title: P2Y(2) receptors and GRK2 are involved in oscillatory fluid flow induced ERK1/2 responses in chondrocytes.
abstract: Mechanical loading is an important factor regulating cartilage metabolism maintained by chondrocytes. However, some of its underlying mechanisms remain poorly understood. In this study, we employed a chondrogenic cell line ATDC5 to investigate roles of P2Y(2) and GRK2 in chondrocyte mechanotransduction. We first confirmed the expression of chondrocyte markers in differentiated ATDC5 cells. We then exposed both differentiated and undifferentiated ATDC5 cells to oscillatory fluid flow, and found that differentiated ATDC5 cells responded to oscillatory fluid flow by increasing COX-2 and aggrecan expressions. More importantly, fluid flow induced ERK1/2 response in differentiated cells was increased more than 10 times compared to those in undifferentiated cells. Furthermore, we found that P2Y(2) mRNA and protein levels in differentiated ATDC5 cells were significantly higher than those in undifferentiated cells. In contrast, GRK2 protein levels in differentiated cells were significantly lower than those in undifferentiated cells. Finally, overexpressions of P2Y(2) and GRK2 in differentiated ATDC5 cells result in a 34% increase and a 21% decrease of the ERK1/2 phosphorylation, respectively, in response to oscillatory fluid flow, suggesting important roles of P2Y(2) and GRK2 in chondrocyte mechanotransduction.
authors.affiliation: Department of Orthopaedics and Rehabilitation, The Pennsylvania State University College of Medicine, Hershey, PA 17033, USA.
authors.forename: Yanghui
authors.initials: Y
authors.lastname: Xing
authors.forename: Yan
authors.initials: Y
authors.lastname: Gu
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Gomes
authors.forename: Jun
authors.initials: J
authors.lastname: You
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000378:metabolism*; D040542:Mechanotransduction, Cellular; D051379:Mice; D058473:Receptors, Purinergic P2Y2 / Q000378:metabolism*
chemical_list: D058473:Receptors, Purinergic P2Y2; D000255:Adenosine Triphosphate; C496568:GRK2 protein, mouse; D054769:G-Protein-Coupled Receptor Kinase 2; D048049:Extracellular Signal-Regulated MAP Kinases