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Al-Shaer A, Lyons A, Ishikawa Y, Hudson BG, Boudko SP, Forde NR. Sequence-dependent mechanics of collagen reflect its structural and functional organization. Biophys J 2021; 120:4013-4028. [PMID: 34390685 DOI: 10.1016/j.bpj.2021.08.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 05/25/2021] [Accepted: 08/06/2021] [Indexed: 01/06/2023] Open
Abstract
Extracellular matrix mechanics influence diverse cellular functions, yet surprisingly little is known about the mechanical properties of their constituent collagen proteins. In particular, network-forming collagen IV, an integral component of basement membranes, has been far less studied than fibril-forming collagens. A key feature of collagen IV is the presence of interruptions in the triple-helix-defining (Gly-X-Y) sequence along its collagenous domain. Here, we used atomic force microscopy to determine the impact of sequence heterogeneity on the local flexibility of collagen IV and of the fibril-forming collagen III. Our extracted flexibility profile of collagen IV reveals that it possesses highly heterogeneous mechanics, ranging from semiflexible regions as found for fibril-forming collagens to a lengthy region of high flexibility toward its N-terminus. A simple model in which flexibility is dictated only by the presence of interruptions fit the extracted profile reasonably well, providing insight into the alignment of chains and demonstrating that interruptions, particularly when coinciding in multiple chains, significantly enhance local flexibility. To a lesser extent, sequence variations within the triple helix lead to variable flexibility, as seen along the continuously triple-helical collagen III. We found this fibril-forming collagen to possess a high-flexibility region around its matrix-metalloprotease binding site, suggesting a unique mechanical fingerprint of this region that is key for matrix remodeling. Surprisingly, proline content did not correlate with local flexibility in either collagen type. We also found that physiologically relevant changes in pH and chloride concentration did not alter the flexibility of collagen IV, indicating such environmental changes are unlikely to control its compaction during secretion. Although extracellular chloride ions play a role in triggering collagen IV network formation, they do not appear to modulate the structure of its collagenous domain.
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Affiliation(s)
- Alaa Al-Shaer
- Department of Molecular Biology and Biochemistry, Burnaby, British Columbia, Canada
| | - Aaron Lyons
- Department of Physics, Burnaby, British Columbia, Canada
| | - Yoshihiro Ishikawa
- Department of Ophthalmology, University of California San Francisco, School of Medicine, San Francisco, California
| | - Billy G Hudson
- Department of Medicine, Division of Nephrology and Hypertension, Nashville, Tennessee; Vanderbilt Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Biochemistry, Nashville, Tennessee; Department of Pathology, Microbiology, and Immunology, Nashville, Tennessee; Department of Cell and Developmental Biology, Nashville, Tennessee; Vanderbilt-Ingram Cancer Center, Nashville, Tennessee; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee
| | - Sergei P Boudko
- Department of Medicine, Division of Nephrology and Hypertension, Nashville, Tennessee; Vanderbilt Center for Matrix Biology, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Biochemistry, Nashville, Tennessee
| | - Nancy R Forde
- Department of Molecular Biology and Biochemistry, Burnaby, British Columbia, Canada; Department of Physics, Burnaby, British Columbia, Canada; Department of Chemistry, Burnaby, British Columbia, Canada; Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, British Columbia, Canada.
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Abstract
Microtubules are structural polymers that participate in a wide range of cellular functions. The addition and loss of tubulin subunits allows the microtubule to grow and shorten, as well as to develop and repair defects and gaps in its cylindrical lattice. These lattice defects act to modulate the interactions of microtubules with molecular motors and other microtubule-associated proteins. Therefore, tools to control and measure microtubule lattice structure will be invaluable for developing a quantitative understanding of how the structural state of the microtubule lattice may regulate its interactions with other proteins. In this work, we manipulated the lattice integrity of in vitro microtubules to create pools of microtubules with common nucleotide states, but with variations in structural states. We then developed a series of novel semi-automated analysis tools for both fluorescence and electron microscopy experiments to quantify the type and severity of alterations in microtubule lattice integrity. These techniques will enable new investigations that explore the role of microtubule lattice structure in interactions with microtubule-associated proteins.
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Lopez BJ, Valentine MT. Molecular control of stress transmission in the microtubule cytoskeleton. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015. [PMID: 26225932 DOI: 10.1016/j.bbamcr.2015.07.016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In this article, we will summarize recent progress in understanding the mechanical origins of rigidity, strength, resiliency and stress transmission in the MT cytoskeleton using reconstituted networks formed from purified components. We focus on the role of network architecture, crosslinker compliance and dynamics, and molecular determinants of single filament elasticity, while highlighting open questions and future directions for this work.
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Affiliation(s)
- Benjamin J Lopez
- Department of Mechanical Engineering and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106-5070, USA
| | - Megan T Valentine
- Department of Mechanical Engineering and Neuroscience Research Institute, University of California, Santa Barbara, Santa Barbara, CA 93106-5070, USA.
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