Carboxypeptidase X-1 (CPX-1) is a secreted collagen-binding glycoprotein

Kim, Yu-Hee, O'Neill, Hayley M. and Whitehead, Jonathan P. (2015) Carboxypeptidase X-1 (CPX-1) is a secreted collagen-binding glycoprotein. Biochemical and Biophysical Research Communications, 468 4: 894-899. doi:10.1016/j.bbrc.2015.11.053

Author Kim, Yu-Hee
O'Neill, Hayley M.
Whitehead, Jonathan P.
Title Carboxypeptidase X-1 (CPX-1) is a secreted collagen-binding glycoprotein
Journal name Biochemical and Biophysical Research Communications   Check publisher's open access policy
ISSN 1090-2104
Publication date 2015-12-25
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.bbrc.2015.11.053
Open Access Status Not Open Access
Volume 468
Issue 4
Start page 894
End page 899
Total pages 6
Place of publication Philadelphia, PA United States
Publisher Elsevier
Collection year 2016
Language eng
Abstract Carboxypeptidase X-1 (CPX-1) is an atypical member of the carboxypeptidase (CP) family of proteins involved in a variety of physiological and pathological processes. However, unlike most other family members CPX-1 lacks catalytic activity making its biological function unclear. CPX-1 contains a 160 amino acid discoidin domain (DSD) that serves as a binding domain in other proteins prompting us to investigate a putative functional role for this domain in CPX-1. Sequence alignment confirmed the overarching homology between the DSD of CPX-1 and other DSDs whilst more detailed analysis revealed conservation of the residues known to form the collagen-binding trench within the DSD of the discoidin domain receptors (DDRs) 1 and 2. Biochemical characterisation of transiently expressed human CPX-1 revealed that CPX-1 was secreted in an N-glycosylation-dependent manner as treatment with the N-glycosylation inhibitor tunicamycin inhibited secretion concomitant with a reduction in CPX-1 mobility on Western blot. Using a collagen pull-down assay we found that secreted CPX-1 bound collagen and this appeared independent of N-glycosylation as treatment with PNGaseF did not affect binding. Further analysis under non-reducing and reducing (+DTT) conditions revealed that CPX-1 was secreted in both monomeric and dimeric forms and only the former bound collagen. Finally, mutation of a key residue situated within the putative collagen-binding trench within the DSD of CPX-1 (R192A) significantly reduced secretion and collagen-binding by 40% and 60%, respectively. Collectively these results demonstrate that CPX-1 is a secreted collagen-binding glycoprotein and provide a foundation for future studies investigating the function of CPX-1.
Keyword Carboxypeptidase
Discoidin domain
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Mater Research Institute-UQ (MRI-UQ)
Official 2016 Collection
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