Myosin X regulates sealing zone patterning in osteoclasts through linkage of podosomes and microtubules.
Osteoclasts use actin-rich attachment structures in place of focal adhesions for adherence to bone and non-bone substrates. On glass, osteoclasts generate podosomes, foot-like processes containing a core of F-actin and regulatory proteins that undergo high turnover. To facilitate bone resorption, osteoclasts generate an actin-rich sealing zone composed of densely packed podosome-like units. Patterning of both podosomes and sealing zones is dependent upon an intact microtubule system. A role for unconventional myosin X (Myo10), which can bind actin, microtubules, and integrins, was examined in osteoclasts. Immunolocalization showed Myo10 to be associated with the outer edges of immature podosome rings and sealing zones, suggesting a possible role in podosome and sealing zone positioning. Further, complexes containing both Myo10 and beta-tubulin were readily precipitated from osteoclasts lysates. RNAi-mediated suppression of Myo10 led to decreased cell and sealing zone perimeter, along with decreased motility and resorptive capacity. Further, siRNA-treated cells could not properly position podosomes following microtubule disruption. Osteoclasts overexpressing dominant negative Myo10 microtubule binding domains (MyTH4) showed a similar phenotype. Conversely, overexpression of full-length Myo10 led to increased formation of podosome belts along with larger sealing zones and enhanced bone resorptive capacity. These studies suggest that Myo10 plays a role in osteoclast attachment and podosome positioning by direct linkage of actin to the microtubule network.
McMichael
Brooke K
BK
Department of Physiology and Cell Biology, The Ohio State University College of Medicine, Columbus, Ohio 43210.
Cheney
Richard E
RE
Department of Cell and Molecular Physiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599.
Lee
Beth S
BS
Department of Physiology and Cell Biology, The Ohio State University College of Medicine, Columbus, Ohio 43210. Electronic address: lee.2076@osu.edu.
D000199:Actins / Q000737:chemistry; D000818:Animals; D001862:Bone Resorption; D002460:Cell Line; D003599:Cytoskeleton / Q000378:metabolism; D005799:Genes, Dominant; D051379:Mice; D008870:Microtubules / Q000378:metabolism*; D009218:Myosins / Q000737:chemistry / Q000502:physiology*; D010010:Osteoclasts / Q000378:metabolism*; D010641:Phenotype; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism
D000199:Actins; C409064:Myo10 protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D009218:Myosins