title: Monocytes/Macrophages Upregulate the Hyaluronidase HYAL1 and Adapt Its Subcellular Trafficking to Promote Extracellular Residency upon Differentiation into Osteoclasts.
abstract: Osteoclasts are giant bone-resorbing cells originating from monocytes/macrophages. During their differentiation, they overexpress two lysosomal enzymes, cathepsin K and TRAP, which are secreted into the resorption lacuna, an acidified sealed area in contact with bone matrix where bone degradation takes place. Here we report that the acid hydrolase HYAL1, a hyaluronidase able to degrade the glycosaminoglycans hyaluronic acid (HA) and chondroitin sulfate, is also upregulated upon osteoclastogenesis. The mRNA expression and protein level of HYAL1 are markedly increased in osteoclasts differentiated from RAW264.7 mouse macrophages or primary mouse bone marrow monocytes compared to these precursor cells. As a result, the HYAL1-mediated HA hydrolysis ability of osteoclasts is strongly enhanced. Using subcellular fractionation, we demonstrate that HYAL1 proteins are sorted to the osteoclast lysosomes even though, in contrast to cathepsin K and TRAP, HYAL1 is poorly mannose 6-phosphorylated. We reported previously that macrophages secrete HYAL1 proforms by constitutive secretion, and that these are recaptured by the cell surface mannose receptor, processed in endosomes and sorted to lysosomes. Present work highlights that osteoclasts secrete HYAL1 in two ways, through lysosomal exocytosis and constitutive secretion, and that these cells promote the extracellular residency of HYAL1 through downregulation of the mannose receptor. Interestingly, the expression of the other main hyaluronidase, HYAL2, and of lysosomal exoglycosidases involved in HA degradation, does not increase similarly to HYAL1 upon osteoclastogenesis. Taken together, these findings point out the predominant involvement of HYAL1 in bone HA metabolism and perhaps bone remodeling via the resorption lacuna.
authors.affiliation: Laboratoire de Chimie Physiologique - URPhyM, University of Namur, Namur, Belgium.
authors.forename: Emeline
authors.initials: E
authors.lastname: Puissant
authors.affiliation: Laboratoire de Chimie Physiologique - URPhyM, University of Namur, Namur, Belgium.
authors.forename: Marielle
authors.initials: M
authors.lastname: Boonen
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D056657:Cathepsin K / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D002809:Chondroitin Sulfates / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism; D005089:Exocytosis; D058851:GPI-Linked Proteins / Q000235:genetics / Q000378:metabolism; D006820:Hyaluronic Acid / Q000378:metabolism; D006821:Hyaluronoglucosaminidase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D037181:Lectins, C-Type / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism; D010012:Osteogenesis; D053245:RANK Ligand / Q000378:metabolism; D000067996:RAW 264.7 Cells; D011956:Receptors, Cell Surface / Q000378:metabolism; D000071681:Tartrate-Resistant Acid Phosphatase / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D058851:GPI-Linked Proteins; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D053245:RANK Ligand; D011956:Receptors, Cell Surface; D006820:Hyaluronic Acid; D002809:Chondroitin Sulfates; C000605511:Acp5 protein, mouse; D000071681:Tartrate-Resistant Acid Phosphatase; C469220:Hyal1 protein, mouse; C469221:Hyal2 protein, mouse; D006821:Hyaluronoglucosaminidase; D056657:Cathepsin K