title: Effects of cysteine proteases on the structural and mechanical properties of collagen fibers.
abstract: Excessive cathepsin K (catK)-mediated turnover of fibrillar type I and II collagens in bone and cartilage leads to osteoporosis and osteoarthritis. However, little is known about how catK degrades compact collagen macromolecules. The present study is aimed to explore the structural and mechanical consequences of collagen fiber degradation by catK. Mouse tail type I collagen fibers were incubated with either catK or non-collagenase cathepsins. Methods used include scanning electron microscopy, protein electrophoresis, atomic force microscopy, and tensile strength testing. Our study revealed evidence of proteoglycan network degradation, followed by the progressive disassembly of macroscopic collagen fibers into primary structural elements by catK. Proteolytically released GAGs are involved in the generation of collagenolytically active catK-GAG complexes as shown by AFM. In addition to their structural disintegration, a decrease in the tensile properties of fibers was observed due to the action of catK. The Young's moduli of untreated collagen fibers versus catK-treated fibers in dehydrated conditions were 3.2 ± 0.68 GPa and 1.9 ± 0.65 GPa, respectively. In contrast, cathepsin L, V, B, and S revealed no collagenase activity, except the disruption of proteoglycan-GAG interfibrillar bridges, which slightly decreased the tensile strength of fibers.
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Vancouver, British Columbia V6T1Z3, Canada.
authors.forename: Preety
authors.initials: P
authors.lastname: Panwar
authors.forename: Xin
authors.initials: X
authors.lastname: Du
authors.forename: Vidhu
authors.initials: V
authors.lastname: Sharma
authors.forename: Guillaume
authors.initials: G
authors.lastname: Lamour
authors.forename: Mickael
authors.initials: M
authors.lastname: Castro
authors.forename: Hongbin
authors.initials: H
authors.lastname: Li
authors.forename: Dieter
authors.initials: D
authors.lastname: Brömme
mesh_terms: D000818:Animals; D056657:Cathepsin K / Q000737:chemistry; D002403:Cathepsins / Q000737:chemistry; D003094:Collagen / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry; D057056:Cysteine Proteases / Q000737:chemistry* / Q000502:physiology; D055119:Elastic Modulus; D005109:Extracellular Matrix / Q000378:metabolism; D006801:Humans; D046911:Macromolecular Substances; D051379:Mice; D018625:Microscopy, Atomic Force / Q000379:methods; D008855:Microscopy, Electron, Scanning / Q000379:methods; D011312:Pressure; D011487:Protein Conformation; D011509:Proteoglycans / Q000378:metabolism; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D046911:Macromolecular Substances; D011509:Proteoglycans; D003094:Collagen; D002403:Cathepsins; D057056:Cysteine Proteases; D056657:Cathepsin K; D003545:Cysteine