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Structural Insights into the Unique Activation Mechanisms of a Non-Classical Calpain and its Disease-Causing Variants

53 Pages Posted: 16 Oct 2019 Publication Status: Published

See all articles by Gabriel Velez

Gabriel Velez

Stanford University - Omics Laboratory

Young Joo Sun

Stanford University - Omics Laboratory

Saif Khan

University of Iowa - Department of Biochemistry

Jing Yang

Stanford University - Omics Laboratory

Jonathan Herrmann

Stanford University - Department of Structural Biology

Teja Chemudupati

Stanford University - Omics Laboratory

Robert E. MacLaren

NHS Foundation Trust - NIHR Biomedical Research Centre for Ophthalmology

Lokesh Gakhar

University of Iowa - Department of Biochemistry

Soichi Wakatsuki

Stanford University - Department of Structural Biology

Alexander G. Bassuk

University of Iowa - Department of Pediatrics

Vinit Mahajan

Stanford University - Omics Laboratory

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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 have been described, the structure of CAPN5, a non-classical calpain, remains undetermined. Herein, we report the 2.8 Å crystal structure of the human CAPN5 protease core (CAPN5-PC). Compared to classical calpains, CAPN5-PC requires high Ca2+ concentrations for maximal activity. Structure-based phylogenetic analysis revealed 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 C2 loop revealed a novel function for this region in 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 the CAPN5-PC structure provides an opportunity for identifying inhibitors that bind to CAPN5-specific residues and lock it in the inactivated form.

Keywords: Calpain, CAPN5, NIV, protease, uveitis, genetic eye disease, structure-based phylogenetics

Suggested Citation

Velez, Gabriel and Sun, Young Joo and Khan, Saif and Yang, Jing and Herrmann, Jonathan and Chemudupati, Teja and MacLaren, Robert E. and Gakhar, Lokesh and Wakatsuki, Soichi and Bassuk, Alexander G. and Mahajan, Vinit, Structural Insights into the Unique Activation Mechanisms of a Non-Classical Calpain and its Disease-Causing Variants (October 15, 2019). Available at SSRN: https://ssrn.com/abstract=3469831 or http://dx.doi.org/10.2139/ssrn.3469831
This is a paper under consideration at Cell Press and has not been peer-reviewed.

Gabriel Velez

Stanford University - Omics Laboratory

United States

Young Joo Sun

Stanford University - Omics Laboratory

United States

Saif Khan

University of Iowa - Department of Biochemistry

United States

Jing Yang

Stanford University - Omics Laboratory

United States

Jonathan Herrmann

Stanford University - Department of Structural Biology

United States

Teja Chemudupati

Stanford University - Omics Laboratory

United States

Robert E. MacLaren

NHS Foundation Trust - NIHR Biomedical Research Centre for Ophthalmology

London
United Kingdom

Lokesh Gakhar

University of Iowa - Department of Biochemistry

United States

Soichi Wakatsuki

Stanford University - Department of Structural Biology

United States

Alexander G. Bassuk

University of Iowa - Department of Pediatrics

United States

Vinit Mahajan (Contact Author)

Stanford University - Omics Laboratory ( email )

United States

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