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Proteolytic processing causes extensive heterogeneity of tissue matrilin forms.
Harald W A Ehlen1, Gerhard Sengle, Andreas R Klatt
1Center for Biochemistry, Medical Faculty, University of Cologne, Cologne, Germany.
The Journal of Biological Chemistry
|June 18, 2009
Summary
Post-translational proteolytic processing creates diverse matrilin proteins in tissues. A conserved cleavage site, particularly active in matrilin-4, generates distinct matrilin forms in vivo.
Area of Science:
- Biochemistry
- Molecular Biology
- Extracellular Matrix Research
Background:
- Matrilins are extracellular matrix proteins with adapter functions.
- Their oligomeric structure and ligand-binding avidity depend on subunit and domain composition.
- Heterogeneity in tissue extracts suggests post-translational modifications.
Purpose of the Study:
- To investigate the role of proteolytic processing in matrilin heterogeneity.
- To identify specific cleavage sites and processing pathways for different matrilins.
- To determine the in vivo relevance of identified processing events.
Main Methods:
- Analysis of matrilin processing in cell culture supernatants and tissue extracts.
- Site-directed mutagenesis to study the role of the hinge region.
- Use of specific antibodies, including a neo-epitope antibody, to detect processed forms.
- Enzyme activity assays involving proprotein convertases and ADAMTS proteases.
Main Results:
- A conserved cleavage site in the hinge region significantly alters matrilin structure.
- Matrilin-2 exhibits complex processing with multiple cleavage sites.
- Matrilin-4 is processed in the secretory pathway, dependent on proprotein convertase activity.
- ADAMTS4 and ADAMTS5 cleave matrilin-3 and matrilin-4, but not matrilin-1.
- Processed matrilin-4 was detected in chondrocytes and cartilage, confirming in vivo cleavage.
Conclusions:
- Proteolytic processing is a key contributor to matrilin heterogeneity.
- The conserved hinge region cleavage site is utilized in vivo, particularly for matrilin-4.
- Specific proteases like ADAMTS4/5 play a role in matrilin processing.
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