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Updated: Jan 12, 2026
Study of Protein Dynamics via Neutron Spin Echo Spectroscopy
Published on: April 13, 2022
Conformational dynamics and energetic perturbations in human β-spectrin-II mediated by calpain cleavage-related
Reshma V Kizhakethil1, Ashok K Varma2, Om V Bhogale1
1Amity Institute of Biotechnology, Amity University, Bhatan, Somathne, Mumbai Pune Expressway, Panvel, Navi Mumbai, Maharashtra 410206, India.
Abstract:
The present study examined the impact of missense mutations in calpain substrates on their interaction with calpains and subsequent cellular functions. Calpains are a family of calcium-dependent cysteine proteases that modify the activity or location of their substrate proteins through cleavage at specific sites in a strictly controlled manner. Recent reports suggested the presence of missense mutations within and around calpain cleavage sites in calpain substrates, termed calpain cleavage-related missense mutations (CCRMs). However, the structural and functional impacts of these mutations on calpain substrates and their interactions with their respective calpains are poorly understood. This study elucidates how the V1463M calpain-cleavage-related mutation in β-II spectrin (SPTB2), identified in the uterine corpus endometrial carcinoma, perturbs substrate architecture and impairs critical cell signalling pathways. Wild-type and mutant SPTB2 were docked with µ-calpain, followed by molecular dynamics simulation and an enhanced sampling technique to study the differences in conformational dynamics and energy perturbations. The sequential and structural analysis of wild-type and mutant SPTB2 indicated differential stability. Molecular docking and MD simulation analyses involving the RMSD, RMSF and Rg values indicate a less stable mutant SPTB2-µ-calpain complex with notable conformational fluctuations and reduced flexibility compared with its wild-type counterpart. Although both wild-type and mutant SPTB2-µ-calpain complexes bind spontaneously (MM-PBSA: -14.85 vs -10.74 kcal/mol), steered MD reveals that the wild-type complex resists dissociation far more strongly (requiring ∼1700 kJ/mol/nm vs ∼1400 kJ/mol/nm for the mutant), underscoring its superior mechanical stability. The assessment of binding stability via the enhanced sampling method revealed that, compared with the mutant SPTB2-µ-calpain complex, the wild-type SPTB2-µ-calpain complex has favourable binding energy. Comprehensive analysis revealed significant variation in the binding of mutant SPTB-2 with µ-calpain, which may influence SPTB2-µ-calpain interactions, leading to aberrations in cellular migration and metastasis. This, in turn, may affect calpain-mediated proteolysis of β-II spectrin, dysregulating cytoskeletal remodelling and downstream adaptor-mediated signalling pathways.
Insights
Missense mutations in beta-II spectrin (SPTB2) disrupt its interaction with µ-calpain, impacting cell signaling and cytoskeletal regulation. This study reveals how cancer-associated mutations in calpain substrates affect protein stability and cellular functions.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Calpains are calcium-dependent proteases regulating cellular functions via substrate cleavage.
- Missense mutations near calpain cleavage sites (CCRMs) may alter substrate interactions and cellular processes.
- The specific impact of CCRMs on calpain substrate structure and function remains poorly understood.
Purpose of the Study:
- To investigate the structural and functional consequences of a V1463M mutation in beta-II spectrin (SPTB2) on its interaction with µ-calpain.
- To elucidate how this mutation affects substrate stability, binding dynamics, and cellular signaling pathways.
- To understand the implications of altered SPTB2-µ-calpain interactions in cancer, specifically uterine corpus endometrial carcinoma.
Main Methods:
- Molecular docking of wild-type and mutant SPTB2 with µ-calpain.
- Molecular dynamics (MD) simulations to analyze conformational dynamics and stability.
- Enhanced sampling techniques and steered MD to assess binding energy and mechanical stability.
- Analysis of RMSD, RMSF, and Rg values to quantify complex stability.
Main Results:
- The V1463M mutation in SPTB2 results in a less stable complex with µ-calpain, exhibiting increased conformational fluctuations.
- The wild-type SPTB2-µ-calpain complex demonstrates superior mechanical stability and stronger resistance to dissociation compared to the mutant complex.
- Binding energy assessments indicate more favorable interactions for the wild-type complex, suggesting impaired binding affinity in the mutant.
Conclusions:
- The V1463M mutation significantly alters SPTB2 binding to µ-calpain, potentially disrupting calpain-mediated proteolysis.
- Dysregulated interactions may lead to aberrant cytoskeletal remodeling and downstream signaling, contributing to cellular migration and metastasis.
- These findings highlight the critical role of CCRMs in disease pathogenesis and provide insights into calpain substrate regulation.
