title: Downregulation of carbonic anhydrase IX promotes Col10a1 expression in chondrocytes.
abstract: Carbonic anhydrase (CA) IX is a transmembrane isozyme of CAs that catalyzes reversible hydration of CO(2). While it is known that CA IX is distributed in human embryonic chondrocytes, its role in chondrocyte differentiation has not been reported. In the present study, we found that Car9 mRNA and CA IX were expressed in proliferating but not hypertrophic chondrocytes. Next, we examined the role of CA IX in the expression of marker genes of chondrocyte differentiation in vitro. Introduction of Car9 siRNA to mouse primary chondrocytes obtained from costal cartilage induced the mRNA expressions of Col10a1, the gene for type X collagen α-1 chain, and Epas1, the gene for hypoxia-responsible factor-2α (HIF-2α), both of which are known to be characteristically expressed in hypertrophic chondrocytes. On the other hand, forced expression of CA IX had no effect of the proliferation of chondrocytes or the transcription of Col10a1 and Epas1, while the transcription of Col2a1 and Acan were up-regulated. Although HIF-2α has been reported to be a potent activator of Col10a1 transcription, Epas1 siRNA did not suppress Car9 siRNA-induced increment in Col10a1 expression, indicating that down-regulation of CA IX induces the expression of Col10a1 in chondrocytes in a HIF-2α-independent manner. On the other hand, cellular cAMP content was lowered by Car9 siRNA. Furthermore, the expression of Col10a1 mRNA after Car9 silencing was augmented by an inhibitor of protein kinase A, and suppressed by an inhibitor for phosphodiesterase as well as a brominated analog of cAMP. While these results suggest a possible involvement of cAMP-dependent pathway, at least in part, in induction of Col10a1 expression by down-regulation of Car9, more detailed study is required to clarify the role of CA IX in regulation of Col10a1 expression in chondrocytes.
authors: Department of Biochemistry, School of Dentistry, Showa University, Shinagawa, Tokyo, Japan.
authors: Toshifumi
authors: T
authors: Maruyama
authors: Yoichi
authors: Y
authors: Miyamoto
authors: Gou
authors: G
authors: Yamamoto
authors: Atsushi
authors: A
authors: Yamada
authors: Kentaro
authors: K
authors: Yoshimura
authors: Tetsuo
authors: T
authors: Suzawa
authors: Masamichi
authors: M
authors: Takami
authors: Tomohito
authors: T
authors: Akiyama
authors: Marie
authors: M
authors: Hoshino
authors: Fuminori
authors: F
authors: Iwasa
authors: Noriharu
authors: N
authors: Ikumi
authors: Tetsuhiko
authors: T
authors: Tachikawa
authors: Kenji
authors: K
authors: Mishima
authors: Kazuyoshi
authors: K
authors: Baba
authors: Ryutaro
authors: R
authors: Kamijo
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases / Q000378:metabolism*; D049108:Cell Enlargement; D015687:Cell Hypoxia; D049109:Cell Proliferation; D019902:Chondrocytes / Q000378:metabolism* / Q000473:pathology; D024121:Collagen Type X / Q000235:genetics* / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006132:Growth Plate / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D034622:RNA Interference; D015398:Signal Transduction; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D000071231:Carbonic Anhydrase IX; D002256:Carbonic Anhydrases; D024121:Collagen Type X; D017868:Cyclic AMP-Dependent Protein Kinases; D000099162:Endothelial PAS Domain-Containing Protein 1; C570620:Col10a1 protein, mouse; C492796:Car9 protein, mouse