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J Mol Biol. 2018 Nov 17. pii: S0022-2836(18)31238-5. doi: 10.1016/j.jmb.2018.11.015. [Epub ahead of print]

Clustering, Spatial Distribution and Phosphorylation of Discoidin Domain Receptors 1 and 2 in Response to Soluble Collagen Type I.

Author information

1
Biomedical Engineering Department, the Ohio State University Columbus, OH 43210, USA.
2
Department of Pathology and Oncology, Wayne State University, Detroit 48201, MI, USA.
3
Biophysics Program, the Ohio State University, Columbus, OH, United States of America.
4
Department of Pathology, the Ohio State University College of Medicine, Columbus, OH, United States of America.
5
Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
6
Biomedical Engineering Department, the Ohio State University Columbus, OH 43210, USA; Biophysics Program, the Ohio State University, Columbus, OH, United States of America. Electronic address: agarwal.60@osu.edu.

Abstract

Discoidin Domain Receptors (DDR1 and DDR2) are receptor tyrosine kinases that signal in response to collagen. We had previously shown that collagen binding leads to clustering of DDR1b, a process partly mediated by its extracellular domain (ECD). In this study, we investigated (i) the impact of the oligomeric state of DDR2 ECD on collagen binding and fibrillogenesis, (ii) the effect of collagen binding on DDR2 clustering, and (iii) the spatial distribution and phosphorylation status of DDR1b and DDR2 after collagen stimulation. Studies were conducted using purified recombinant DDR2 ECD proteins in monomeric, dimeric or oligomeric state, and MC3T3-E1 cells expressing full-length DDR2-GFP or DDR1b-YFP. We show that the oligomeric form of DDR2 ECD displayed enhanced binding to collagen and inhibition of fibrillogenesis. Using atomic force and fluorescence microscopy we demonstrate that unlike DDR1b, DDR2 ECD and DDR2-GFP do not undergo collagen-induced receptor clustering. However, after prolonged collagen stimulation, both DDR1b-YFP and DDR2-GFP formed filamentous structures consistent with spatial re-distribution of DDRs in cells. Immunocytochemistry revealed that while DDR1b clusters co-localized with non-fibrillar collagen, DDR1b/DDR2 filamentous structures associated with collagen fibrils. Antibodies against a tyrosine phosphorylation site in the intracellular juxtamembrane region of DDR1b displayed positive signals in both DDR1b clusters and filamentous structures. However, only the filamentous structures of both DDR1b and DDR2 co-localized with antibodies directed against tyrosine phosphorylation sites within the receptor kinase domain. Our results uncover key differences and similarities in the clustering abilities and spatial distribution of DDR1b and DDR2 and their impact on receptor phosphorylation.

KEYWORDS:

Atomic force microscopy; Fibrillogenesis; Fluorescence microscopy; Oligomer; Receptor tyrosine kinase

PMID:
30458172
DOI:
10.1016/j.jmb.2018.11.015

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