1. Academic Validation
  2. Fibrillin-1 directly regulates osteoclast formation and function by a dual mechanism

Fibrillin-1 directly regulates osteoclast formation and function by a dual mechanism

  • J Cell Sci. 2013 Sep 15;126(Pt 18):4187-94. doi: 10.1242/jcs.127571.
Kerstin Tiedemann 1 Iris Boraschi-Diaz Irina Rajakumar Jasvir Kaur Peter Roughley Dieter P Reinhardt Svetlana V Komarova
Affiliations

Affiliation

  • 1 Faculty of Dentistry, McGill University, 3640 rue University, Montreal, Quebec, Canada, H3A 0C7.
Abstract

Mutations in the fibrillin-1 gene give rise to a number of heritable disorders, which are all characterized by various malformations of bone as well as manifestations in other tissues. However, the role of fibrillin-1 in the development and homeostasis of bone is not well understood. Here, we examined the role of fibrillin-1 in regulating osteoclast differentiation from primary bone-marrow-derived precursors and monocytic RAW 264.7 cells. The soluble N-terminal half of fibrillin-1 (rFBN1-N) strongly inhibited osteoclastogenesis, whereas the C-terminal half (rFBN1-C) did not. By contrast, when rFBN1-N was immobilized on calcium phosphate, it did not affect osteoclastogenesis but modulated osteoclast resorptive activity, which was evident by a larger number of smaller resorption pits. Using a panel of recombinant sub-fragments spanning rFBN1-N, we localized an osteoclast inhibitory activity to the 63 kDa subfragment rF23 comprising the N-terminal region of fibrillin-1. Osteoclastic resorption led to the generation of small fibrillin-1 fragments that were similar to those identified in human vertebral bone extracts. rF23, but not rFBN1-N, was found to inhibit the expression of Cathepsin K, matrix metalloproteinase 9 and Dcstamp in differentiating osteoclasts. rFBN1-N, but not rF23, exhibited interaction with RANKL. Excess RANKL rescued the inhibition of osteoclastogenesis by rFBN1-N. By contrast, rF23 disrupted RANKL-induced CA(2+) signaling and activation of transcription factor NFATc1. These studies highlight a direct dual inhibitory role of N-terminal fibrillin-1 fragments in osteoclastogenesis, the sequestration of RANKL and the inhibition of NFATc1 signaling, demonstrating that osteoclastic degradation of fibrillin-1 provides a potent negative feedback that limits osteoclast formation and function.

Keywords

Calcium signaling; Fibrillin; NFATc1; Osteoclastogenesis; RANKL.

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