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Velez G, Sun YJ, Khan S, Yang J, Herrmann J, Chemudupati T, MacLaren RE, Gakhar L, Wakatsuki S, Bassuk AG, Mahajan VB. Structural Insights into the Unique Activation Mechanisms of a Non-classical Calpain and Its Disease-Causing Variants. Cell Rep 2020; 30:881-892.e5. [PMID: 31968260 PMCID: PMC7001764 DOI: 10.1016/j.celrep.2019.12.077] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 11/26/2019] [Accepted: 12/19/2019] [Indexed: 12/12/2022] Open
Abstract
Increased calpain activity is linked to neuroinflammation including a heritable retinal disease caused by hyper-activating mutations in the calcium-activated calpain-5 (CAPN5) protease. Although structures for classical calpains are known, the structure of CAPN5, a non-classical calpain, remains undetermined. Here we report the 2.8 Å crystal structure of the human CAPN5 protease core (CAPN5-PC). Compared to classical calpains, CAPN5-PC requires high calcium concentrations for maximal activity. Structure-based phylogenetic analysis and multiple sequence alignment reveal that CAPN5-PC contains three elongated flexible loops compared to its classical counterparts. The presence of a disease-causing mutation (c.799G>A, p.Gly267Ser) on the unique PC2L2 loop reveals a function in this region for regulating enzymatic activity. This mechanism could be transferred to distant calpains, using synthetic calpain hybrids, suggesting an evolutionary mechanism for fine-tuning calpain function by modifying flexible loops. Further, the open (inactive) conformation of CAPN5-PC provides structural insight into CAPN5-specific residues that can guide inhibitor design.
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Affiliation(s)
- Gabriel Velez
- Omics Laboratory, Department of Ophthalmology, Byers Eye Institute, Stanford University, Palo Alto, CA 94304, USA; Medical Scientist Training Program, University of Iowa, Iowa City, IA 52242, USA
| | - Young Joo Sun
- Omics Laboratory, Department of Ophthalmology, Byers Eye Institute, Stanford University, Palo Alto, CA 94304, USA
| | - Saif Khan
- Protein and Crystallography Facility, University of Iowa, Iowa City, IA 52242, USA; Department of Biochemistry, University of Iowa, Iowa City, IA 52242, USA; Department of Biology and Biochemistry, University of Bath, Bath BA2 7AX, UK
| | - Jing Yang
- Omics Laboratory, Department of Ophthalmology, Byers Eye Institute, Stanford University, Palo Alto, CA 94304, USA
| | - Jonathan Herrmann
- Department of Structural Biology, Stanford University, Palo Alto, CA 94305, USA; Photon Science, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Teja Chemudupati
- Omics Laboratory, Department of Ophthalmology, Byers Eye Institute, Stanford University, Palo Alto, CA 94304, USA
| | - Robert E MacLaren
- NIHR Biomedical Research Centre, Oxford University Hospitals NHS Foundation Trust, Oxford EC1V 2PD, UK; Oxford Eye Hospital, University of Oxford NHS Trust, John Radcliffe Hospital, Oxford OX3 9DU, UK
| | - Lokesh Gakhar
- Protein and Crystallography Facility, University of Iowa, Iowa City, IA 52242, USA; Department of Biochemistry, University of Iowa, Iowa City, IA 52242, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
| | - Soichi Wakatsuki
- Department of Structural Biology, Stanford University, Palo Alto, CA 94305, USA; Photon Science, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | | | - Vinit B Mahajan
- Omics Laboratory, Department of Ophthalmology, Byers Eye Institute, Stanford University, Palo Alto, CA 94304, USA; Veterans Affairs Palo Alto Health Care System, Palo Alto, CA 94304, USA.
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