Surface distribution of heterogenous clathrin assemblies in resorbing osteoclasts

• Published in: Experimental cell research Vol. 399; no. 1; p. 112433
• Main Authors: Akisaka, Toshitaka, Yoshida, Atsushi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.02.2021
• Subjects: 3D imaging; 60 APPLIED LIFE SCIENCES; ACTIN; ADHESION; APATITES; Bent clathrin; Cell-shearing; DRUGS; flat clathrin sheet; Heterogenous clathrin assemblies; MEMBRANES; MICROSCOPY; PLATINUM; Platinum replica EM; Podosome; Podosome belt; Resorbing osteoclasts; Sealing zone; SUBSTRATES; Tubular clathrin; 3D imaging; Bent clathrin; SZ; Sealing zone; Resorbing osteoclasts; ECM; Platinum replica EM; RB; 3D; 2D; Podosome belt; Podosome; flat clathrin sheet; Cell-shearing; Tubular clathrin; SEM; Heterogenous clathrin assemblies; TEM; OCs
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/j.yexcr.2020.112433

Osteoclasts seeded on either glass coverslips or apatite pellets have at least two morphologically distinct substrate adhesion sites: actin-based adhesion structures including podosome belts and sealing zones, and adjacent clathrin sheets. Clathrin-coated structures are exclusively localized at the podosome belts and sealing zone, in both of which the plasma membrane forms a tight attachment to the substrate surface. When cultured on apatite osteoclasts can degrade the apatite leading to the formation of resorption lacunae. The sealing zone divides the ventral membrane into different domains, outside and inside of the sealing zones. The former facing the smooth-surfaced intact apatite contains relatively solitary or networks of larger flat clathrin structures; and the latter, facing the rough-surfaced degraded apatite in the resorption lacunae contain clathrin in various shapes and sizes. Clathrin assemblies on the membrane domain facing not only a resorption lacuna, or trails but also intact apatite indeed were observed to be heterogeneous in size and intensity, suggesting that they appeared to follow variations in the surface topography of the apatite surface. These results provide a detailed insight into the flat clathrin sheets that have been suggested to be the sites of adhesion and mechanosensing in co-operation with podosomes. •Platinum replica microscopy has revealed new structural data on the clathrins on the ventralmembrane of osteoclasts.•Various clathrins were visualized, suggesting that they followed variations in the surface topography of the apatite.•Most of the flat clathrins may participate in the adhesive and mechnosensory functions in co-operation with podosomes.•The present findings in osteoclast biology reveal potential novel drug targets or treatment regimens.