Oral Histology, Institute for Oral Science, Matsumoto Dental University, Shiojiri, Japan. nakam@po.mdu.ac.jp
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakamura
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nagaoka
authors.forename: Azumi
authors.initials: A
authors.lastname: Hirata
authors.forename: Miho
authors.initials: M
authors.lastname: Inoue
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Ozawa
authors.forename: Toshio
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002116:Calcitonin / Q000494:pharmacology*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D007150:Immunohistochemistry; D008855:Microscopy, Electron, Scanning / Q000379:methods; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010010:Osteoclasts / Q000737:chemistry / Q000187:drug effects* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000199:Actins; D003598:Cytoskeletal Proteins; D002116:Calcitonin; D048049:Extracellular Signal-Regulated MAP Kinases; C491617:Mras protein, rat; D009218:Myosins; D020559:Monomeric GTP-Binding Proteins