2020 Volume No 39 – pages 48-64
Title: YAP/TAZ regulates the expression of proteoglycan 4 and tenascin C in superficial-zone chondrocytes |
Authors: E Delve, V Co, SC Regmi, J Parreno, TA Schmidt, RA Kandel |
Address: Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, 600 University Avenue, Suite 6-500, Toronto, M5G 1X5, Ontario, Canada. |
E-mail: rita.kandel at sinaihealthsystem.ca |
Abstract: The roles of cell division control protein 42 homologue (CDC42) and actin polymerisation in regulating the phenotype of superficial-zone chondrocytes (SZCs) have been demonstrated in vitro; however, the signalling pathway(s) downstream have yet to be fully elucidated. The study hypothesis was that Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) act downstream to regulate proteoglycan 4 (PRG4) and tenascin C (TNC). Bovine SZCs grown in monolayer were treated with ML141 (CDC42 inhibitor) or the actin depolymerising agents, latrunculin B and cytochalasin D, to determine the effect on YAP/TAZ. Verteporfin (YAP/TAZ inhibitor) and YAP/TAZ siRNA-mediated knockdown were used to determine their role in regulating PRG4 and TNC. ML141 treatment reduced total YAP/TAZ protein, nuclear TAZ levels and the YAP/TAZ target gene, connective tissue growth factor (CTGF) mRNA levels. Latrunculin B decreased nuclear TAZ, while cytochalasin D treatment trended towards increased nuclear TAZ (p = 0.06), correlating with decreased and increased CTGF mRNA levels, respectively. Verteporfin treatment decreased PRG4 and TNC expression, with no effect on actin polymerisation. siRNA-mediated knockdown of YAP/TAZ revealed that PRG4 was regulated by YAP/TAZ while TNC was regulated by TAZ only. As cytochalasin D can activate myocardin-related transcription factor-A (MRTF-A), siRNA-mediated knockdown was performed to determine the role of MRTF-A in regulating YAP/TAZ. Although nuclear TAZ decreased, no significant changes in total protein levels were observed. Findings suggested that CDC42 and actin polymerisation regulated SZCs through multiple actin-regulated pathways. Understanding the regulation of these chondroprotective molecules may have important implications for prevention/treatment of osteoarthritis. |
Key Words: Cell division control protein 42 homologue, actin polymerisation, superficial-zone chondrocyte, primary chondrocyte phenotype, proteoglycan 4, tenascin C, Yes-associated protein, transcriptional co-activator with PDZ-binding motif, myocardin-related transcription factor-A. |
Publication date: January 9th 2020 |
Article download: Pages
48-64 (PDF file) |
