title: Label-Free Quantitative Proteomics Reveals Survival Mechanisms Developed by Hypertrophic Chondrocytes under ER Stress.
abstract: Emerging evidence implicates ER stress caused by unfolded mutant proteins in chondrocytes as the underlying pathology of chondrodysplasias. ER stress is triggered in hypertrophic chondrocytes (HCs) in a mouse model (13del) of metaphyseal chondrodysplasia type Schmid (MCDS) caused by misfolded mutant collagen X proteins, but the HCs do not undergo apoptosis; rather chondrocyte differentiation is altered, causing skeletal abnormality. How 13del HCs can escape from apoptosis and survive ER stress is not understood. Here we compared the proteomes of HCs isolated from 13del growth plates with normal HCs using a label-free quantitative mass spectrometry approach. Pathway enrichment analyses of differentially expressed proteins showed significant changes in glycolysis and ER-mitochondria pathways in 13del HCs as well as in ATDC5 cell lines expressing wt and 13del collagen X. In vivo, we showed expression of mitochondrial calcium channels was reduced while mitochondrial membrane polarity was maintained in 13del chondrocytes, while in vitro, glucose uptake was maintained. We propose 13del HCs survive by a mechanism whereby changes in ER-mitochondria communication reduce import of calcium coupled to maintenance of mitochondrial membrane polarity. These findings provide the initial insights into our understanding of growth plate changes caused by protein misfolding in the pathogenesis of chondrodysplasias.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Kudelko
authors.forename: Cecilia W L
authors.initials: CW
authors.lastname: Chan
authors.affiliation: Department of Biology and Chemistry, City University of Hong Kong , Tat Chee Avenue, Hong Kong, China.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Sharma
authors.forename: Qing
authors.initials: Q
authors.lastname: Yao
authors.forename: Edward
authors.initials: E
authors.lastname: Lau
authors.forename: Ivan K
authors.initials: IK
authors.lastname: Chu
authors.forename: Kathryn S E
authors.initials: KS
authors.lastname: Cheah
authors.forename: Julian A
authors.initials: JA
authors.lastname: Tanner
authors.forename: Danny
authors.initials: D
authors.lastname: Chan
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D019902:Chondrocytes / Q000378:metabolism*; D059865:Endoplasmic Reticulum Stress; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D006984:Hypertrophy / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism; D021381:Protein Transport; D059748:Proteolysis; D020543:Proteome / Q000378:metabolism*; D040901:Proteomics; D053719:Tandem Mass Spectrometry; D056811:Unfolded Protein Response
chemical_list: D016326:Extracellular Matrix Proteins; D020543:Proteome
keywords: calcium signaling; glycolysis; metaphyseal chondrodysplasia type Schmid; mitochondrial membrane polarity