Calcitonin induces podosome disassembly and detachment of osteoclasts by modulating Pyk2 and Src activities.
Osteoclasts (OCs) attach to the extracellular matrix via specialized attachment structures called podosomes, which form a prominent F-actin-rich ring that is thought to correspond to the sealing zone of resorbing OCs. Calcitonin (CT), a 32-amino acid polypeptide, inhibits bone resorption by decreasing motility, inducing retraction, disassembling podosome, and disrupting the actin-ring structure of OCs. However, the detailed mechanisms of how CT induces the disassembly of podosome and disruption of the adhesive structures in OCs are not well characterized. Pyk2 localizes in the sealing zone of OCs. It is activated by ligation of integrins, and then activates Src, an important signaling molecule for bone resorption. Thus, the Pyk2/Src complex in podosome could be a potential target for the CT-induced signaling. Using interference reflection, phase contrast, and confocal microscopy, CT effects on the dynamic changes of peripheral adhesive structure in living OCs were examined. CT induced dephosphorylation at Tyr(402) of Pyk2 and decreased its labeling at peripheral adhesion region, which would prevent formation of the Pyk2/Src complex in this region. CT induced increase of intracellular phosphorylation of Tyr(402) Pyk2 and increase of dephosphorylation at Tyr(527) of Src and Pyk2/Src colocalization in the central region of OCs. This evidence suggested that Src might function as an adaptor protein that competes for Pyk2 and relocates it from peripheral adhesive zone to the central region of OCs. In conclusion, CT may induce podosome reassembly and peripheral adhesive zone detachment by modulating Pyk2 and Src phosphorylation state and their intracellular distribution in OCs.
Shyu
Jia-Fwu
JF
Department of Biology and Anatomy, National Defense Medical Center, Taipei, 161 Ming-Chuan East Rd., Sec. 6, 114 Taipei, Taiwan, ROC. jiafwu.shyu@msa.hinet.net
Shih
Chung
C
Tseng
Chiung-Ying
CY
Lin
Chi-Hung
CH
Sun
Der-Tzong
DT
Liu
Hsiao-Tung
HT
Tsung
Hui-Chu
HC
Chen
Tien-Hua
TH
Lu
Ru-Band
RB
D000818:Animals; D002116:Calcitonin / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects; D048430:Cell Shape; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D051418:Focal Adhesion Kinase 2 / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011554:Pseudopodia / Q000187:drug effects; D011817:Rabbits; D015398:Signal Transduction; D019061:src-Family Kinases / Q000378:metabolism*
D002116:Calcitonin; D051418:Focal Adhesion Kinase 2; D019061:src-Family Kinases; D011493:Protein Kinase C